'Illlllllllllllnirla

} o

l

THESIs

ii.

., .

TATE LIBRARIE

IllullllllllllllII

lililllllllll
3 1293 01826 4790

in

LIBRARY
Michigan State

University

 

 

 

 

 

 

 

 

 

 

 

 

 

This is to certify that the

dissertation entitled

Coordination Chemistry of Chelating Phosphines:
Stabilizationof Metalloradicals and the Elaboration of
Extended Structures

presented by

Calvin E. Uzelmeier, III

has been accepted towards fulfillment
of the requirements for

QUAD degreein dfiemié‘fl’y

Major professor

Date [0’22/ / / 1/ q?

MSU is an Affirmative Action/Equal Opportunity Institution 0- 12771

_-——___

—._
F—

 

 

PLACE IN RETURN BOX to remove this checkout from your record.
TO AVOID FINE return on or before date due.
MAY BE RECAU£D with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ma WWW.“

 

 

[OORDIX
ECL’SPHINIS:
IVD THE E

 

1n par

 

 

 

COORDINATION CHEMISTRY OF CHELATING
PHOSPHINES: STABILIZATION OF METALLORADICALS
AND THE ELABORATION OF EXTENDED ARRAYS

By

Calvin Edward Uzelmeier, III

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements

for the degree of

DOCTOR OF PHILOSOPHY

Department of Chemistry
1998

IZEMTIOX C .

{ll llElALLO

 

'1 V'-‘ b
'o|‘\. 'I. .Ll,
. It. ‘.‘5
e
v. f, ‘
.4 if ‘
~ 1~."' F“. —.

 

ABSTRACT

COORDINATION CHEMISTRY OF CHELATIN G : STABILIZATION
0F NIETALLORADICALS AND THE ELABORATION OF

EXTENDED ARRAYS

Calvin Edward Uzelmeier, III

Tertiary phosphine are one of the most versatile ligands in
coordination and organometallic chemistry. Their cooperative o-donor, 1t-
acceptor bonding allows for the stabilization of complexes with metals in a
wide range of oxidation states. Furthermore, they allow for tuning of the
electronic and steric properties of the resulting metal-phosphine complexes
by changes in the R groups. Modifications of the electronic and steric
properties tertiary phosphines is well-documented in homogeneous catalysis
to be a convenient method for altering the rates of reactions and
stereoselectivity of the desired product.

Tris(2,4,6-trimethoxyphenyl)phosphine (TMPP) is an excellent ligand
for stabilizing reactive metal radicals and coordinatively unsaturated,

electron deficient complexes. In addition to the phosphorus atom, the metal

\drs

‘mn ~Ih-u..

N V
v--.-o-.O»~ \1‘?\
b L

‘ ‘

.n -- q
I“ V \

I- sun.» 5.54

n‘. . . '
’o)“9‘»' I "
”-v-Ao‘eovh .-

'2
V'Z'Iv 0‘ .

n , ' ‘.§
--. l V \' ~
nu, ‘hy “Iv.‘

g ‘ v

M ' a L‘.Ua ‘1.

I,‘ _.
I; "i: ”f?"-
“‘"“5VIA\:-.

”PR
‘ . “
a.“ £3 .39»
-\A4
‘3'
'Ir '
. FHA“
. d‘ ‘I,‘
«”54 _r>
.4 -.
“I.-“
.“N-fl ”.m'1ro
5., ,0-
karu_l
- ' ‘
|

'1‘.“ i
.__.,-u,. .
-. "flirt ATL?‘
-.v‘.
m} .
4... 0f Pr" |
Wat.-
‘
“x. a

o.“

W:
F! v-
» ‘

‘,
d" 9

Cr‘

(1‘

O

 

 

can coordinate to ether functionalities, resulting in mono-, bi-, or tridentate
coordination modes. The combination of steric bulk and chelating ability
allowed for the stabilization of the unusual series of homoleptic TMPP
complexes, [Rh(TMPP)2][BF4]n (n = 1, 2, 3) which span the (I), (II), and (III)
oxidation states. Subsequent dealkylation of the coordinated methoxy groups
by nucleophiles yields metal complexes with the phosphino-phenoxide ligand
(TMPP-0 = [P{C6H2(OMe)3}2(C5H2(OMe)2O]1'). This ligand is very useful for
the preparation of heterobimetallic as well as much larger clusters as
evidenced by the isolation and X-ray studies of [C0113(u2-0H)3(u3-OH){0011013-
TlVIPP- 0)2} 3] [BF4].

The incorporation of Pth groups as functional groups on the organic
donor TTF, is a method for incorporating redox active organic molecules into
"hybrid" inorganic/organic arrays with metal complexes. Indeed, the
mononuclear complexes, [M(o-P2)2][BF4]2 (M = Ni, Co, Pd, Pt, Fe), where o-P2
= 3,4-dimethyl-3',4'-bis(diphenylphosphino)tetrathiafulvalane, exhibit redox
properties characteristic of both the ligand and metal components. Stepwise
formation of complexes that contain cis-MClz moieties allows for the
formation of mono- and dinuclear complexes that contain one, two, or three
TTF units. The reactivity of these phosphine ligands with metal-metal
bonded compounds has also been investigated.

The o-P2 complexes may be viewed as models for extended arrays that

contain the tetradentate ligand tetrakis(diphenylphosphino)-

tetrathiafulvalene (P4).

A series of soluble products, formulated as
[M(P4)]n[BF4]2n (M = Ni, Co, Pd, Pt, Fe) and [M(P4)]n[BF4]n (M = Rh), have
been prepared and characterized by 31P{1H} NMR spectroscopy, and cyclic
voltammetry, among other methods. The combined results of the studies are

in accord with the formulation of these products as cyclic oligomers.

In memory of my grandfathers:

Calvin E. Uzelmeier, Sr. and Donald A. Ottinger.

. . I .

- u gr wuf:u ‘)

‘~ -5. gm“.\\
. 5

| I
.-. 93-4..” 2.. a W
_- ~‘nohd- “50% AA

3 " 3"‘1'3” FF!
3-. .. sip.“ ,
.

  
   
    

. ' ' '
' '. ‘4'". .~:a ‘F'iu.
‘""““' ha¥ Leah.

.‘V .0. ~
' .. 2‘ top"-

I Q
' "9... ~
« HA. I m
‘ ‘- . a; “‘5‘“ ‘
5 Hi

i" " 'i ‘ 013'“
.‘k. H \ V
50. 3"

 

~. ‘. I g
a, —‘ r».
‘4. '(‘u>\
'n‘-. I.
"‘ hi‘ L? .L'In-
b ““6. '\
l :.
_:’ o.
.‘.“I ' 'a;.;.
N. 1“ ‘
"~31. 0§ ’5;
I I 15

 

 

'5... ‘l
I. . -
a
\
‘ J. “-9“.
7“ ‘.
.‘.
I. H
l l ‘
‘- ' .a I .
\‘~. ‘ . ‘ha
.1, Lu" 9 .
Q \

 

ACKNOWLEDGEMENTS

This work would not have been possible if not for the help and support of many
peOple. First and foremost I would like to thank my advisor, Prof. Kim R. Dunbar.
Through her guidance and example I have learned much of what it means to be a
scientist, teacher, and mentor. I will always cherish her advice and friendship. I would
also like to express my appreciation to Dr.s Marc Founnigué and Patrick Batail for all
their help, and the chance to work with such wonderful compounds. Thank you to the
members of my committee, all of which lent their advice and support on numerous
occasions throughout my graduate carrier. 1 would like to thank all the past and present
members of the Dunbar group for their friendship and partnership in science. A special
thanks to my 'big-sister" Jui-Sui Sun (Alice), for her patience in helping this over-zealous
rookie through his first years of research, and my lab twin, Kemal Catalan, who always
helped me keep things in perspective. Much of the research reported here is due to the
efforts of Julia Meinershagen and Gulio Grandinetti. I am grateful for the opportunity to
be a small part of the development of these two scientists. I have truly been spoiled by
my comrades at Michigan State, and will be hard-pressed to find a place where I have
such admiration and respect for my co—workers. They made graduate school a truly
enjoyable experience, and I pray to maintain their friendships for decades to come. To
the entire Department of Chemistry at Michigan State University I express my deepest
appreciation for their support during the times when it looked as though I would not reach
this day. It is through difficult times such as those that we realize how much people care.

I would also like to acknowledge the University's Herbert T. Graham Memorial, Margaret

vi

i fl'.‘ :'
‘ .w_l-.‘n
— .
a
I. we!" ."
3.3;31“ ' :a... AK-
,,.‘..bn --
" i v
.-
o-«r
.P Z ”-3.3 \ .

pus-5 v o-\s4
v- ‘

u
n . ."'=‘

. '7". .I‘
s t .

us.“ I? we
‘l.- ‘

3th. ‘

‘n ‘4. “i O 4

I

~' ‘ V‘ ~..

v... ..i ‘
U

u.‘

 

 

Yates Memorial, and Carl H. Brubaker Endowed Fellowships and a Sigma Xi graduate
student research grant for partial funding of this work.

On a more personal note, I would like to thank Rebecca Marcus for her love and
support over these last two years. She was the glue that held me together through the
final stages of my graduate career. To my family: this is because of you. Without my fan
club at home, I could have never succeeded. I would like to thank my parents for staying
by my side, quite literally, through all the highs and lows of the past 6 years. There were
times when I thought I couldn't take another step, but you encouraged me to try. You
have set an example of love before me that you cannot comprehend. Finally, I thank God
for the gifts that I have been given, and the chance to use them in new ways every day.

In closing, I would like to share something a young 1“ grade girl told me once. It
is the reason that we all satisfy our curiosities through research, and continue to try and

understand the world around us: "Science is Cool!" Never forget that!

vii

 

"“t'rr‘nnv ~
‘ ”V -'l \
~...~‘.9‘U"U~

v...“
.1

_l:l;\fpt3tf

.. ‘fifi‘ Y
.1" u I ‘
“ NM 1.

 

t he a

TABLE OF CONTENTS

Page
LIST OF TABLES ........................................................................................... xix
LIST OF FIGURES .......................................................................................... xxi
LIST OF SYMBOLS AND ABBREVIATIONS ............................................... xxv
LIST OF COMPOUNDS .................................................................................. xxix
CHAPTER I. INTRODUCTION ............................................................. 1
A. Fuctionalized Phosphines as Ligands in Transition Metal
Complexes ........................................................................................ 2
B. The Chemistry of Tris(2, 4, 6-trimethoxyphenyl)phosphine ......... 7
C. The Design of Molecule-Based Materials with Phosphine
Ligands ............................................................................................ 14
(1) The Use of Organic Acceptors in Molecular Materials ....... 17
(2) Derivative Chemistry of the Organic Donor,
Tetrathiafulvalene ................................................................ 18
D. The Development of Phosphine-Fuctionalized
Tetrathiafulvalenes ......................................................................... 22
List of References ................................................................................... 28
CHAPTER II. COORDINATION CHEMISTRY OF TRIS(2,4,6-
TRIMETHOXYPHENYL)PHOSPHINE WITH
PLATINUM GROUP TRANSITION METALS .............. 37
1. Introduction ...................................................................................... 38
2. Experimental .................................................................................... 40

('I_I
:34

3. X-r:

 

.l Re

C- Re

 

A. Synthesis ................................................................................ 4O

(1) Preparation of [Rh1(TMPP)2][BF4] (3) ....................... 40
(1) Reduction of [Rh11(n3-TMPP)2][BF4]2 with
COsz ............................................................... 40
(ii) Reduction of [Rhnm 3-TMPP)2][BF4]2 with
Zn (8). ............................................................... 41
(2) Dealkylation of [RhI(TMPP)2][BF4] (3):
Formation of RhI(TMPP)(TMPP-O) (4) ..................... 42

(3) Dealkylation of ax-[Rhm(TMPP)(TMPP-
O)][BF4]2: Formation of ax,ax-[Rhm(TMPP-

O)2][BF4] (5) ................................................................ 43
(4) Reaction of CoII(TMPP-O)2 with PtHC12(NC7H5)2 ..... 43
(5) Reaction of CoII(TMPP-O)2 with
[.Mn(NCCH3)4] [BF4]2 .................................................. 44
B. X—ray Crystallography ........................................................... 44
(1) [RhImz-MPPM[BF4l°[RhH(n3-TMPP1[BF412
(3'[Rh11(n3-TMPP)2] [BF4]2) ......................................... 46
(i) Data Collection and Reduction ........................ 46
(ii) Structure Solution and Refinement. .............. 46

(2) [00113013-01'D(ii-0H)3{COH(P'113-TMPP'
0)2}3] [BF 4]2° [CHs-TMPP] [BF4]° CH3CH2)2O°
(CH2)2CO (6- [CHs-TMPP] [BF 4]°(CH3CH2)2O°

(CH2)2CO) ................................................................... 47
(i) Data Collection and Reduction ..................... 47
(ii) Structure Solution and Refinement .............. 48
(3) Pd(TMPP-0)2-3.73CH2C12-H20 (7-3.7BCH2012-
H20). ........................................................................... 49
(i) Data Collection and Reduction ..................... 49
(ii) Structure Solution and Refinement .............. 49
3. Results and Discussion ...................................................................... 51
A. Reduction of [RhH(TMPP)2][BF4]2: Formation of
[Rh1(TMPP)2][BF4] (3) .......................................................... 51
(1) NMR Spectroscopic Studies ....................................... 52
B. Crystal Structure of [Rh1(TMPP)2][BF4] (3) ......................... 56
C. Reactivity of [RhICI‘MPP)2][BF4] (3) ...................................... 61
(1) Decomposition of [Rh1(TMPP)2][BF4] (3) ................... 61
(2) Dealkylation of [RhI(TMPP)2][BF4] (3) ...................... 61

(i) Synthesis and spectroscopic
characterization of Rh1(TMPP)-
(TMPP-0) (4) .................................................. 62

D. Pre

"Tl

,-
LI...

OE

G. C:

1 t
l 'H'lu‘1.,\
Vvdylu‘..h

v. P A
1‘! -oD,._'_
4:\ ~P,5

'0 Aux"‘

. ‘9‘
'.u' .:l YYT

\
‘T‘ban ‘11. ‘

 

‘
\.v
. Q

 

(ii) Decomposition of Rh1(TMPP)(TMPP-O)

(4) ................................................................... 63
D. Preparation and Spectroscopic Studies of ax, ax-
[RhHICI‘MPP-O)2][BF4] (5) ..................................................... 64
E. Reactions of Con(TMPP-O)2 with Reactive Metal
Complexes ............................................................... 65
(I) PtuC12(NC7H5)2 ........................................................... 65
(2) [NIDH(NCCH3)4][BF4]2 ................................................ 66
F. Formation and Crystal Structure of [C0113(u3-OH)(u-
OH)3{C0H(u-n3-TMPP-O)2}3] [BF4]2 (6) .................................. 67
(1) Crystal Structure ....................................................... 68
(2) EPR Spectroscopy ...................................................... 73
G. Crystal Structure of Pd(TMPP-O)2 (7) ................................. 73
4. Concluding Remarks ........................................................................ 73
List of References ................................................................................... 79
CHAPTER III. SYNTHESIS AND REACTIVITY OF [M(o-P2)2]-
[BF4]x (M = Fe, Co, Ni, Pd, Pt, x = 2; M = Rh, x = 1) ...... 83
1. Introduction ...................................................................................... 84
2, Experimental .................................................................................... 85
A. Synthesis .......................................................... i ...................... 85
(1) Preparation of [M(o-P2)2]['BF4]2 ................................. 87
(i) [Ni(o-P2)2][BF4]2 (8). ..................................... 87
(ii) [Co(o-P2)2][BF4]2 (9) ...................................... 88
(iii) [Pd(o-P2)2][BF4]2 (10) .................................... 89
(iv) [Pt(o-P2)2][BF4]2 (11). ................................... 89
(v) [Fe(o-P2)2][BF4]2 (12). ................................... 9O
(2) Reactions of M(CF3803)2 with o-P2 (1) ..................... 90
(i) Preparation of [Ni(o-P2)2] [CF380312
(13) ................................................................. 90
(ii) Reaction of Fe(CF3803)2 with o-P2 (1) .......... 91
(3) Oxidation of [Rh1(o-P2)2][BF4] with NOBF4:
Preparation of [Rh1(o-P2)2][BF4]3 (l4) ....................... 91
(4) Reaction of [Rh1(o-P2)2][BF4] with [Li] [TCNQ] ......... 92
B. X-ray Crystallography ........................................................... 92

 

(1) [Ni(o-P2)2][BF4]2 °C7H3°CH3CN (8°C7H8-

CH3CN) ....................................................................... 94
(i) Data Collection and Reduction ..................... 94
(ii) Structure Solution and Refinement. ............. 94
(2) [Pt(O-P2)2][BF4]2 °C7H8'CH3CN (11°C7H3"
CHscN) ....................................................................... 96
(i) Data Collection and Reduction. .................... 96
(ii) Structure Solution and Refinement .............. 96
3. Results and Discussion ..................................................................... 97
A. Preparation of [M(o-P2)2][BF4]2 (M = Ni, Co, Pd, Pt,
Fe) ......................................................................................... 98
B. Spectrosopic Characterization of [M(o-P2)2][BF4]2 (M
= Ni, Co, Pd, Pt, Fe) .............................................................. 99
(1) NMR Spectroscopic Studies of [M(o-P2)2][BF4]2
(8-12) .......................................................................... 99
(i) 1H and 31P{1H} NMR ..................................... 99
(ii) Variable Temperature 19F and 31P{1H}
NMR of [Fe(o-P2)2] [BF 4]2 (12) ....................... 101
(2) Infrared and Electronic Absorbance
Spectroscopy ............................................................... 102
(3) FAB-MS of [M(o-P2)2][BF4]2 (M = Ni, Co, Pd,
Pt, Fe) (8-12) .............................................................. 102
C. Crystal Structures of [M(o-P2)2][BF4]2 (M = Ni (8), Pt
(11)) ....................................................................................... 103
D. Magnetic Studies of [Co(o-P2)2][BF4]2 (9) ............................. 109
(1) Variable Temperature Magnetic Susceptibility ....... 109
(2) EPR Spectroscopic Studies ........................................ 109
E. Electrochemistry of [M(o-P2)2][BF4]x (M = Ni, Pd, Pt,
=2;M=Rh,x=1) ................................................................ 114
(1) Redox Properties of [M(o-P2)2][BF4]2 (M = Ni,
Pd, Pt) ......................................................................... 114
(2) Oxidation of [Rh(o-P2)2][BF4] ................................... 117
F. Reactivity of M(CF3S03)2 with o—P2 (M = Ni, Fe) ................ 119
G. Metathesis of [Rh(o-P2)2][BF4] with [Li] [TCNQ] ............... 120
4. Concluding Remarks ......................................................................... 120
List of References ................................................................................... 124

xii

3 Ram.
“54415 av
K.

p,
"U

In

0‘

’71

8.3?

P—
3.
r
I

77.3

 

 

 

CHAPTER IV REACTIVITY OF METAL-METAL BONDED
COMPLEXES WITH PHOSPHINE-

FUN CTIONALIZED TETRATHIAFULVALENE ......... 127
1. Introduction ...................................................................................... 128
2. Experimental .................................................................................... 130
A. Synthesis ................................................................................ 130
(1) Reaction of [Rh2(NCCH3)1o][BF4]4 and
(thP)MeaTTF to form (15) ....................................... 131
(2) Reaction of [Re2(NCCH3)1o][BF4]4 and
(thP)2Me2TTF .......................................................... 131
(3) Reactions of [Bu4]2[Re2C18] with o-P2 ....................... 132
(i) Synthesis of [ReC12(o-P2)2][Re2C16(o-P2)]
(17°18) for short reaction times. .................... 132
(ii) Reaction time of 2 hours ................................ 133
(4) Reduction of [ReC12(o-P2)2][Re2C16(o-P2)]
(16- 17) to yield ReC12(o-P2)2 (18). ............................. 133
(5) Oxidation of ReClz(o-P2)2 (18) .................................... 134
(i) Preparation of [ReC12(o-P2)2][Cl]
(16-[Cl]) .......................................................... 134
(ii) Preparation of [ReC12(o-P2)2][BF4]
(16°[BF4]) ........................................................ 134
(6) Reaction of M02014(SMe2)4 with o-P2 ......................... 135
(i) In CH3CN ....................................................... 135
(ii) In CHzclz under aerobic conditions.
Preparation of MoClez(o-P202) (19) ............ 135
B. X-ray Crystallography ........................................................... 136
(1) [ReC12(o-P2)2] [R92C16(0-P2)]°4 CH2C12 (16° 17.4
CH2C12) ....................................................................... 136
(i) Data Collection and Reduction. .................... 136
(ii) Structure Solution and Refinement .............. 139
(2) MoClez(o-P202) (19) .................................................. 140
(i) Data Collection and Reduction. .................... 140
(ii) Structure Solution and Refinement .............. 140
3. Results and Discussion ..................................................................... 142
A. Reactions with [Mz(NCCH3)1o][BF4]4 (M: Rh, Re). .............. 142
B. Preparation, Characterization and Reactivity of
[Re012(o-P2)2] [Refine-132)] (16- 17) .................................... 145
(1) Reactivity of [(n-Bu)4N]2[RezCls] with o-P2 (1) .......... 145

xiii

(2) Crystal Structure of [ReClz(o-P2)2] [Re2C16(o-

P2)] (16° 17) ................................................................ 147
(3) Spectroscopic Characterization of [ReClz(o-
P2)2] [Re2C16(o-P2)] (16- 17) ........................................ 154
(4) Isolation of [ReC12(o-P2)2]+ (16) ................................. 155
(i) Reduction of [ReC12(o-P2)2][Re2(o-
P2)C16] (16° 17). .............................................. 155
(ii) Oxidation of ReC12(o-P2)2 (18) ....................... 155
(5) Electrochemical Studies ............................................ 156
(6) Magnetic Studies ....................................................... 159
(i) [ReC12(0-P2)2] [Re2C16(o-P2)] (16.17) ............. 159
(a) Magnetic susceptibility. .......................... 159
(b) EPR SpectrOSCOpy ................................... 161
(ii) [ReC12(o-P2)2][BF4] (16-[BF4]) ....................... 161
(iii) ReC12(o-P2)2 (18) ............................................ 161
C. Reactions of M02[S(CH3)2]4C14 with o-P2 ............................... 165
(1) Synthethesis ................................................................ 165
(2) Crystal Structure of MoC1202(o-P202) (19) .............. 167
(3) Spectrocscopic Characterization of MoC1202(o-
P202) (19) ................................................................... 170
4. Concluding Remarks ........................................................................ 173
List of References ................................................................................... 175

CHAPTER V STEP-WISE SYNTHESIS OF METAL
CONTAINING ARRAYS WITH BI- AND
TETRADENTATE TETRATHIAFULVALENE-

PHOSPHINE LIGANDS .................................................. 179
1. Introduction ...................................................................................... 180
2. Experimental .................................................................................... 182
A. Synthesis ................................................................................ 182
(1) Preparation of PtC12(o-P2) (20) ................................ 182
(2) Preparation of [Pt(o-P2)(NCCH3)2][BF4]2 (21) ........ 183
(3) Preparation of Pt2Cl4(P4) (22) ................................... 183
(4) Preparation of [Pt2(P4)(NCCH3)4][BF4]4 (23). ........... 184
(5) Preparation of [Pt2(P4)(o-P2)2][BF4]4 (24) ................. 184
(i) Reaction of [Pt(o-P2)(NCCH3)2][BF4]2

(21) with P4 (2) .............................................. 184

(ii) Reaction of [Pt2(P4)(NCCH3)4][BF4]4 (23)
with o-P2 (1) ................................................... 185

xiv

(6) Preparation of PdC12(o-P2) (25) ................................. 185

(7) Preparation of [Pd(o-P2)(NCCH3)2][BF4]2 (26) .......... 186
(8) Preparation of Pd2Cl4(P4) (27) .................................. 187
(9) Preparation of [Pd2(P4)(NCCH3)4][BF4]4 (28) ........... 187
(10) Preparation of Ni2C14(P4) (29) ................................. 187
B. X-ray Crystallography ........................................................... 188
(1) PtC12(o-P2)-CH30N (20-CH3CN) ............................... 188
(i) Data Collection and Reduction. .................... 188
(ii) Structure Solution and Refinement. ............. 190
(2) Pt2C14(P4)-3CHsCN (22-3CH3CN) ............................. 190
(i) Data Collection and Reduction. .................... 190
(ii) Structure Solution and Refinement. ............. 191
3. Results and Discussion ..................................................................... 192
A. Preparation, Spectroscopy, and Redox Properties of
MClz(o-P2) [M = Pt (20), Pd (23)] ......................................... 193
(1) Synthesis .................................................................... 193
(2) 1H and 31P{1H} NMR Spectroscopic Studies .............. 194
(3) Infrared and Electronic Absorbance
Spectroscopy ............................................................... 196
(4) Electrochemistry ........................................................ 200
B. Crystal Structure of PtC12(o-P2) (20) ................................... 200
C. Preparation and Spectroscopic Properties of M2Cl4(P4)
(M = Pt (22), Pd (27), Ni (29)) .............................................. 207
D. Crystal Structure of M20134) (22) 208
E. Reactioins of MC12(o-P2) and M2Cl4(P4) (M = Pt, Pd,
Ni) With AgBF4 ..................................................................... 211
(1) Synthesis .................................................................... 211
(2) Spectroscopic Studies ................................................. 212
(3) 1H and 31P{1H} NMR Spectroscopic Studies .............. 213
F. Synthesis and Characterization of [Pt2(o-P2)2(P4)]-
[BF4]4 (24) ............................................................................. 215
(1) Synthesis .................................................................... 215
(2) Spectrosc0pic Characterization ................................. 215
(3) 1H and 31P{1H} NMR Spectroscopic Studies .............. 216
(4) Electrochemistry ........................................................ 217
4. Concluding Remarks ........................................................................ 218
List of References ................................................................................... 224

-‘avfi ("Y
A

'I
‘0’0

0
I I..,f"'\vl.

A 5.1-. Jid H'. .

‘
.7 Erig‘rfir
.‘ “b -nA.“

 

 

CHAPTER VI ASSEMBLY OF OLIGOMERIC SYSTEMS FROM
HOMOLEPTIC PLATINUM GROUP NITRILE

COMPLEXES AND
TETRAKIS(DIPHENYLPHOSPHINO)TETRATHI
AFULVALENE (P4) ......................................................... 226
1. Introduction ...................................................................................... 227
2. Experimental .................................................................................... 228
A. Synthesis ................................................................................ 228
(1) Reaction of [Rh2(NCCH3)1o][BF4]4 with P4:
Formation of [Rh(P4)][BF4] (30) .............................. 228
(2) Reaction of [MH(NCCH3)n][BF4]2 (M = Pt, 11 = 4;
M = Pd, Co, Fe, Ni, n = 6) with P4 ........................... 229
(i) Formation of [Pt(P4)]n[BF4]2n (31). .............. 229
(ii) Formation of [Pd(P4)]n[BF4]2n (32) ............... 229
(iii) Formation of [Co(P4)]n[BF4]2n (33) ............... 230
(iv) Formation of [Fe(P4)]n[BF4]2n (34) ............... 231
(v) Formation of [Ni(P4)]n[BF4]2n (35) ............... 231
(3) Reactions with excess P4 ........................................... 232
(i) [Rh2(NCCH3)1o] [BF4]4 .................................... 232
(ii) [PdH(NCCH3)5][BF4]2 ..................................... 232
3. Results and Discussion ...................................................................... 233
A. Preparation and Characterization of WI(P4)]D[BF4]m
(M = Rh, x = 1; M = Pt, Pd, Co, Fe, Ni, x = 2) (30-35) ......... 233
(1) Synthesis .................................................................... 234
(2) Spectrosopic Characterization ................................... 234
(i) NMR Spectroscopic Studies .......................... 234
(ii) Infrared and UV-Visible Spectroscopy ......... 238

(iii) Magnetic Susceptibility and EPR
Spectroscopic Studies of [Co(P4)]n[BF4]2n

(33) ................................................................. 239
(iv) Electrochemistry of [Rh(P4)]n[BF4]n
(30) ................................................................. 241
(v) Fast Atom Bombardment Mass
Spectrometry .................................................. 241
(3) Proposed Cyclic Oligomers ....................................... 242
(i) Molecular Visualization ................................ 243
(ii) Gel Permeation Chromatography ................. 243
(iii) Variable Temperature 1H NMR
Spectrscopy .................................................... 245

xvi

h

.
' :n-O-v-
“. . l w
“. _-. ‘DLd-O
*-

1
’.-.~I"."V
A...‘.‘«|

:
-5.

 

 

 

B. Reactivity of [Rh2(NCCH3)1o] [BF4]4 and

[PdH(NCCH3)e][BF4]2 with excess P4 ................................... 245
4. Concluding Remarks ......................................................................... 246
List of References ................................................................................... 248
CHAPTER IX CONCLUSION ................................................................. 250
List of References ................................................................................... 255
APPENDIX ........................................................................................... 256
APPENDIX A PHYSICAL MEASUREMENTS ...................................... 257
APPENDIX B STRUCTURAL ANALYSIS OF
FUNCTIONALIZED TETRATHIAFULVALENES ........ 261
1. Introduction ...................................................................................... 262
2. Experimental .................................................................................... 263
A. X-ray Crystallography ........................................................... 263
(1) ortho-(CH3)2TTF (36) ................................................. 263
(i) Preparation, Data Collection and
Reduction. ...................................................... 263
(ii) Structure Solution and Refinement .............. 264
(2) ortho-(CH3)2[(C6H5)2P]2TTF (1) ................................. 264
(i) Preparation, Data Collection and
Reduction. ...................................................... 264
(ii) Structure Solution and Refinement .............. 265
(3) [(C6H5)2P]4TTF (2) ...................................................... 266
(i) Data Collection and Reduction. .................... 266
(ii) Structure Solution and Refinement. ............. 266
3. Results and Discussion ..................................................................... 268
A. Molecular Structure of ortho-(CH3)2TTF (36) ..................... 268
B. Molecular Structure of ortho-(CH3)2[(C6H5)2P]2'ITF (1) ....... 273
C. Molecular Structure of [(CsH5)2P]4TTF (2) .......................... 277
4. Concluding Remarks ........................................................................ 282
List of References ................................................................................... 283

,I .
‘r‘b‘

.....~\- C

a
I.-

1 Y‘

bvl;P‘W‘l_
. “use...“-

0
Q
ok- 5‘
D

‘ v
. -4..¢-

I F ‘ w
‘ ‘I'.";‘.'
a

T‘“HM-A..

o
A

no. F

. .0...

M... .‘ ‘~!:‘

'
.- ,
\iro
ml -f.
i‘va-o'
”H
.\
._.\
' h.

 

APPENDIX C SYNTHESIS OF [Bu4N]2[RezClg] FROM
RHENIUM-CONTAINING LABORATORY

RESIDUES ....................................................................... 284 .
1. Introduction ...................................................................................... 285
2. Experimental .................................................................................... 286
A. Synthesis ................................................................................ 286
(1) Preparation of KReO4 from Rhenium-
Containing Residue ................................................... 286
(2) Metathesis of KRe04 to form [(n-Bu)4N]2[Re04] ....... 289
(3) Synthesis of [(n-Bu)4N]2[Re2C13] ................................ 289
3. Results and Discussion ..................................................................... 290
A. Preparation and Characterization of [(n-
Bu)4N]2[Re2Clg] from Rhenium Residues ............................ 290
4. Concluding Remarks ........................................................................ 292
List of References ................................................................................... 295
APPENDIX D 31P{1H} NMR ANALYSIS OF PtCl(TMPP)-
(TMPP-O) .......................................................................... 296
1. Introduction ...................................................................................... 297
2. Experimental .................................................................................... 298
A. Synthesis and Physical Methods .......................................... 298
3. Results and Discussion ..................................................................... 298
A. 31P{1H} NMR Simulation and Interpretation for
PtCl(‘I‘MPPXTMPP-O) (37) .................................................. 298
4. Conclusing Remarks ......................................................................... 299
List of References ................................................................................... 302
APPENDIX E COMPILATION OF 31P NMR SPECTRAL DATA ......... 304

xviii

 

 

I III
I u . f4“ _~
‘ ‘1
~ . . r. P
I It . s 1-]. vi
I. .. hm . .f PM. mt. .. ha. 0...
. a 2 Va r . is L» Iii ‘. V l; rfi. l
I t .. u
.- . W.” rt. nfiu DU still” 1% . Niel? .m ATHA.x NM; «v I 5 N mu.
v . Fill .r. V . HWU .\~ .I.. 1‘4 H! A at. U 5‘ I‘A . l s M 9“.
, i 1.. . . . n .L .t . . ..
.. . ll fl... DU M»Iut B 7m Ifllu pha~ ”HI; his... NCO. 4?.N w .1 ~\ JI~J .8 m \Vx 51V
. Y . ~ - y a r. . ... V
O D is .1 or. .... I A . _.... .. . 3. i
a. a: ".11.- n c .t .1. s. L» .. w. FM ill. 9... .7. Tu 3.. .\t
.l MIL—Urn .y\. .. - M)“ ”V. DO 4» u .-3. u .‘I... §\,~ 3 c
.1“ . . at -. .1. m: 1... 3.. fix... I.
a. 1". n. r. at... .1.
w: New on. ~lc -43 «Ex —1.
.fi t. . u . . 1
a yr. .

10.

LIST OF TABLES

Crystallographic Data for [Rh1(n2-TMPP)2] [BF4]°[RhU(n3-
TMPPHBF412 (3'thH(n3-TMPPl-[BF4]2), [Cons(u3-0H)(H-

0H)3{CoH(TMPP-0)2}3l[BF4]2-[CH3-TMPP][BF4]-(CH30H2)2O-
2(CH2)2CO (6- [CHg-TMPP][BF4]-(CH30H2)2O-2(CH2)2CO), and

PdCI'MPP-O)2°3.7BCH2C12° H20, (7-3.73CH2C12° H20) ....................

Selected Bond Distances (A) and Angles (deg) for [Rh1(n2-

TMPP)2][BF4] (3). ...............................................................................

Selected Bond Distances (A) and Angles (deg) for [C0113(u3-

0H)(u-Ol-I)3{Con(u-n3-TMPP-O)2}3] [BF4]2 (6). ...................................
Selected bond distances (A) and angles (deg) Pd(TMPP-O)2 (7) .....

Summary of crystallographic data for [Ni(o-P2)2][BF4]2-2C7Hg

(8’2C7H8) and [Pt(o-P2)2][BF4]2'2C7H3 (11°2C7H3) ...........................

Selected Bond Distances (A) and Angles (deg) for [Ni(o-

P2)2] [BF4]2 (8) and [Pt(o-P2)2][BF4]2 (11) ..........................................

Electrochemical data (in V vs Ag/AgCl) for 8-11, o-P2, and [Rh(o-
P2)2] [BF4], in 0.2 M TBABF4/CH2C12 solutions, at 200 mV/s ..........

Summary of crystal data for [ReClz(o-P2)2] [RezCle(o-

P2)]‘4CH2012 (16'17‘4CH2C12). ..........................................................

Summary of crystal data for MoC1202(o-P202)-CH2C12

(l9-CH2C12). .......................................................................................

Summary of bond distances (A) and angles (deg) for the cation

[ReC12(o-P2)2]+ (16), in 16°17 ............................................................

Page

....45

....57

....69

....74

....93

....104

....115

....137

....138

....148

n ‘ ‘ ’
't,.... " r. V
U “ I» ‘O:_‘

L .u-ohfi'

.. "'71 en

E ' 'm. osai '
r
." .C

Q
\y‘wwcfi' ~" ’
WN‘

5 an
.A, ’N Y
D'i'h '(i‘
5-. A-
a. A
\“Iv-w-n v -
. .15 .II
.1 an r~ -
.0'.n_tf\

f

\V'~m~ - .o
3"

53““. .'.
u

k

\"erA . , o

~h~~d~ l
v

-A

32?;4 Sr

“3.1 '1'

‘ r
. , 1

~-.:'.":A L.
l.»“ J; v-
ar ’ '-I

.- . p~ .|

- "uh I) '
J ~A J‘
I

 

 

11. Summary of bond distances (A) and angles (deg) for the anion

[R82C16(0-P2)]' (17), in 16°17. ............................................................... 150
12. Possible redox reactions for the salt [ReIHC12(0-P2)2]-

[RezII’nIC16(0-P2)] (16' 17). ................................................................... 156
13. Summary of bond distances (A) and angles (deg) for MoC1202(o-

P202) ' CH2C12 (19° CH2C12) ................................................................ 168
14. Summary of crystallographic data for PtC12(o-P2)-CH3CN

(20-CH3CN) and PtzCl4(P4)-3CH3CN (22-3CH3CN). ........................... 189
15. Summary of NMR spectrosopic data for compounds 20-29. ................ 197
16. Summary of cyclic voltammetry, electronic absorbance and

infrared spectroscopy data for compounds 20-29. ................................ 199
17. Selected Bond Distances (A) and Angles (deg) for PtClz(o-P2)

(20) and Pt2C124(P4) (22) ....................................................................... 202
Appendix
18. Crystallographic data for ortho-(CH3)2TTF (36), ortho-

(CH3)2[(CGH5)2PIZTTF (1), and [(CeH5)2P]4TTF't01uene,

(2-toluene) .............................................................................................. 267
19. Selected bond distances (A) and angles (deg) for ortho-

(CH3)2TTF (36) and ortho-(CH3)2[(C5H5)2P]2TTF (1). ........................ 269
20. Selected bond distances (A) and angles (deg) for

[(CsH5)2P]4TTF (2). ............................................................................... 279

fit
...~..ap‘p:-
u 4
y‘.n-.uub.\;

'- r
IQ'QI'H‘. - -
, ,5
twig-lb
.

Q a

w; . Mn-

~.'“‘ SLIM:

‘ ..

P. Q. . .
r Vignp I

““““h m‘- ii

- !
'v’F1.-J __.
dick-‘7'; 2.
d..__ '
m‘v
“mart;
P‘ 1
'7‘”! A _
novk‘.“ if ):

"an H.
CH“. (13“
in

5.13::it’9

h. ,_ '
do.” *r-‘I i
.I

 

 

10.

11.

LIST OF FIGURES

(a) Schematic drawing and (b) ORTEP representation with 50%

ellipsoids of tris(2, 4, 6-trimethoxyphenyl)phosphine (TMPP). .......

Schematics depicting the crystallographically determined

binding modes for TMPP bound to a single metal center. ...............

Schematics depicting the crystallographically determined

binding modes for [P{CsH2(0Me)3}2(C¢;H2(0Me)20]2' (TMPP-0).

Ball and stick representation of the interlocking MnHeCuHe

hexagons of (rad)2Mn2[Cu(opda)]3(DMSO)2-2H20 .............................

ORTEP representation of the stacked salt, [TTF][TCNQ]. ..............

Extended structures proposed by Hoffman et. al.: (a) two
dimensional slab structure, (b) zig-zag layered structure, (c)
ribbon or sheet polymers, and (d) two-dimensional layer

structure ..............................................................................................

Schematics of the monodentate (P1), bidentate (o-P2, E-P2, Z-

P2), and tetradentate (P4) phosphine ligands ...................................

Variable Temperature 1H NMR spectra of [Rh1(n2-TMPP)2]-

[BF4] (3) in ds-acetone. .......................................................................

PLUTO representation of [Rh1(n2-TMPP)2][BF4] (3) from the

mixed salt [Rh1(r12-TMPP)2][BF 4] - [Rh11(n3-TMPP)2][BF4]2 ..............

PLUTO representation of the unique atoms, showing the
disorder in the molecular structure of [Rh1(n2-

TMPP)2] [BF4] ' [Rh11(n3-TMPP)2] [BF4]2. .............................................

ORTEP representation of [C0113(u3-0H)(u-0H)3{Con(unit-TMPP-
0)2}3][BF4]2 (6) with 50% probability ellipsoids. Hydrogen atoms

and labels have been removed for clarity ..........................................

xxi

Page

....8

....10

....11

16

....20

....23

....25

...54

...58

...59

...70

,p-u-q
. - V vs"
volnub A': ‘

. ‘

.I‘I ”P.3‘ ‘
l

:Juuflrb ‘

V I
5 -....
"uh -H-

v A

. AR.-
9:!— "_. I, Y
|~—-"“ 5-0

9
.tc‘a.A“'..

| ‘V'\
can..»-“ 4“

 

..,,
'D 1';V‘v

.
"NILA A.»..

"r Cle .

”.5 “J

’“?P
v.2,ry
A s

P -
¢.|L~

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.
22.

23.

24.

25.

26.

ORTEP representation of the immediate coordination sphere for

each metal in [0033(143-OH)(u-0H)3{Con(u-n3-TMPP-O)2}3] [BF4]2

(6) with 50% probablility ellipsoids. All other atoms have been
removed for clarity ................................................................................. 71

ORTEP representation of Pd(TMPP-O)2 (7) with 50% ellipsoids

viewed ..................................................................................................... 7 5
Interconversion pathways of the Rh-TMPP complexes ....................... 78
ORTEP representation of [Rh(o-P2)2][BF4] viewed from the (a)

top and (b) side with 50% probability ellpsoids .................................... 87
ORTEP representation of [Ni(o-P2)2][BF4]2 (8) with 50%

ellipsoids viewed from the (a) top and (b) side ..................................... 105
Packing diagram of [Ni(o-P2)2][BF4]2 (8) .............................................. 106
ORTEP representation of [Pt(o-P2)2][BF4]2 (11) with 50%

ellipsoids viewed from the (a) top and (b) side ..................................... 107
Plot of pea (p.13) and Xmol (emu/mol) vs. temperature (K) of [Co(o-

P2)2] [BF 4]2 (9) ......................................................................................... 110
EPR spectrum of [Co(o-P2)2][BF4]2 (13) in 50:50 CH3CNzToluene

at 107 K .................................................................................................. 112

EPR spectrum of [Co(o-P2)2][BF4]2 (9) as a solid sample at 4 K. ......... 113

Cyclic voltammogram of [Pt(o-P2)2][BF4]2 (11) in 0.2 M TBABF4
in CHzclz. ............................................................................................... 116

EPR spectrum of [Rh(o-P2)2][BF4]3 (13) in 50:50 CH3CNzToluene
at 95 K. ................................................................................................... 118

Schematic drawings of the proposed ligands (a) 3,4 dimethyl-
3’,4’-bis(dimethylphosphino)tetrathiafulvalene and (b) 3,4
dimethyl-3’,4’-bis-(phospholyl)tetrathiafulvalene ................................ 123

EPR spectrum of green paramagnetic solid from
[Rh2(NCCH3)1o] [BF4]4 + P1 in a toluene/CH3CN glass at 133 K ......... 143

Thermal ellipsoid plot of the cation [Re(o-P2)2014]+ (16) with non-
hydrogen atoms represented by their 50% probability ellipsoids ....... 149

I

 

1.,‘j

k .u'. Mud“
.

11”.; rh‘

h ’
Mad b Llhk -

I‘l
r'; Mr,

‘ 1
p0» -
In C...
dint-h.

"-2.... . ,1.
I'- 0' A
'44.M~~Au J“

a _ 1
.--’ .1113 ,r

b .. - .
r»- .o ‘
uuty“ Y

~\‘A H
n
o.,,_' “U
'-o"- ”i |
'“' 5A.
-

27.

28.

29.

30.

31.

32.

33.

34.
35.

36.

37.

38.

39.

40.

Thermal ellipsoid plot of the anion [Re2C16(o-P2)]' (17) with
non-hydrogen atoms represented by their 50% probability
ellipsoids ................................................................................................. 151

Packing diagram of [ReClz(o-P2)2][Re2C16(o-P2)] (16° 17).. ................. 152

Cyclic voltammogram of (a) [ReC12(o-P2)2][Re2C16(o-P2)] (16° 17)
and (b) [ReC12(o-P2)2][BF4] in 0.1 M TBABF4/CH2C12 vs Ag/AgCl
at a Pt disk electrode. ............................................................................ 157

Magnetic data for [ReC12(o-P2)2][Re2C16(o-P2)] (16- 17): (a) peg

(uB) and xmol (emu/mol) vs. temperature (K) and (b) xT (emu K

mol'l) vs. temperature (K) fit to the Curie-Weiss law with a

slope 0f XTIP ............................................................................................. 160

EPR spectrum of [ReC12(o-P2)2][Re2Cls(o-P2)] (16- 17) in a 1:1
toluene/CHzClz glass at 4 K. ................................................................. 162

Plots of (a) peg (11B) and Xmol (emu/mol) vs. temperature (K) and
(b) xT (emu K mol'l) vs. temperature of [Re(o-P2)2C12][BF4]

(16'[BF4]). ............................................................................................... 163
Plot of pea" (uB) and xmor (emu) vs. temperature (K) of ReC12(o-

P2)2 (18) .................................................................................................. 164
PLUTO representation of MoC1202(o-P202) (19) ................................. 169

Correlation of 31P NMR coordination chemical shift A631P in
MC12(L-L) (M = Ni, Pd, Pt) complexes with the free ligand 31P

NMR chemical shift 531P ....................................................................... 195
Cyclic voltammogram of PdClz(o-P2) (25) in 0.2 M TBABF4 in

CH2C12. ................................................................................................... 201
ORTEP representation of PtC12(o-P2) (20) with 50% ellipsoids

viewed from the (a) top and (b) side ...................................................... 203
Packing diagram of PtC12(o-P2) (20). .................................................... 204
ORTEP representation of Pt2C14(P4) (22) with 50% ellipsoids

viewed from the (a) top and (b) side ...................................................... 209
Packing diagram of Pt2Cl4(P4) (22) viewed down the a-axis. .............. 210

.
'1. Ill .
’.V‘ I
t-.“l‘
..
fil'fii'.“

p l

\
'. s-¢~-M|IA.
- g n ."
O.

l l
' "n A p.
Q i 4

‘r
. .ur‘. .mu _.

:-::r

‘fi-vya
. u r.'
. nu...‘ ‘7‘
r
.V‘ ‘
w~—. -
u ‘ “

-m.\..“
A

 

" r
”Ia—l“ .J

t 4 . In. ,
5““; “!

 

ID.“
if u
4h.~‘ rLV
I‘ ‘
:- "‘..‘
4..-,1.
\ .p
:1 I"""' J.
r g “
I u
‘5,
V" .,
Nc‘l‘d V
~
f
IO. 0
5. it." Q
h'I'l. 0
I
”m.
.:;‘v" 1- ‘r
- u-Q \
\..
‘ Q
.
u 'T
‘4‘." :L
0
”If"v.,
c.' ..r‘. f...
' l
O
IN

5.

‘1. \

'1‘..‘ . .
~ A ’n
N (p:

H ‘

uh.)

.' ‘7'.

.“‘:d"' ‘

F A '-.

2.1-“ l

‘ ..

M. - -
L... ‘:‘o

D V“

:|.. Q

N: "rh

“‘14 'rL
M-

Nu

I

9‘.

 

41. Reaction scheme depicting the step-wise synthesis of [Mz(o-

P2)2(P 4)] [BF 4]4 (1)/I = Ni, Pd, Pt (24)) ..................................................... 219
42. Schematic showing the potential coordination of [TCNQP' (n =

0, 1) to "[C02(o-P2)2(P4)]m+" (m = 4, 6, 7). .............................................. 223
43. Plot of 11950113) and me1 (emu/mol) vs. temperature (K) of

[Co(P4)]n[BF4]2n (33). ............................................................................. 240
44. Molecular model of the proposed cyclic hexamer [Ni(P4)6]12+ ............. 244
Appendix
45. ORTEP representation of ortho-(CH3)2TTF (36) with 50%

ellipsoids ................................................................................................. 270
46. Packing diagram of ortho-(CH3)2TTF (36) viewed down the a-

axis ......................................................................................................... 272
47. PLUTO representation of ortho-[(CeH5)2P]2(CH3)2TTF (1) .................. 274
48. Packing diagram of ortho-[(C6H5)2P]2(CH3)2TTF(1) viewed down

the a-axis ................................................................................................ 275
49. ORTEP representation of [(C5H5)2P]4TTF (2) with 50%

ellipsoids ................................................................................................. 280
50. Packing diagram of [(C6H5)2P]4TTF (2) ............................................... 281
51 Infrared spectrum of impure [K][Re04] obtained from the

recovery of rhenium—containing residues. The far-infrared

region is shown in the inset .................................................................. 291
52. Infrared spectrum of impure TBARe04 obtained from the

recovery of rhenium-containing residues. The far-infrared

region is shown in the inset .................................................................. 293
53. Calculated (a) and experimental (b) room temperature 31P{1H}

NMR spectra of PtCl(TMPP)(TMPP-O) (40) in acetonitrile-da.

The 1:3 satellitezparent intensity ratio resulting from the 33%

abundance of 195Pt is not drawn to scale in spectrum (a). .................. 300
54. Illustration of PtCl(TMPPCI‘MPP-O) (37) ............................................. 301

xxiv

‘W
1:31]

oh-b-v

:rnr :

, .
uuua' A.

 

 

A

Ag/AgCl
BEDT-TTF

br
ca.
cnr
cm'1
cod
(TV
°C

d

5

dd
depe
tfippb
dnfit
dppa
dppb
dppe
dppee
dppnr
dtpe
Ep,a

EPR
emu
esd
ES-MS
Et
EtOH
EtzO

LIST OF SYMBOLS AND ABBREVIATIONS

Angstrtim

silver-silver chloride reference electrode
bis(ethylenedithio)tetrathiafulvalene
broad

circa, about

centimeter

wavenumber

1,5-cyclooctadiene

cyclic voltammetry

degree centigrade

doublet (NMR), day, deuterated
parts per million (ppm)

doublet of doublets
bis(diethylphosphino)ethane
bis(diisopropylphosphino)benzene
4,5-dimecapto-1,3-dithiole-2-thione
bis(diphenylphosphino)amine
bis(diphenylphosphino)benzene
bis(diphenylphosphino)ethane
bis(diphenylphosphino)ethene
bis(diphenylphosphino)methane
bis(ditolylphosphino)ethane
anodic peak potential

cathodic peak potential

electron paramagnetic resonance
electromagnetic unit

estimated standard deviation
electrospray mass spectrometry
ethyl

ethanol

diethyl ether

('1
a 0
r1:

-‘ngra

~ :-r‘
..a- «A»

I.)

 

EtS

FAB-MS

MHz

mmol
mult

1.13 or B. M.

<

NBA
OTf'
ox
P1
E-P2

o-P2

Ethylthio-

molar extinction coefficient

Fast Atom Bombardment Mass Spectrometry
epr g-value, gram

Gauss

hour

Me gaHertz

infi'ared

Kelvin

wavelength

medium

molar

Matrix Assisted Laser Desorption Ionization
methyl

acetonitrile

methanol

milligram

minute

milliliter

millimole

multiplet

bridging ligand

Bohr magneton

microliter

nanometer

frequency

3-nitrobenzyl alcohol

nuclear magnetic resonance

triflate anion

oxidation
trimethyl-diphenylphosphino-
tetrathiafulvalene
(E)-dimethyl-bis(diphenylphosphino)-
tetrathiafulvalene
3,4-dimethyl-3',4'-bis(diphenylphosphino)-
tetrathiafirlvalene

xxvi

 

of“
>5...
.0

.l“-
\‘g Y
.qg‘

‘31P:
.Q‘MJ“
I~\.

‘~.I

 

"‘Vt‘h

“”44“;

5,;

b'PL.
'4

‘N
l'Q
p.

4‘}

0-P202

P4

P402

PPm
Pri

red

r.t.

5

sh
SQUID

t

TBA
TBABF4
TCNQ
TCNQF4

tppb

THF

TMPP
TMPP-0
[TMPP-CH3]+

[TMPP-CHzCl]+
TMS

TMTSF

TSF

TTF

UV

V

VS

3,4-dimethyl-3',4'-
bis(diphenylphosphino)dioxide-
tetrathiafulvalene
tetrakis(diphenylphosphino)-
tetrathiafulvalene
tetrakis(diphenylphosphino)-(Z)-dioxide-
tetrathiafulvalene

parts per million

isopropyl

reduction

room temperature

singlet (NMR), strong (IR)

shoulder

Superconducting Quantum Interference
Device

triplet

tetra-n-butylammonium
tetra-n-butylammonium tetrafluoroborate
7, 7,8,8-tetracyanoquinonedimethane
2,3,5,6-tetrafluoro-7,7,8,8-
tetracyanoquinodimethane
tetra(diphenylphosphino)benzene
tetrahydrofuran
tris(2,4,6-trimethoxyphenyl)phosphine
P[{C6H2(CH30)3}2{CGH2CH30)20}I'
tris(2,4,6-trimethoxyphenyl)methyl
phosphonium
tris(2,4,6-trimethoxyphenyl)chloromethyl
phosphonium

tetramethylsilane
tetramethyltetraselenofulvalene
tetraselenofulvalene

tetrathiafulvaene

ultraviolet

Volt

versus, very strong

xxvii

Z-P‘Z

 

 

w weak

X halide ligand
Z—P2 (Z)-dimethyl-(diphenylphosphino)—
tetrathiafulvalene

xxviii

LIST OF COMPOUNDS

 

(1)
(2)

 

(3)

 

(4)

 

 

(5)
(6)

 

<7)"-

(8)

 

 

(9)

(10) -
(11) -

(12)
(13)
(14)
(15)
(16)
(17)
(18)

(19) -

(20)

(21) -

 

 

 

 

 

 

 

 

 

 

 

o-P2

P4

[RhI (TMPP)2] [BF4]

RhI TMPP)(TMPP-0)

ax,ax- hm(n3-TMPP-O)2][BF4]
[C0113(0H)4{Cou(TMPP-0)2}3] [BF4] 2
Pd11(n3-TMPP-O)2

[Ni11(o-P2)2] [BF4]2

[Con(o-P2)2] [BF4] 2

[Pd11(o-P2)2] [BF4]2

[PtH(o-P2)2] [BF4]2

[FeH(o-P2)2] [BF4] 2

[Nin(o-P2)2] [CF3803] 2
[RhI(O-P2)2][BF4]3

[RhIL II2(NCCH3.)10][BF4]4 + 4 P1
['RemC12(o-P2)2]+

[RezlL mCle(0-P2)l'
ReHClz(o-P2)2
MoIVC1202(o-P202)
PtIIC12(o-P2)

-- [Pt11(o-P2)(NCCH3)2][BF4IZ

xxix

(22)
(23)
(24)
(25)
(26)
(2 7)
(28)
(29)
(30)
(31)
(32)
(33)
(34)
(35)
(36)
(3 7)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ptzn' II(314(P4)

[Pt2H(P4)(NCCH3)4] [BF4I4
[Pt2H,n(P4)(0-P2)2] [BF-d4
PdHC12(0-P2)
[PdH(O-P2)(NCCH3)2] [BF4]2
PM 1101494)

[Ptn' II2(P4)(NCCH3)4] [BF4]4
NiZH'HCl4(P4)
[RhI(P4)]n[BF4]n
[PtII(P4)]n[BF4]2n
[PdH(P4)]n[BF4]2r
[Ni11(P4)]n[BF4]2n
[FeH(P4)]n[BF4]2n
[001104)]nlBF 4]2n
ortho-(CH3)2TTF

PtHCl(TMPP)(TMPP-O)

CHAPTER I

INTRODUCTION

:, function:
Complete

f
.‘f‘: ' Y‘
'1 r

, .
‘,.\5m
I

. Q
4. .. 4. -
..E.'—"-."Y “ ‘
_ ...n .. V's “a“

V
o

.3... -.v' - :-

w y 35 4'

a..'....r ~ 1.4..
.

v v
,"4 2..'. ’h - -
---“.c~ £A—6-‘\.

~
“\~-.
We. 0 -
F u; r

5.... ‘
.- su' ‘
. ~‘- ‘1.

-

.“varo, -
- .

‘ ‘ -

"..~Us‘- n [:|

‘k
'u“ u

j’iszw- "
K.‘.\ GI phr
’T '0 - r

Vinithc P
~ L

 

 

 

A. Functionalized Phosphines as Ligands in Transition Metal

Complexes

Tertiary phosphines have played an important role in the history of
modern coordination and organometallic chemistry due to their extraordinary
versatility as ancillary ligands.1 Transition metal-phosphine complexes,
particularly those of the later transition metals catalyze a wide range of
industrially important organic processes from olefin hydrogenation,
hydroformylation, hydrosilation and hydrocyanation to polymerization and
oligomerization of olefins and acetylenes.2 In addition to catalytic processes,
transition metal phosphine complexes are also capable of performing
numerous stoichiometric organic transformations.3 One reason for the
popularity of phosphines is their ability to stabilize transition metals in a
range of oxidation states,4 a consequence of cooperative o-donor, n-acceptor

bonding interactions.5 Another reason for the widespread use of PR3 ligands

is that they allow for electronic and steric tuning of metal complexes with
changes in the R groups. By modifying the electronic and steric properties of
the ligand one can, in turn, affect the reactivity and stereoselectivity of the
desired product. Tertiary phosphines act as leaving groups in stoichiometric
and catalytic reactions and stabilize polynuclear as well as mononuclear
structures.

Bulky phosphine complexes of low valent, early transition metals, have

been demonstrated to bind small molecules such as dinitrogen and

y A .1
._ ‘- o». 1'
.'1\ ’ " (at

--‘ "‘ ‘\

.
"-. ‘-.-"“'".
..—
::..... a~~o~t-'“'

 

I a
"T4 v- «n
. r .. I
«us-.4 u»..‘...

“‘9 Q ‘ ‘
. Y' F" ‘
«-w r.‘ lb .

“-,-. A
, f, p .mv
-2“... .L

f

..urm' q“
— ~ " ii

.-.~ “a

.' F0 .
«a ‘~r
Q - II I.‘
- .05“ L .

 

,
l

l

r

. d

I
..a .

I
(7')

 

unsaturated organic molecules.6 The steric influence of the phosphine
ligands force the metal to adopt a coordinatively unsaturated geometry. This
electron deficient metal center is activated towards small molecule addition.
An excellent example comes from the research of Kubas and co-workers, who
prepared coordinatively unsaturated Mo0 and W0 complexes of general
formula trans-M(CO)3(PR3)2 (R = cyclohexyl, isopropyl).7 These five-
coordinate complexes have been found to bind small molecules such as
dihydrogen which hints at the possibility of using phosphine-stabilized
complexes for the activation of other o-bonded molecules, e. g. methane.
Although they have been studied for many years, there is an
increasing number of transition-metal complexes containing tertiary
phosphine ligands being reported in the literature, including examples of
varying denticity and functionality.3 Over the years a myriad of functional
groups have been added to phosphine ligands in order to effect specific
properties. In response to the need for a good, leaving group to use as a
pendent substituent on a phosphorus atom, researchers have explored ether-
phosphine ligands (P,0) that participate in a strong metal-phosphorus
interaction and weak metal-oxygen interaction(s). The use of (P,0) ligands
for homogeneous catalysis has been extensively explored by Lindner and co-
workers,3 with earlier work being carried out by Anderson,9 Rauchfuss10 and
Shaw.11 The usefulness of ether-phosphines was demonstrated by the ability

to stabilize elusive species such as mononuclear Rh2+ and Ir2+ via the

oy“‘ cafvv-QMA
rd .0 ,'\ -|
-... ucnuvb‘ Ab
' l
*4 '- ‘eOr .v--
. A
L... Ambit.
P
(I
v \ I.
NJ 0
' 00"
\—
h

 

I“_ '
'\: h)“
'- r
34
\
.-‘ ~I“

\o ‘5. N

w‘ ‘ '-\.. \~

a
Q

\
.‘ ‘9“ .

It

'M

‘1
.V'N

r;

("‘b

formation of five-membered metallacycles as depicted in (scheme 1). Specific
ligand modifications have been found to affect the reactivity and
stereoselectivity of the desired product, producing an unusual selectivity

efi‘ect in catalysisfi’12

2R2PO+M2+——»©t r30
P/\0
R2

MeO
R = Me, tBu M = Rh, Ir
Research in our laboratories has focused on changes in the R group of
tertiary phosphines that affect the denticity. In the case of (P,0) ligands, the
presence of both phosphorus and oxygen atoms with lone pairs available for
coordination allows the ligand to be potentially multidentate. Ether-
phosphines and phosphinoenolates can vary from mono- to tridentate,
depending on the number and location of the oxygen substituents.8n

Braunstein and coworkers showed that a-phosphinoenolates such as
[PthCHmC(:_-.=O)R]' (R = Ph, Me, p-C6H4Me) form homoleptic complexes
with CoIII , Nin, Pd”, and Pt“.13 The Ni complex can function as a four-

electron donor by chelating to CoI2 through cis-oxygen atoms to form

Ph2 Ph2

P P
I \ -/ l
/N1\ R = Ph, p-C 6H4Me, Me
R o o R

. -v'
_, ..m‘f
av. ..‘httéw‘

‘.,..

r I
, .n. 11“
\ ‘5: u_.u.4

.
...r ; I: F
u‘ . .. . u,

--_-H w-

.
h ' ~ -.|-.1>¢
.-.. utAfiq a ‘.

'fl
‘93“;

~~vodvy

""h'.“ , .1
. ...w '-
—y..._~__. Mont

.

‘3...~u.._
.._ .
‘-I-\.~..‘: I
'IA‘. ‘
I
\“ "',’_!1na
”9...“ . 4
. - a.“
i C
""J' .-v
s, b-
“.1.
A
/
./
t l
‘
".J '
i‘,‘ b
9 A4
I
1.,

A":
‘a

 

 

 

heterobimetallic complexes.13a Other examples of multidentate phosphines of
this type include thio- ( e.g. P(CeH4-o-SH)3 and Ph3-nP(CZH4SH)n n = 1, 2),14
amino- (e.g. Ph2P(CsH4-o-NHEt)),15 seleno-ether (e.g. Ph2P(Ce;H4-o-SeMe),16
arseno-ether (e.g. Ph2P(Ce;H4-o-AsPh2),17 and telluro-ether phosphines
(Ph2P(Ce;H4-o-TePh).18

Besides monophosphines there are a number of polydentate
phosphines, including diphosphine ligands that posses heteroatom functional
groups. Chelating diphosphines such as bis(diphenylphosphino)ethane
(dppe), -amine (dppa), -ethene (dppee) and their relatives are commonly used
because of their ability to stabilize metal complexes through the formation of
- five-membered (chelating), and six-membered (bridging) rings.19 Such
diphosphine ligands have been used extensively in the preparation of metal-

metal bonded complexes and cluster complexes in general.20 In particular,

H
N
/\ /\

thP PPh2 PhZP 13th EtzP PEtz thP 13th

dppm dppa depe dppe

/—\ /_\
thP PPh2 thP PPh2 T012P PT012
dppee dppb dtpe
diphosphine molecules with a single bridgehead atom separating the

phosphorous atoms, e.g. dppm and dppa, act as excellent binucleating

ligands for metal-metal bonded complexes due to the formation of a stable

I
u' p'”"’;fl
n " r u
...‘n-MIV"

Q ‘
2'”3'l3"‘

,_,...‘..»u l“
.

...q. "hi." '1- b
- ...4.‘.u. H La

”1
(t;'*"
\nh‘u.-~

M . v ‘

-'o~q..n'.-.r'..
' \

"I- m-ua-LA..
a A

" “9- -O,-
" - "lfi- 24
‘n—n w-.ul
..

'l1
:5".

C
‘ 'rnq“,
I. ..::‘ ‘I-IU ‘
“n.,
»

-‘:"!~m... , '
t '
v H
.-un.b,g
IA

1. "v.
|-.
Y
. "by‘ L: ‘>
x
.
.‘~
”‘3 rfn’ '
a... ‘
‘F “A"
'u, ‘4.;‘
Nu“.:

 

 

five-membered ring?1 The diphosphines with a ethene backbone are
particularly attractive due to their tendency to form interactions with nearly
all transition metals,22 even metals in high oxidation states.23

Changes in bite angle (defined as the P-M-P angle upon complexation)
of the diphosphine ligand lead to dramatic differences in the reactivity of the
resulting metal complex.24 A diphosphine that exhibits one of the larger
bite angles is bis(diphenylphosphino)ferrocene (dppf) (95.28(2)° -
104.2(7)°).25’26 Dppf has proven to be a useful ligand for metal mediated C-S
bond cleavage,27 the preparation of Fischer-type carbyne complexes,28 and
the reductive elimination of cyclooctatetraene.22d In addition to the large bite
angle, dppf is redox active, exhibiting a reversible oxidation couple at 0.183
V.29 This redox behavior, combined with the ability of the Cp rings to freely
rotate, makes dppf a desirable ligand for di- and polynuclear metal
compounds.30 It has been suggested that changes in the oxidation state of
the dppf influence the electron density of the central metal without changing
the immediate coordination sphere, thus allowing for better control over the

reactivity at the metal center.30i

Fe

thp©

dppf

The Chem

1
WW?"
new...

warq-‘N-fi
‘.
...‘euvu

l

‘-... 7"“

«an... 'L... ..
.a

l

.

V"p-'.c .

V pl

w» v!
1‘

a
A

’ 'I“'IA» r.
. —

I ‘ I
-- n-.
‘ iH§§ U.

 

 

\ v», ‘
--..._ w
a Mu
((II "I
u’.
'1'"
p

 

B. The Chemistry of Tris(2, 4, 6-trimethoxyphenyl)phosphine
Research in our laboratories has revealed interesting and novel
coordination chemistry for the phosphine ligand tris(2,4,6-
trimethoxyphenyl)phosphine (TMPP).31 TMPP was first prepared by
Protopopov et al. from the reaction of PC13 and 1,3,5-trimethoxybenzene in
the presence of ZnClz.323'b The phosphine was later prepared by Wada et al.,
by an alternate route involving lithiation of 1,3,5-trimethoxybenzene,
followed by coupling with triphenylphosphite.320d This procedure was further

modified in our laboratories (scheme 2), and the X-ray structure of

OMe OMe
BuLi Roma OMe ()2
eEtzOM

lZCh

 

the compound was reported was determined by Haefner and Dunbar in
1994.33

The unusually large steric bulk (cone angle = 184°) of this ligand
combined with its high basicity (pKa of [HTMPP]+ = 11.2) allow TMPP to be
quite versatile in its ability to stabilize a wide range of oxidation states, and
for stabilizing coordinatively unsaturated, electron deficient complexes. The
basicity and bulk of TMPP are consequences of the presence of ortho and para

methoxy groups on the phenyl rings. As a result of the mesomeric efi‘ect on

{we 1. [la

‘- l

 

Me—o

 

Figure 1. (a) Schematic drawing and (b) ORTEP representation with 50%
ellipsoids of tris(2, 4, 6-trimethoxyphenyl)phosphine (TMPP).

the phenyl ring, the methoxy groups donate extra electron density to the lone
pair of the phosphorus, serving to increase its basicity. There is, however, an
opposing effect of the bulky groups which can hinder the ability of the lone
pair to strongly bind to the metal. This tends to render TMPP rather labile,
but the chelate effect involving bonding the ether substituents precludes the
high reactivities observed for PPhs, as for example in Wilkinson's catalyst.
The ligation of the ortho-methoxy substituents is an important facet of
the chemistry of TMPP. The presence of two such groups on each ring allows
TMPP to act as a mono-, bi-, or even tri-dentate ligand (Figures 2 and 3). The
tridentate mode was first observed in the metalloradical [Rh(n3-
TMPP)2][BF4]2 reported by Dunbar and Haefnerfilal Apart from Co(II) and to
a lesser degree Ni(III), little is known regarding the chemistry of d7 metal
ions such as Rh(II), since these species are highly reactive, and appear only
as short-lived intermediates or impurities in the chemistry of d6 and d8 metal
complexes. It is of considerable interest, then, to design d7 complexes and
study their reactivity in stoichiometric and catalytic reactions of the late
transition elements. This is especially true for Rh”, whose presence has been
detected in reactions involving Wilkinson's catalyst, but whose potential role
in the chemistry is not known.34 Metalloradicals exhibit promise for
undergoing reversible reactions with important molecules such as CO and 02
since they bind much less tightly to substrates than their d8 counterparts.

For these reasons, and for the general purpose of delineating reaction

0
,Me
Me
R O \/o \ O’Me
Me
, \o \ O’Me M—P----...R
M P'WHR \ O
\ M P """ "R /O \ Me
R \ Me
R
O‘Me

 

 

 

 

Figure 2. Schematics depicting the crystallographically determined binding
modes for TMPP bound to a single metal center.

10

 

 

 

 

 

 

o‘
M 'Me
. e
O O
/o \ 0’Me Me
O/
M—P--~ R \
o \ O’Me \ \ o o
/ /0 Me / \ /P""'IR
M—P-----uR Me M—M \
\ H R
R
0‘Me
2 3
TI 71 u-O,n2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

112-P, 0, 11 4- diene

 

 

 

 

 

 

Figure 3. Schematics depicting the crystallographically determined
binding modes for [P{CsH2(OMe)3}2(CeH2(OMe)2O)]1‘ (TMPP-0).

11

pathways for elusive metalloradicals, we have been engaged in efforts to
design mononuclear d7 complexes of the platinum group metals e.g., Co(II),

Ni(III), Rh(II), with the goal of engendering stability in the solid-state by

M90
0' Me MeO “/1303 j
0 = MeO/I/I:M ..u\\\P 3 m
Me ‘0 GM e P MeO</!\P [MW 'TMPP)2l
P MeO
MeO

using a bulky ligand that possesses pendent ether groups that are easily
displaced in solution.

The remarkably stable compound [Rh(n3-TMPP)2] [BF4]2, which
contains two tri-dentate phosphine ligands, has been shown to exhibit
reversible reactions with CO and to undergo non-redox substitution reactions
with isocyanides RCN (R = tBu, iPr, Cy).31by‘=’e One of the products of the CO
reaction is [Rh(TMPP)200]+, which possesses one TMPP ligand acting as a
bidentate ligand, with the second phosphine being bound only through the
phosphorus atom. The overall trigonal bipyramidal geometry is completed by
the CO ligand. This molecule nicely illustrates TMPP's ability to flexibly
alter its coordination geometry to accommodate the electronic and geometric
requirements of a given metal center.

A reaction that can complicate the chemistry of the TMPP ligand is

demethylation of one or more of the coordinating methoxy groups. The

12

. l
. v.
v': "H? 'nv“
"on“ r ‘

,... ”'I‘f‘ "I
. v . ‘ \
u..- I“‘P"
‘ Q
I u
.v.-“F-.'v ;

.4‘,

...a-m‘u‘ A-A
, .

l !

... _‘ . .
'., a, ~7- __!‘
c~>u ‘vv ‘5.-.-

I

-|"‘.~..‘
' \ v.7. '4'
”C‘sb-‘m u.

q
~‘ 'V"\ .i \

'lb\ ".

-
:““v~ ,‘ .\
. '1'. "v‘-‘

~‘ "\ K '5 "
“‘ “‘vu ..

’m
I"
“wanit

‘4. 1
‘. ,M ..
tut :'

.~. ‘
., .
«‘_ _. ~
“~49: 1:
.~.
“w
\ bl

- »

>._
«2 in; s
u~~ ‘he 1

g .

~v
U
.
9
.
\f". ‘P
\. r l
u
w;- m

 

 

resulting phenoxide ligands are more strongly bound to the metal than the
ether groups, which causes any remaining coordinated methoxy groups to be
increasingly labile. The presence of the phosphine-phenoxide ligand allows
metal complexes of this ligand to act as "ligands" themselves by the donation
of a lone pair on the phenoxide oxygen atom to a second metal center. They
can also be labile and allow for binding of small molecules as shown by

Braunstein and coworkers who demonstrated that a-phosphino-enolate

complexes of Ni, Pd, and Pt react with organic isocyanates, C02, or activated
alkynes such as MeOzCCsCCOzMe via formation of a carbon-carbon bond.35
Chapter II of this thesis describes the isolation and reactivity of Rh(I),
Rh(III), and Co(II) complexes of TMPP. The fist section of the chapter deals
with the synthesis and reactivity of the homoleptic complexes,
[RhICTMPP)2][BF4] and [ax, ax-RthTMPP-O)2][BF4]. The role of these
complexes in the interconversion of d6, d7, and d8 homoleptic TMPP
complexes of Rh will also be presented. The second part of Chapter II
describes the use of Co(TMPP-O)2 as an inorganic "ligand" for the deliberate
preparation of bi-, heterobi- and heterotrimetallic complexes, as well as for
the assembly of the hexanuclear cluster [Colls(u-OI-I)3(u3-OH){C0H(n3-TMPP-
O)2}3][BF4]. The properties of these complexes, including the magnetic
susceptibility and EPR spectral properties of the paramagnetic complexes

will also be discussed.

13

 

 

‘I. TheDesif:

.___

{.1

(Ti
CL.
1‘

Ziléfl'f S‘l

.
"J '°!-\ '. ~
. ”-1 )l '-
.-«avhbs «O- ‘
'u

I ‘-‘ ‘1
F ‘2' ‘
-....4. u..

G

'va-vln .
a a

’-‘-‘...v.

. .

“1"”!

.
"' “d- . u..‘
.

.‘ '

“,-
'~~'~. ._‘. F ‘T.
' '%¢.

"0.

._v-» . v
‘r. ‘I\
“K,
a
v. ‘

- 1
|~‘V~AI ’
E. A, Y‘
on '

‘N ",_
‘9
\- “.A

’I
lt‘
f?
1
l.

.
‘w.

 

 

 

C. The Design of Molecule-Based Materials with Phosphine Ligands

The design of molecule-based materials with tunable conducting,
magnetic or optical properties is the focus of much research activity in
synthetic organic and inorganic chemistry.36’37 The deliberate assembly of
molecular building blocks into two- and three-dimensional structures is, in
principle, a way to control molecular orientation and the overall architecture.
The long-range orbital overlap created by controlled assembly determines
electronic band structure, local magnetic interactions, and polarizability,
which are at the core of the electrical conductivity, bulk magnetism, and
optical nonlinearity properties exhibited by organic, inorganic, and polymeric
materials. In this vein, the rational preparation of materials using
individual organic and inorganic components is an approach of considerable
current interest.38 In particular, the introduction of transition metal ions
into a conjugated polymer chain could lead to partially filled bands with
significant intrinsic conductivity.38

In order to prepare conductive materials from molecular
organic/inorganic units, two criteria must be met.39 First, the redox-active
centers (inorganic, organic, or a combination of the two) must be oriented to
permit strong interactions, often requiring close spatial proximity and
similar crystallographic and electronic environments for the units. Second,
the polymers must be partially oxidized or reduced (forming mixed-valence

species) to permit free charge transfer along the chain.40

14

 

. v
I'” \r'pfl‘flfi
v . .
Iv «an vb v a ~KJ>b$ s

- v Q ,
‘q .A',-4|..
In. .‘.uL‘-‘AA-¢

'_I-- ; T“;|o"r
"~-—-n-u. Li. _.

‘.f-.2:Cu.

fim'w .

"'n-u'»

- .. H

.- ..;,‘J"- h"

A..:‘“““¢\.’.:
.

v... ‘ .
"'53 JLE:

 

 

 

»
I
.
I ‘
{11*
C "1‘- ,:
\. J {“7-
s.’
A
v;
' 1
“I: :mh‘
..F-

‘P:\. l V ‘
.‘ ‘, .
i“ ‘3, r
\
‘;‘. u
._4 F
“‘ -=£. - I"
q».‘fl“.
K“
‘1

 

In a more general sense, the design of molecular inorganic/organic
materials depends on the accessibility of specifically engineered building
blocks that can be assembled in solution. Products of this strategy include
metal coordination polymers of tetrathiooxalate,41 dihydroxybenzoquinoneflz
and benzodithiolene.43 In other work, Kahn and coworkers prepared
ferrimagnetically coupled bimetallic chains, consisting of alternating Mn (S =
5/2) and Cu (S = 1/2) metals linked by oxamato bridges.44 In the crystal
structure of MnCu(pbaOH)(H20)2 (pbaOH = 2-hydroxy-l,3-

propanediylbisoxamato), the ferrimagnetic chains are aligned such that the

shortest interchain separations are Mnu-Cu which creates a two dimensional
structure with a ferrimagnetic ordering (Tc = 30 K). The same laboratory has
also reported a three-dimensional compound that is ferromagnetic below 22.5
K, namely (rad)2Mn2[Cu(opda)]3(DMSO)2°2H20 (rad = 2-(4-N-
methylpyridinium)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; opda =
ortho-phenylene-bisoxamato) in which MnneCuHs hexagons are interlocked in

a "chain-link" motif (see Figure 4).45

In the previous examples, the organic portions of the materials were
"innocent" diamagnetic molecules. Recently, emphasis has been placed on
the use of open-shell bridging ligands that also contribute to the magnetic
and/or electronic properties of the molecular or ionic solids. For example,
Gatteschi et al. synthesized one-dimensional magnetic chains consisting of
metal hexafluoroacetonates M(hfac)2 linked by nitronyl nitroxides (NITR)
where M = Cu, Ni, Co, and Mn. The result is a material that undergoes

15

 

Figure 4. Ball and stick representation of the interlocking ManCuHe
hexagons of (rad)2Mn2[Cu(opda)]3(DMSO)2-2H20.

16

: ...po"
I!" y

. _.
_..w““' b v

o I I
'.~,..OO'|' F
a V

I...“ .n 5H~ “

Tue ['56

‘WIfl‘
yuhadh.
A

M.

'L'fi"'.".’ q'w

J.‘.. d..
.

\
.. .
. war"?

~ ’ u-.‘.A—~A‘
.

~.Hl\Q r- .

‘4-

 

 

 

ferrimagnetic ordering at Tc = 7.6 K, in the case of M = Mn and R = iPr, as a
result of the non-cancellation of alternating spins of S = 5/2 and 1/2.46

(1) The Use of Organic Acceptors in Molecular Materials

Semiquinone radicals such as the organic acceptors [TCNQ]" (7,7 ,8,8-
tetracyanoquinodimethanide), and DCNQI’s (N,N'-dicyanoquinonediimides)

have recently been employed as bridges via o-coordination to metal centers

H3C
NC CN
/= N
CH3
DM-DCNQI TCNQ

through the nitrile groups. Although it has been almost nearly four decades
since researchers at Dupont discovered that products of general formula
M(TCNQ) and M(TCNQ)2 can be isolated,47 it has not been until recently
that structures of these materials have been elucidated in our laboratories.48
A related compound, Cu(DM-DCNQI)2, is a three-dimensional network solid
that exhibits unusually high conductivities that persist even at low
temperatures.49 Another organic acceptor, TCNE (tetracyanoethene) was
shown by Miller et. al. to form a room temperature ferromagnet formulated
as V(TCNE)2-1/2(CHzClz).5° The direct coordination of organic radicals and
metal ions ofi'ers the potential for achieving new pathways for electronic

coupling through pn-dn overlap in addition to the usual p1: overlap found in

17

organic donor/acceptor salts. It has been proposed that with the proper
energy match of metal and organic orbitals, it may be possible to achieve an
interplay between superexchange and charge-transport pathways, perhaps
even leading to a synergistic state wherein superconductivity and
ferromagnetism co-existfi"1
(2) Derivative Chemistry of the Organic Donor, Tetrathiafulvalene

Another approach to preparing materials with paramagnetic metal
centers in the same structural framework as Open-shell n-organic radical
cations is the formation of salts from organic donors and high-moment metal
cluster anions. The most widely used organic donors are derivatives of
tetrathiafulvalene (TTF). Since its synthesis in 1970, TTF and its
derivatives have played a key role in the preparation of conducting and
superconducting charge-transfer complexes.” One example of their use in
hybrid inorganic/organic systems is their incorporation into salts with
polychalcogenide, halide and mixed chalcogenide/halide cluster anions of Re.
The clusters exhibit remarkable variations in properties, differences that
have been attributed to changes in the size, shape and redox properties of the
organic donor and inorganic acceptors.53

Tetrathiafulvalene contains four sulfur atoms that participate in the
molecule's n-system. The molecule readily undergoes a one-electron
oxidation to form a stable radical cation which packs in parallel stacks with

extended n-overlap occurring above and below the molecular planes through

18

. \ ft
. '."";l; "I,
' ”H...“

  

-~tmm“’
i Cl '
‘v. -xmb—I‘o

... .--, 0-
vv‘. l."

m.-. ‘5\v - ~—‘
I

31;“ ..- .‘
, ‘ \ - I
'5‘ ghu“
. “I --.-
-, 1L
"as...
I-."'H n
‘ P-
.-“ u i ,1"
.. v \\

 

3:9 55 I}
.A i

~o
bl

 

 

 

 

p2 orbitals.54 The electrons in these systems are delocalized, thereby allowing

for charge-transport along the stack, but allowing only a minimum of inter-
stack communication. Cowan et al. first reported the synthesis of the organic
donor-acceptor salt, TTF-TCNQ in 1973.55 The salt was the first example of a

molecular crystal exhibiting metallic conductivity (CRT = ~5OO Q'lcm'1,54 omax

= 104 Q'lcm'1 at 66 K55). The TTF-TCNQ salt forms one-dimensional

segregated molecular stacks with intermolecular S---S contacts of 3.47 A
between stacked TTF cations, as opposed to 3.62 A for the neutral
molecule.56'57 This stacking phenomenon is an important factor in the
formation of conducting solids and can occur one of two ways: in mixed stacks
wherein the donors and acceptors stack alternatively within a given stack, or
segregated stacks where donors and acceptors stack independently of one
another.58 The majority of molecular compounds with mixed stacks are not
very conductive because of electron localization on the acceptor species, but
segregated stacks such as TTF-TCNQ exhibit a strong charge-transfer
interaction between stacked molecules causing the unpaired electrons to
delocalize and enhance the conduction in that direction.

In attempts to improve the conductivity of TTF salts, researchers have
turned to using derivatives of TTF.59 Early modifications involved the
replacement of sulfur atoms with larger selenium atoms to make
tetraselenathiafulvalene, TSF.60 The more difi‘use orbitals of selenium leads

to increased stacking interactions for the TSF-TCNQ and a two-fold increase

19

Figure 5. ORTEP representation of the stacked salt, [TTF] [TCNQ].

2O

[SHE] [HE

TSF
Me S S Me Me S
_ S S- S S
ISHSI s=< I I H I 1
M6 Me 8 8- Me S S S

TMTTF DMIT DMET

(ifsifi
\s s s s
BEDT-TTF
in the electrical conductivity. Bechgaard and co-workers advanced this

notion further by preparing tetramethylselenafulvalene (TMTSF).61 At
lowtemperatures (~1 K) and high pressure (8-10 kbar), salts (now known as

"Bechgaard salts") of ['I‘MTSF]+ with monovalent inorganic anions such as
[PF5]', B904}, and [BF4]' were found to be the first molecular organic

compounds to behave as superconductors. [TMTSF]2[ClO4] is the first
example of a superconducting material (Tc = 1.3 K) at ambient pressure.62
More recently, salts of [BEDT-TTFF have been found to be superconducting

at much higher temperatures (10-11 K).*33

R S S R s S S s
1M1 8%1MIH
R s s R S s/ s 5

Classic Metal Dithiolate Classic Metal "DMIT"

21

.0. -‘.,L . _
w ‘ \-: a\
u ._

.-., -u;

 

.\.‘-.“
1“;

 

 

Early work by Interrante, Miller and Epstein on the use of bisdithiolenes for
the development of electronic materials paved the way for TTF derivatives to
be used as ligands.64 While most bisdithiolenes are semiconductors, some
salts such as [TTF] [Ni(dmit)2]2 have been found to exhibit metallic behavior

down to 4 K,65 while other M(dmit)2 salts have been found to be

superconductors under pressure.66 More recently, Underhill and co-workers

prepared homoleptic HgII and NiII complexes with cis-[S2TTF(SR)2]D- (n = O, 2)

units that are involved in intermolecular stacking at ca. 3.4 A and S---S
contacts of 351(2) A.67 Related work by McCullough and Belot led to the
preparation of homoleptic tetrathiafulvalene-tetrathiolate complexes with
Tisz, Tisz*, and Pt(PPh3)2,68 wherein the tetradentate ligand bridges two
metal centers to yield dinuclear species. These dinuclear compounds are
reminiscent of extended structures proposed by Hoffman et. al. in 1985,69
who suggested that the ribbons, stacked, two-dimensional layers, and zig-zag
layers shown in Figure 6 would make for very interesting properties. The
unfortunate reality of these structures is that, in all likelihood, they will
produce insoluble products that would pose serious characterization
problems.70
D. The Development of Phosphine-Fuctionalized Tetrathia-

fulvalenes

Much of the research being conducted in the field of TTF-metal

coordination chemistry involves TTF-sulfur derivatives, but it is attractive to

22

 

{ii}

l

ll;Fr

3e 6.

 

I
\Z"

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

/
\ I \ / \
8 ~ I:
H \ / /M
‘/SHS\ / SpMjs
L. _ n I I
(a) (b)
S S\ /S S\
M M
I \ I
S S S S
n
(o)
- s s s s -
/ \ /
/ \M: M”
\\ l I \
.z/S S\ /S S\ /?
\1 /M\ /M\
_\s s s s _
n
(d)
Figure 6. Extended structures proposed by Hofiman et. al.: (a) two

dimensional slab structure, (b) zig-zag layered structure, (c)
ribbon or sheet polymers, and (d) two-dimensional layer
structure.

23

.
”up? out
w__...-,. Lax

' l .
.V.HA.1' r
-..£.Jtr:bl.

 

.
f hwfih'y
any .3

 

‘ru~ fi“?.’“-

L...‘ ‘2' » xv“
.

.‘ -'
I A
\ t: .
1“ V
n.

 

 

"u.
. ‘I ‘
N'd“ ll- _
9 (8‘
A“
'I
..

 

consider the potential for incorporating non-chalcogenide linking groups.
Inconsidering candidates for functional groups it is important to retain the
redox functionality of the TTF, but to include the capability for engendering
strong metal-ligand interactions through chelation. The tetrathiafulvalene-
based phosphorus ligands depicted in Figure 7 fit these criteria quite well.
The groups of Batail and Fourmigue’ et al., first demonstrated in 1992 that
the molecules 3,4-dimethyl-3',4'-bis(diphenylphosphino)tetrathiafulvalene (0-
P2) and tetrakis(diphenyl-phosphino)tetrathiafulvalene (P4) can be
synthesized from the appropriate TTF precursors.71 More recently the E and
Z isomers of the diphosphine ligand were also prepared.” These ligands are
similar to the ethylene-bridged ligands bis(diphenylphospohino)ethene
(dppee) and -benzene (dppb).

The availability of monodentate (P1), bidentate (PZ) and tetradentate
(P4) ligands allows for a wide range of structural possibilities. In order to be
able to build polymeric structures two ingredients are required: (i) a bridging
diphosphine or tetraphosphine, and (ii) a metal center capable of coordinating
two phosphines or two diphosphine ligands. The E-P2 or P4 ligands meet
these ligand requirements. The chelating ability of the TTF diphosphines
was first demonstrated by the isolation of NiX2(o-P2) (X = Cl, Br).713 More

recently the structure of the homoleptic phosphine cation [Rh(o-P2)2]+ was

determined as its [BF4]'.72

24

Ph2

S S P
IHI m
S S
s s PPh2
1H1
S S PPh2

S S PPh2
I H— i
p S S

P s s 13th
I H 1
s s

Ph2

Ph2

I>—<— i .4
thp S S Pth

Figure 7. Schematics of the monodentate (P1), bidentate (o-P2, E-P2, Z-
P2), and tetradentate (P4) phosphine ligands.

25

- ‘d‘luv ,‘
\‘ "\‘us‘a;
‘29-'_‘ ‘. ,1
.~. 0- b
' '4 Li
s
- T)? i
'u n
'..‘J‘ 1| Vi
4'
s... M

u.

.“ -
'.v-.
5“.

‘9.

-. ..

.r. ‘

 

| v

'\

 

"u
A.
h .-
.-
\
i“: f,”—
'u
AN
?-~.'
‘1-
“'k ‘FH'PYV
N -|‘-
F H
~
-‘m-
u A I
.. 1‘
‘ '3 I:
\
.‘D
~=.‘= 3L
‘ ~§c :o
\
'\
- I,
' K. ll” .
«t? .
3;
\Q
\
'0
.\'. u

 

 

 

 

 

 

 

 

 

R2 R R
P—M 2 P2
\
/M
P P P
R2 n R2 R2 n
E- P2 P4

Chapter III of this thesis reports the synthesis and characterization of
a series of mononuclear o-P2 complexes of formula [M(o-P2)2][BF4]2 (M = Ni,
Co, Pd, Pt, Fe). These complexes serve as models for the extended molecules
that contain the tetradentate ligand, P4. Oxidation of the previously
reported [Rh(o-P2)2][BF4] to [Rh(o-P2)2][BF4]3, and metathesis of [Rh(o-
P2)2] [BF4] with LiTCNQ are also described. Chapter IV details the reactivity
of the rlvl‘F-phosphine ligand with metal-metal bonded compounds. The
similarities between these new phosphines and the well-known diphos ligand
(dppe) render them attractive candidates for exploiting their ability to act as
both chelating and bridging ligands. Reactivity of o-P2 with [RezClsP' results
in the formation of a mixed-nuclearity salt, [ReC12(o-P2)2][Rezcls(o-P2)],
which includes the first example of an oc-M2X6(L-L) complex, where on is the
chelating mode. The chemistry of o-P2 is further described in Chapter V,
where the stepwise build-up of extended arrays is outlined. The use of cis-
MClz moieties with o-P2 and P4 ligands allows for the preparation of mono-
and dinuclear metal complexes that contain one, two, or three TTF units.

The use of the tetradentate P4 complex to form high nuclearity extended

26

materials is reported in Chapter VI. reaction of the solvated cations,
[Rh2(NCCH3)1o] [BF 4]4 and [M(NCCH3)n][BF4]2 (M = Pt, n = 4; M = Ni, Co, Pd,
Fe, 11 = 6) led to the formation of phosphine bound complexes formulated as
[M(P4)]n[BF4]2n for M = Ni, Co, Pd, Pt, Fe and [M(P4)]n[BF4]n for M = Rh.
These products are highly soluble and do not exhibit 31P{1H} NMR spectral
properties expected for straight chain oligomers.4o Various experiments

designed to elucidate the identity of these complexes are discussed.

27

List of References

(al Stelzer, O. In Topics in Phosphorus Chemistry, Eds. Grayson, M.;
Griffith, E. J. Wiley & Sons: New York, 1980, 10, 193. (b) Fluck, E.
In Tepics in Phosphorus Chemistry, Eds. Grayson, M.; Griffith, E. J.
Wiley & Sons: New York, 1977, 9, 1. (c) Homogeneous Catalysis with
Metal Phosphine Complexes, Ed. Pignolet, L. H. Plenum Press: New
York, 1983.

a) Parshall, G. W. Homogeneous Catalysis: The Applications and
Chemistry of Catalysis by Soluble Transition Metal Complexes; Wiley:
New York, 1980. (b) Cornils, B. In New Syntheses with Carbon
Monoxide; F albe, J., ed.; Springer-Verlag: Berlin, 1980. (c) Catalytic
Aspects of Metal Phosphine Complexes, Advances in Chemistry Series
196'; Alyea, E. C.; Meek, D. W. Eds; American Chemical Society:
Washington, D. C. 1982. ((1) Hughes, R. P. in Comprehensive
Organometallic Chemistry; Wilkinson, G.; Stone, F. G. A.; Abel, E. W.,
eds.; Pergamon: New York, 1982; vol. 5, p 228.

Collman, J. P.; Hegedus, L. 8.; Norton, J. R.; Finke, R. G. Principles
and Applications of Organotransition Metal Chemistry; University
Science Books: Mill Valley, Ca. 1987, and references therein.

McAulifi'e, C. A. In Comprehensive Coordination Chemistry; Wilkinson,
G.; Gillard, R. D.; McCleverty, J. A., eds; Pergamon: Oxford, 1987,
chapter 14, p 989.

(a) Cruickshank, D. W. J. J. Mol. Struct., 1985, 130, 1771. (b) Beach,
D. B.; Jolly, W. L. Inorg. Chem. 1984, 23, 4774.

Kubas, G. J. Acc. Chem. Res. 1988, 12,120.

Kubas, G. J.; Unker, C. J.; Swanson, B. F.; Fukushima, E. J. Am.
Chem. Soc. 1986, 108, 7000.

(a). Lindner, E.; Reber, J. P.; Wegner, P. Z. Naturforsch. 1988, 43b,
1268. (b) Lindner, E.; Sickinger, A.; Wegner, P. J. Organomet. Chem.
1988, 349, 75. (c) Lindner, E.; Schrober, U.; Glaser, E.; Norz, H.;
Wegner, P. Z. Naturforsch. 1987, 42b, 1527. (d) Lindner, E.; Mayer, H.
A.; Wegner, P. Chem. Ber.1986, 119, 2616. (e) Lindner, E.; Sickinger,
A.; Wegner, P. J. Organomet. Chem. 1986, 312, C37. (f) Lindner, E.;
Raudeler, H ; Scheytt, C.; Mayer, H. A.; Hiller, W.; Fawzi, R.; Wegner,
P. Z. Naturforsch. 1984, 39b, 632. (g) Lindner, E.; Scheytt, C. Z.
Naturforsch. 1986, 41b, 10. (h) Lindner, E.; Scheytt, C.; Wegner, P. J.

28

Organomet. Chem. 1986, 308, 311. (i) Lindner, E.; Fawzi, R.; Mayer, H.
A.; Eichele, K.; Pohmer, K. J. Organomet. Chem. 1990, 386, 63. (i)
Lindner, E.; Schober, U.; F awzi, R.; Hiller, W.; Englert, U.; Wegner, P.
Chem. Ber. 1987, 120, 1621. (k) Lindner, E.; Karle, B. Chem. Ber.
1990,123, 1464. (l) Lindner, E.; Karle, B. Z. Naturforsch. 1990, 45b,
1108. (m) Lindner, E.; Schober, U. Inorg. Chem. 1988, 27, 212. (n)
Lindner, E.; Andres, B. Chem. Ber. 1987, 120, 761. (o) Lindner, E.;
Andres, B. Chem. Ber. 1988, 121, 829. (p) Lindner, E.; Norz, H. Chem.
Ber. 1990, 123, 459. (q) Lindner, E.; Norz, H. Z. Naturforsch. 1989,
44b, 1493. (r) Lindner, E.; Meyer, S. J. Organomet. Chem. 1988, 339,
193. (s) Lindner, E.; Andres, B. Z. Naturforsch. 1988, 43b, 369. (t)
Lindner, E.; Speidel, R. Z. Naturforsch. 1989, 44b, 437. (u) Bader, A.;
Lindner, E. Coord. Chem. Rev. 1991, 108, 27. (v) Lindner, E.;
RothfuB, H.; Fawzi, R.; Hiller, W. Chem. Ber. 1992, 125, 541. (w)
Lindner, E.; Bader, A.; Mayer, H. A. Z. Anorg. Allg. Chem. 1991,
598/599, 235. (x) Lindner, E.; Dettinger, J .; Méickel, A. Z. Naturforsch.
1991, 46b, 1519. (y) Lindner, E.; Scheiber, R.; Kemmler, M.; Mayer, H.
A.; Fawzi, R.; Steimann, M. Anorg. Allg. Chem. 1993, 619, 202. (z)
Lindner, E.; Schreiber, R.; Kemmler, Schneller, T.; Mayer, H. A.
Chem. Mater., 1995, 7, 951. (aa) Lindner, E.; Haustein, M.; Mayer, H.
A.; Gierling, K.; Fawzi, R.; Steimann, M. Organometallics, 1995, 14,
2246. (bb) Lindner, Kemmler, M.; Schneller, T.; Mayer, H. A. Inorg.
Chem., 1995, 34, 5489, (cc) Lindner, E.; Geprags, M.; Gierling, K;
Fawzi, R.; Steimann, M. Inorg. Chem., 1995, 34, 6106. (dd) Lindner,
E.; Schreiber, R.; Schneller, T.; Wegner, P.; Mayer, H. A.; Gopel, W.;
Ziegler, C. Inorg. Chem., 1996, 35, 514. (ee) Lindner, E.; Pautz, S.;
Haustein, M. J. Organomet. Chem., 1996, 509, 215. (ii) Lindner, E.;
Keppeler, B.; Mayer, H. A.; Gierling, K. J. Organomet. Chem., 1996,
515, 139. (gg) Lindner, E.; Yin, Y. C.; Geprags, M; Yih, K. H.; Fawzi,
R.; Steimann, M. J. Organomet. Chem., 1996, 512, 101. (hh) Lindner,
E.; Pautz, S.; Haustein, M. Coord. Chem. Rev., 1996, 155, 145. (ii)
Lindner, E.; Keppler, B.; Mayer, H. A.; Gierling, K.; Fawzi, R.;,
Steimann, M. J. Organomet. Chem., 1996, 526', 175. (jj) Lindner, E.;
Jager, A.; Schneller, T; Mayer, H. A. Chem Mater., 1997, 9, 81. (kk)
Lindner, E.; Jager, A.; Kemmler, M.; Auer, F.; Wegner, P.; Mayer, H.
A.; Benez, A; Piles, E. Inorg. Chem., 1997, 36, 862. (ll) Lindner, E.;
Keppeler, B.; Wegner, P. Inorg. Chim. Acta 1997, 258, 97. (mm)
Lindner, E.; Schneller, T.; Mayer, H. A.; Bertagnolli, H.; Ertel, T. 8.;
Homer, W. Chem. Mater., 1997, 9, 1524. (nn) Lindner, E.; Gierling, K.;
Keppeler, B.; Mayer, H. A. Organometallics, 1997, 16, 3531. (00)
Lindner, E.; Gierling, K.; Fawzi, R.; Steimann, M. Inorg. Chim. Acta,
1998, 269, 13. (pp) Lindner, E.; Jager, A.; Auer, F.; Wegner, P.; Mayer,
H. A.; Benez, A.; Adam, D.; Plies, E. Chem. Mater., 1998, 10, 217.

29

in;;‘

151. ..

1‘s-

(“r

‘3

H
(D

(‘1‘) Fr) ('1)
O.)

r—4
(O
J)

1'1 I
, F ‘4
U l s

(LT.

lg:

' I
_~—

 

10.

11.

12.

13.

14.

16.

17.

(a) Anderson, G. K.; Kumar, R. Inorg. Chem. 1984, 23, 4064. (b)
Anderson, G. K.; Corey, E. R.; Kumar, R. Inorg. Chem. 1987, 26', 97.
(c) Anderson, G. K.; Kumar, R. Inorg. Chim. Acta 1988, 146, 89. (d)
Anderson, G. K.; Lumetta, G. J .; Siria, J. W. Organomet. Chem. 1992,
434, 253.

(a) Rauchfuss, T. B.; Patino, F. T.; Roundhill, D. M. Inorg. Chem. 1975,
14, 652. (b) Jeffrey, J. C; Rauchfuss, T. B. Inorg. Chem. 1979, 18,
2658.

(a) Mason, R.; Thomas, K. M.; Empsall, H. D.; Fletcher, S. R.; Heys, P.
N.; Hyde, E. M.; Jones, C. E.; Shaw, B. L. J. Chem. Soc., Chem.
Commun. 1974, 612. (b) Jones, C. E.; Shaw, B. L.; Turtle, B. L. J.
Chem. Soc., Dalton Trans. 1974, 992. (c) Empsall, H. D.; Heys, P. N.;
Shaw, B. L. J. Chem. Soc., Dalton Trans. 1978, 257.

(a)Keim, W. Chem. Ing. Techn. 1984, 56, 850. (b) Reber, J. -P., Ph. D.
Dissertation, Universit'at Tubingen, 1991. (c) Knowles, W. S. Acc.
Chem. Res. 1983, 16, 106. (d) Brunner, H. Angew. Chem. Int, Ed. Engl.
1983, 22, 897. (e) Brown, J. M.; Cook, S. J.; Khan, R. Tetrahedron
1986, 42, 5105.

(a) Andrieu, J .; Braunstein, P.; Tiripicchio, A.; Ugozzoli, F. Inorg.
Chem., 1996, 35, 5975. (b) Braunstein, P.; Kelley, D. G.; Tiripicchio,
A.; Ugozzoli, F. Inorg. Chem., 1993, 32, 4845. (c) Braunstein, P.;
Kelley, D. G.; Dusausoy, Y.; Bayeul, D.; Lanfranchi, M.; Tiripicchio, A.
Inorg. Chem., 1994, 32, 233. (d) Andrieu, J.; Braunstein, P.; Drillon,
M.; Dusausoy, Y.; Ingold, F.; Rabu, P.; Tiripicchio, A.; Ugozzoli, F.
Inorg. Chem., 1996, 35, 5986.

(a) Nicholson, T.; Cook, J .; Davison, A.; Jones, A. G. Inorg. Chim. Acta
1994, 218, 97. (b) Chatt, J .; Dilworth, J. R.; Schmutz, J. A.; Zubieta, J.
A. J. Chem. Soc., Dalton Trans. 1979, 1595. (c) Geigy, J. R., F. P.
1,401,930/1965.

(a) F ryzuk, M. D.; Montgomery, C. D. Coord. Chem. Rev. 1989, 95, 1.
(b) Farnetti, E.; Nardin, G.; Granziani, M. J. Organomet. Chem.,
1991, 417, 163. (c) Park, S.; Hedden, DD.; Roundhill, D. M.
Organometallics, 1986, 5, 336.

Harbom, S. K.; Higgins, S. J.; Hope, E. G.; Kemmitt, T.; Levanson, W.
Inorg. Chim. Acta 1987, 130, 43.

(a) Meek, D. W.; Nicpon, P. E.; Meek, V. I. J. Am. Chem. Soc. 1970,
92, 5351. (b) Nicpon, P.; Meek, D. W. Inorg. Chem. 1967, 6, 145.

30

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

29.

Gysling, H. J.; Luss, H. R. Organometallics, 1984, 3, 596.
Cotton, F. A.; Hong, B. Prog. Inorg. Chem., 1992, 40, 179.

Cotton, F. A.; Walton, R. A. Multiple Bonds Between Metal Atoms, 2nd
Ed., Clarendon Press: Oxford, 1993, and references therein.

Puddephatt, R. J. Chem. Soc. Rev. 1983, 99.

(a) Higgins, S. J.; Levanson, W. J. J. Chem. Soc., Dalton Trans. 1986,
317. (b) Gray, L. R.; Higgins, S. J .; Levanson, W. J .; Webster, M. J. J.
Chem. Soc., Dalton Trans. 1984, 1433. (0) Fox, M. A.; Chandler, D. A.
NATO ASI Ser. C. 1987, 214, 405. (d) Gray, L. R.; Gulliver, D. J.;
Levanson, W. J.; Webster, M. J. J. Chem. Soc., Dalton Trans. 1983,
133. (e) Warren, L. F.; Bennett, M. A. Inorg. Chem. 1976, 15, 3126.

(a) Mahadevan, C.; Seshasayee, M.; Ramakrishna, B. L.; Manoharon,
P. T. Acta Crystallogr., Sect. C 1985, 41, 38. (b) Bennett, M. A.;
Robertson, G. B.; Rosalky, J. M.; Warren, L. F. Acta Crystallogr., Sect.
A 1975, 31, S136.

(a) Oberhauser, W.; Bachmann, C.; Brfiggeller, P. Inorg. Chim. Acta
1995, 238, 35. (b) Miedaner, A.; Haltiwanger, R. C.; DuBois, D. L.
Inorg. Chem. 1991, 30, 417. (c) Liu, S.-T.; Chen, J.-T.; Peng, S.-M.;
Hsiao, Y.-L.; Cheng, M.-C. Inorg. Chem. 1990, 29, 1169. (d) Brown, J.
M.; Guiry, P. J. Inorg. Chim. Acta, 1994, 220, 249.

Housecroft, C. E.; Owen, S. M.; Raithby, P. R.; Shaykh, A. M.
Organometallics, 1990, 9, 1617.

Butler, I. R.; Cullen, W. R.; Kim, T.-J.; Rettig, S. J.; Trotter, J.
Organometallics, 1985, 4, 972.

smith, C. M.; Aplin, R. T.; Brown, J. M.; Hursthouse, M. B.; Karalulov,
A. I.; Abul Malik, K. M.; Cooley, N. A. J. Am. Chem. Soc. 1994, 116,
5180.

Sekino, M.; Sato, M.; Nagasawa, A.; Kikuchi, K. Organometallics,
1994, 13, 1451.

Pilloni, G.; Longato, B.; Corain, B. J. Organomet. Chem. 1991, 420,
57.

31

30.

31.

32.

33.

34.

35.

(a) Hayashi, T.; Konishi, M.; Kobari, Y.; Kumada, <.; Higuchi, T.;
Hirotsu, K. J. Am. Chem. Soc. 1984, 106, 158. (b) Cullen, W. R.; Kim,
T.; Einstein, F. W. B.; Jones, T. Organometallics, 1985, 4, 346. (c)
Butler, I. R.; Cullen, W. R.; Kim, T.; Rettig, S. J.; Trotter, J.
Organometallics, 1985, 4, 972. (d) Onaka, S. Bull. Chem. Soc. Jpn.
1986, 59, 2359. (e) Miller, T. M.; Kazi, J. A.; Wrighton, M. S. Inorg.
Chem., 1989, 28, 2347. (f) Hill, D. T.; Girard, G. R.; McCabe, F. L.;
Johnson, R. K.; Stupik, P. D.; Zhang,. H.; Reiff, W. M.; Eggleston, D. S.
Inorg. Chem., 1989, 28, 3529. (g) Casellato, U.; Corain, R.; Graiani, R.;
Longato, B.; Pilloni, G. Inorg. Chem., 1990, 29, 1193. (h) Longato, B.;
Pilloni, G.; Graziani, R.; Casellato, U. J. Organomet. Chem., 1991, 407,
369. (i) Pilloni, G.; Graziani, R.; Longato, B.; Corain, B. Inorg. Chim.
Acta, 1991, 190, 165. (j) Pilloni, G.; Longato, B. Inorg. Chim. Acta,
1993, 208, 17.

(a) Dunbar, K. R.; Haefner, S. C.; Pence, L. E. J. Am. Chem. Soc. 1989,
111, 5504. (b) Dunbar, K. R.; Haefner, S. C.; Bender, C. J. Am. Chem.
Soc. 1991, 113, 9540. (c) Dunbar, K. R.; Haefner, S. C.; Swepston, P.
N. J. Chem. Soc., Chem. Commun. 1991, 640. (d) Chen, S.-J.; Dunbar,
K R. Inorg. Chem., 1991, 30, 2918. (e) Dunbar, K. R.; Haefner, S. C.
Organometallics 1992, 11, 0000. (f) Dulebohn, J. I.; Haefner, S. C.;
Bergland, K. A.; Dunbar, K. R. Chem. of Mat., 1992, 4, 506. (g)
Dunbar, K. R.; Quillevéré, A. Organometallics, 1993, 12, 618. (h)
Dunbar, K. R.; Matonic, J. H.; Saharan, V. Inorg. Chem., 1994, 33, 25.
(i) Dunbar, K. R.; Quillevéré, A.; Sun, J.-S. Inorg. Chem., 1994, 33,
2598. (i) Dunbar, K. R.; Sun, J .-S. J. Chem. Soc. Chem. Comm., 1994,
2387. (k) Dunbar, K. R.; Haefner, S. C.; Uzelmeier, C. E.; Howard, A.
Inorg. Chim. Acta., 1995, 240, 527.

(a) Protopopov, I. S.; Kraft, M. Ya. Med. Prom. USSR 1959, 13,5. (b)
Protopopov, I. S.; Kraft, M. Ya. Zhurnal Obshchei Khimii 1963, 33,
3050. (c) Wada, M.; Higashizaki, S. J. Chem. Soc., Chem. Commun.
1984, 482. (d) Wada, M. J. Chem. Res. 1985, (S), 38; (M), 0467.

(a) Dunbar, K. R.; Haefner, S. C. Polyhedron, 1994, 13, 727.

(a) Osborn, J. A.; Jardine, F. H.; Wilkinson, G. J. Chem. Soc. (A) 1966,
1712. (b) Taqui-Khan, M. M.; Samad, S. A.; Siddiqui, M. R. H.; Bajaj,
H. C.; Ramachandraiah, G. Polyhedron 1991, 10, 2729. (c) Howe, J. P.;
Lung, R.; Nile, T. A. J. Organomet. Chem. 1981, 208, 401.

(a) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J .; Miyschler, A.;
Ricard, L. J. Am. Chem. Soc. 1981, 103, 5115. (b) Braunstein, P.;
Matt, D.; Nobel, D. Chem. Rev., 1988, 88, 747. (c) Bouaoud, S.-E.;
Braunstein, P.; Grandjean, D; Matt, D.; Nobel, D. J. Chem. Soc., Chem.

32

36.

37.

38.

39.

40.

Commun. 1987, 488. (d) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D;
Matt, D.; Nobel, D. Inorg. Chem. 1988, 27, 2279. (e) Braunstein, P.;
Nobel, D. Chem. Rev. 1989, 89, 1927. (f) Balegroune, F.; Braunstein,
P.; Gomes Carneiro, T. M.; Grandjean, D.; Matt, D. J. Che. Soc.,
Chem. Commun. 1989, 582. (g) Braunstein, P.; Gomes Carneiro, T.
M.; Balegroune, F.; Grandjean, D. Organometallics, 1989, 8, 1737.

(a) Manriquez, J. M.; Yee, G. T.; McLean, S.; Epstein, A. J .; Miller, J.
S. Science 1991, 252, 1415-1417. (b) Pei, Y.; Kahn, O.; Nakatani, K.;
Codjovi, E.; Mathoniére, C.; Sletten, J. J. Am. Chem. Soc. 1991, 113,
6558-6564. (c) Cornelissen, J. P.; LeLoux, R.; Jansen, J.; Haasnoot,
J.G.; Reedijk, J.; Horn, E.; Spek, A.L.; Pomaréde, B.; Legros, J.;
Reefman, D. J. Chem. Soc. Dalton Trans. 1992, 2911-2921. (d) Serroni,
S.; Denti, G.; Campagna, S.; Juris, A.; Ciano, M.; Balzani, V. Angew.
Chem. Int. Ed. Engl. 1992, 31, 1493-1495. (e) Kollmar, C.; Kahn, O.
Acc. Chem. Res. 1993, 26' , 259-265. (f) Miller, J .; Epstein, A. Angew.
Chem. Int. Ed. Engl. 1994, 33, 385-415. (g) Molecular Magnetism,
Kahn, O. VCH, 1993. (h) Pomaréde, B.; Garreau, B.; Malfant, I.;
Valade, L.; Cassoux, P.; Legros, J .; Audouard, A.; Brossard, L.; Ulmet,
J.; Doublet, M.; Canadell, E. Inorg. Chem. 1994, 33, 3401-3414. (i)
Stumpf, H. O.; Pei, Y.: Michaut, C.; Kahn, O.; Renard, J.; Ouahab, L.
Chem. of Mater. 1994, 6, 257-259. (j) Miller, J.; Epstein, A. Angew.
Chem. Int. Ed. Engl. 1994, 33, 385-415.

(a) Saito, G.S; Kagoshima, S. Eds, The Physics and Chemistry of
Organic Superconductors Springer: Berlin, 1990. (b) Wudl, F. Acc.
Chem. Res. 1984, 17, 227-232. (c) Saito, G.S.; Kagoshima, S. Eds, The
Physics and Chemistry of Organic Superconductors; Springer: Berlin,
1990. (d) Williams, J. M.; Wang, . H.; Emge, T. J .; Geiser, U.; Beno,
M.A.; Leung, P. C. W.; Carlson, K. D.; Thorn, R. J.; Schultz, A. J.;
Whangbo, H. H. In Progress in Inorganic Chemistry Lippard, S. J .; Ed;
Wiley: New York 1987; 35, 51-218.

(a) Day. P. Philos. Trans. R. Soc. London Ser., A 1985, A314, 145. (b)
Ogawa, M. Y.; Hofi‘inan, B. M.; Lee, S.; Yudkowsky, M.; Halperin, W.
P. Phys. Rev. Lett. 1986, 57, 1177. (c) Kurmoo, M.; Graham, A. W.;
Day, P.; Coles, S. J .; Hursthouse, M. B.; Caulfield, J. L.; Singleton, J .;
Pratt, F. L.; Hayes, W.; Ducrtasse, L.; Guionneau, P. J. Am. Chem.
Soc. 1995, 117, 12209.

Marks, T. J. Angew. Chem., Int. Ed. Engl. 1990, 29, 857.

Wang, P.-W.; Fox, M. A. Inorg. Chem. 1994, 33, 2938.

33

41.

42.

43.

44.

45.

46.

47.

48.

49.

Reynolds, J. R.; Lillya, C. P.; Chien, J. C. W. Macromolecules 1987,
20, 1184.

Wrobleski, J. T.; Brown, D. B. Inorg. Chem. 1979, 18, 2738.

Dirk, C. W.; Bousseau, M.; Barrett, P. H.; Moraes, F.; Wudl, F.;
Heeger, A. J. Macromolecules 1986, 19, 266.

(a) Nakatani, K; Bergerat, P.; Codojovi, E.; Mathoniére, C.; Pei, Y.;
Kahn, O. Inorg. Chem. 1991, 30, 3977. (b) van Koningsbruggen, P. J .;
Kahn, O.; Nakatani, K.; Pei, Y.; Renard, J. P.; Drillon, M.; Legroll, P.
Inorg. Chem. 1990, 29, 3325. (c) Pei, Y.; Nakatani, K; Kahn, O.;
Sletten, J.; Renard, J. P. Inorg. Chem. 1989, 28, 3170. (d) Kahn, O.;
Pei, Y.; Verdaguer, M.; Renard, J. P.; Sletten, J. Inorg. Chem. 1988,
110, 782. (e) Lloret, F.; Nakatani, K; Journaux, Y.; Kahn, O.; Pei, Y.;
Renard, J. P. J. Chem. Soc., Chem. Commun. 1988, 642. (f) Pei, Y.;
Verdaguer, M.; Kahn, O.; Sletten, J .; Renard, J. P. Inorg. Chem. 1987,
26, 138.

Stumpf, H. O.; Ouahab, L.; Pei, Y.; Grandjean, D.; Kahn, O. Science
1993, 261, 447.

(a) Caneschi, A.; Gatteschi, D.; Renard, J. P.; Rey, P.; Sessoli, R. Inorg.
Chem. 1989, 28, 3314. (b) Caneschi, A.; Gatteschi, D.; Sessoli, R. Acc.
Chem. Res. 1989, 22, 392. (c) Caneschi, A.; Gatteschi, D.; Renard, J.
P.; Rey, P.; Sessoli, R. Inorg. Chem. 1989, 28, 1976. (d) Caneschi, A.;
Gatteschi, D.; Rey, P.; Sessoli, R. Inorg. Chem. 1988, 27, 1756.

(a) Middelton, W. J .; Little, E. L.; Coffman, D. D.; Englehardt, V. A. J.
Am. Chem. Soc., 1958, 80, 2795. (b) Webster, 0. W.; Mahler, W.;
Benson, R. E. J. Am. Chem. Soc., 1962, 84, 3678. (c) Melby, L. R.;
Harder, R. J .; Hertler, W. R.; Mahler, W.; Benson, R. E.; Mochel, W. E.
J. Am. Chem. Soc., 1962, 84, 3374.

(a) Zhao, H.; Heintz, R. A.; Rogers, R. D.; Dunbar, K. R. J. Am. Chem.
Soc., 1996, 118, 12844. (b) Zhao, H.; Cowen, J. A.; Ouyang, X.;
Grandinetti, G.; Heintz, R. A.; Dunbar, K. R. manuscript in
preparation. (c) Dunbar, K R.; Heintz, R. A.; Zhao, H.; Ouyang, X.;
Rogers, R. D. manuscript in preparation. ((1) Ouyang, X., Ph. D.
Dissertation, Michigan State University, 1998.

(a) Amiiller, A; Hiinig, S. Liebigs Ann. Chem. 1986, 142. (b) Sinzger,
K; Hiinig, S.; Jopp, M.; Bauer, D.; Bietsch, W.; von Schiitz, J. U.; Wolf,
H. C.; Kremer, R. K.; Metzenthin, T.; Bau, R.; Khan, S. I.; Lindbaum,
A.; Lengauer, C. L.; Tillmanns, E. J. Am. Chem. Soc., 1993, 115, 7696.

34

50.

51.

52.

54.

55.

56.

57.

58.

59.

60.

(c) Kato, R.; Kobayashi, H.; Kobayashi, A. J. Am. Chem. Soc., 1989,
111, 5224.

Manriquez, J. M.; Yee, G. T.; McLean, R. S.; Epstein, A. J .; Miller, J. S.
Science, 1991, 252, 1415.

Dunbar, K. R. Angew. Chem., Int. Ed. Engl. 1996, 35, 1659.

Wudl, F.; Smith, G. M.; Hufnagel, E. J. J. Chem. Soc., Chem. Commun.
1970, 1453.

(a) Davidson, A.; Boubekeur, K.; Pénicaud, A.; Auban, P.; Lenoir, C.;
Batail, P.; Hervé, G. J. Chem. Soc. Chem. Commun. 1989, 1373-1374.
(b) Pénicaud, A.; Boubekeur, K; Batail, P.; Canadell, E.; Auban-
Senzier, P.; Jérome J. Am. Chem. Soc. 1993, 115, 4101-4112. (c)
Coulon, C.; Livage, C.; Gonzalvez, L.; Boubekeur, K; Batail, P. J.
Phys. I France 1993, 3, 1. (d) Coronado, E.; Gémez-Garcia, C. J.
Comments Inorg.Chem., 1995, 17, 255. (e) Gémez-Garcia, C. J.;
Giménez-Saiz, Triki, S.; Coronado, E.; Magueres, P. L.; Ouahab, L.;
Ducasse, L.; Sourisseau, C.; Delhaes, P. Inorg, Chem., 1995, 34, 4139.

Ferraro, J. R.; Williams, J. M. Introduction to Synthetic Electric
Materials. Academic Press: Orlando, Florida, 1987.

(a) Ferraris, J.; Cowan, D. O.; Walatka, V. V.; Perstein, J. H. J. Am.
Chem. Soc. 1973, 95, 948. (b) Coleman, L. B.; Cohen, M. J .; Sandman,
D. J.; Yamagishi, F. G.; Garito, A. F.; Heeger, A. J. Solid State
Commun. 1973, 12, 1135.

Kistenmacher, T. J.; Phillips, T. E.; Cowan, D. 0. Acta. Cryst., B
1974, B30, 763.

Phillips, T. E.; Kistenmacher, T. J .; Ferris, J. P.; Cowan, D. O. Chem.
Commun. 1973, 471.

Torrance, J. B. Mol. Cryst. Liq. Cryst. 1985, 126, 55.

(a) Becker, J. Y., In International Symposium on New Organic
Materials, Seoane, C.; Martin, N., Organizers, 1994, 37. (b) Rovira,
C.; Veciana, J.; Tarrés, J.; Santalé, In International Symposium on
New Organic Materials, Seoane, C.; Martin, N., Organizers, 1994, 58.
(c) Garin, J., In International Symposium on New Organic Materials,
Seoane, C.; Martin, N., Organizers, 1994, 72.

Engler, W.; Patel, V. V. J. Am. Chem. Soc., 1974, 96', 7376.

35

61.

62.

63.

64.

65.

66.

67.

68.

69.

70.

71.

72.

Bechgaard, K; Jacobsen, C. S.; Anderson, N. H. Solid State Commun.
1980, 25, 875.

Bechgaard, K; Carneiro, K; Rasmussen, F. B.; Olsen, H.; Rindorf, G.
Jacobsen, C. S.; Pederson, H.; Scott, J. E. J. Am. Chem. Soc. 1981,
103, 2440.

(a) Williams, J. M.; Beno, M. A.; Wang, H. H.; Leung, P. C. W.; Emge,
Y. J.; Geiser, U.; Carlson, K. D. Acc. Chem. Res, 1985, 18, 261. (b)
Urayama, H.; Yamochi, H.; Sato, G.; Nozawa, K; Sugano, T.;
Kinoshita, M.; Osgima, K; Kawamoto, A.; Tanaka, J. Chem. Lett.
1988, 55. (b) Nuzawa, K; Sugano, T.; Urayama, H.; Yamochi, H.;

Sato, G.; Kinishita, M. Chem. Lett. 1988, 617.

(a) Interrante, L. V.; Browall, K. W.; Hart, H. R.; Jacobs, I. S.;
Watkins, G. D.; Lee, S. H. J. Am. Chem. Soc. 1975, 97, 889. (b) Bray,
J. W.; Hart, H. R., Jr.; Interrante, L. V.; Jacobs, 1. S.; Kasper, J. S.;
Piacente, P. A.; Watkins, G. D. Phys. Rev. B. 1977, 16, 1359.

Bousseau, M.; Valade, L.; Legros, J.-P.; Cassoux, P.; Garbaukas, M.;
Interrante, L. V. J. Am. Chem. Soc. 1986, 108, 1908.

Bryce, M. R. Chem. Soc. Rev. 1991, 20, 355 and references therein.

Le Narvor, N.; Robertson, N.; Weyland, T.; Kilburn, J. D.; Underhill,
A. E.; Webster, M.; Svenstrup, N.; Becher, J. Chem. Commun. 1996,
1363.

McCullouch, R. D.; Belot, J. A. Chem. Mater. 1994, 6, 11396.

Alvarez, S.; Vicente, R.; Hoffman, R. J. Am. Chem. Soc. 1985, 107,
6253.

(a) Rivera, N. M.; Engler, E. M. J. Chem. Soc., Chem. Commun. 1979,
184. (b) Poleschner, H.; John, E.; Hoppe, F.; Fanghanel, E. J. Prakt.
Chem. 1983, 325, 957.

(a) Fourmigué, M.; Batail, P. Bull. Soc. Chim. Fr. 1992, 129,
829-836. (b) Jarchow, S.; Fourmigué, M.; Batail, P. Acta Cryst.
1993, C49, 1936. (c) Fourmigué, M.; Huang, Y.-S.
Organometallics, 1993, 12, 797. (d) Gerson, F.; Lamprecht, A.;
Fourmigué, M. J. Chem. Soc., Perkin Trans. 2, 1996, 1.

Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.; Bartley, S. L.;
Dunbar, K R., J. Organomet. Chem., 1997, 52.9, 343.

36

CHAPTER II

COORDINATION CHEMISTRY OF TRIS(2,4,6-

TRIMETHOXYPHENYL)PHOSPHINE WITH PLATINUM GROUP

TRANSITION METALS

37

1. Introduction

A considerable quantity of research in our laboratories has involved
the use of the bulky and basic ligand tris(2,4,6-trimethoxyphenyl)phosphine
(TMPP) in organometallic and transition metal coordination chemistry.1
Several years ago Haefner and Dunbar reported the successful stabilization
of an unusual paramagnetic, homoleptic RhII complex with TMPP.13 The
metalloradical, [Rh(n3-TMPP)2][BF4]2, was shown to exhibit a rich and
reversible chemistry with CO and non-redox substitution reactions with
isocyanides RCN (R = tBu, iPr, Cy).1b’cve Results indicate that the use of a
bulky, yet flexible ligand allows for the kinetic stabilization of ordinarily
unstable intermediates, and renders possible the monitoring of reactions by
NMR and infrared spectroscopy. Very often, ligands with large cone angles
form complexes that are too sterically congested to undergo further
reactions,2 a situation that is not the case with the TMPP ligand. Mixed-
donor ligands such as TMPP with its nine methoxy substituents, may be
envisioned as possessing "built-in" solvent molecules in the form of weak
ether interactions with the metal center. These prove to be sufficiently labile
in solution and even in the solid-state,3 thereby providing requisite vacant
coordination sites. Such properties of ether-phosphine ligands have been
referred to as hemi-labile, with the complexes themselves being labeled as
"incipiently coordinatively unsaturated".4 The properties and catalytic

applications of ether-phosphines have recently been extensively reviewed.5

38

More recently our laboratories have reported the synthesis of
bis(phosphino-phenoxide) ligands derived from TMPP with Ni,1i where the
ligand is in it's demethylated form (TMPP-O). While the phenoxides
positions in the NiII complex are trans to one another, evidence for a cis
conformation has been observed with Rhm.6 The ability to form phenoxides
that are cis to each other opens up the possibility for preparing
heterobimetallic complexes via bridging phenoxides. The possibility of
preparing early-late and late-late transition metal combinations occurred to
us, given that the ligand possesses both “soft” and “hard” O-donors. There
are several reports in the literature by Wolczanski and co-workers of these
types of complexes (e.g. Cp*Zr(u-OCH2Ph2P)2RhMe).7 Darensbourg et al.
have utilized a similar approach to form bi- and heterometallic compounds
from square-planar NiII complexes possessing a N2S2 environment.8 Of most
relevance to our work is that of Braunstein and co-workers who synthesized a
series of cis-coordinated phosphino-enolate complexes with nickel(II),
palladium(II), and platinum(II).9 The nickel compound of this series was
demonstrated to act as a metalloligand toward C012 and AlMez units; in the
latter case the compound exhibits reactivity as an ethylene polymerization
catalyst.10

In order to ascertain whether it was feasible to use a basic tertiary
phosphine such as TMPP to stabilize 3d metals, we set out to investigate the

chemistry of this ligand with Con. The successful use of the solvated

39

dirhodium(II,II) species, [Rh2(NCCH3)1o][BF4]4,,13 in earlier studies prompted
us to make use of [Co(NCCH3.)6]2+ as the starting material for these reactions.
2. Experimental
A. Synthesis

Starting Materials and Reaction Procedures.
[Rh11('I‘MPP)2][BF4]2,lb [Rhm(TMPP)('I‘MPP-O)][BF4]2,1b Co(TMPP-O)2,1°
PtC12(NCCesH5)2,11 [Mn(NCCH3)4][BF4]212 and Pd(TMPP-O)2li were prepared
according to previously reported procedures. [MegO][BF4] and [(C4H9)4N][I]
were purchased from Aldrich Chemical Co. and Con2 was purchased from
Strem Chemical Co. All three reagents were used as received. Zn (s) pellets
were purchased from Fisher Scientific, activated with HCl and washed with
diethyl ether prior to use. Acetone was distilled over 3 A molecular sieves.
Diethyl ether, tetrahydrofuran, and hexanes were distilled over sodium-
potassium/benzophenone. Unless otherwise specified, all reactions were
carried out under an argon atmosphere by using standard Schlenk-line
techniques.
(1) Preparation of [Rh1(TMPP)2] [BF4] (3)
(i) Reduction of [Rhn(n3-TMPP)2] [BF4]2 with Con2. Solutions of
[RhUCI'MPP)2][BF4]2, (0.107 g, 0.080 mmol) Co(C5H5)2 (0.028 g, 0.148 mmol),
and [Me30][BF4] (0.022 g, 0.149 mmol), were prepared separately by
dissolving the respective solids in 10 mL of acetone. The cobaltocene and
trimethyloxonium solutions were then simultaneously added to the Rh(II)

complex dropwise, with stirring, resulting in a color change from purple to

40

brown after 1 h. The solvent was removed by vacuum and the brown residue
was washed with 3 x 10 mL of THF, producing a yellow solution, indicative of
[Rhm(TMPP)(TMPP-O)][BF4]2. The residue was finally washed with copious
amounts of EtzO, and dried in vacuo; yield 0.048 g (mixture of 3 and
[Con2][BF4]) 1H NMR: (ds-acetone) 5 ppm: -OCH3, 3.63 (b), 3.86 (s) (27H
combined); m -H, 6.25 (b, 6H); [Con2]+, 5.91 (s, 10H). 31P{1H } NMR (d6-
acetone) 5 ppm: +17.9 ppm (d, lJRh-P = 158.1 Hz). After ~ 1h the solution
changed color to yellow-orange: 1H NMR: (dB-acetone) 5 ppm: -OCH3, 3.04 (s),
3.15 (s), 3.31 (s), 3.45 (s), 3.55 (s), 3.59 (s), 3.65 (s), 3.67 (s), 3.72 (s), 3.79 (s),
3.87 (s), 3.89 (s), 3.91 (s), 3.92 (s), 3.93 (s), 3.95 (s), 4.35 (s), 4.44 (s), 4.67 (s);
m -H, 5.69 (dd), 5.75 (dd), 5.82 (dd), 6.04 (dd), 6.12 (dd), 6.17 (dd), 6.24 (dd),
6.36 (dd), 6.41 (dd), 6.45 (dd), 6.68 (dd), 6.84 (dd), 7.05 (dd); [Con2]+, 5.94.
31P{1H} NMR (dc-acetone) 5 ppm: +3823 (dd, lJRh-P = 139.2 Hz, 2J1>.1> = 13.3
Hz), +32.31 (dd, lJRh-P = 41.6 Hz, ZJP-P = 13.3 Hz).

(ii) Reduction of [Rhn(n3-TMPP)2] [BF4]2 with Zn (5). [RhHCI'MPP)2]-
[BF4]2 (0.103 g, 0.077 mmol) and 0.024 g (0.162 mmol) of [Me30][BF4] were
dissolved in 10 mL and 5 mL of acetone respectively. The two solutions were
then simultaneously added, with stirring, to a Schlenk flask containing an
excess of activated Zn pellets (4-5 pellets). The stirring was discontinued and

the flask was allowed to sit for ~24 h, during which time a subtle color

change from dark purple to red-brown became evident. The solution was

transferred by cannula to a Schlenk tube, and the solvent was removed by

41

vacuum, leaving a rose-colored residue. The residue was washed with THF
to remove demethylated impurities, followed by copious amounts of EtzO,
and finally dried in vacuo; yield 0.067 g (70%). Slow diffusion of hexanes into
an acetone solution of the solid yielded red-brown crystals suitable for X-ray
diffraction. Red-brown crystals: 1H NMR: (deg-acetone) 5 ppm: -OCH3, 3.54
(b), 3.86 (s) (27H combined); m -H, 6.16 (b, 6H). 31P{1H} NMR (ds-acetone) 5
ppm: 17.8 (d, 1JRhP = 158.7 Hz), 17.9 (d, 1JRh-p = 158.7 Hz). EPR (50:50
acetone/toluene, 110 K) gxx = 2.24, gw = 2.30, gzz = 2.00.
(2) Dealkylation of [Rh‘(TMPP)2] [BF4] (3): Formation of RhI(TMPP)-
(TMPP-0) (4)

A flask containing 0.108 g (0.086 mmol) of [RhICI‘MPP)2][BF4] (3) and
0.030 g (0.081 mmol) of [n-Bu4N][I] was cooled to -40°C and treated with 10
mL of acetone, after which time the flask was allowed to slowly warm to room
temperature. After 1 h, the color of the solution changed to a darker shade of
brown. The solvent was removed and the residue was dissolved in 10 mL of
THF. The solvent was removed under vacuum, and the tan residue was
washed with copious amounts of hexanes; yield 0.784 g. 1H NMR: (de-acetone)
5 ppm: -OCH3, 3.56 (s), 3.40 (s), 3.42, (s), 3.46 (s), 3.47 (s), 3.62 (s), 3.66 (s),
3.80 (s), 3.83 (s); m -H, 5.50 (dd), 5.83 (dd), 5.88 (m), 5.91 (d), 6.06 (br), 6.23
(br); 6.15 (t). 31P{1H} NMR (dc-acetone) 5 ppm: 4, +200 (dd, 1JRh-P = 164.0 Hz,
lJp.p= 21.8 Hz), +10.3 (dd, 1JRh.P = 135.5 Hz, ZJP-P = 21.8 Hz); +15.4 (d, 1JRh-P =

146.4 Hz); 5, +35.7 (d, 1JRh-P = 152.5 Hz).

42

(3) Dealkylation of ax-[Rhm(TMPP)(TMPP-O)][BF4]2: Formation of
ax, ax-[Rhm(TMPP-O)2] [BF4] (5)

A mixture of ax-[Rh(TMPP)(TMPP-O)][BF4]2 (0.103 g, 0.078 mmol) and
[TBA][I] (0.032 g, 0.087 mmol) was dissolved in 10 mL of acetone and exposed
to a brief vacuum before being stirred for 3 h. During this time no color
change was observed. The solvent was removed under vacuum, and the solid
was washed with copious amounts of EtzO before being dried under vacuum;
yield 0.063 g (66%). 1H NMR: (dc-acetone) 5 ppm: -OCH3, 3.11 (s, 6H), 3.34 (s
,6H), 3.39 (s, 6H), 3.45 (s, 6H), 3.65 (s, 6H), 3.85 (s, 6H), 4.27 (s, 6H); m -H,
5.49 (br, 2H), 5.63 (br, 2H), 5.85 (br, 2H), 5.95 (br, 2H), 6.27 (br, 2H), 6.72 (br,
2H). 31P{1H} NMR (dc-acetone) 5 ppm: 35.5 (dd, lJRh-P = 153.4 Hz). FAB-MS
(sz): 1137 (1%").

(4) Reaction of Con(TMPP-O)2 with PtHC12(NC7H5)2

A quantity of PtC12(NCCsH5)2 (0.0416 g, 0.088 mmol) Co(TMPP-O)2
and (0.099 g, 0.091 mmol) were dissolved in 10 mL of acetone and stirred for
12 h. After this time the solution was reduced to a residue, washed 3 times
with 20 mL of EtzO and dried in vacuo; yield 0.089 g (74% for
ClthCo(TMPP-O)2). IR (Nujol, cm'l): 329 (th431), 480 (vcgc), 1032 (vcoc),

1228 (Vas-coc), 1579 (vs, vcgc + vc_._.c), 1595 (vs, vcgc + v c._.o). FAB-MS (m/z):

1093 ([Co(TMPP-O)2]+).

43

(5) Reaction of Co"(TMPP-0)2 with [Mn11(NCCH3)4][BF4]2

A solid mixture of Co(TMPP-O)2 (0.202 g, 0.185 mmol)) and
[Mn(NCCH3)4][BF4]2 (0.037 g, 0.094 mmol) were dissolved in 15 mL of
acetone, and stirred at 40°C for .5 h. The dark green solution was then
allowed to stir for 12 h while it cooled to ambient temperature. At that time
the solution was reduced to a residue, washed 3 times 20 mL of EtzO and
dried in vacuo; yield: 0.181 g (81% for [Mn{Co(TMPP-O)2}2] [BF 4]2). IR (Nujol,
cm'l): 481 (vcgc), 1098 (vs, VB-F), 1232 (Vas-COC), 1578 (vs, vc._.c + vcgo) + 1599
(vs, vcgc + vcgo), FAB-MS (m/z): 1093 ([Co(TMPP-O)2]+), 576 ([MnCoCI‘MPP-
0H)2]2*) .
B. X-ray Crystallography

The structures of complexes 3, 6, and 7 were determined by
applications of general procedures described elsewhere.13 Geometric and
intensity data were collected on a Bruker SMART diffractometer for
compounds 3 and 6, and on a Rigaku AFC6S diffractometer for compound 7;

both are equipped with graphite monochromated MoKu (1,, = 0.71069 A and

0.71071 A, respectively) radiation. The data were corrected for Lorentz and
polarization efi'ects. Computing for 3, 6 and 7 was performed on a Silicon
Graphics Indigo II workstation using the Texsan and SHELXTL14 software
systems. Crystal parameters and basic information pertaining to data
collection and structure refinement for compounds 3, 6, and 7 are

summarized in Table 1.

44

 

 

i

3.71;..30bv A v....__ 03—. ufl— _. v7.5.3 o:««»..—.——\<.—.:..~ 7:: .AA v. v.41; 7. :3 ca Kim‘s. X; T. vvox....~«~\\.~.-.<.~. is 5 v\

a- —. er]. 0A vmnAr..- -» v. - -. UV I-n...-u--n-l—-<.-. ..- —. v~ -.u-.»~u§“.__nhq.A\ V nfinhh.<.h.v-.v.. V»...A§~§ b- u‘VAN‘Q V ..~\»..\~.u. V\.A..\~..Nh\\
<.—...-¢--.-.-./_.-. ...u...-s-—ou...--.~...~.-I~.~,..-....--\ ...~ ..6.‘.~ .u-\.\.~u~1..~\osslu-.v .! .o\|\o\.\.

.v...-v-— onwv

s z......_...._z-....z§ _ .8 _ - ...m :35 u 8.8-388 8
.Comcub: n 3 “259883. Nzufimomdobvi Wm H mm? a mom—N: Tm. - 7...: _N n Hm a

 

 

 

83 84 88 838.888 8.8-883

888 83 83 game

82 .o 83 83 .2

88 3.88 88 .83 2.3:: .oz

31. E -m 84 .38 .8 3:2 ._8 83

w w e N

s: 82: A888 8.88 31>

8.8 8.8H 8.8 38 s

8.8 8.8 8.8 388 .n

8.8 8.8 8.8 m8 .8

a c 838 3:88 @888 .4. .8

S 8.8 @838 @888 4 .8.

as 88.8 @838 @883 4 .8

:25 0mm N82 385 8me

SAUNAHE OmdwmhmmUUm «HhmmwmwbcwwmmumuerO fibmflvheaOmfiEmSUmfim gzauorm

Cam gas—Oufimpdo o b «OmmeU .03 mvo ovhmmaogmwao .@ chamumwucccmvuofim on
.68 388288 .88 80.38.88.383 8 488888858»38:82:81,
e 8.88 888.88.8885..Ea3.6.88555088.382 £8 22.
A

5255.8. .9 88:82:58. 2.888.229.8528. 5 83 82882288

45

(1) [Rh1(n3-TMPP)2] [BF4] ° [Rh11(n3-TMPP][BF4]2 (30[Rh11(n3-TMPP)2]-
[BF4]2).

(i) Data Collection and Reduction. Single crystals of 3' [Rh11(n3-
TMPP)2][BF4]2 were grown by slow diffusion of diethyl ether into an acetone
solution of the complex. A red-brown crystal of dimensions 0.21 x 0.18 x 0.11
mm3 was secured on the tip of a glass fiber with Dow Corning silicone grease
and placed in a cold N2(g) stream at —123 i 1 °C. Least-squares refinement
using 21 well-centered reflections in the range 25 S 20 S 35° indicated an
orthorhombic crystal system. The data were collected in a 6 range of 1.94 to
28.28°. Of the 18047 reflections that were collected, 6846 reflections were
used for F2 refinement, and 4323 data were observed with I > 2.006(I). The
data were corrected for Lorentz polarization effects and an empirical
absorption correction based on azimuthal w-scans near x = 90° was applied.

(ii) Structure Solution and Refinement. The space group was
determined to be Aba2 based on the observed systematic absences. The
structure was solved by the SHELXTL program.14 The metal center was
found to reside on a center of inversion, rendering half the molecule unique.
Rh(l), P(1), and the trimethoxyphenyl rings defined by C(l) through C(6) and
C(19) through C(24) were refined anisotropically with occupancies of 1.0. The
third trimethoxyphenyl ring was found to be disordered as two fully resolved
rings, defined by C(10) through C(15) and C(10A) through C(15A). Each

disordered ring was refined isotropically, with free variables resulting in

46

occupancies of ~0.50 for each. The disordered rings were constrained to the

calculated positions of a normal phenyl ring. The [BF4]' anion was found to
exhibit a rotational disorder and was refined as two independent molecules
with the B(1) and F(l) atoms in the same positions. The common atoms were
refined with free variables resulting in occupancies of 1.0. The flourine atoms
F(2)/(2A), F (3)/(3A), and F(4)/(4A) were such that the summed occupancies of
the two representations equaled the ocupancies of B(1) and F(1). All atoms

associated with the anion were refined anisotropically. Restraints were used

on all F---F distances associated with a given molecule. F2 refinement of 452
parameters resulted in residuals of R1 = 0.061 and wR2 = 0.131. The
goodness-of-fit index was 0.982, and the maximum shift in the final
difi‘erence map was 0.483 A associated with H(14B') (symmetry code C) - x, 1-

y, z). The mean shift/esd was 0.072 and the highest peak in the difference

Fourier map is 0.49 e'IA3 which is associated with C(14).

(2) [Coms(p.3-OH)(p.-OH)3{COU(p—n 3-TMPP-0)2}3] [BF4]2 ° [CH3-TMPP]-
[BF4] ° (CH3CH2)2O ' (CH2)2CO (7 ° [CHsTMPP] [BF4] 0 (CH3CH2)2O
°CH2)2CO).

(i) Data Collection and Reduction. A dark green crystal of approximate
dimensions 0.37 x 0.26 x 0.23 mm3 was selected and mounted at the end of a
glass fiber with silicon grease and placed in a N2 cold stream at —123 i 1°C.
Initial data indicated a monoclinic system, but subsequent solution and

successful refinement of the structure was carried out in the rhombahedral

47

STTECCJI}

ii,» Struc

 

c
r».
- n f‘
"m" ;
. o
-
’ 1
v-
. .
. ;‘ \‘.
.‘ ‘3
7‘6! fit
.

 

 

 

 

 

space group R3c. The data were collected in a 0 range of 1.48 to 28.28°. Of
the 65724 reflections that were collected, 17871 reflections were used for F2
refinement, and 9352 data were observed with I > 2.000(1). The data were
corrected for Lorentz polarization effects and an empirical absorption
correction based on azimuthal w-scans near x = 90° was applied.

(ii) Structure Solution and Refinement. The structure was solved using
the SHELXTL program.l4 Due to the size of the structure, initial least
squares cycles were run using the Kennert-Hendrickson conjugate-gradient
algorithm,15 with the final cycles run using blocked refinement. The methoxy
methyl groups associated with C(39) was found to be disordered, and was
refined isotropically as three methyl groups, A, B and C, with a combined

occupancy of 1.0 and with restraints on CD. All other non-hydrogen atoms
were refined anisotropically, except for [BF4]' and solvent molecules. The

[BF4]' anion was found to undergo a rotational disorder and was refined as
three molecules sharing the B(11) and F(13) atoms, which were refined
anisotropically. The flourine atoms F(nl), F(n2), and F(n4) (n = 1,2,3) were
refined isotropically with free variables such that the summed occupancies of
the three representations equaled 1.0. Restraints were used on all F(n)---F(n)
and F(n)-~F(13) distances. The acetone molecule was refined isotropically
with restraints on C(1/3)---O(4). The oxygen atom of the diethyl ether

molecule was refined isotropically with restraints on O(96)-C(91/95). All

hydrogen atoms are located at calculated positions.

48

L-
I
l
(

.-~-,.. ,
v' "
Us“. ._.

m
.‘5- h
.. .1— 1..
‘5‘.

Q “
‘. ‘
‘ .

 

 

 

Final full-matrix least-squares refinement Was based on 17871
reflections that were used to fit 957 parameters with 83 restraints to give R1
= 0.089 and wR2 = 0.189. The goodness-of-fit index was 1.034, and the
maximum shift in the final difference map was 0.195 A associated with

H(3SC). The mean shift/esd was 0.032, and the highest peak in the difference

Fourier map is 0.95 e'/A3 which is associated with H(38C). The structure
was additionally solved in the lower symmetry space groups Cc (#9) and P-l
(#1) with no improvement in the final refinement.

(3) Pd(TMPP-0)2 ' 3.73 CH2C12 ' H20 (7) 0 3.73 CH2C12 0 H20.

(i) Data Collection and Reduction. Single crystals of 7 were grown by
slow diffusion of diethyl ether into a CHzclz solution of compound 7. An
orange crystal of dimensions 0.40 x 0.98 x 0.22 mm3 was secured on the tip of
a glass fiber with Dow Corning silicone grease and placed in a cold N2(g)
stream. Least-squares refinement using 25 well-centered reflections in the

range 15.0 S. 29 5 223° indicated that the crystal is consistent with an
orthorhombic crystal system. The data were collected at - 85 i‘ 1 °C using the
00-29 scan technique to a maximum 26 value of 47°. Of the 10169 reflections

that were collected, 815 were systematically absent. An empirical absorption
correction based on azimuthal scans of three reflections with x near 90° was
applied which resulted in transmission factors ranging from 0.55-1.00.

(ii) Structure Solution and Refinement. The data were corrected for

Lorentz and polarization effects. The structure was solved in the space group

49

so. A»...
‘ “I.
hub ydxa.

"hp-unr- ~
In
"b-5u- _.

""‘ I3,-
‘ .

‘M.~_.

. .‘ -
_, fip-‘
.,~ .1—

...~~

.-

 

-
‘\
\T'T-“—
t...“.:.
L;- .L
\_ \ .
\. ~

—‘

I):
*, "

‘__l
(7"-

 

 

4
if
L‘
‘u
.“ l
-.‘
\,‘:.v- 9..
v -F
‘
"‘
x} ‘4.‘
"A: 2
‘C
\
._{\~
“ l
‘l ,‘N
A
1'. - -
"k’y‘:
‘ KQ.‘
\

 

3.»

ll'
(1'

Pbcn using the MITHRIL16 and DIRDIF17 structure solution programs and
refined by full-matrix least-squares refinement on F2.18 Methoxy methyl
groups associated with atoms C39, C47, and C48 were found to be disordered,

and each was refined isotropically in two orientations, A and B, with a

combined occupancy of 1.0 and with restraints on the C-0 and C---C
distances. All other non-hydrogen atoms were refined anisotropically, except
for the solvent molecules. Treatment of the dichloromethane molecules is
described in the following section. The final full-matrix least-squares
refinement was based on 9199 reflections that were used to fit 774
parameters with 540 restraints to give R1 = 0.1065 and wR2 = 0.2598. The
goodness-of-fit index was 1.030, and the maximum shift in the final
diflerence map was 0.002 A associated with Cl(73). After convergence, the
mean shift/esd was 0.006 and the highest peak in the difference Fourier map
was 1.16 e'lA3 which is associated with the solvent molecule containing
Cl(72).

Dichloromethane molecules were located using electron density
difl'erence maps generated using the SHELXTL software package.14 The

disordered CH2C12 molecules were modeled with restraints on the C-Cl and

Cl---Cl distances. All C-Cl bond distances were constrained to 1.79 A.
Occupancies were also refined, resulting in a total of 3.73 dichloromethane
molecules per Pd atom. An additional isolated atom was added as the oxygen

of a water molecule and refined isotropically.

50

3. Results and Discussion
A. Reduction of [Rhn(TMPP)2][BF4]2: Formation of [Rh1(TMPP)2]-
[BF4] (3).

The unstable d3 complex, [Rh1(TMPP)2][BF4] (3), was prepared by two
different reduction methods, neither of which yielded an analytically pure
product. The inability to isolate the product from the cobaltacene reaction is
due to similarities in the solubility of 3 and the byproduct, [Con2][BF4].
Preliminary 31P{1H} and 1H NMR results reported by Dunbar and Haefner
involving the reduction of [RhH(TMPP)2][BF4]2 by Con2 support the
formation of minor quantities of [TMPP—CH3]+ salts and an extremely
unstable dealkylated species.19 In light of this, a methylating agent was
added in order to prevent dealkylation of the reduction product, and to allow
for a complex with two neutral TMPP ligands to be isolated. An excess (1.4
equivalents) of reducing agent appears to be necessary, as reactions using 1:1
equivalents of Con2 produced no color change or new 31P{1H} NMR signals.
This may be explained by the decomposition chemistry of 3, which will be
discussed later.

The reaction with Con2 appears to be considerably faster, producing
an immediately visible color change, whereas reduction with Zn (s) requires
extended reaction times and is accompanied by a very subtle color change

that is diffith to detect.

51

“" ‘\~--
“ \ ;.
'~'~ h...

,‘f-‘!. ..
M~ll -
. A
‘fi‘l ‘
\ J“ A
n ~. \
g; I.

~ -
...‘l
n‘.‘
-41 .
§.-‘~ "
x"?!
..~
\_‘. >
'. ‘P$
\ .- ~
‘~. ..1
I ' \
g
-.
V.‘ If

\)
K v,_ .
' JgLv
.‘.,
.f "
.\t \
C‘-

\
O‘ I
‘.‘"‘.l n
._q c
.._ ‘
\t;|" ‘
k ‘-
5 .
1‘ ...A
I “4-
‘k.
i...
..J.)
'\ 1‘. .
'i ,—

 

 

(1) NMR Spectroscopic Studies

The 31P NMR spectra of the product of the cobaltocene reduction shows
a doublet that is shifted +839 ppm downfield from the free phosphine,20
indicating the presence of equivalent phosphorus nuclei with Rh-P coupling.
This signal is shifted upfield relative to [RhIII(TMPP)2][BF4]3, which is
understood in terms of increased shielding of the phosphorus nuclei due to
increased electron density about the metal center. Curiously, the NMR
spectra for the cobaltocene product and the crystalline product from zinc are
slightly difierent. The product from the reduction by cobaltocene, and the
crystals formed from the reduction by Zn contain the same doublet pattern in
the their 31P NMR spectra, but the latter, from which the crystals were
formed, occasionally show a doublet of doublets centered at +17.7 3 ppm. This
pattern of only one doublet of doublets cannot be reconciled with
magnetically inequivalent phosphorus atoms, as two doublets of doublets
should occur as a result of coupling first to the Rh center, and then to the
other P nucleus. It was then thought that the pattern may be the result of
two overlapping doublets (+17.78 ppm, +17 .67 ppm), caused by two distinct
isomers. To verify this a 31P NMR spectrum was taken of the same sample
on both a 300 MHz and a 500 MHz NMR spectrometer. This was performed
to check if the doublet positions would shift relative to one another when the
field was varried. The results revealed the true pattern to be two doublets
centered at 17.8 ppm (U = 158.7 Hz) and 17.7 ppm (U = 158.7 Hz). Both

signals are extremely close to that observed for the product of the

52

metallocene reaction, with nearly identical le-p coupling constants. A
pattern such as this must arise fiom at least two separate species in solution.

1H NMR studies of [Rh(TMPP)2][BF4] (3) in acetone-d6 indicate that
the TMPP ligands are involved in a highly fluxional process similar to the
previously reported PdII analog.“ The room temperature 1H NMR spectrum
of 3 from Con2 contains a broad resonance at 6.16 ppm due to the m-protons
of the phenyl rings, a sharp resonance at 3.86 ppm assigned to the equivalent
para-methoxy substituents and a broad signal at 3.54 ppm due to the ortho-
methoxy substituents. The broad resonances in the meta-hydrogen and
ortho-methoxy regions of the 1H spectrum support the fluxionality of the
ligand, probably due to an on-ofi' binding interaction of methoxy groups at the
axial positions. This type of fluxional behavior is not uncommon for these
types of complexes.21 An added feature of the spectrum is a singlet at 8 =
5.91 ppm due to the ring protons of the metallocinium ion.

The 1H NMR spectrum from the Zn(s) reduction, shown in Figure 8,
reveals the same resonances, with an absence of the singlet at 6 = 5.91 ppm.
Upon cooling the sample from to 20°C, two additional broad resonances
appear at 8 = 3.49 and 6.34 ppm, respectively. At -40°C the intense signal at
3.86 ppm has shifted slightly upfield to 3.83 ppm, but is otherwise
unchanged. The broad signals shift and sharpen slightly, but not sufficiently
enough to reveal additional peaks. Continued cooling to -80°C leads to

broadening of the resonances at 6.34 and 3.95 ppm and the appearance of an

53

.3888 5. 8 58382528 80 288m 822 E 858883 28:3, .8 258m

 

 

 

 

 

 

sag m m o v m . v o m m m o m m m
— — — — _ p - — — — . — — — PLL — » — p _ — _ _ — — — u _ — p — — b p _ — _ L!
2‘ Ea 88 88 :8 68 8.8
00 CV.
88 8.8 8% 8.8
00 ON-
I’lqu/fillj % Jxll/xlllll-
o. o
_ /\{. . J ?\l ll
88 8.8 88 8.8
o. 8

 

Ema own

54

additional peak at 3.68 ppm. The formation of two broad resonances in both
the meta-proton and ortho-methoxy positions supports the theory that two
species are present in solution. The resolution of two 1:1 singlets in the m-H
region, and three 1:1:1 singlets in the methoxy region at -40 °C can be
explained by the presence of two different species in a nearly 1:1 ratio. The
three difi‘erent methoxy resonances would be caused by one o-OCH3 for each
compound, and a p-OCHs resonance common to both. This is supported by
the 1:1 integration of the two doublets in the 31P NMR spectrum. The
identity of the second species is undetermined. One possibility is the
formation of a the trans-[Rh(TMPP)2][BF4] isomer. This would explain the
NMR data, but is unusual given the only trans-TMPP complex reported to
date is Ni('I‘MPP-0)2,1i where both ligands have undergone demethylation.
Furthermore, the observed 1:1 ratio of species is cause for suspicion, as an
exact 50:50 mixture of cis and trans isomers is highly unlikely. A second
possibility that we considered is the coordination of TMPP to the Zn ions.
Given the similarities between the reactivities of ZnII and Cd“,22 it is not
without reason to expect that the formation of [Zn(TMPP)2][BF4]2 would be
favored. However, the [Zn(TMPP)2][BF4]2 would not account for either NMR
spectrum based on the fact that [Cd(TMPP)2][BF4]2 exhibits a singlet in its
31P NMR spectrum, and symmetrical nl-coordinated TMPP in its 1H NMR

spectrum.10 Deliberate methods to prepare the Zn complex have thus far

55

been unsuccessful. Clearly, further studies are needed to identify the second
product that occurrs from reduction of the RhII compound with Zn (s).
B. Crystal Structure of [Rh1(TMPP)2][BF4] (3).

X-ray quality single crystals of [RhI(TMPP)2][BF4] (3) were grown by
slow diffusion of diethyl ether into an acetone solution of the compound. A
PLUTO representation of the molecular cation as well as selected bond
distances and angles for 3 are provided in Figure 9 and Table 2. The crystal
structure displays a very unusual disorder as a result of two separate Rh
species having co-crystallized in the sample. The two species are the salts
[Rhn(n3-TMPP)2] [BF4]2 and the reduction product [Rh1(n2-TMPP)2][BF4]. The
Rh atom in the divalent species resides at the center of an octahedron defined
by two phosphorus atoms (P(1), P(1')), two ether-oxygen atoms (0(1), 0(1')) in
an equatorial arrangement, and two ether oxygen atoms 04 and 04' at the
axial positions. The distortion of the equatorial positions away from
planarity is easily understood in terms of the requirements of the five-
membered metallacycles Rh(1)-P(1)-C(1)-C(2)-O(1) and Rh(1)-P(2)-C(19)-
C(20)-O(10) that involve acute angles (P(1)-Rh(1)-O(1) = 77.71 (11)°, and P(2)-
Rh(1)-O(10) = 78.1 (2)°). The Rh-Oaxia1 distance of 2.405(12) A in the Rh(II)
complex is comparable to the previously reported value of 2.398(5) A.lb The
Rh(I) center is coordinated in a square-planar environment, also defined by
atoms (P(1), P(1')), 0(1), and 0(1'), but with a much more elongated Oaxial

distance of 2.812 A (defined by O(4A) and O(4A)'). The elongated axial

56

Table 2.

TMPP)2][BF4] (3).

Selected Bond Distances (A) and Angles (deg.) for [Rh1(n2-

 

 

 

 

Atom 1 Atom 2 3
Rh(l) P(1) 2.209(2)
Rh(l) 0(1) 2.219(4)
Rh(l) 0(4) 2.405(12)
Rh(l) O(4A) 2.812(7)
P(1) C(1) 1.819(6)
P(1) C(10) 1.838(10)
P(1) C(10A) 1.838(10)
P(1) C(19) 1.788(6)
0(4) C(11) 1.39(2)
0(4A) C(11A) 135(2)

Atom 1 Atom 2 Atom 3 3
P(1) Rh(l) P(1)‘ 106.44(8)
P(1) Rh(l) 0(1) 77 .7 1(11)
0(1) Rh(l) 0(1) 100.0(2)
Rh(l) 0(4) C(11) 114.5(7)
P(1) C(1) C(2) 114.5(5)
P(1) C(1) C(2) 122.2(5)

57

PLUTO representation of [Rh1(n2-TMPP)2][BF4] (3) from the

mixed salt, [Rh1(n2-TMPP)2][BF4] ° [Rhn(n3-'I'MPP)2][BF4]2.

Figure 9.

58

 

Figure 10. PLUTO representation of the unique atoms, showing the
disorder in the molecular structure of [Rh1(n2-

TMPP)2] [BF4] ' [Rhnm 3-TMPP)2] [BF4]2.

59

distance arises from distortion of the ligand, resulting in two, fully resolved
phenyl rings with an angle between the rings (planes defined as C(10)-C(15)
and C(10A)-C(15A)) of 07°. The geometry of the square plane for 3° [Rh11(r|3-
TMPP)2][BF4]2 is very similar to that found in the bona fide Rh(II) structure,

with Rh-P distances of 2.029(2) A versus 216(2) A and P- Rh-P angles of

106.44(8) versus 105.2(1). Attempts to model the [BF4]’ groups to account for
the 2:1 ratio of counterions in the Rh(II) vs. Rh(l) complexes were
unsuccessful.

Due to the close similarities of the above structure with that of our
earlier X-ray study of [RhH(n3-TMPP)2][BF4]2, it became necessary to verify
that the structure was not merely a result of disorder in the structure of
[Rhn(n3-TMPP)2][BF4]2. Accordingly, 1H and 31P NMR spectra were
measured on microcrystals of [RhH(n3-TMPP)2][BF4]2, grown from slow
diffusion of E20 into a concentrated acetone solution of the complex. The
resulting 1H NMR spectrum was broad and unresolved with no observable
31P NMR signals, supporting that only the paramagnetic Rh(II) is present.
After reduction of this Rh(II) sample with Zn (s), EPR measurements of the
resulting crystals in a 1:1 acetone/toluene glass were taken at 110 K. The
observed signal was identical to that reported for [Rhn(n3-TMPP)2][BF4]2,
confirming that it is present in crystals representative of the one used in the
X-ray investigation. 1H and 31P NMR spectral studies on representative

samples from the same crystal "batch" exhibited the spectra discussed

60

previously for the proposed Rh(I) complex These combined results indicate
that the sample is not composed entirely of Rh(II), but that it also contains a
diamagnetic species. This is also supported by the noticeable color difference
between the two crystals (purple for Rh(II) versus red-brown for the one that
contains both Rh(I) and Rh(II)).
C. Reactivity of [Rh1(TMPP)2] [BF4] (3).
(1) Decomposition of [Rh1(TMPP)2][BF4] (3).

The yellow-orange solution which eventually results fiom solutions of
3 can be identified by 31P NMR spectroscopy as [Rhm(TMPP)(TMPP-
0)] [BF4]2, which supports the conclusion that there must have been two
TMPP ligands on the metal originally. This is a result of oxidation of the
Rh(I) complex with concomitant dealkylation of a methoxy group. At the
present time the pathway for the demethylation/oxidation of this compound
is unknown. The only clue that is available is the gradual appearance of a
peak at 2.85 ppm in the 1H NMR spectrum. This resonance has not yet been
assigned, but grows over time along with the resonances for the RhIII product.
(2) Dealkylation of [RhI(TMPP)2] [BF4] (3).
(i) Synthesis and spectroscopic characterization of Rh1(TMPP)-
(TMPP-O) (4). A solution of [RhI(TMPP)2][BF4] was cooled to -40'C, and
reacted with 1 equivalent of [TBA] [I]. No reaction was observed until the
temperature was allowed to warm to room temperature, after which time the
“3101‘ Of the solution darkened slightly. The resulting product is soluble in

THF Which tends to be the case for all Rh-TMPP complexes with at least one

61

demethylated TMPP ligand“),19 In contrast, all complexes with both TMPP
ligands in their neutral form are invariably insoluble in THF.1b This
solubility change indicates the formation of the highly reactive d8 species
Rh1(TMPP)(TMPP-0) (4).

The 1H NMR spectrum of 4 is very complicated owing to the presence
of several different species in solution, which causes the 31P NMR spectrum
to be the most reliable tool for analysis of the product(s). The twin doublet of
doublets at 20.0 (lJRh-P = 164.0 Hz, lJPA-PB =21.8 Hz) and 10.3 ppm (lJRh-P
=135.5 Hz, ZJPA-PB =21.8 Hz) indicate a species containing inequivalent
phosphorus nuclei where the observed couplings are due to Rh-P, and P-P
coupling. This pattern is typical for a mono-demethylated Rh-TMPP
complex , but is further upfield than any pattern previously observed for Rh
TMPP complexes, which supports that there is increased electron density at
the metal center.

The resonance patterns exhibited in the 31P NMR spectrum of 4
suggests the presence of several different complexes, due to its instability in
solution. The doublet located furthest downfield (35.7 ppm, lJRh-P = 152.5
Hz) in the 31P{1H} NMR spectrum was identified as the previously
characterized compound (max-[Rhm(TMPP-0)2][BF4].19 The upfield doublet

at 15.4 ppm (le.p =146.4 Hz) is still unidentified, with a possible candidate

being the bis-demethylated [RhICPMPP-O)2]’. This assignment would explain

the pattern, and its upfield position relative to the [RhI(TMPP)2]+ cation.

62

However, this is a highly unlikely formulation given it is doubtful the metal
center could support the increased electron density of this anionic complex.
This instability of the Rh(TMPP)(TMPP-O) compound caused further
characterization, specifically by elemental analysis, impossible.

(ii) Decomposition of Rhl(TMPP)(TMPP-O) (4). Exposure of 4 to air
results in an instantaneous color change fiom brown to yellow. Room
temperature acetone solutions of 4 kept under rigorously anaerobic
conditions produces identical results over a period of several minutes. 1H and
31P NMR spectra of the resulting solutions confirmed complete conversion to
ax,ax-[Rh111(TMPP-O)2][BF4], without evidence for the formation of [CH3-

TMPP]+ salts. This observation is consistent with dealkylation resulting
from attack by [BF4]'.23 Several examples of transition metal complexes that

activate [BF4]' have been reported,24 and this mechanism has been proposed
for the solid-state decomposition of [Rh(TMPP)2][BF4]3 to [Rh(TMPPXTMPP-
0)] [BF 4]2.19

D. Preparation and Spectrosc0pic Studies of ax,ax-[Rhm(TMPP-

0)2] [BF4] (5).

Previous work by Steven Haefner led to the identification of two

isomers fiom the addition of 1 equivalent of TMPP to [RthI‘MPPXTMPP-

0)] [BF4]2.19 These isomers were assigned on the basis of their 31P NMR

spectra as ax, ax-[RthI‘MPP-O)2][BF4] , and ax, eq- [Rthl‘MPP-O)2][BF4] in

a 59:41 ratio. The isomers occur due to the availability of two possible sites

63

for the second dealkylation reaction to occur; namely in the equatorial plane,
trans to the neutral TMPP ligand or in the axial position, trans to the
phenoxide group. The two isomers are distinguishable fi'om each other due to
the presence of a doublet at +35.7 ppm (CD3CN, 1JRh.p=152.5 Hz) for the ax,
ax, and two doublet of doublets at +47.1 ppm (CD3CN, 1JR}..1>=152.5 Hz, 2Jp.
p=16.7 Hz) and +199 ppm (CD3CN, lJRh-P3122.9 Hz, 2J1:.1>=16.7 Hz)
respectively for the ax, eq isomer. Although subsequent attempts to isolate
either pure isomer had proved unsuccessful, an in situ NMR reaction
revealed that reaction of the mono-demethylated Rh(III) with an alkyl
ammonium salt may preferentially form the ax, ax isomer.

Reaction of [Rthl‘MPP)('l‘MPP-O)][BF4]2 with an equimolar amount
of tetra-n-butyl ammonium iodide ([TBA] [1]), was shown by 31P NMR
spectroscopy to form exclusively ax, ax— [RthI‘MPP-O)2][BF4]. No evidence
for the formation of the ax, eq isomer was found. The product is a yellow
solid that is nearly identical in appearance to its mono-demethylated
precursor. The 1H NMR spectrum shows six doublets of doublets of equal
intensity in the meta-proton region between 5 = 5.4 and 6.8 ppm, and seven
equal resonances in the methoxy region between 5 = 3.1 and 3.9 ppm. This
supports the presence of two magnetically equivalent demethylated-TMPP
ligands. The presence of the TBABF4 byproduct was also detected.

E. Reactions of Co"(TMPP-0)2 with Unsaturated Metal Complexes.

Our successful isolation of C12MC0(TMPP-O)2 ( M = Co, Mn) fiom

64

v " ‘°‘. ‘

..‘L u.»-

~°~ \w

"O.‘ ‘-

'.
-- u...

-- .Q“

L‘.‘

a
H
., A.“
5‘-
:‘II
'N

' \
‘ .
’ J-
‘l. .1
U
..‘A.
sf."
.‘K‘.
_ v
\f‘g

.
.“
«K;
'I
I\
,‘-
\p‘r-
u
1‘
\.
I‘m
.. .
e 9

 

reactions of the high spin (17 complex, Co(TMPP-0)2 with the appropriate
metal chloride sparked our interest in the assembly of early-late transition
metal heterobimetallic complexes. There are several reports in the literature
of these types of complexes, e.g. trans-MezRTaQi-CHz)(p-OCMez-
CH2Ph2P)2PtMe,25 and Cp"‘Zrfli-OCH2Ph2P)RhMez.26 An interesting twist
on these types of compounds is the combination of magnetic centers to form
high spin-count complexes which may exhibit interesting pr0perties by virtue
of communication through the phenoxide bridge.
(1) PtnClz(NC7H5)2

The reaction of stoichiometric amounts of PtC12(NC7H5)2 with
Co(TMPP-0)2 does not lead to a discernible color change from the original
green color. This is not surprising given that the O-metallated complex cis-
Pt(Ph2PCHC-0Ph)2 is white,27 and the color of Co(TMPP-0)2 would be
expected to dominate. 1H and 31P NMR spectral studies of the resulting green
solid exhibits broadening properties typical of a paramagnetic species in
solution. The infi'ared spectrum exhibits modes attributable to the vPem

stretching frequency, but without vibrations characteristic of nitriles. The

presence of absorption associated with the [v(C=C) + v(CmO)] vibrations at

157 9 and 1595 cm'1 are in the range reported to be an indication of chelation
to a second metal center by cis-oriented phosphino-enolate ligands.10a FAB-

MS analysis reveals a base peak of m.’z = 1093 for the [Co(TMPP-O)2]+ ion,

with the detection of several higher mass peaks that have yet to be identified

65

(up to m/z = 1349, 7% of base). These data support the presence of an intact
Co(TMPP-O)2 moiety with the phenoxide groups acting as a bridge between
two metal centers, possibly forming ClthCoCI‘MPP-O)2.
(2) [Mnn(NCCH3)4] [BF 412

The reaction of [Mn(NCCH3)4][BF4]2 with two equivalents of Co(TMPP-
O)2 results in the eventual isolation of an emerald green product. 1H and 31P
NMR spectral studies of this solid indicate the presence of a paramagnetic
species in solution. The infrared spectrum exhibits an intense feature at

1098 cm'1 attributable to the VB-F stretching frequency. The absence of any

modes characteristic of bound nitriles supports complete ligand substitution

around the Mn(II) ion. Modes at 1578 and 1599 cm1 [v(C=C) + v(CmO)]
support chelation of a second metal center by the phenoxide groups of
Co(TMPP-0)2.10a The FAB-MS spectrum contains a base peak of m/z = 1093
for the [Co("l‘MPP-O)2]+ ion, with the detection of a peak at m/z = 576 that can
be formulated as [MnCo(TMPP-0H)2]2+, resulting from loss of a Co(TMPP-O)2
with protonation of the phenoxide groups. Such a mass ion would require
reduction of one of the metal centers by two electrons. This protonantion of
a bound phenoxide group has been previously demonstrated by reaction of
[Rhm(TMPP)(TMPP-O)][BF4]2 with HBF4. 19 These data support coordination
of two Co(TMPP-0)2 "ligands" to the Mn center, resulting in the
heterotrinuclear moiety, [Mn{Co(TMPP-O)2}2 2*. Both octahedral and

tetrahedral complexes are known for Mn(II). Although acetonitrile was not

66

detected in the IR. spectrum, we cannot rule out the possibility of axial

coordination to the manganese center.

F. Formation and Crystal Structure of [C0113(u3-OH)(u—0H)3{Gown-113—
TMPP-O) 2}3] [BF4]2 (6)

It has been noted that the compound Co(TMPP-O)2 is highly moisture-
sensitive.1n This has been illustrated by our isolation of [C03(u3-0H)(p2-
OH)3{C0(TMPP-O)2}2][BF4]2 (6) from the slow diffusion of diethyl ether or
hexanes into acetone solutions of Co(TMPP-O)2. This is presumed to be a
result of hydrolysis caused by residual amounts of water in the system. The
formation of partial cubanes such as 6 has been previously reported in the
chemistry of Re, Mo, and Cr in aqueous media.28 A similar core, [C03(p3-
0)(p.2-OH)3]4+, was reported by Christou and Ama to be present in difl'erent
compounds.29 The triply bridging hydroxide is not unprecedented in Co
chemistry, having been reported previously for the complex [(py)5003(p.3-
OI-I)(OAc)3(cat)].30 In the cases of the above Co(III) complexes, reactions were
carried out in aqueous media with the addition of H202, but the
paramagnetic Co(II) complex containing the 113-OH was prepared by the
addition of Et4N0H to Co(OAc)2'4H20 in ethanol. Coucouvanis and co-

workers found that substitution of 113-OMe for OH could be achieved by the

use of NaOMe in "strictly nonaqueous" solutions.30

67

(1) Crystal Structure

An ORTEP representation of 6 is shown in Fig. 11 and important bond
distances and angles are listed in Table 3. The structure of 6 contains a
partial cubane core of [C03(p3-OI-I)(u2-OH)3]2+, with each metal within the
core ligated to a Co(TMPP-O)2 moiety through the cis-phenoxides in a p-nz-
fashion. The triply bridging hydroxide, 0(3), is situated on a special position
of three-fold symmetry. The molecular structure of the Co(TMPP-0)2
fragment in 6 is essentially the same as that found in the dinuclear
compound C12C02(TMPP-O)2.1n The coordination sphere about Co(1) in 6 is
nearly equivalent to the octahedral Co environments in C12M(CoTMPP-O)2
(M = C0, Mn) with the largest difference occurring in the wider 0(32)-Co(1)-
0(26) and tighter P(1)-Co(1)-P(2) angles of 6 versus the dinuclear complexes
(81.3(2) and 108.35(9)° versus 79.5(2) for Co and 110.10(9)° for Mn). The C0
atoms within the partial cubane core lie within a distorted trigonal
bipyramidal coordination sphere. The atoms 0(1) and 0(32) can be
considered to be the axial ligands, with an 0(1)-Co(2)-0(32) angle of
175.6(2)°, where 0(26), 0(2) and 0(2)' occupy the equatorial positions. The
pz-OH oxygen atoms deviate fiom 90°, towards the p3-0H, with 0(2)-Co(2)-
0(1) angles of 78.9(2) and 79.2(2)°. The Co-O distances for the pz-OH groups
are 1.947(5) A and 1.961(5 A, with the p3-0H bonds being slightly longer, at
2.191(4) A. These values are in good agreement with previously reported

Co(pZ-OH) and Co(p3-0H) distances of 1.971(5)-2.03(1) A and 2.09(1)-2.13(1)

68

Table 3

/ /

Table 3. Selected Bond Distances (A) and Angles (deg) for [C0113013-

OH)(u-OH)3{CoH(p-n3-TMPP-0)2}3] [BF 4]2 (6).

 

 

 

 

Atom 1 Atom 2 6
Co(1) 0(32) 1.938(5)
Co(1) C(26) 1.958(5)
Co(1) P(1) 2.187(2)
Co(1) P(2) 2.194(2)
Co(1) C(46) 2.284(5)
Co(1) 0(56) 2.320(5)
Co(2) 0(2') 1.947 (5)
Co(2) 0(2) 1.961(5)
Co(2) C(26) 2.027(5)
Co(2) C(32) 2.111(5)
00(2) 0(1) 2.191(4)

Atom 1 Atom 2 Atom 3 6
0(32) Col) 0(26) 81.3(2)
0(26) Co(1) P(1) 166.6(2)
P(1) Co(1) P(2) 108.35(9)
P(1) Co(1) 0(56) 78.17(15)
0(46) Co(1) 0(56) 177.1(2)
0(2) Co(2) 0(2') 113.7(3)
0(26) Co(2) 0(32) 75.6 (2)
0(2) Co(2) 0(1') 79.2(2)
0(2) Co(2) 0(1) 7 8.9(2)

69

 

Figure 11. ORTEP representation of [C0113(l13-OI-I)(p-OI-I)3{Con(p-n3-TMPP-
O)2}3][BF4]2 (6) with 50% probability ellipsoids. Hydrogen atoms
and labels have been removed for clarity.

70

 

a.
.Jre 12
. (

 

Figure 12. ORTEP representation of the immediate coordination sphere for
each metal in [Cons(p3-OH)(p-OI-I)3{Con(p-n3-TMPP-O)2}3][BF4]2
(6) with 50% probablility ellipsoids. All other atoms have been
removed for clarity.

71

,. o‘...

fl ’1‘}:—

 

‘-‘. We;
"-- «L

1'7

II. '
u.‘\

 

 

'-
.. .
‘2 ~’\

 

-fii. *:
‘1 HI.
q‘

\.. 2.
\d L

'\

A respectivelyfiov31 This elongation of the Co(2)-0(1) distance relative to
Co(2)- 0(2) is indicative of u3-OH, as u3-O groups have nearly identical
distances to 112-OH groups. 29
A recent report by Wood and Palenik examines the potential for
calculating the oxidation state of Co complexes using equation 1, where rij is
Sij = exp[(Re - nil/bl (1)
the C-0 bond lengths of the Co center in question, b is a constant (usually
0.37), and Re is the constant under investigation by the authors.32 The
authors found an R0 value of 1.661 A can be used to calculate the oxidation
state of a C0 atom in complexes containing only Co-O bonds with no prior
assumptions. Using this value and the Co-O distances associated with the Co
atoms of the partial cubane core in 6, a bond valence sum (BVS) of 1.81 is
calculated. This is significantly lower than 2.00, possibly due to the distorted
geometry about the metal centers. Using R0 = 1.686 A, the experimental
value found for use with five-coordinate metal centers, a BVS = 1.94 A is
obtained. This is in good agreement with the presence of Co(II) according to
the experimental errors listed by Wood and Palenik. This calculation
supports our assignment of the central 0 in the core as a 113-OH group rather

than ”3.0, because the later would result in an over all charge of +1, and does

not match the number of [BF4]' ions found in the structure.

72

('1! Eli

T l
EM" :'

J~I

-n,-. ,
Ar~

v4 O‘
“M-\

~-4._
‘ yo.

l-‘-A\.

_ .
"a
v k.

D.
."\.‘

'3. C:

J

‘4

ll

Ll)

//

(2) EPR Spectroscopy

The EPR spectrum of 6 in a 1:1 acetone/toluene glass exhibits a strong,
broad signal with g1 = 4.46, g2 = 2.25, and g3 = 2.03. The lowest field signal is
typical for high spin six-coordinate systems, and the intensity is indicative of
a high spin count. Five-coordinate high spin cobalt complexes exhibit

changes in g|| and g J. with changes in the A-Co-B angle (tetrahedral

distortions).28 The distortions evident in the molecular structure of 6 may
give rise to the higher field pattern. An added complication is the second g
tensor for the six-coordinate systems which should also be seen near g = 2.

G. Crystal Structure of Pd(TMPP-O)2 (7)

An ORTEP representation of the molecular cation in 7 is displayed in
Figure 13, with selected bond distances and angles provided in Table 4. The
geometry about the Pd atom of 7 is square planar, consisting of a cis
arrangement defined by P(1), P(2) and the phenoxide oxygen atoms 0(22) and
0(52). Ring strain in 7 is evidenced by angles of O(22)-Pd(1)-0(52) = 81.4
(3)°, 0(52)-Pd(1)-P(2) = 846° (2), and P(2)-Pd(1)-P(1) = 109.4° (2). Axial
ether-oxygen atoms C(16) and O(46) are at distances of 2.887 and 3.025 A
which are much longer than the analogous interactions in
[PdCTMPP)2][BF4]2.15
4. Concluding Remarks

The combination of both hard and soft donor groups on tris(2,4,6-

trimethoxyphenyl)phosphine provides the ability to stabilize a metal atom in

73

Table 4. Selected bond distances (A) and bond angles (°) for Pd(TMPP-O)2.

Bond Distances

 

 

 

 

 

A B A-B (A) A B A-B (A)

Pdl P1 2.270 (4) P1 011 1.822 (13)

Pdl P2 2.251 (4) P1 021 1.832 (12)

Pdl 022 2.047 (7) P1 031 1.824 (13)

Pd1 052 2.047 (8) P2 041 1.81 (2)

022 022 1.363 (4) P2 051 1.78 (2)

052 052 1.363 (4) P2 061 1.87 (2)
Bond Angles

A B C A-B—C (°)

P2 Pdl P1 109.4 (2)

022 Pdl P1 84.9 (2)

052 Pdl P1 165.2 (2)

022 Pdl 052 81.2 (3)

011 P1 Pdl 118.1 (5)

021 P1 Pdl 97.6 (4)

011 P1 031 111.5(6)

011 P1 021 104.2 (6)

022 022 Pdl 121.1 (7)

052 052 Pdl 117.5 (8)

 

74

 

Figure

  

/.'.
C18 '4." C28

014

Figure 13. ORTEP representation of Pd(TMPP-O)2 (7) with 50% ellipsoids
viewed.

75

E 1‘30?“

v.‘
" l' .2
‘ ‘ur-‘fi

1"“
9

a variety of coordination geometries and oxidation states. Although
considered sterically bulky, the ligand is quite flexible as evidenced by the
fluxional and isomerization processes which have been observed for metal
complexes of TMPP.1 This flexibility has rendered it possible to access
different oxidation states of the rhodium center while maintaining the same
ligand set. Each of the complexes described in this study exhibit more than
one accessible redox state. The most rich redox and electrochemical/chemical
interconversions are found in the Rh series. Relationships between the
various rhodium-TMPP complexes isolated in this study are illustrated in
Figure 14. The ability of the TMPP ligand to adjust to the available
coordination sites and the electronic requirements of the metal center is
readily apparent when one examines the structural changes in going fi'om
[Rh1(n2-TMPP)2][BF4] to [RhH(n3—TMPP)2] [BF 4]2. As the metal center is
reduced, the hapticity of the phosphine ligand decreases from n3 to n2 in
response to the decreased need for electron density at the metal center.
Heteropolymetallic molecules are of interest due to the unusual
properties that can arise from electronic interactions between different metal
centers. The availability of cis-oriented phosphine phenoxide ligands
renders Co(TMPP-O)2 an excellent "ligand" in the preparation of novel bi-,
heterobi-, poly-, and heteropolymetallic complexes. The high spin d7
parmagnetic species such as Co(TMPP-O)2 produces paramagnetic

compounds nuclearities ranging from dinuclear to hexanuclear. Such

76

i
h

‘D

~1’}
:‘J-J‘J

synthons based on cis phenoxides should be generally useful for the

deliberate preparation of clusters.

77

.—.:£._- \\

..-v~.v-*—— . n N m — v
...-m ...vu A . V .-A - . 1
..........\.....-x/.... pp.......v-. 1—|| .—_ - - .....-::.A.-.-p)..-. ...v....-~

2....2:C..5E~ / .

- l . .- a . ‘1 ~...t.:§...:<.>-n20...»:
o. -\!noa-.Un.'
...ho-A '2

00083800 mmEfiAfl 05 mo mmmgfiwn 20800288005 .«A 0.235

Emioézbaénee.8 .emm=§ézb_=§_§§

       
     
 

:18 8x:
85:. 25
aim—=5-mmECEmECE:E-§ 0:908 0:208
20.50 0.8

NEE2082;825:2586 n NEE8820825253 8-82.85.22.52.”—

 

18:880.
m + m
mm m no .2582:
25.
.EE 83:.
nemmzomgum 5 18:53.2.
8.68.85.28.51... ...ee__.§2._.-.s__é V 88:28:55.8.

 

A emmOZ cN .5 0030

78

List of References

(a) Dunbar, K. R.; Haefner, S. C.; Pence, L. E. J. Am. Chem. Soc. 1989,
111, 5504. (b) Dunbar, K. R.; Haefner, S. C.; Bender, C. J. Am. Chem.
Soc. 1991, 113, 9540. (c) Dunbar, K. R.; Haefner, S. C.; Swepston, P.
N. J. Chem. Soc., Chem. Commun. 1991, 640. (d) Chen, S.-J.; Dunbar,
K. R. Inorg. Chem., 1991, 30, 2918. (e) Dunbar, K. R.; Haefner, S. C.
Organometallics 1992, 11, 0000. (f) Dulebohn, J. I.; Haefner, S. C.;
Bergland, K. A.; Dunbar, K. R. Chem. of Mat., 1992, 4, 506. (g)
Dunbar, K. R.; Quillevéré, A. Organometallics, 1993, 12, 618. (h)
Dunbar, K. R.; Matonic, J. H.; Saharan, V. Inorg. Chem., 1994, 33, 25.
(i) Dunbar, K. R.; Quillevéré, A.; Sun, J.#S. Inorg. Chem., 1994, 33,
2598. (j) Dunbar, K. R.; Sun, J .-S. J. Chem. Soc. Chem. Comm., 1994,
2387. (k) Dunbar, K. R.; Haefner, S. C.; Uzelmeier, C. E.; Howard, A.
Inorg. Chim. Acta., 1995, 240, 527 . (1) Quillevéré, A.; Uzelmeier, C.
E.; Sun, J .-J .; Dunbar, K. R. manuscript in preparation. (m) Haefner,
S. C.; Uzelmeier, C. E.; Dunbar, K. R. manuscript in preparation. (11)
Quillevéré, A. Ph. D. Dissertation, Michigan State University, 1992.
(0) Sun, J .-J . Ph. D. Dissertation, Michigan State University, 1994.

(a) Jones, R. A.; Lasch, J. G.; Norman, N. C.; Whittlesey, B. R.; Wright,
T. C. J. Am. Chem. Soc. 1983, 105, 6184. (b) Kreter, P. E.; Meek, D. W.
Inorg. Chem. 1983, 22, 319. (c) Carty, A. J. Adv. Chem. Ser. 1982, 196',
163. (d) Breen, M. J.; Geoffroy, G. L. Organometallics 1982, 1, 1437.
(e) Jones, R. A.; Stuart, A. L.; Atwood, J. L.; Hunter, W. E.; Rogers, R.
D. Organometallics 1982, 1, 1721. (i) Atwood, J. L.; Hunter, W. E.;
Jones, R. A.; Wright, T. C. Inorg. Chem. 1983, 22, 993. (g) Jones, R. A.;
Wright, T. G.; Atwood, J. L.; Hunter, W. E. Organometallics 1983, 2,
470.

see for example: (a) Lindner, E.; Dettinger, J. Z. Naturforsch. 1991,
46b, 432 and references therein. (b) Werner, H.; Stark, A.; Schultz,
M.; Wolf, J. Organometallics 1992, 11, 1126.

(a) Jeffrey, J. C.; Rauchfuss, T. B. Inorg. Chem. 1979, 18, 2658. (b)
Anderson, G. K.; Kumar, R. Inorg. Chem. 1984, 23, 4064. (c)
Braunstein, P.; Matt, D.; Dusausay, Y. Inorg. Chem. 1983, 22, 2043.
(d) Podlahova, J.; Kratochvil, B.; Langer, V. Inorg. Chem. 1981, 20,
2160. (e) Empsall, H. D.; Johnson, S.; Shaw, B. L. J. Chem. Soc.,
Dalton Trans. 1980, 302. (f) O'Flynn, K. H. P.; Mc Donald, W. S. Acta
Cryst. 1977, B33, 194.

79

10.

11.

12.

13.

14.

15.

(a) Popov, L. D.; Shevts, A. A.; Kogan, V. A. Koord. Khim. 1989, 15,
1299. (b) Bader, A.; Lindner, E. Coord. Chem. Rev. 1991, 108, 27.

Dunbar, K. R.; Haefner, S. C.; Uzelmeier, C. E. manuscript in
preparation.

(a) Ferguso, G. S..; Wolczanski, P.T.; Parkanyi, L.; Zonnevyle, M. C.
Organometallics, 1988, 7, 1967. (b) Baxter, S.M.; Wolczanski, P.T.;
Parkanyi, L.; Zonnevyle, M. C. Organometallics, 1990, .9, 2498.

Mills, D. K.; Hsiao, M. H.; Farmer, P. J.; Atnip, E. V.; Reibenspies, J.
H.; Darensbourg, M. Y. J. Am. Chem. Soc. 1991, 113, 1421.

(a) Andrieu, J.; Braunstein, P.; Tiripicchio, A.; Ugozzoli, F. Inorg.
Chem., 1996, 35, 5975. (b) Braunstein, P.; Kelley, D. G.; Tiripicchio,
A.; Ugozzoli, F. Inorg. Chem., 1993, 32, 4845. (c) Braunstein, P.;
Kelley, D. G.; Dusausoy, Y.; Bayeul, D.; Lanfranchi, M.; Tiripicchio, A.
Inorg. Chem., 1994, 32, 233. (d) Andrieu, J .; Braunstein, P.; Drillon,
M.; Dusausoy, Y.; Ingold, F.; Rabu, P.; Tiripicchio, A.; Ugozzoli, F.
Inorg. Chem., 1996, 35, 5986.

(a) Andrieu, J .; Braunstein, P.; Drillon, M.; Dusausoy, Y.; Ingold, F.;
Rabu, P.; Tiripicchio, A.; Ugozzoli, F., Inorg. Chem., 1996, 35, 5986. (b)
Klabunde, U.; Mulhaupt, R.; Herskovitz, T.; Janowicz, A. H.;
Calabrese, J.; Ittel, S. D., J. Polym. Sci., 1987, 25, 1989. (c) Klabunde,
U.; Ittel, S. D., J. Mol. Catal., 1987, 41, 123.

Uchiyana, T., Bull. Chem. Soc. Jap., 1981, 54, 181.

Hathaway, B. J.; Holah, D. G.; Underhill, A. E. J. Chem. Soc. 1962,
2444.

(a) Bino, A.; Cotton, F. A.; Fanwick, P. E. Inorg. Chem. 1979, 18, 3558.
(b) Cotton, F. A.; Frenz, B. A.; Deganello, G.; Shaver, A. J. Organomet.
Chem. 1973, 227.

SHELXTL v. 5.04, G. M. Sheldrick and Siemens Analytical X-Ray
Systems, Inc., 1997, 6300 Enterprise Lane, Madison WI. 53719.

Computing in Crystallography, Diamond, R.; Ramasesham, S.;
Venkatesan, K., Eds.; IUCr and the Indian Academy of Sciences,
Banglore, 1980; p.13.01.

80

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

MITHRIL: Integrated Direct Methods Computer Program, Gilmore, C.
J. J. Appl. Cryst. 1984, 17, 42.

DIRDIF: Direct Methods for Difference Structure, An Automatic
Procedure for Phase Extension; Refinement of Difference Structure
Factors: Beurskens, R. T. Technical Report, 1984.

Backes, G.; Reinen, D. Z. Anorg. Allg. Chem. 1975, 418, 217.
Haefner, S. C. Ph. D. Dissertation, Michigan State University, 1992.
Wada, M.; Higashizaki, S. J. Chem. Soc., Chem. Commun. 1984, 482.

Boeré, R. T.; Montgomery, C. D.; Payne, N. C.; Willis, C. J. Inorg.
Chem. 1985,24, 3680.19. (a) Dimitrou, K.; Folting, K.; Streib.;
Christou, G., J. Am. Chem. Soc., 1993, 115, 6432. (b) Ama, T.;
Miyazaki, J-i.; Hamada, K.; Okamoto, K-i.; Yonemura, T.; Kawaguchi,
H.; Yasui, T., Chem. Lett., 1995, 267.

Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry, 3rd Ed.
John Wiley & Sons: New York, 1972.

(a) Igau, A.; Gladysz, J. A. Polyhedron 1991, 10, 1903. (b) Ferandez, J.
M.; Gladysz, J. A. Organometallics 1989, 8, 207.

(a) Gorrel, I. B.; Parkin, G. Inorg. Chem. 1990, 29, 2452. (b) Thomas,
R. R.; Chebolu, V.; Sen. A. J. Am. Chem. Soc. 1986, 108, 4096. (c)
Crabtree, R. H.; Hlatky, G. G.; Holt, E. M. J. Am. Chem. Soc. 1983,
105, 7302. (d) Hitchcock, P. B.; Lappert, M. F.; Taylor, R. G. J. Chem.
Soc., Chem. Commun. 1984, 1082. (e) Reedijk, J. Comments Inorg.
Chem. 1982, 6, 379 and references therein.

Baxter, S. M.; Wolczanski, P. T. Organometallics 1990, .9, 2498.

Ferguso, G. S.; Wolczanski, P. T; Parkanyi, L.; Zonnevylle, M. C.
Organometallics, 1988, 7, 1967 .

Carlin, R. L.; Magnetochemistry, Springer: New York, 1986.

(a) Richens, D.T.; Guille-Photin, C. J. Chem. Soc., Dalton Trans,
1990, 407. (b) Alberto, R.; Egli, A.; Abram, U.; Hegetschweiler, K.;
Gramlich, V.; Schubiger, P. A. J. Chem. Soc., Dalton Trans, 1994,

81

29.

30.

31.

32.

33.

2815. (c) Speiccia, L.; Marty, W .; Giovanoli, R. Inorg. Chem., 1988,
27, 2660.

(a) Dimitrou, K.; F olting, K.; Streib.; Christou, G., J. Am. Chem. Soc.,
1993, 115, 6432. (b) Ama, T.; Miyazaki, J-i.; Hamada, K.; Okamoto,
K-i.; Yonemura, T.; Kawaguchi, H.; Yasui, T., Chem. Lett., 1995, 267.

Reynolds, R.A.; Yu, W.O.; Dunham, W.R.; Coucouvanis, D., Inorg.
Chem., 1996, 35, 2721.

Kitajima, N.; Hikichi, S.; Tanaka, M.; Moro-oka, Y., J. Am. Chem. Soc.,
1993, 115, 5496.

Wood, R. M.; Palenik, G. J. Inorg. Chem., 1998, 37, 4149.
Banci, L.; Bencini, A.; Benelli, C.; Gatteschi, D.; Zanchini, C. In
Structure and Bonding, Vol. 52, Eds. Clarke, M. J .; Goodenough, J. B.;

Hemmerich, P.; Ibers, J. P.; Jergensen, C. K.; Neilands, J. B.; Reinen,
S.; Weiss, R; Williams, R. J. P. Springer-Verlag: New York, 1962, 37.

82

CHAPTER III

SYNTHESIS AND REACTIVITY OF [M (o—P2)2] [BF4]x

(M = Fe, Co, Ni, Pd, Pt, x = 2; M = Rh, x = 1)

83

1. lntrod

‘

33m

1“?
p...

on

p.
5

Twof

:w

2'?
.s

m

4.
<4“:

5.!“

p12
as

0
a:
'K
I‘Y'N‘
3'.”

a.

33131

1. Introduction

The incorporation of transition metal ions into a conjugated polymer
backbone to form coordination polymers is the subject of considerable interest
in View of the possible electrical and magnetic properties of such chains. One
approach to covalent inorganic/organic materials involves the assemblies of
transition metals into an organic array or polymer through direct o/n
bonding. It has been proposed that the introduction of metal ions into a
conjugated chain could lead to partially-filled bands and possibly metallic
conductivity.1 In terms of paramagnetic systems, several coordination
polymers with magnetic metal ions (Cu2+, Mn3+) bridged by organic ligands
have been reported by Kahn and others to exhibit ferrimagnetic interactions
in the solid state.2

In spite of the considerable activity in the fields, little emphasis has
been placed on the use of open-shell ligands to bridge metal ions which could
provide the linking bidentate or tetradentate functionality with a
simultaneous contribution to the electronic and/or magnetic properties of the
whole composite chain. For example one may anticipate ferrimagnetic
behavior in composite chains formed of both metal (S > 1/2) and organic (S =
1/2) spins.

In this vein, we are investigating the reactivity of multidentate ligands
bearing the extra redox functionality of a TTF core. The use of phosphorus as

the central atom in connecting TTF molecules is particularly intriguing, not

84

:nazenzlal
TL. ’ .;
.LJT IllL'L
. . .. _;
:Dcucu

' M

has ,
-T‘

ma‘cnI

Fl:

In

n-‘J
.. q

only for engendering new radical TTF-TTF n-interactions, but for their

potential as ligands in new mixed-valence mono- and polymetallic species.
The mixing of dn-pn metal-TTF frontier orbitals in such "hybrid" systems is
expected to lead to unique electronic and/or magnetic behavior that is quite
different from the "all-organic" charge transfer materials.

Fourmigué et al. first demonstrated that phosphorus(III) compounds of
the types in Figure 7 could readily be synthesized fiom the
tetrathiafulvalenyl lithium derivatives by preparing ortho-(CH3)2(PPh2)2TTF
(o-P2, l).3 While o-P2 will not form extended structures, it can act as an
excellent ligand for forming mononuclear complexes which may be viewed as
models for the extended structures anticipated for P4 (2). Precedence for
homoleptic compounds containing two o-P2 ligands exists in the form of
[Rh(o-P2)2] [BF 4], prepared from the reaction of 4 equivalents of o-P2 (1) with
the dinuclear complex [Rh2(NCCH3)1o][BF4]4.4 This chapter describes the
preparation and characterization of the homoleptic series [M(o-P2)2][BF4]2 (M
= Ni, Co, Pd, Pt, Fe) as well as the chemical oxidation and metathesis with
[Li][TCNQ] 0f [Rh(O-P2)2l[BF4]-

2. Experimental
A. Synthesis

Starting Materials and Reaction Procedures. Ortho-

[P(C6H5)2]2(CH3)2TTF (o-P2),3 [M(NCCH3)X][BF4]2 (M = Ni, Co, Fe,5 Pd,6 x = 6;

M = Pt,7 x = 4), M(CF3SOa)2 (M = Ni, Fe)8 and [Rh(o-P2)2][BF4]4 and

85

 

Figure 15. ORTEP representation of [Rh(o-P2)2][BF4] viewed from the (a)
top and (b) side with 50% probability ellpsoids.

86

[Li][TCNQ]9 were prepared according to published procedures. NOBF4 was
purchased from Aldrich Chemical Co. and was used as received. Acetonitrile,
acetone, and CH2C12 were distilled over 3 A molecular sieves. Diethyl ether
and toluene were distilled over sodium-potassium/benzophenone. Unless
otherwise specified, all reactions were carried out under an argon atmosphere
by using standard Schlenk-line techniques.

(1) Preparation of [M(o-P2)2][BF4]2.

(i) [Ni(o-P2)2] [BF4]2 (8). In separate flasks, [Ni(MeCN)5.5][BF4]2 (0.040 g,
0.080 mmol) and o-P2 (1) (0.306 g, 0.510 mmol) were dissolved in 5 mL of
acetonitrile and 15 mL of CHzClz respectively. A 5 mL (0.170 mmol) aliquot
of the orange phosphine solution was added via syringe to the blue nickel
solution, prodwhich produced an immediate color change to brown. After
stirring for 12 h, the solution was concentrated to a volume of 5 mL, treated
with 20 mL of EtzO to produce a red-brown solid, and filtered in air. The
solid was then washed with capious amounts of EtzO, and dried in vacuo;
yield 0.098 g (85%). Single crystals were grown by slow diffusion of toluene
into an CHzClz solution of 8. 1H NMR (CDscN) 5 ppm: -CH3, 1.82 (s); Ph-H,
7.16 (m), 7.35 (m), 7.68 (m). 13C NMR (CDsCN) 8 ppm: 15.2 (-CH3), 107.2
(inner C=C), 119.2 (inner C=C), 124.3 (outer C=C), 125.8 (outer C=C), 132.6
(Ph), 136.2 (Ph), 136.6 (Ph), 150.0. 31P{1I-I} NMR (CDsCN) 8 ppm: 42.1. IR
(Nujol, cm'l): 1058 (br, VB-F), 691 (m, won), 506 (s, vc=c). C.V. (0.2 M

CHzClijBABF4, Pt electrode vs Ag/AgCl): Em) = -0.27 V, E1/2(ox)1 = +0.68 V,

87

E1/2(ox)2 = +1.08 V. UV/Visible (CH3CN) kmax, nm (2, M-lcm-l); 510 (3.5x103),
325 (2.1x104), 266 (3.0x104). FAB-MS (m/z): 630 (l\/IZ+/2), 1260 (NY)

(ii) [Co(o-P2)2] [BF4]2 (9). In separate flasks, 0.040 g (0.084 mmol) of
[Co(NCCH3)s][BF4]2) was dissolved in 5 mL of acetonitrile, and 0.103 g (0.171
mmol) of o-P2 (1) was dissolved in 5 mL of CH2C12. The cobalt solution was
added to the TTF solution, which effected a color change to dark brown, and
the reaction solution was stirred for 12 h. The solution volume was reduced
by ~50%, treated with 20 mL of toluene and reduced in volume to afi‘ord a
brown solid that was isolated by filtration in air. The remaining solid was
washed with 3 x 10 mL of toluene to remove unreacted o-P2, and 4 x 5 mL of
EtzO until the washings became colorless. Finally, the solid was dried in
vacuo; yield 0.098 g (83%). Anal. Calcd for 8, CoP4S3C64H52B2F3: C, 53.87; H,
3.86. Found: C, 54.65; H, 3.90. 1H NMR (CD3CN) 8 ppm: broad and
unresolved. 31P{1H} NMR (CD3CN) 6 ppm: not observed. IR (Nujol, cm‘l):
1058 (br, VB-F), 692 (m,v»c-H), 534 (s, vc=c). C.V. (0.1 M CH3CN/TBABF4, Pt
electrode vs Ag/AgCl): E(p,c)1 = -0.91 V, E(p,c)2 = -1.19 V, E1/2(ox)1 = +0.63 V,
E1/2(ox)2 = +1.07 V. UV/Visible (CHsCN) kmax, nm (e, M'lcm'l): 506 (5.0x103),
326 sh(1.5x104), 291 (1.8x104), 261 (2.3x104). FAB-MS (m/z): 629 (Mz+/2),

1259 (M+). EPR (50:50 CH3CN/toluene, 107 K) g l = 2.29, g" = 2.04 (IAI =
70.7 G); (solid, 4 K) g = 4.08, gi = 2.22, g" = 2.05. Magnetic moment: peer =

4.62 up, (320 K, S = 3/2), 2.51 MB (5 K, S' = 1/2).

88

(iii) [PdH(O-P2)2] [BF 4]2 (10). A 5 mL aliquot (0.172 mmol) of a 15 mL
stock solution of o-P2 (1) (0.309 g, 0.515 mmol total) in CHzClz was added to a
solution of [Pd(NCCH3)6][BF4]2 (0.042 g, 0.080 mmol) dissolved in 5 mL of
acetonitrile, causing an immediate color change from orange to brown. The
solution was stirred overnight, concentrated to ~5 mL, and treated with 20
mL of EtzO to afford a brown precipitate. The solid was isolated by filtering
in air, was washed with copious amounts of Et20, and dried under reduced
pressure. 1H NMR (CD3CN) 5 ppm: -CH3, 1.83 (s); Ph-H, 7.25 (m), 7.60 (m).
31P(1H} NMR (CD3CN) 5 ppm: 43.9. IR (Nujol, cm'l): 1057 (br, vB-F), 690 (m,
won), 519 (s, vc=c). C.V. (0.2 M CH2C12/TBAPF6, Pt electrode vs Ag/AgCl):
E1/2(red) = -0.31 V, E1/2(ox)1 = +0.64 V, E1/2(ox)2 = +1.16 V. UV/Visible
(CH3CN) Am”, nm (e, M'lcm'l): 421 (5.7x103), 332 (8.0x104), 295 sh(5.5x104),
265 (3.3x104). FAB-MS (m/z): 653 (MW/2), 1306 (M+).

(iv) [Pt(o-P2)2] [BF4]2 (11). [Pt(NCCH3)4l[BF4]2 (0.046 g, 0.075 mmol) and
o-P2 (0.109 g, 0.182 mmol) were dissolved in 10 mL of CH2C12, to give a red-
orange solution, which was stirred for 12 h. The solution was then reduced to
5 mL, and 20 mL of EtzO was added to precipitate a red-orange solid. The
mixture was filtered in air, washed with 15 mL diethyl ether, and dried in
vacuo; yield 0.078 g (67%). Single crystals were grown by slow diffusion of
EtzO into a CH2C12 solution of 11 following treatment with, and removal of,
toluene. 1H NMR (CD3CN) 6 ppm: -CH3, 1.82 (s); Ph-H, 7.38 (m), 7.56 (m).

31P{1H} NMR (CDaCN) 6 ppm: 35.8 (2th-1> = 2357 Hz). IR (Nujol, cm'l): 1059

89

(br, VB-F), 690 (m, won), 525 (s, vc=c). C.V. (0.2 M CHzCMTBAPFs, Pt
electrode vs Ag/AgCl): E1/2(red) = -0.45 V, E1/2(ox)1 = +0.70 V, E1/2(ox)2 = +1.19
V. UV/Visible (CH3CN) kmax, nm (e, M'lcm'l): 458 (1.7x103), 315 (2.5x104),
248 (2.9x104). FAB-MS (m/z): 698 (MWZ), 1296 (Mt).

(v) [Fe(o-P2)2] [BF4]2 (12). A quantity of [Fe(NCCH3)6][BF4]4 (0.041 g, 0.086
mmol) was loaded into a Schlenk flask and dissolved in 5 mL of acetonitrile.
A stock solution of 0.309 g (0.515 mmol) of o-P2 (1) dissolved in 15 mL of
CH2C12 was prepared. A 5 mL (0.172 mmol) aliquot of the phosphine stock
solution was added to the metal complex and the solution was stirred for 12
h. The solution was concentrated to ~5 mL, treated with 20 mL of EtzO, and
the solution was decanted from the red solid. The solid was washed with 10
mL portions of EtzO until the washings were clear, and dried under reduced
pressure; yield 0.041 g (34%). 1H NMR (CD3CN) 5 ppm: Ph-H, 7.54 (m), 7 .68
(m). 31P{1I-I} NMR (CD3CN) 5 ppm: 56.1, 75.5. 19F NMR (CD3CN) 5 ppm:
-503.0, -148.6. IR (Nujol, cm'l): 1063 (br, vB-F), 699 (m, v=C-H), 519 (s, vcac).
FAB-MS (m/z): 1256 (NP), 1275 ([M+F]+).

(2) Reactions of M(CFsSOa)2 with o-P2 (1).

(i) Preparation of [Ni(o—P2)2] [CF3S03]2 (13). In separate flasks,
Ni(CF3803)2 (0.040 g, 0.112 mmol) and o-P2 (1) (0.306 g, 0.510 mmol) were
dissolved in 5 mL of acetonitrile and 15 mL of CH2C12 respectively. A 5 mL
aliquot (0.17 0 mmol) of the orange phosphine solution was added via syringe

to the blue nickel solution, producing an immediate color change to brown.

90

After stirring for 12 h, the solution was concentrated to a volume of 5 mL,
treated with 45 mL of EtzO, and cooled in an ice bath to precipitate a red-
brown solid. The liquid was decanted, and the solid was washed 3 times with
5 mL amounts of EtzO, and dried under reduced pressure; yield 0.098 g
(85%). 1H NMR (CD3CN) 5 ppm: -CH3, 1.82 (s, 12H); Ph-H, 7.16 (m, 16H),
7.32 (m, 16H), 7.35 (br, 8H). 31P{1H} NMR (CD3CN) 5 ppm: 46.6. FAB-MS
(m/z): 629 M2+/2), 1260 (Mt), 1409 ([M+OTf]+).
(ii) Reaction of Fe(CFaSOa)2 with o-P2 (l). Fe(CF3S03)2 (0.056 g, 0.158
mmol) was dissolved in 5 mL of acetonitrile, and o-P2 (1) (0.2032 g, 0.339
mmol) was dissolved in 11 mL of CH2C12. A 5.5 mL (0.169 mmol) aliquot of
the phosphine stock solution was added to the metal complex and the
solution was stirred several days. The solution was treated with 15 mL of
toluene and concentrated under vacuum resulting in the formation of orange
needles. Analysis of one such crystal by single crystal X-ray diffraction
revealed its identity to be unbound o-P2 (1). 31P{1H} NMR (CDzClz) 5 ppm:
-18.1.
(3) Oxidation of [Rh1(o-P2)2][BF4] with NOBF4: Preparation of [Rh1(o-
P2)2] [BF 4]: (14).

Quantities of [RhI(o-P2)2][BF4] (0.111 g 0.080 mmol) and NOBF4 (0.028
g, 0.240 mmol) were loaded into a 150 mL pear-shaped Schlenk flask, covered
in aluminum foil to avoid light, cooled in an ice bath, and dissolved in 10 mL

of CHzClz. The foil and cold bath were removed, the flask was briefly exposed

91

to a vacuum, and the dark green solution was stirred for 12 h. The solution
volume was reduced to dryness under vacuum and the resulting residue
redissolved in 5 mL CH2C12 and treated with 20 mL of EtzO to afford a green
precipitate. The solid was isolated by filtration through Celite, extraction
with additional CH2C12, concentration of the resulting solution to ~5 mL, and
treatment with 20 mL of EtzO to re-precipitate the product. The liquid was
decanted, the solid was washed 4 times with 7 mL of EtzO, and dried in
vacuo; yield 0.114 g (86% for [Rh1(o-P2)2][BF4]3). EPR (50:50
CH3CN/toluene, 95 K) g = 2.02.

(4) Reaction of [Rh1(o-P2)2][BF4] with [Li] [TCNQ].

An acetone solution of [Li][TCNQ] (0.019 g, 0.090 mmol, 40 mL) was
filtered through a Schlenked fiit to remove undissolved solid, and added to a
CH2C12 solution of [Rh(o-P2)2][BF4] (0.032 g, 0.022 mmol, 10 mL). The
reaction mixture was stirred with slight warming for 3 h (to ensure
dissolution of the [Li] [TCNQ]), during which time a fine green precipitate
formed. The mixture was filtered, the solid washed 3 times with 5 mL of
acetone, and finally dried in vacuo; yield 0.030 g (91%). IR (Nujol, cm'l): 2178
(m, vc+N), 2153 (m, mm), 692 (8, won), 521 (s, vc=C).

B. X-ray Crystallography
The structures of the compounds [Ni(o-P2)2][BF4]2 (8) and [Pt(o-

P2)2][BF2]2 (11) were determined by application of general procedures that

92

Table 5. Summary of crystallographic data for [Ni(o-P2)2][BF4]2-2C7Hs
(8-2C7Hg) and [Pt(o-P2)2][BF4]2-2C7H3 (ll-ZC7Hg).

 

 

8-ZC7H8 11-2C7H8
Formula N iSsP4F 8098B2H52 Pt53P4F8C9oBzH52
Formula weight 1842.1 1882.39
Space group C2/m C2/m
a, A 24.677(2) 24.617(2)
b, A 14.322003) 14.3476(13)
c, A 15.446503) 15.529203)
01, deg 90 90
0, deg 127.169(10) 127.072(10)
7, deg 90 90
V, A3 4350.2(6) 4376.2(6)
z 2 2
dcalc, g/cm3 1.406 1.429
9. cm-l 0.554 1.928
Temperature, °C 293 i 2 293 d: 2
R18 0.075 0.060
szb 0.195 0.162
quality-of-fitc 1.142 0.675

 

aR=2l IaR=zI lFol - chl I/ZIFOI. bWRzzlz[W(F02'Fc2)2l/Z[W(F02)2l1/2

c quality-of-fit = EV“ l F0 I ' I Fc l )2/(Nob3'Nparameter>l1/2

93

 

have b
Lima
51:311.
:Z'UCUI
refiner:
1’1) [Ni
(i) I
3'7.- "‘0

"vi“

'Wv ha

mil

12"..
51

have been fully described elsewhere.10 Crystal parameters and basic
information pertaining to data collection and structure refinement are
summarized in Table 5. Structure was solved using the SHELXL 93
structure solution program and refined by full-matrix least-squares
refinement on F2.11v12

(1) [Ni(o-P2)2] [BF 4]2 ' 2C7H8 (8 ° 2C7H8)

(i) Data Collection and Reduction. Single crystals of [Ni(o-
P2)2][BF4]2°2C7H8 (8-2C7H3) were grown by slow diffusion of Et20 into an
CH2C12 solution of 8. A brown platelet of dimensions 0.15 x 0.11 x 0.027
mm3 was mounted on the tip of a glass fiber and secured with epoxy. Data
for 8 were collected on a Stoe IPDS diffi'actometer ' equipped with
monochromated MoKa radiation at 293+2 °C in a 9 range of 1.9 to 260°.
Initial data indicated that the crystal belonged to a monoclinic system;
subsequent solution and successful refinement of the structure was carried
out in the C2/m space group. Of the 21449 reflections that were collected,
4411 were unique, and 2767 data were observed with I > 2.000(I). The data
were corrected for Lorentz polarization effects, and an empirical absorption
correction based on azimuthal w-scans near x = 90° was applied which
resulted in transmission factors ranging from 0.822 to 0.971.

(ii) Structure Solution and Refinement. The structure was solved by
direct methods and refined by full-matrix least squares refinement. All non-

hydrogen atoms, except those associated with the solvent, were refined

94

anisotropically. Hydrogen atoms were not included in refinement. Atoms
C(51) through C(57) were found to define a toluene molecule disordered over

two positions with a center of inversion relating the two solvents. The

molecule was refined with restraints keeping C(52)~~C(57) and C(56)---C(57)
equidistant. Occupancies were refined such that the independent toluene
fi'agments possessed an occupancy of 0.5, resulting in a sum of 1.0. A second
toluene molecule defined by atoms C(21) through C(27) was located and

refined with restraints on the CC distances within the ring, as well as on the

C---C distances between alternating C atoms of the ring (e.g. C(24)-C(22)).
Additional restraints were added to keep C(22)-C(27) and C(26)-C(27)
distances equal. Hydrogen atoms were not included with the solvent
molecules.

The final refinement was based on 5000 reflections that were used to
fit 261 parameters to give R1 = 0.0752 and wR2 = 0.1949. The goodness-of-fit
index was 1.142, and the maximum shift in the final difference map was
0.030 A associated with C(57) After the last least squares cycle, the mean
shift/esd was 0.043 and the highest peak in the difference Fourier map was
2.15 e°lA3 which is associated with C(22). This peak is at the center of the
solvent ring defined by C(21)-C(26), and indicates additional disorder

associated with the ring that must be modeled.

95

(2) [Pt(o-P2)2] [BF4]2° 2C7Hs (ll ' 2C7H8)

(i) Data Collection and Reduction. Single crystals of [Pt(o-P2)2][BF4]2°
2C7Ha (11'2C7H3) were grown by slow diffusion of diethyl ether into an
acetonitrile solution of the compound. A red-orange platelet of dimensions
0.06 x 0.06 x 0.03 mm3 was mounted on the tip of a glass fiber and secured
with epoxy. Data for 11 were collected on a Stoe IPDS diffractometer
equipped with monochromated MoKa radiation at 293+2 °C in a 0 range of
1.70 to 259°. Initial data indicated that the crystal belonged to a monoclinic
system; subsequent solution and successful refinement of the structure was
carried out in the CZ/m space group. Of the 21325 reflections that were
collected, 4404 were unique, and 2426 data were observed with I > 2.000(1).
The data were corrected for Lorentz polarization effects, and an empirical
absorption correction based on azimuthal w-scans near x = 90° was applied
which resulted in transmission factors ranging from 0.7870 to 0.9175.

(ii) Structure Solution and Refinement. The structure was solved by
direct methods and refined by full-matrix least squares refinement. All non-
hydrogen atoms, except those associated with the solvent, were refined
anisotropically. Hydrogen atoms were not included in refinement. Atoms
C(31) through C(35) were found to define a toluene molecule disordered over

two positions with a center of invresion relating the two solvents. The

molecule was refined with restraints keeping C(32)---C(31) and C(34)---C(31)

equidistant. Occupancies were refined such that the independent toluene

96

fragments are at an occupancy of 0.5, resulting in a sum of 1.0. A second
toluene molecule defined by atoms C(51) through C(57) was located and

refined with restraints on the C-C distances within the ring, as well as on the

C---C distances between alternating C atoms of the ring (e.g. C(54)--~C(52)).
Additional restraints were added to keep C(52)-C(57) and C(56)-C(57)
distances equal. Hydrogen atoms were not included with the solvent
molecules. The final refinement was based on 5000 reflections that were
used to fit 266 parameters to give R1 = 0.0603 and wR2 = 0.1616. The
goodness-of-fit index was 0.675, and the maximum shift in the final
difference map was 0.148 A associated with C(56). After the last least
squares cycle, the mean shift/esd was 0.224 and the highest peak in the
difference Fourier map was 1.79 e°/A3 which is associated with C(58). This
peak is at the center of the solvent ring defined by C(51)-C(56), with C(58)
part of an unresolved solvent molecule, indicating further modeling is
needed.
3. Results and Discussion

The homoleptic complexes [M(o-P2)2][BF4]2 (M = Ni (8), Co (9), Pd (10),
Pt (11), Fe (12)) can be prepared by reacting the appropriate acentonitrile
complex, [M(NCCH3)X][BF4]2 (x = 4, 6), with 2 equivalents of the phosphine
ligand, o-P2 (1). The complexes have been characterized by NMR, infrared,
and electronic absorbance spectroscopies, as well as FAB-MS. EPR and

magnetic susceptibility studies of the paramagnetic CoII complex have also

97

\1 0
cv- |.

\ 1
N~Pkl

been conducted, indicating a change from high spin in solution to low spin in
the solid state. 19F NMR spectroscopy and FAB-MS support the tendency for
12 to coordinate F-, to yield [Fe(o-P)2F]+ species. Compounds 8, 10, and 11
display redox chemistry which involve both the divalent metal center and the
TTF groups.

The structures of 8 and 11 have been determined by single crystal X-
ray difiraction methods. Crystal parameters and basic information
pertaining to data collection and structure refinement are summarized in
Table 5. ORTEP representations of [Ni(o-P2)2][BF4]2 (8) and [Pt(o-P2)2][BF4]2
(11) are depicted in Figures 16 and 18. Selected bond distances and angles
for each structure are listed in Table 6.

Oxidation of [Rh(o-P2)2][BF4] with 3 equivalents of NOBF4 results in
oxidation of the TTF units and formation of [Rh(o-P2)2][BF4]3 (13). The
organic radical, 13, has been studied by EPR spectroscopy. Preliminary

infrared anaylsis suggest that the counterion in [Rh(o-P2)2][BF4] can be

replaced with another organic radical, [TCNQ]', by metathesis with
[Li][TCNQ]-
A. Preparation of [M(o-P2)2][BF4]2 (M = Ni, Co, Pd, Pt, Fe)

The reaction of [M(NCCH3)x][BF4]2 (M = Ni, Co, Pd, Fe, x = 6; M = Pt, x
= 4) with 2 equivalents of o-P2 (1) result in the formation of the appropriate
homoleptic complex, [M(o-P)2][BF4]2 (8-12). The reactions were all performed

with the metal complex dissolved in acetonitrile and the ligand in CHzClz,

98

with the exception of M = Pt, where both reactants were dissolved in CH2C12.
The procedures are similar to that used in the synthesis of [Rh(o-P2)2][BF4],
but mononuclear, rather than dinuclear, solvated cations were used as
starting materials. The displacement of acetonitrile for phosphine is rapid,
as evidenced by the immediate color changes observed for M = Ni, Co, and
Pd. The products range in color from red to brown, with the TTF
chromophore dominating the perceived color. These colors indicate that the
reactions occur with retention of the metal’s oxidation state, as green is
indicative of oxidized TTF.

The products are all air stable and relatively insensitive to light in the
solid state, but 10 and 11 are prone to decomposition if exposed to light for
extended periods of time in solution (> 3 days). Such photochemical
sensitivity has been well documented for other complexes of both metals.13
The decomposition of these compounds is accelerated in the presence of
chlorinated solvents, most likely owing to the instability of the phosphine
ligand in this medium.14 The complexes are soluble in nitriles, chlorinated
solvents, and acetone.

B. Spectrosopic Characterization of [M(o-P2)2][BF4]2 ( M = Ni, Co,
Pd, Pt, Fe)

(1) NMR Spectrosc0pic Studies of [M(o-P2)2][BF4]2 (8-12)

(i) 1H and 31P{1H} NMR. The 1H NMR spectra of 8 and 10-11 in CDsCN

exhibit a series of multiplets in the region 5 = 7.2 - 7.7 ppm due to the phenyl

99

protons, and a singlet at 5 = ~1.8 ppm due to the methyl protons. The 31P{1H}
NMR spectra of 8 and 10 each contain a single resonance at 5 = 42.1 and 43.9

ppm respectively, while 11 shows a singlet with platinum satellites at 35.8
ppm (JPt.P = 2357 Hz). The downfield shift of the signal from the free
phosphine at -18.8 ppm is a result of 5-coordinate ring stabilization,3 and
indicates that the phosphine chelates the metal whereas the th-p value is
indicative of trans-disposed chlorides.15 Compound 9 exhibits no resonances
in its 31P{1H} NMR spectrum, and only broad signals in the 1H spectrum,
indicating a paramagnetic complex.

The presence of an NMR signal for [Fe(o-P2)2][BF4]2 (12) indicates a
diamagnetic product, with the metal behaving as a low-spin, d6, FeII center.
A freshly isolated sample of 12 contains a singlet in its 31P{1H} NMR
spectrum at 56.1 ppm. The downfield shift is in the range expected for
coordinated o-P2 and supports bound phosphine atoms, while the absence of
additional signals indicates one phosphorus environment. Shortly after
recovery of the product a second signal can be observed at 5 = 76.2 ppm.
Eventually the upfield peak is completely replaced by the downfield singlet,
which indicates that it is a separate species that forms over time. The signal
is at considerably lower fields than the region expected for coordinated o-P2,
a fact that may indicate the presence of coordinated fluoride.16 The 1H NMR

spectrum of 12, while containing the expected phenyl resonances between 5 =

7.5 and 7 .7 ppm, exhibits no observable methyl-proton resonance. This

100

discrepancy in the 1H NMR spectrum of 12 remains unresolved and is cause
for further investigation.

(ii) Variable Temperature 19F and 31P{1H} NMR of [Fe(o-P2)2] [BF4]2
(12). The 19F NMR spectrum contains singlets appearing at 5 = -148.6 and

-503.0 ppm. The resonance at -148 ppm falls in the range for uncoordinated

[BF4]', but some M-BF4 complexes exhibit 19F NMR signals near the position
of the uncoordinated anion due to their free F atoms.16d The singlet at -503.0

ppm is indicative of bound fluoride, and falls into the range for both

coordinated [F]' and [BF4]'.1‘5b"‘3 31P{1H} NMR spectra measured at
temperatures as low as -40°C revealed no splitting due to the coordinated

fluoride, possibly due to fast anion exchange if the fluoride interaction is a

result of coordinated [BF4]'. 161’ Additional variable temperature studies of
the 31P{1H} NMR spectra of 12 reveal that the coordinated flouride can be
affected by temperature. The room temperature 31P{1H} NMR spectrum of a
representative sample of 12, taken shortly after isolation, displayed a ratio
of roughly 2.311 for the downfieldzupfield shift integrations. Upon cooling to
-40°C, this ratio shifts dramatically in favor of the F-coordinated peak,
leaving a ratio of 3:1. At higher temperatures the opposite behavior was
found, with a ratio of 1.4:1 observed at 60°C, indicating that the coordinated
group can be forced outersphere with increased temperature. This
"fluxionality" may indicate the bound group is [BF4]', as coordinated [F]'

would be less likely to dissociate with mild heating. These changes are

101

mirrored in the 19F spectrum, where the resonance at -148 ppm was found to

dominate at higher temperatures, supporting the partial loss of bound [BF 4]‘.
(2) Infrared and Electronic Absorbance Spectroscopy
The infrared spectra of 8-12 display bands at ca. 690 and 520 cm'1

attributable to out-of-plane bends for the phenyl rings of o-P2. Strong

features at ca. 1058 cm:1 are due to the BF stretch of the [BF4]' groups. The
absence of peaks at higher wavenumbers (ca. 2300 cm'l) supports complete
displacement of acetonitrile, but is not conclusive due to the fact that the
frequency and intensity of the CsN stretching vibration can be quite variable,
and in some cases be absent when coordinated nitrile is present.17 Electronic
spectra of 8-11 recorded in acetonitrile exhibit transitions attributable to the
phenyl groups between 248 and 266 nm, and the TTF group at 291-332 and
421-510 nm.
(3) FAB-MS of [M(o-P2)2][BF4]2 ( M = Ni, Co, Pd, Pt, Fe) (8-12)

Fast Atom Bombardment Mass Spectrometry (FAB-MS) of 8-12 vary
with the identity of the metal center. The FAB-MS spectra of compounds 8-
11 contain peaks associated with the appropriate mono-cationic complex,
[M(o-P2)2]+ and the di-cationic species, [M(o-P2)2]2+. Retention of the [BF4]'
moiety is seen in 10 and 11 through the presence of [M(o-P2)2][BF4]+ as a
medium intensity peak.18 Compounds 812 all produce peaks which
represent oxygen addition to the intact molecule, [M(o-P2)2+O]+. Similarly,

the spectra of 9 and 12 display peaks representing [o-P2]+ (m/z = 600), [o-

102

P2+O]+ (sz = 616), and [o-P2+20]+ (m/z = 632). This oxygen addition has
been seen previously in the isolation of dioxidized P4 (trans-P402).19 The
most intense peak in the FAB-MS spectrum of [Fe(o-P2)2] [BF 4]2 (12) is sz =
1275, which is 19 a.u. greater than the molecular cation and which fits well
with the assignment [Fe(o-P2)2+F]+. The same [M(o-P2)2+F]+ ion was
observed in the FAB-MS spectrum of [Ni(o-P2)2][BF4]2 (8) and [Co(o-
P2)2][BF4]2 (9). The absence of such fluorine adducts in the spectra of [Pd(o-
P2)2][BF4]2 (10) and [Pt(o-P2)2][BF4]2 (11) can be explained by simple
hard/soft acid/base (HSAB) theory.20 Based on HSAB theory, one would
predict that the smaller, harder first row transition metals will have a
stronger affinity towards fluoride than would the second and third row
transition metal ions.
C. Crystal Structures of [M(o-P2)2] [BF4]2 ( M = Ni (8), Pt (11))

ORTEP diagrams for compounds 8 and 11 are shown in Figures 16 and
18, respectively. The compounds, which are isostructural, consist of two o-P2
ligands bound to the metal center in a square planar geometry. The inclusion
of toluene molecules in the lattice with 11 is thought to be a result of the
samples exposure to the solvent during previous, unsuccessful, slow diffusion
experiments. The bonding arrangements are identical to that observed in the
RhI analog, [Rh(o-P2)2][BF4].4 Selected bond distances and angles for both
structures are given in Table 2. The average Ni-P and Pt-P distances are

2.2551(13) A and 2.342(2) A respectively, with P(1)-M(1)-P(1)' five-ring

103

Table 6.

Selected Bond Distances (A) and Angles (deg.) for [Ni(o-
P2)2] [BF 4]2 (8) and [Pt(o-P2)2][BF4]2 (ll).

 

 

 

 

Atom 1 Atom 2 8 11
Ni/Pt(1) P(1) 2.2550(13) 2.341(2)
P(1) C(1) 1.810(6) 1.817(7)
C(l) S(1) 1.751(5) 1.741(7)
C(2) S(1) 1.760(4) 1.761(5)
C(2) C(3) 1.335(11) 1.338(13)
C(3) S(2) 1.752(4) 1.753(6)
C(4) S(2) 1.762(7) 1.767(8)
C(4) C(5) 1.508(10) 1.506(11)
Atom 1 Atom 2 Atom 3 8 11

P(1) Ni/Pt(1) P(1)A 9382(7) 95.05(10)
P(1) Ni/Pt(1) P(1)B 8618(7) 84.95(10

C(l) S(1) C(2) 92.4(3) 92.6(4)

S(1) C(2) S(1)B 113.0(4) 113.2(5)

S(2) C(3) S(2)B 113.7(4) 113.9(6)

C(4) S(2) C(3) 95.2(3) 95.0(4)

C(4)B ‘ C(4) C(5) 128.2(5) 129.0(5)

 

A = 1-x, y, -z; B = 1-x, -y, -z

104

‘l

 

Figure 16. ORTEP representation of [Ni(o-P2)2][BF4]2 (8) with 50%
ellipsoids viewed from the (a) top and (b) side.

105

 

 

Figure 17. Packing diagram of [Ni(o-P2)2][BF4]2 (8).

106

 

Figure 18. ORTEP representation of [Pt(o-P2)2][BF4]2 (11) with 50%
ellipsoids viewed from the (a) top and (b) side.

107

chelate angles of 93.82(7)° for Ni and 95.05(10)° for Pt. This distortion fi'om
90° is in the range observed in the previously reported RhI complex, as well
as N iC12(o-P2),3 [Ni(dppee)2] [ClO.4]2,11 [Ni(dppb)2] [PF 1;]2,21
[Pt(dppee)2][BPh4]2.15 The 0(1)-0(1) double bond distances of 1.328(12) A in
8 and 1.354(14) A in 11 are similar to that in the free ligand, o-P2 (1) (135(3)
A, see Appendix I), and within errors of 1.337(6) A, which is expected for a
standard C=C double bond, indicating no significant M-to-P 1t -interactions.15
All other distances and angles within the TTF core are comparable to those
found in o-P2 (1), NiBr2(o-P2),2 and [Rh(o-P2)2] [BF4].4

The TTF units are folded along the S(1)~-S(1)' axis of the phosphine-
functionalized dithiole ring by 31.2° in the case of [Ni(o-P2)2][BF4]2 (8) and
316° in [Pt(o-P2)2] [BF4]2 (11). Although such deviations from planarity are
not unusual, and have been observed in several other non-oxidized TTF
derivatives,22 the deformation in 11 is the largest out-of-plane bending
reported for a non-strained TTF unit. The packing diagram of 8 is shown in
Figure 17 and shows the close intermolecular interactions between the outer
dithiole rings of the neighboring molecules with a plane-to-plane distance of
~3.5 A. A packing diagram of 11 reveals the same packing motif. Similar

interactions were observed in the packing of [Rh(o-P2)2][BF4], which exhibits

an out-of-plane bend of 24.2(2)° along its S(1)---S(2) axis. In a strictly planar

geometry the bulky phenyl rings would prevent adequate TTF-TTF

intermolecular interactions. Thus, the favored energetics of these close S-o-S

108

intermolecular contacts might be the main driving force for the bending of
the TTF ligands.
D. Magnetic Studies of [Co(o-P2)2][BF4]2 (9).
(1) Variable Temperature Magnetic Susceptibility

Figure 19 shows the experimental molar magnetic susceptibilities (c,
indicated by circles), corrected for diamagnetisim, and the corresponding
effective magnetic moment (neg, indicated by squares), from 5 to 320 K for
[Co(o-P2)2][BF4]2 (9). Studies of the magnetic susceptibility of 9 revealed a
peg range of 4.62 NE at 320 K to 2.51 1113 at 5 K; these values are in good
agreement for a typical high-spin, S = 3/2 spin system, with pseudo-
octahedral geometry.23 Explanations for this behavior are identical to that
presented in Chapter I for Co(TMPP-O)2. The moment observed at higher
temperatures is a result of the large spin-orbit contribution to the expected
spin-only moment of 3.87 MB The large spin-orbit coupling constant for high
spin CoII (A ~ -180 cm°1 for free ion) is also an important contributor to zero-
field splitting effects, causing the 4T1 ground state to split into a set of three
levels. Temperatures below 20 K result in population of the doubly-
degenerate ground state and an observed 8’ = 1/2.
(2) EPR Spectroscopic Studies

Based on the results of the magnetism studies, an EPR signal would
not be expected until very low temperatures due to fast electronic relaxation,

but in fact this is not the case. EPR measurements of 9 were initially carried

109

 

 

 

 

0.16 s 1 1 1 1 1 1 5
[:1 Cl Cl
0.14 — D D ‘3 D D
A l. [:1 D j 4
0 BEDS
g 0.1 3 DD _ 3 9;:
E 0.08 f A
Q) . I
v_ 0.06 -- ‘ 2 ”L
g 0 04 .
x . .. _. 1
. - ’00
002 .. C . . . . . . . . . .
0 1 1 1 1 1 0
0 50 100 150 200 250 300 350

T (K)

Figure 19. Plot of Ilefl' (1113) and Xmol (emu/mol) vs. temperature (K) of [Co(o-
P2)2] [BF4]2 (9).

110

l'l

.‘.J..

out in CH3CN/toluene (1:1) glasses at 298, 107 and 4 K. Spectra of 9 in

solvent media display an axial signal with g _L = 2.29 and g“ = 2.04 (Figure

20).

o
O
I
'O
4T1 X Degeneracies in parentheses.
—‘ \ . 1. = spin-orbit coupling constant.
\‘ \ ‘ ~ {42 6 /4 A.
\
‘
Oh field ‘~

~, (2) 15/42.

spin-orbit
coupling

The g|| tensor is split into eight distinct lines (IAul = 3.3x10°3 cm'l) due to

the hyperfine interaction with the I = 7/2 nucleus of 59Co. The appearance of
such a signal suggests the metal center is in a four-coordinate, S = 1/2,
configuration; a result in direct conflict with the observed magnetic moment
in the solid state. To further probe this issue, EPR studies of 9 were carried
out in the solid state at 4 K. The resulting spectrum contains the previously
described axial signal, as well as a very broad signal at g = 4.84 (Figure 21).

This falls in the range expected for g i of a six-coordinate high-spin CoII
system, and appears to be the result of the superposition of 2 g .1. tensors.24

The average g value for regular octahedral complexes may range from 4.43 to
4.0 depending on the orbital reduction factor and the strong or weak field

approximation which is appropriate for the particular complex. Based on this

111

—l9’0

P

-10

D ' ’29l'lb 1||[1l9

 

 

 

5.

wmhm

.m 2: a. eeeseeuzOmmo Snow 5 a: «50:23-98. 05 8253... FE .3 250E

 

 

.L»

'bbllkkb’FD

30 u =0

thb’brthDPPb'

1‘4‘i ‘G‘i‘.“d ‘

mud n 90

DblLPFDD

wmbm

‘1“‘411|1l“““4 ‘

11

Jd‘i

J-i‘ {1‘11

wmbfi

 

 

 

D’PthP’I’FP’.l>l

Pb

-11p-->1p

 

pill hi?»

 

>?fiFi}

112

.m e a. 22:5 38 e 2. 5 «50:23-95. 05 558% 000 .3 2:03

.2
000v 00mm ooom comm ooom oom— coon Dom

 

I1 com:

mo.m .1. =m

.1 com:

l 09.1

 

l 8.
New .... 4»
mavum

l. oom

 

 

1 com

 

 

1,00

113

gavg = (g _L + g .L + g||)/3, g” would be expected to fall in the range masked by the

previously observed axial signal.

It is possible that fluxionality is occurring in the coordination sphere of
the metal center, resulting in a change from six- to four-coordinate upon
dissolving the solid. One possibility for this is the axial coordination of
CH3CN, resulting in [Co(o-P)2(NCCH3)2][BF4]2, but this is contradictory to
elemental analysis results. Thermal Gravimetric Analysis is warranted to
prove/disprove the presence of solvent. Another possibility is the axial
coordination of [BF4]'. This is supported by the presence of [Co(o-P2)2+F]+
(m/z = 1278) in the FAB-MS spectrum. Such coordination of [BF4]' is not
uncommon among the first-row transition metals such as cobalt.25 but does
not explain the presence of the "low-spin" signal in the solid state EPR
spectrum. One explanation for this might be that the observed axial signal is
only a minor impurity, thus having very little effect on the measured
susceptibility. Given the traditionally greater intensity of the EPR signals
for low-spin versus high spin Con, it is possible that a significantly higher
spin-density is associated with the broader "high-spin" signal, although the
"low-spin" signal dominates the spectrum.

E. Electrochemistry of [M(o-P2)2][BF4]x ( M = Ni, Pd, Pt, x = 2; M =
Rh, x = 1).

(1) Redox Properties of [M(o-P2)2] [BF4]2 (M = Ni, Pd, Pt)

114

The cyclic voltammetry data for 8-11 are presented in Table 3 and

compared to that of the free phosphine, o-P2 (1), and [Rh(o-P2)2][BF4]. The

Table 7. Electrochemical data (in V vs Ag/AgCl) for 8-11, o-P2, and [Rh(o-
P2)2] [BF 4]. in 0.2 M TBABF4/CH2C12 solutions, at 200 mV/s.

 

 

E1/2(ox)1’e" E1/2(ox)2’e" E0011" E(p,c)2i"
o-PZ (1) 0.46 0.91 - -
[Ni(o-P2)2][BF4]2 (8) 0.68 1.08 .027 -
[Co(o-P2)2][BF4]2 (9)a 0.63 1.07 -091 -1.19
[Pd(o-P2)2][BF4]2 (10) 0.64 1.16 -031 -
[Pt(o-P2)2][BF4]2 (11) 0.70 1.19 -045 -
[Rh(o- P2)2][BF4] 0.63 1.01 - -

 

a 0.1 M CH3CN; rev reversible, 1“ irreversible

first oxidation couple of the TTF unit in the metal complexes is shifted to
more positive potentials as expected for coordinated versus free ligands.
Shifts in the second TTF couple vary from +160 mV for 9, to 280 mV for 11.
These potentials are within the range previously reported for [Rh(o-
P2)2] [BF4] and NiX2(o-P2) (X = Cl, Br).4'3 The presence of only two oxidation
couples rather than four one-electron couples indicates that the TTF units
are not in communication, and are acting as isolated redox centers. It can be
surmised that each couple is the superposition of two one-electron processes,
but coulometry studies are needed to be certain of this. The irreversible

reduction waves are attributed to reductions of the metal centers. The first

115

E1/2(ox)1 = +0.70 V
E1/2(red) = -0.45 V

E112(ox)2 = 1.19 V

 

l l l l

+1.6 +1.0 +0.5 0.0 +0.5 +1.0 +1.6

Volts vs. Ag/AgCl

Figure 22. Cyclic voltammogram of [Pt(o-P2)2][BF4]2 (11) in 0.2 M TBABF 4
in CH2C12.

116

reduction pathway is due to the MH/MI process for 8-11. The two-electron
MU/Mo reduction is common in bis-diphosphine complexes of Pd and Pt, but
typically occur at much more negative potentials (-0.71 to -1.07 V).2L26 The
second reduction in 9 can be assigned to the Col/Co0 reduction. This is most
likely accompanied by substantial decomposition, although zero-valent
phosphine complexes of Co are actually known (e.g. Co(PMe3)4).13

(2) Oxidation of [Rh(o-P2)2][BF4]

The addition of three equivalents of NOBF4 to [Rh(o-P2)2][BF4] results
in an immediate color change from yellow to green. Addition of one
equivalent of oxidizing agent results in a brief color change that returns to
the original yellow after several minutes. The color change to green is
indicative of oxidized TTF. The lack of communication between the TTF
cores causes them to be oxidized at the same potential, thus a mixed valence
state with only one TTF moiety oxidized is not possible. Addition of less than
one equivalent is expected to result in a mixture of [Rh(o-P2)2][BF4] and
[Rh(o-P2)2][BF4]3, while the addition of three equivalents would produce a
combination of paramagnetic [Rh(o-P2)2][BF4]3 (14) and diamagnetic [Rh(o-
P2)2][BF4]5. The EPR spectrum of this product in a 1:1 CH3CN/toluene glass
at 96 K exhibits a sharp signal with anisotropic g values of g1 = 2.08 and g2 =
2.07. The narrow line width of the signal (55 G) indicates that it is due to an

organic radical, with anisotropy typical for oxidized TTF.27

117

.m 3 .5 5533.20.48 88 a a: ”5&3?sz do 858% mum .3 250$

«Nam

 

 

 

 

 

 

 

“I. 1 ifi 1 ‘4‘11‘4 1! 1 .111 ‘11l‘d‘1‘{ 1‘1“l 11111 .1944 4 {‘4‘ {‘1‘ “‘+1‘
_ O
O
O
o
-
.
.
.
.
_
m
A
. Ila
N. N
I‘
. Ila
Dbblb.Lll’bblbrbbbPlbkbhkbhlh75>llLPPfFDDDPlrbfir’b‘lhhbb ? lllpl D filth D l} FFDDP

 

118

F. Reactivity of M(CF3803)2 with o-P2 (M = Ni, Fe)

The addition of two equivalents of o-P2 to M(CF3S03)2 (M = Ni, Fe)
produces very different results for each metal. Upon addition of phosphine to
the Ni precursor, an immediate color change to brown ensues. Subsequent
isolation of a product yields a green solid. The 1H NMR spectrum in CD30N

exhibits a series of multiplets in the region 5 = 7.1 - 7.7 ppm due to the
phenyl protons, and a singlet at 5 = 1.82 ppm due to the methyl protons. The
31P{1H} NMR spectra contains a singlet at 5 = 46.6 ppm. The downfield shift

of the signal from the free phosphine at -18.8 ppm indicates metal-
coordination of the phosphines to form [Ni(o-P2)2][CF3803]2 (13).3 The
downfield shift relative to 8 supports a decrease in the electron density about
the Ni center, possibly due to axial coordination of the triflate groups. This is

supported by the presence of [Ni(o-P2)2][CF3S03]+ (m/z = 1409), where the

equivalent [BF4]' adduct is not seen in 8.

The same reaction performed using the Fe complex resulted in no color
change, which is not surprising given the color of 12 (red-orange) is the same
as the physical mixture of o-P2 and Fe(CF3803)2. After stirring for 12 h, a
31P{1H} NMR spectrum of the reaction mixture revealed only free o-P2.
Continued stirring for several days affected no change in the 31P{1I-I} NMR
spectrum, indicating no reaction had occurred. As further proof of this, single
crystals of the free ligand were grown from slow evaporation (under vacuum)

of CHsCN/toluene solutions of the reaction mixture.

119

'-

G. Metathesis of [Rh(o-P2)2][BF4] with [Li] [TCNQ].

Reaction of [Rh(o-P2)2][BF4] and [Li][TCNQ] in warm acetone/CH2C12
solutions produces a finely divided green precipitate. Infrared analysis of the
solid reveals nitrile stretching frequencies at 217 8 and 2153 cm‘l. These are
similar to the values obtained for [FeCp*2][TCNQ] (2179, 2153 cm'l) and
[CGC*2][TCNQ} (2178, 2153 cm'l), but quite different from the [Li]+
precursor (2200, 2114 cm'l).28 The presence of aromatic out-of-plane bending

vibrations at 692 and 521 cm:1 support the presence of the o-P2 ligand. The

absence of a strong band ca. 1069 cm:1 supports the absence of [BF4]'.

Due to the shift to more positive potentials in the oxidation couples of
the ligand after complexation, TCNQ is no longer an adequate oxidizing
agent for the metal complexes. Because oxidation of o-P2 by TCNQ prior to
reaction with the metal would introduce a competing ligand in the form of
[TCNQ]’, metathesis is currently the best method of forming the TCNQ salt.
The more accessible reduction of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-
quinodimethane (TCNQF4)29 is more suitable for oxidations of M-(o-P2)
complexes, and offer a different method of introducing a radical semiquinone
into the formula.

4. Concluding Remarks

The 'I'l‘F-phosphine complexes, [M(o-P2)2][BF4]2 (M = Ni (8), Co (9), Pd

(10), Pt (11), Fe (12)), can be prepared by addition of two equivalents of the

free phosphine to the appropriate homoleptic mononuclear acetonitrile

120

complex. These complexes retain the redox functionality of the TTF unit,
while introducing the redox (and magnetic in the case of Con) properties
associated with the metal. The presence of two superimposed reversible
oxidations associated with the two TTF moieties in the electrochemical
studies of 8-11 support previous observations regarding a lack of
communication through the phosphine atoms. The successful preparation of 9
illustrates the potential for incorporating magnetic metal centers into TTF
structures through direct coordination. Given the success of coordination
with CoII and FeII (although diamagnetic), the next logical progression is the
preparation of [MnH(o-P2)2][BF4]2. The d5 complex would exhibit magnetism
associated with a S = 5/2 spin system, and characterization by EPR would be
much more straight-forward given the strong signals typically associated
with Mn.

The introduction of additional spins by way of TTF oxidation, the
inclusion of organic acceptors, or a combination of the two, offers new
strategies to access compounds with magnetic and possibly conducting
properties. The oxidation of TTF is expected to lead to significant structural
changes due to forced planarity of the organic core.3° Such a change would
eliminate the ability of the complexes to form S~S contacts, as the bulky
phenyl groups are expected to preclude stacking interactions. For this
reason, synthesis of the less bulky PMez and phosphole derivatives, shown in
Figure 24, are worth exploring as alternatives. An additional pr0perty of

phosphole is the inclusion of the heteroatom in the ring system. This may

121

change the electronic effects of the functional group and allow for

communication between bound TTF moieties.

/
P

\
Phosphole

122

HC P
3104— 81 4. ..
a
CH
H30 S S 1") 3
CH3

ISHSI a»

Figure 24. Schematic drawings of the proposed ligands (a) 3,4 dimethyl-
3’,4’-bis(dimethylphosphino)tetrathiafulvalene and (b) 3,4
dimethyl-3’,4’-bis-(phospholyl)tetrathiafulvalene.

123

10.

11.

12.

13.

14.

15.

List of References

Fox, M. A.; Chandler, D. A. Adv. Mater., 1991, 3, 381.

Kahn, O.; Pei, Y.; Verdaguer, M.; Renard, J.P.; Sletten, J. J. Am.
Chem. Soc. 1988, 110, 782.

Fourmigué, M.; Batail, P. Bull. Soc. Chim. Fr. 1992, 12.9, 829.

Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.; Bartley, S. L.;
Dunbar, K. R., J. Organomet. Chem., 1997, 52.9, 343.

Hathaway, B. J .; Holah, D. G.; Underhill, A. E., J. Chem. Soc., 1962,
2444.

Thomas, R. R.; Sen, A., Inorg. Synth., 1989, 26, 128.

DeRenzi, A.; Panunzi, A.; Vitagliano, A., J. Chem. Soc., Chem.
Commun., 1976, 47 .

Dixon, N. E.; Lawrance, G. A.; Lay, P. A.; Sargeson, A. M.; Taube, H.
Inorg. Chem. 1984 23, 243.

Melby, L. R.; Harder, R. J .; Hertler, W. R.; Mahler, W.; Benson, R. E.;
Mochel, W. E., J. Am. Chem. Soc., 1962, 84, 3374.

(a) Bino, A.; Cotton, F. A.; Fanwick, P. E. Inorg. Chem. 1979, 18, 3558.
(b) Cotton, F. A.; Frenz, B. A.; Deganello, G.; Shaver, A. J. Organomet.
Chem. 1973, 50, 227.

North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Cryst., 1968, A24,
351.

Sheldrick, G. M. SHELXL93. Program for the Refinement of Crystal
Structures, 1993, University of Gottingen, Germany.

Cotton, F.A.; Wilkinon, G., Advanced Inorganic Chemistry, 3rd Ed.,
Wiley & Sons, New York, 1972.

Fourmigué, M., personal communication.

Oberhauser, W.; Bachmann, C.; Briiggeller, P., Inorg. Chim. Acta,
1995, 238, 35.

124

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

(a) Honeychuck, R. V.; Hersh, W. H. Inorg. Chem. 1987, 26, 1826. (b)
Honeychuck, R. V.; Hersh, W. H. Inorg. Chem. 1989, 28, 2869. (c)
Lundquist, E. G.; Folting, K.; Hofiman, J. C.; Caulton, K. G.
Organometallics, 1990, .9, 2254. (d) Fernandez, J. M.; Gladysz, J. A.
Inorg. Chem., 1986, 25, 2672.

Johnson, A.; Taube, H., J. Indian. Chem. Soc., 1989, 66', 503.

Asara, J. M.; Uzelmeier, C. E.; Dunbar, K. R.; Allison, J. Inorg. Chem.,
1998, 37, 1833.

Fourmigué, M.; Jarchow, S.; Batail, P. Phosphorus, Sulfur, Silicon
Relat. Elem. 1993, 75,175.

Miller, J. N.; Jones, T. R.; Deacon, G. B. Inor. Chim. Acta 1979, 32,
L75.

Miedaner, A.; Haltiwanger, R. C.; DuBois, D. L. Inorg. Chem., 1991,
30, 417 .

(a) Fourmigué, M.; Batail, P. J. Chem. Soc., Chem. Commun., 1991,
1370. (b) Garreau, R. R.; de Montauzon, D.; Cassoux, P.; Legros, L.-P.;
Fabre, J.-M.; Saoud, K.; Chakroune, S. New J. Chem., 1995, 19, 161.
(c) Izuoka, A.; Tachikawa, T.; Sugawara, T.; Suzuki, Y.; Konno, M.;
Saito, Y.; Shinohara, H. J. Chem. Soc., Chem. Commun. 1992, 1472.
(d) Jergensen, T.; Girmay, B.; Hansen, T. K.; Becher, J .; Underhill, A.
E.; Hursthouse, M. B.; Harman, M. E.; Kilburn, J. D. J. Chem. Soc.,
Perkin Trans. 1992, 2907. (6) J ergensen, T.; Becher, J .; Hansen, T. K.;
Chrisiansen, K.; Roepstorff, P.; Larsen, S.l Nygaard, A. Adv. Mater.
1991, 10, 486. (f) Endres, H. Z. Naturforsch, 1986, 41b, 1351.

Carlin, R. L.; van Duyneveldt, A. J. Magnetic Properties of Transition
Metal Compounds, Springer: New York, 1977.

Banci, L.; Bencini, A.; Benelli, C.; Gatteschi, D.; Zanchini, C. In
Structure and Bonding, Vol. 52, Eds. Clarke, M. J .; Goodenough, J. B.;
Hemmerich, P.; Ibers, J. P.; Jergensen, C. K.; Neilands, J. B.; Reinen,
S.; Weiss, R; Williams, R. J. P. Springer-Verlag: New York, 1962, 37.

(a) Egan, J. W.; Theopold, K. H. Acta Crystallogr., C. 1990, 46, 1013.
(b) Shah, N.; Adak, A. K.; Data, K. M. Synth. React. Inorg. Met.-Org.,
1984, 14, 731.

Davies, J. A.; Staples, R. J. Polyhedron, 1991, 10, 899

125

27.

28.

29.

30.

Clérac, R. Ph. D. Dissertation, Université Bordeaux, I., 1997.

(a) Melby, L. R.; Harder, R. J .; Hertler, W. R.; Mahler, W.; Benson, R.
E.; Mochel, W. E. J. Am. Chem. Soc. 1962, 84, 3374. (b) Miller, J. S.;
Reifi, W. M.; Zhang, J. H.; Preston, L. D.; Reis, A. H., Jr.; Gebert, E.;
Extine, M.; Troup, J .; Dixon, D. A.; Epstein, A. J .; Ward, M. D. Phys.
Chem. 1987, .91, 4344. (c) Broderick, W. E.; Hoffman, B. M. J. Am.
Chem. Soc. 1991, 113, 6334.

Miller, J. 8.; Dixon, D. A.; Calabrese, J. C.; J. Phys. Chem., 1989, .93,
2284.

Kistenmacher, T. J .; Phillips, T. E.; Cowan, D. 0. Acta. Crystallogr. B.,
1974, B30, 763.

126

 

CHAPTER IV

REACTIVITY OF METAL-METAL BONDED COMPLEXES WITH

PHOSPHINE-FUNCTIONALIZED TETRATHIAFULVALENE

127

1. Introduction

Chelating diphosphines such as bis(diphenylphosphino)ethane (dppe), -
ethene (dppee) and their relatives are commonly used for their ability to
stabilize metal complexes through the formation of five- (chelating), and six-
membered (bridging) rings.1 Diphosphine ligands have been used extensively
in the preparation of metal-metal bonded complexes as well as other cluster
complexes2 due to the fact that they exhibit several characteristics applicable
in multiply bonded systems; they are bidentate, the donor orbitals of the
phosphorus atoms are oriented parallel to each other, and the distance
between the heteroatoms is typically 2.025 A? Diphosphine molecules with
a single bridgehead atom separating the phosphorous atoms, e.g. dppm and
bis(diphenylphosphino)amine (dppa), are particularly useful as bridging
ligands for metal-metal bonded complexes due to the formation of a stable
five-membered ring.3 The diphosphines with an ethene backbone are
attractive due to their tendency to strongly coordinate to nearly all transition
metals4 and stabilize high oxidation states.5 Several “diphos” ligands have
been reported to coordinate to dinuclear metal centers in both the chelating
(01) and bridging ([3) modes. The structural characterization of several a- and
B-M02X4(LL)2 compounds, where "LL" is a diphos ligand, has led to a clearer
understanding of factors that influence M-M bond distance and has prompted
Cotton to suggest a mechanism for internal rotation of a M2 unit within its

ligand sphere.‘3’7

128

One of our early interests in pursuing TTF phosphine chemistry was to
merge the redox activity of the tetrathiafulvalene functionality8 with the
extensive chemistry of metal-metal bonded compounds},9 Many of these
metal-metal bonded compounds have been found to exhibit fascinating
photophysical properties and are known to display rich redox chemistry.10
The use of TTF itself as a ligand for metal-metal bonded systems has
witnessed little activity in the literature, with the only reported examples
being the dinuclear compound Rh2(OzCCH3)4(TTF)2, wherein neutral TTF
ligands are bound to the axial positions through sulfur atoms.11 More
recently, [Cu2(u-Cl)2(u-TMT-TTF)],, (TMT-TTF = tetrakis(methylthio}tetra-
thiafulvalene) with no direct M—M interaction was reported to contain TTF

ligands bound via methylthio groups. An interesting feature of this structure

are the close Sn-S contacts of 3.53 and 3.63 A between layers of the 2D
sheets.12 A third structure, while not involving directly bonded TTF, is an
interesting example of the use of TTF in stacking arrangements, in this
instance with alternating [Pt(dmit)2]3“'1 anions. In this structure, two of the
[Pt(dmit)2]n’3' units are connected by a Pt-Pt bond, and the TTF is present in
both its neutral and oxidized forms. Crystals of this material are
semiconducting from 100-300 K.13

The present studies of new TTF-phosphines build on the wealth of
known chemistry of metal-metal bonded compounds with phosphine ligands.

The reactions of the quadruply-bonded compounds [Re2C13]2' and

129

[Pt(dmit)2lz
M02Cl4(SMe2)4 with the diphosphine ligand o-P2 (1) have been explored and
the products characterized by a combination of structural, spectroscopic,
electrochemical and magnetic studies.

2. Experimental

A. Synthesis

Starting Materials and Reaction Procedures. Ortho-
[P(CGH5)2]2(CH3)2TTF,83 P(C6H5)2(CH3)3TTF,8b [Rh2(NCCH3)10][BF4]414
[Rez(NCCH3)1o][BF4]4,15 [(n-Bu)4N]2[Re2C13],16 and M02Cl4[S(CH3)2]417 were
prepared according to published procedures. NOBF4 and C014 were
purchased from Aldrich Chemical Co. and was used as received. Acetone,
acetonitrile, and methylene chloride were distilled over 3 A molecular sieves,
and ethanol was distilled over Mg(OMe)2 under a nitrogen atmosphere.
Diethyl ether and toluene were distilled over sodium-
potassium/benzophenone. Unless otherwise specified, all reactions were
carried out under an argon atmosphere by using standard Schlenk-line

techniques.

130

(1) Reaction of [Rh2(NCCH3)1o] [BF4]4 and (Ph2P)Me3TTF to form (15).

Samples of [ha(NCCH3)1o][BF4]4 (0.026 g, 0.03 mmol) and
(thP)Me3TTF (Pl) (0.046 g, 0.12 mmol) were dissolved in 10 mL of
acetonitrile, and stirred for 12 hours at r.t. A large excess of EtzO (~50 mL)
was then added to the dark green solution, and the reaction flask was chilled
in an ice bath to allow the precipitate to settle. The mixture was filtered
through Celite, and both the green solid and orange filtrate were dried under
reduced pressure. The orange solid was washed with hexanes and dried by
suction filtration in air; yield 0.011 g. The green solid was washed with
copious amounts of EtzO and dried in vacuo. Recovery of the green solid was
complicated by its finely divided nature, making it subject to static problems.
Consequently an accurate mass could not be obtained. Doubling the reaction
A scale did not improve the recovery of the green solid. 1H NMR (CDC13) 5
ppm: broad and unresolved. 31P{1H } NMR (CDC13) 5 ppm: not observed. IR
(Nujol, cm'l): 475 (m), 530 (s, P1), 695 (m, P1), 720 (m), 750 (w), 890 (w), 1050
(s-br, VB-F). UV-Vis. (CHzClz) Amax (nm) 510, 600. EPR (T=133 K,
CH3CN/CH2012): g = 2.00.
(2) Reaction of [Re2(NCCH3)10] [BF4]4 and (thP)2Me2TTF.

Solutions of [Rez(NCCH3)1o][BF4]4 (0.024 g, 0.02 mmol) and o-P2
(0.053 g, 0.14 mmol) were prepared separately by dissolving the solids in 10
mL of acetonitrile and 7 mL of dichloromethane respectively. Approximately

one-half of the phosphine containing solution was added to the dirhenium

131

complex, resulting in a color change from orange to green. After stirring for 5
h, the reaction solution was heated to reflux and stirred for an additional 12
h. The solution was reduced to dryness by application of a dynamic vacuum,
and the resulting residue washed six times with 5 mL of EtzO, and dried in
vacuo: Recovery was extremely difficult due to the susceptibility of the solid
to static problems. Much of the product remained in the flask, and as a
result the mass would be inaccurate; approximate yield 0.059 g. 1H NMR
(CD3CN): broad and unresolved. 31P{1H} NMR (CD3CN) 5 ppm: none
observed. EPR (1:1 toluene/CH3CN, 133K): g = 2.00.

(3) Reactions of [Bu4]2[RezCls] with o-P2.

(i) Synthesis of [ReC12(o-P2)2][Re2C16(o-P2)] (16017) for short reaction
times. A flask charged with a mixture of [n-Bu4N]2[RezCls] (0.104 g, 0.091
mmol) and o-P2 (0.131 g, 0.219 mmol) was treated with 10 mL of ethanol and
refluxed for 1 h, during which time the solution became yellow-orange with
the deposition of a red solid. The mixture was filtered in air, and the solid
was washed with copious amounts of EtOH and CH3CN to remove unreacted
starting materials, followed by ~50 mL EtzO to dry the solid. The solid was
dried in vacuo. Single crystals of the dichloromethane tetrasolvate were
obtained by slow diffusion of CH3CN into a dichloromethane solution of the
compound; yield 0.115 g (72%). Anal. Calcd for 16-17-CHzClz,
Re3C110312P6097H30: C, 42.70; H, 2.95. Found: C, 42.74; H, 2.72. IR (Nujol,

cm'l): 329 (VRe-c1), 333 sh(vRe.c1), 352 (vRe.01), 517 (V=C.H), 691 (Vcac). UVoViS.

132

(CHzClz) Amax (nm) (e (M‘1,cm'1)): 976 (4.80x101), 448 (5.0x103), 322 (6.4x104),
276 (7.5x104). C.V. (0.1M TBABF4, CH2C12, Pt disk electrode vs Ag/AgCl):
E1/2(red)1 = +0.03 V, Emoz = -0.79 V, E(p,c)3 = -l.12 V, E1/2(0X)1 = +0.31 V,

E1/2(0X)2 = +0.50 V, E1/2(0X)3= +0.67 V, B(p,a)4 = +1.05. FAB-MS (m/z): 1457
ReC12(o-P2)2]+), -1186 ([Re2(o-P2)C15]‘). Magnetic moment (1113): 11.5 = 5.2 at

340 K (1T), pea: 1.9 at 5 K (1T).

(ii) Reaction time of 2 hours. [n-Bu4N]2[Re2Clg] (0.031 g, 0.03 mmol) and
o—P2 (0.069 g, 0.13 mmol) were dissolved in 10 mL of ethanol and stirred
under refluxing conditions for 2 h. The yellow-orange solution was cooled to
room temperature and transferred to a second flask. The solvent was
removed under vacuum, the solid was washed with EtzO, and then dried
under reduced pressure to give a green solid. FAB-MS (m/z): +1457 ([Re(o-
P2)2C12]+).

(4) Reduction of [ReClz(o-P2)2] [RezC16(o-P2)] (16-17) to yield

ReClz(o—P2)2 (18).

A solution of Co(CsH5)2 (0.01 g, 0.053 mmol) in 2 mL of CH2C12 was
added to [ReC12(o-P2)2][Re2C16(o-P2)] (16°17) (0.100, 0.038 mmol) in 5 mL
CH2C12 which led to an immediate color change to brown-green ensued. The
reaction mixture was stirred for 12 hours, to give a yellow precipitate that
was isolated by filtration, washed 3 times with 5 mL of CH2C12, and dried in
vacuo. yield = 0.031g (56%). IR (Nujol, cm'l): 330 (VRe-Cl), 513 (won), 702

(Cue). FAB-MS (m/z) = +1457 ([ReC12(o-P2)2]+), -1457 (very low intensity,

133

[ReC12(o-P2)2]'). Magnetic moment (1113): 11.5 = 5.0 at 300 K (1T), Hefi' = 1.8 at 2
K (1T).

(5) Oxidation of ReC12(o-P2)2 (18).

(i) Preparation of [ReClz(o-P2)2] [Cl] (16-[Cl]). A small quantity of
ReC12(o-P2)2 (18) (0.020g, 0.014 mmol) was stirred in a mixture of 5 mL of
CH2012 and 10 mL of CCl4 under refluxing conditions for 3 days. The yellow-
orange solution was reduced in volume under vacuum and 30 mL of EtzO was
added to precipitate a yellow-orange solid which was washed with capius
amounts of EtzO and dried in vacuo; yield = 0.008 g (38%). IR (Nujol, cm'l):
327 (meal), 518 (won), 695 (vc--c). FAB-MS (m/z): 1457 ([ReClz(o-P2)2]+)

(ii) Preparationof [ReC12(o-P2)2][BF4] (16-[BF4]). An aliquot (4.2 mL) of
a stock solution of NOBF4 (0.014 g, 0.120 mmol, 10 mL CHzClz) was slowly
added to a mixture of ReClz(o-P2)2 (18) (0.054 g, 0.037 mmol) in 5 mL of
CH2C12 (a slight excess of stock solution was added due to the poor solubility
of N OBF4 in CHzClz). The mixture was stirred for 3 days, during which time
the solution color gradually became red-brown. The reaction mixture was
filtered in air to remove unreacted ReClz(o—P2)2 (18) and treated with 30 mL
of EtzO to afi'ord a red-brown precipitate. The resulting solid was isolated by
filtration, washed with copious amounts of EtzO and dried under vacuum;
yield 0.035 g (61%). C.V. (0.2 M TBABF4, CHzClz, Pt disk electrode vs

Ag/AgCl): E1/2(ox)1 = +0.75 V, E1/2(0x)2 = +1.14 V, E1/2(red)1 = +0.07 V,

134

Eu2(red)2 = - 0.97 V. Magnetic moment (1113): 11.5 = 4.9 at 300 K (1T), 11.5 = 0.7
at 2 K (1T).
(6) Reaction of MozCl4(SMe2)4 with o-P2.

(i) In CH3CN. Solutions of M02C14(SMe2)4 (0.059 g, 0.137 mmol) and o-P2
(0.122 g, 0.202 mmol), each in 10 mL of CH3CN, were combined and stirred
for 8 h. During this time, the solution became dark brown in color, and a
green precipitate was observed to have formed. The liquid was decanted and
the green solid was washed 3 times with 5 mL of EtzO before being dried
under reduced pressure; yield 0.059 g. 1H NMR (CDsCN (integration)) 5 ppm:
1.85 (s, 2.08), 1.95 (s, 3.87), 2.15 (s), 7.37 (m, 6.12). 31P{1H} (CD3CN) 5 ppm: -
17.60 (s). UV-Vis. (CH3CN) Amax (nm)): 600. The addition of CH2C12 to the

green solid led to a dark brown solution that was reduced to dryness under
reduced pressure and washed with copious amounts of EtzO. 1H NMR
(CD3CN) 5 ppm: 1.806 (s), 1.84 (s), 1.95 (s), 2.13 (s), 7.27 (br), 7.36 (br), 7.46
(m), 7.61 (m). 31P{1H} (CD3CN) 5 ppm: -0.64 (d, le.p = 17.1 Hz), -2.72 (d, le.p
= 19.5 Hz), 40.71 (s). UV-Vis. (CH2C12) Amax (nm)): 460.

(ii) In CH2C12 under aerobic conditions. Preparation of MoClez(o—
P202) (19). A solution of o-P2 (0.048 g, 0.080 mmol) in 5 mL of CHzClz was
added to a solution of M02C14(SMe2)4 (0.023 g, 0.047 mmol) in 8 mL of CH2C12
and stirred for 8 h, thereby effecting a color change from blue to dark brown.
The solution was treated with 15 mL of EtzO to afford a brown precipitate

which was collected by filtration in air. The remaining solid was washed 3

135

times with 5 mL of EtzO and dried in vacuo; yield 0.041 g (61%). Needle-
like single crystals were obtained by slow evaporation in air of a
dichloromethane solution of the compound.

B. X-ray Crystallographic Studies

(1) [ReC12(0—P2)2] [Re2C16(o-P2)]-4 CH2C12 (16017-4 CH2C12)

(i) Data Collection and Reduction. Crystallographic data for 16-17 were

collected on a Siemens SMART/COD area detector diffractometer equipped
with monochrmoated MoKa radiation. Crystallographic computing was
performed using SHELXTL version 5.0.18 Crystal parameters and basic
information pertaining to data collection and structure refinement are
summarized in Table 8.

Single crystals of [ReC12(o-P2)2][RezCle(o-P2)]°4CH2012 (16°17°
4CH2C12) were grown by slow diffusion of acetonitrile into a dichloromethane
solution of the title compound. A red-orange parallelepiped of approximate
dimensions 0.16 x 0.17 x 0.55 mm3 was secured on the tip of a glass fiber
with silicone grease and cooled to —100 i 1°C during data collection by using
a cold nitrogen stream. The data were collected in a 0 range of 0.99 to 21.7 2°.
Successful refinement of the structure was carried out in the triclinic P-1
space group. Of the 21,397 reflections that were collected, 13,226 were
determined to be unique (R(int) = 0.067) and 11,595 data were observed (I >

2.006(1)). The data were corrected absorption with transmission factors

ranging from 0.63 to 0.99.

136

Table 8. Summary of crystal data for [ReC12(o-P2)2][RezCle(o-P2)]°4CH2C12

(16'17-4CH2C12).

 

16'17'4CH2012

 

Formula
Formula weight

Space Group

a,A
b,A
c,A

Density (calc), Mg/cm3
11, mm:1

Temp, °C
Goodness-of-fit on F2
R18

wR2b

C100H86C116P6Re3s 12
2984.03

P-l

13.456 (1)

20.402 (3)

21.554 (1)
88.26 (1)

72.99 (1)
84.93 (1)
5635.85 (10)
2

1.76

3.95

-100

1.29

0.075

0.159

 

aR1=>3l IFol - lFel I/ZlFol.wa2=[Zw(lFol - ch|)2/ZW|F0|2]1’2;

W = 1/0'2(| Fol).

137

Table 9. Summary of crystal data for MoClez(o-P202)-CH2C12 (19-CH2C12).

 

19'CH2C12

 

Formula

Formula weight
Space Group

a, A

b, A

c, A

on, deg

B. deg

7. deg

v, A3

Z

Density (calc), Mg/cm3
)1, mm'1

Temp, °C
Goodness-of-fit on F2
R1a

wRZb

C37H2504C14P2MOS4
961.33

P21/n

10.747 (3)

17.309 (4)

21.101 (5)
90.00

100.36 (2)
90.00
3862 (2)

4

1.58

0.82

-85

0.832
0.1028
0.3521

 

a51:21 1F.1 - 1F.1 I/ZlFo|.wa2=[2w(lFo| - 1F.1)2/zw1F,12]1/2

w= 1/62(|Fo|)-

138

(ii) Structure Solution and Refinement. The asymmetric unit consists

of one [Re2C15(o-P2)]' (17) moiety, two half [ReC12(o-P2)2]+ (16) cations

residing on centers of inversion, and four solvent molecules. Solvent disorder
and poor packing severely affected the scattering ability of the crystal at
higher theta angles; data collection was therefore limited to 0 less than
21.72°. The poor scattering and the high absorption led to a variety of issues
during the refinement of the structure. The solvent disorder was completely
resolved for only one of the solvent molecules (C(100), Cl(15), and Cl(16)).
The atoms Cl(15), Cl(16), Cl(15B), and Cl(16B) were refined at 50%
occupancy in alternate least squares cycles. There is also a possibility that
the phenyl groups that involve C(15)-C(20) and C(21)-C(26) are undergoing a
wagging motion (i.e. a rotational twist along the P-C bond). Atoms C(1),
C(34), C(41), C(59), C(66), and C(67) were refined isotropically and hydrogen
atoms were placed in calculated positions and allowed to ride on the bonded
atom. The methyl hydrogen atoms were included as rigid groups with
rotational freedom at the bonded carbon atom. Refinement of nonhydrogen
atoms was carried out with anisotropic temperature factors except as noted
above.

The structure was solved by direct methods and refined by full-
matrix-block least squares refinement. The final refinement was based on

13,219 reflections that were used to fit 1,232 parameters to give R1 = 0.0751

139

and wR2 = 0.1594. The goodness-of-fit index was 1.291. After the last least
squares cycle, the highest peak in the difference Fourier map was 2.398 e'/A3.
(2) MoC1202(O—P202) (19).

(i) Data Collection and Reduction. Single crystals of 19 were grown by
slow evaporation, in air, from a CH2C12 solution of the compound. A brown
crystal of dimensions 0.23 x 0.34 x 0.47 mm3 was secured on the tip of a glass
fiber with Dow Corning silicone grease and placed in a cold N2 (g) stream.
Least-squares refinement using 24 well-centered reflections in the range 2 S

20 _<_ 24° indicated that the crystal was consistent with an orthorhombic

crystal system. The data were collected at - 85 i 1 °C using the (1)-20 scan
technique to a maximum 20 value of 47°. Of the 6327 reflections that were

collected, 358 were systematically absent. An empirical absorption correction
based on azimuthal scans of three reflections with xnear 90° was applied
which resulted in transmission factors ranging from 0.705 - 1.00. The data
were corrected for Lorentz and polarization effects.

(ii) Structure Solution and Refinement. The structure was solved in the
space group P21/n using the MITHRIL19 and SHELXL 9320 structure solution
programs and refined by full-matrix least-squares refinement on F2.21 The
final full-matrix least-squares refinement was based on 5743 reflections that
were used to fit 426 parameters with 4 restraints to give R1 = 0.1028 and
wR2 = 0.3521. The goodness-of-fit index was 0.832, and the maximum shift

in the final difference map was 0.175 A associated with C105. After the last

140

least squares cycle, the mean shift/esd was 0.065 and the highest peak in the
difference Fourier map was 1.22 e'/A3 which is associated with M01 and 02.
The methyl group centered about atom C8 was found to be disordered,

and was refined isotropically as twin methyl groups, A and B, with a
combined occupancy of 1.0. Restraints were introduced to keep the 08A---S4

distance similar to C7-o-S3, and 08A---C5 similar to 07-06 (0.01 A deviation
allowed). The phenyl ring carbon atoms C25 and C26 were found to be
disordered and were refined isotopically as groups 025A, 025B and 026A,

026B, with combined occupancies of 1.0 for each set and restraints to keep

025A---024, C25Bm024 and 026A---C21, 026B---021 equivalent. All other
non-hydrogen atoms were refined anisotropically, except for solvent
molecules.

All hydrogen atoms except H24, and H26B were placed at calculated
positions. Those hydrogen atoms which are exceptions to this were located in
the difl'erence map and refined with their temperature factors riding the
atoms to which they are bonded. No hydrogen atoms were placed on 025A,
025B, or 026A. There is currently one unresolved area in the structure
containing 0104, 0105, C106, and 0107 which is contributing to the overall
poor refinement level. It appears that this group may be two overlapping
CH2012 molecules. The highest peaks remaining in the difference map are
currently located around the metal atom, and are near the terminal oxygen

atoms in the current model.

141

3. Results and Discussion
A. Reactions With [M2(NCCH3)10] [BF4]4 (M: Rh, Re).

The reaction of [Rh2(NCCH3)1o][BF4]4 and P1 in a 1:4 ratio
instantaneously produced an opaque green solution in acetonitrile. A dark
green, nearly black, solid was obtained by precipitation with diethyl ether
which left behind an orange solution. The solubility of P1 in diethyl ether is
quite high, thus it is most likely the source of the color. Based on the
recovery of 0.011 g of unreacted P1, the actual reaction stoichiometry is 1:1.
Unfortunately, attempts to grow crystals suitable for a single crystal X-ray
difiraction study have proven unsuccessful to date. The color change to green
is indicative of TTF oxidation, most likely accompanied by partial reduction
of the han,II dinuclear precursor to ham. Such a redox reaction has been
observed in the reaction between [Rh2(NCCH3)1o][BF4]4 and o-P2 as well.3b
The green color is also reminiscent of the powder samples of the
paramagnetic material {[Rh(N00H3)4][BF4]1,5}a, which is obtained from bulk
electrolysis of reactions of [Rh2(NCCH3)1o][BF4]4.22

The 1H NMR spectrum of the green product (15) is essentially
featureless, exhibiting only broad resonances from 1.5 to 2.5 and 7.0 to 9.0
ppm. A 31P NMR signal was not observed, further supporting its assignment
as a paramagnetic species. An EPR spectrum of the product at 133 K in a 1:1

CHaCN/toluene glass displays a sharp signal with anisotropic g values of g1

142

.M m2 00 000E 2003902533

0 E Hm + AQEGXAEOOZVEE 89a 0200 ofimawmamuwa G000» mo 85.50050 mmm .mu 0.3mm...“

 

 

 

 

 

.2 85
ommm Oman
.1 1 at 1 1% 1 4111 <1 1 1 «111 11111u141 1 11 .11 11111.411 1 1.111 111 1.4 1 111i1
L .
o
8.013
w
Sena
Pliib)>.>-1 +>pi>>)b?>iib>pbe>>1r+51>>|l|>p>>P>>ip>bpitrbppppbi >p1v1-rlp>p p>pb + r b - pp pppi

 

 

 

143

= 2.01 and g2 = 2.00, as seen in Figure 25. This anisotropy is characteristic of
[TTF]'+ (g1 = 2.011, g2 = 2.009, g3 = 2.002).23 The narrow signal spans 51 G,
which is indicative of an organic rather than metal-based radical which
supports the [TTF] "*‘ oxidation product mentioned previously.

The electronic absorption spectrum of 15 recorded in CH2012 exhibits
the characteristic phenyl and TTF chromophore absorption bands for an

oxidized TTF at Amax = 510 and 600 nm. The transition at 510 nm can be

assigned as an intermolecular excitation of the TTF'+ radical by analogy to
previous studies of TTF.24 The infrared spectrum of the product displays
bands assignable to the phenyl rings of the ligand at 695 and 530 cm'l, as
well as a broad feature at 1050 cm:1 which is indicative of the [BF4]' counter-
ion. A salient feature of the spectrum is the absence of any bands indicative
of acetonitrile. It has been noted that the solvated Rh wire,
{[Rh(NCCH3)4][BF4]1,5}u, exhibits very weak nitrile stretches in its IR
spectrum.25 Another possibility is that the orange product is actually a
combination of unreacted ligand and [Rh2(NCCH3)10][BF4]4, with the green
product being [Pl][BF4]. If indeed the true stoichiometry of the reaction is
1:1 there must be acetonitrile to complete the coordination sphere. This
would account for the absence of the typical absorbances associated with the
expected Rh species in the electronic spectrum, as well as the lack of
acetonitrile bands in the infrared spectrum. It does not, however, account for

the small amount of solid which was recovered from the orange filtrate.

144

The reaction of [Re2(NCCH3)1o][BF4]4 with 4 equivalents of o-P2
produces similar results. Upon combination of both reactants in acetonitrile,
the reaction solution becomes dark green in color. Precipitation with diethyl
ether reveals a paramagnetic green solid as evidenced by its 1H and 31P{1H}
NMR spectra. An EPR spectrum of this product in a 1:1 CHsCN/toluene
glass at 133 K reveals a very sharp signal at g = 2.00. Based on this signal it
can be surmised that the product is a radical resulting from oxidation of o-P2,
possibly accompanied by reduction of the R624+ core from R9211.II to Rezn’l.

B. Preparation, Characterization and Reactivity of [Re012(o-

P2)2] [R82C16(o-P2)] (16.17)

(1) Reactivity of [(n-Bu)4N]2[RezCls] with o-P2 (1).

The unusual salt [Re012(o-P2)2] [Re2016(o-P2)] (16017) is prepared in
highest yields fi'om the reaction of [(n-Bu)4N]2[RezCls] with 2.4 equivalents of
o-P2 in refluxing ethanol. The reaction is extremely time and solvent
dependent. The use of solvents other then ethanol, such as acetonitrile or
acetone result in a different set of product(s) or in no reaction. Refluxing the
mixture for longer than 1.5 h. results in a green product which is more
soluble than 16°17 in acetone and acetonitrile. This type of solvent
dependence has been documented in similar reactions?”3 The time
dependence is most likely a result of 17 being an intermediate complex for
another product, possibly a-Re2014(o-P2)2 or [Re012(o-P2)2]Cl, where 0: refers

to the chelating ligand, and B the bridging form.

145

The mononuclear cation [trans-Re012(o-P2)2]+ (16) results from
nonredox cleavage of the dimetal unit, which is not particularly surprising
given the demonstrated ability of bidentate phosphines to cleave the
quadruple bond of [RersP- species. Similar reactions involving other
bidentate phosphine ligands with an ethene backbone, such as
bis(diphenylphosphino)ethene (dppee)27 and bis(diphenylphosphino)benzene
(dppb)26 performed in alcohols produce the analogous complexes [trans-
ReX2(LL)2]X (LL = dppb, dppee; X = Cl, Br). Analogous behavior has also
been noted with ligands such as bis(diphenylphosphino)ethane (dppe),2'28‘a
bis(diphenylphosphino)amine (dppa),28b bis(diethylphosphino)ethane
(depe),28c and bis(ditolylphosphino)ethane (dtpe).28d

The anion in the structure, [a-Re2016(o-P2)]' (17), results from the
substitution of two chlorides on [Re2013]2' with concomitant reduction of the
rhenium core from Re26+ to Re25+. The reaction conditions are similar to those
reported for the synthesis of a-Re2X4(dppee)2 (X = Cl, Br),29 but in the present
case only one chelating diphosphine ligand enters the coordination sphere. It
is interesting to note that the dppee reactions proceed with M-M cleavage to
yield the mononuclear Re(III) cation [ReX2(dppee)2]+ with no evidence of the
more substituted products of the type encountered in this study. The
dinuclear anion 17 appears to be a previously undetected intermediate in the
conversion of [ReraP' compounds to the bis-substituted Re2014(P-P)2

compunds.

146

(2) Crystal Structure of [Re012(o-P2)2] [Re2016(o-P2)] (16°17).

Thermal ellipsoid plots drawings of the ions [ReClz(o-P2)2]+ (16) and

[Re2016(o-P2)]‘ (17) are depicted in Figures 26 and 27. Selected bond

distances and angles are provided in Tables 10 and 11 respectively. The

asymmetric unit consists of one [Re2016(o-P2)]‘ (17) moiety, two half [Re012(o-

P2)2]+ (16) units, and four solvent molecules. The cations are six-coordinate
with trans chelating phosphine ligands. The angles P(3)-Re(3)-P(4) and P(4)-
Re(3)-Cl(7) are 80.62 (13)° and 92.50 (13)° for one cation, and P(5)-Re(4)-P(6)
= 79.63 (14)° and P(6)-Re(4)-Cl(8) = 88.42 (14)° for the second independent
cation. These values are comparable to those observed in similar cations?“-28
The average Re-Cl and Re-P values of 231(1) A and 2.459(3) A respectively
are similar to corresponding distances reported for analogous bis-diphosphine
complexes, [Re012(P-P)2]+ (P-P = dppee, dppbe, dppe, dppa, depe, dtpe). In
the o-P2 ligand, representative distances e.g., C(33)-C(34) = 1.33(2) A and
S(5/6)-C(33/34) = 174(2) A are essentially unchanged relative to the bond
lengths in the free phosphine ligand.30 These data suggest that there is no
pronounced electronic change in the dithiole system due to the electronic
donation of the phosphorus to the metal center. The out-of-plane bend of 22°
at the 8(5) and S(6) positions is similar to those observed for [Rh(o-
P2)2][BF4],3b [Ni(o-P2)2][BF4]2 (8), and [Pt(o-P2)2][BF4]2 (11)31 and is most
likely due to packing influences. The corresponding bend in the cation

containing Re(4) is much smaller, being only 11°. This difference in the out-

147

Table 10. Summary of bond distances (A) and angles (deg) for the cation
[ReClz(o-P2)2]+ (16) in 16° 17.

Bond Distances

 

 

A B A-B (A) A B A-B (A)

Re(3) P(3) 2.456(4) Re(3) P(4) 2.457 (4)

Re(3) 01(7) 2.296 (4) P(3) C(33) 1.840 (14)

P(3) C(41) 1.83 (2) C(33) C(34) 1.33 (2)

C(33) 8(5) 1.74 (2) 8(5) C(35) 1.77 (2)

S(7) C(37) 1.73 (2) C(37) C(38) 1.33 (3)
Bond Angles

 

A B C A-B-C (°) A B C A-B—C (°)

 

P(3) Re(3) P(4) 80.62 (13) P(3) Re(3) P(4A) 99.38 (13)
01(7) Re(3) P(4) 92.50 (13) Re(3) P(3) C(33) 105.5 (5)

Re(3) P(3) C(41) 123.7 (5) P(3) C(33) C(34) 120.3 (12)
C(33) S(5) C(35) 93.6 (7) 8(5) C(35) S(6) 114.2 (8)

148

.mEOwnEm 323303 £8 £9: .3 3338an
macaw ammouvznéo: 8:3 85 +SONANméVwE qoflg wfi mo .53 383—3 _waumnfi an 0.2—mum

om Mm 3.“ 80
n. .. u. .4 m8 . .
a
a
.. 20 A e,
4 n.»
x O
c" 01. 0 V4. KIND

I
8 a .., 38

 

149

Table 11. Summary of bond distances (A) and angles (deg) for the anion

[R92C15(o-P2)]' (17) in 16-17.

Bond Distances

 

 

 

 

150

A B A-B (A) A B A-B (A)
Re(l) 125(2) 2.2402 (2) Re(l) P(1) 2.335(5)
Re(l) P(2) 2.337 (5) Re(l) 01(1) 2.330 (4)
Re(l) 01(2) 2.337 (4) Re(2) 01(3) 2.315(4)
Re(2) 01(4) 2.325 (4) Re(2) 01(5) 2.351 (4)
Re(2) 01(3) 2.313 (5) P(1) 0(9) 1.34 (2)
P(1) 0(1) 1.32 (2) 0(1) 0(2) 1.33 (2)
0(1) S(1) 1.75 (2) 0(3) 0(4) 1.33 (2)
0(4) 8(4) 1.72 (2) 0(5) 0(3) 1.32 (3)
Bond Angles
A B 0 A-B-C (°) A B C A-B-C (°)
Re(l) Re(2) 01(4) 110.04 Re(l) Re(2) 01(3) 100.2
Re(2) 115(1) 01(1) 107.2 113(2) Re(l) 01(1) 111.3
Re(2) Re(l) P(1) 97.2 01(2) Re(l) 01(1) 33.1
P(2) Re(2) 01(1) 157.0 01(3) Re(2) 01(3) 35.9
01(3) Re(2) 01(5) 150.9 Re(l) P(2) 0(2) 105.3
01(2) 115(1) P(2) 93.1 P(2) 0(2) 0(1) 113.7
0(1) 0(2) 8(2) 115.3 S(2) 0(3) S(1) 114.3

 

Figure 27 . Thermal ellipsoid plot of the anion [RezCls(o-P2)]' (17) with non-
hydrogen atoms represented by their 50% probability ellipsoids.

151

 

Figure 28. Packing diagram of [ReC12(o-P2)2][Re2C16(o-P2)] (16-17).

152

of-plane bend may account for the slight differences in the magnitude of the
bonds and angles of the dithiole rings for the two cations.

The anion, 17, is an unsymmetrical mixed-valence Re(II)-Re(III)
molecule with four chloride ions residing on Re(2), and two chloride ions
along with one chelating o—P2 ligand being coordinated to Re(l) in an eclipsed
conformation when viewed down the Re-Re axis. The Re-Re distance is
2.2402(9) A, which, based on the qualitative overlap scheme for the M2L3
geometry, represents a bond order of 3.5 (027146231 electronic configuration).
This is reasonable given that it is a little longer than the Re-Re quadruple
bond in [Bu4N]2[RezCla] which is 2.222(2) A} but shorter than the metal-
metal distance in the triply bonded compound Re2C14(dth)2 (2.293(2) A).30 It
should be noted that this distance is much longer than the those in the more
symmetrical Re2(II,III) phosphine cations [RezCl4(PMe3)4]+ (2.205(1) A) and
[Re2C14(PMe2Ph)4]+ (2.218(1) A). This may be due to the fact that the orbitals
are more contracted in the cations and therefore the metal ions are required
to be closer in order to achieve good overlap.32 The Re-Cl distances on the
"formally" Re(III) center range from 2.313(5) to 2.351(4) A, as compared to
the average distance of ~2.29(2) A in [Re2C13]2-.33 The Re-Cl distances to
Re(l) are Re(1)-Cl(1) = 2.330(4) A and Re(1)-Cl(2) = 2.337(4) A. These are
longer than corresponding values in [RezCh(PMe2Ph)4]+ (Re-Cl = 2.33 A) and
[Re2C14(PMe3)4.]+ (Re-Cl = 2.34 A).32 The only other dinuclear complexes with

a single chelating ligand of which we are aware are [Bu4N] [RezCl7(dto)] (dto =

153

3,6-dithiaoctane) and [Bu4N][RezCl7(dth)],34 however in both of these cases
the coordination mode for the bidentate ligand is axial-equatorial rather than
equatorial-equatorial.

(3) Spectroscopic Characterization of [ReClz(o-P2)2] [Re2C13(o—P2)]

(16°17)

The paramagnetic nature of [ReC12(o-P2)2][RezC13(o-P2)] leads to a
broad, featureless 1H NMR spectrum and the complete absence of 31P{1H}
NMR signals. The IR spectrum confirms the presence of v(Re-Cl) stretches at
329, 333 and 352 cm'l. The electronic absorbance spectrum reveals the
characteristic phenyl and TTF-based transitions that are attributable to the
ligand at 276, 322, and 448 cm‘l. The extinction coefiicients of the TTF bands
are reliable indicators of the number of chromophores in the molecule.8a
Thus based on the fact that free o-P2 with four phenyl groups exhibits a band
at 276 nm with an 8 value of 25,000 M'lcm'1 and [ReC12(o-P2)2][Re2C16(o-P2)]
exhibits a transition at 27 6 with 3 value of 74,600, one can ascertain that the
compound contains three TTF phosphines (or 12 phenyl groups). The low-
energy transition at 976 nm in the near-IR region signifies a 8 —> 6*
transition for a mixed-valence Rem-ReIII complex.2 The FAB mass spectrum
of 16°17 displays the highest mass peak at m/z = +1457 which is consistent
with the presence of the cation [Re2C12(o-P2)2]+. In the negative ion mode, the

highest mass peak is at m/z = -1186 which is consistent with the anion,

[R62C16(0-P2)]'.

154

(4) Isolation of [ReClz(o—P2)z]+ (16)

(i) Reduction of [ReClz(o-P2)2] [Re2(o-P2)C13] (16°17). Reaction of 16°17
with a slight excess of the reducing agent (30sz affords a yellow solid
identified as ReC12(o-P2)2 (18) on the basis of infi'ared, mass spectroscopic
and magnetic susceptibility measurements. This reaction is similar to one
reported by Walton et. al. for the reduction of [ReC12(dppee)2]Cl to
ReClz(dppee)2.27 The neutral compound 18 is fairly insoluble, thereby
allowing it to be separated from the by-product salt [Con2][RezCls(o-P2)].
The FAB mass spectrum of 18 contains a parent ion peak at m/z = 1457 for
both positive and negative ion spectra which is consistent with ReC12(o-P2)2.
These results are in accord with 18 being neutral since both positive and
negative ions were detected. The infiared spectrum of 18 exhibits modes due
to o-P2 at 513 and 702 cm"1 and a characteristic v(Re-Cl) feature at 330 cm'l.
(ii) Oxidation of ReC12(o-P2)2 (18). In order to further characterize the
cation as found in the original compound, ReC12(o-P2)2 was re-oxidized by
gently refluxing the compound in CCl4/CH2C12. It had been reported earlier
that such conditions led to the oxidation of ReC12(dppb)2 to
[ReC12(dppb)2][Cl].26 Mass spectroscopic analysis of 16° [Cl] gives a parent
ion peak at m/z = +1457, which is in accord with the presence of [ReC12(o-
P2)2]+. Based on the chemistry of similar complexes, it is reasonable to
assume that 16 retains the trans configuration throughout the redox

reactions.”27 Alternatively one can treat 18 with NOBF4 to yield [ReClz(o-

P2)2][BF4] (16°[BF4]), but care must be taken not to add excess oxidant, as
this will lead to oxidation of the TTF substituents as well. If this occurs, the
solution assumes an intense green color.
(5) Electrochemical Studies

As Figure 29 shows, the electrochemistry of [ReC12(o-P2)2][Re2Cle(o-
P2)] in 0.1 M TBABF4/CH2C12 is complicated. This is due to the presence of
three redox-active Re ions as well as three TTF phosphine ligands that are
each capable of undergoing two one-electron oxidations. The most likely
possibilities for redox processes based on the established electrochemistry of
the o-P2 molecule and similar Re compounds whose electrochemical
properties have been reported are provided in Table 12.;. The compound

Table 12. Possible redox reactions for the salt [RemC12(o-P2)2]-[Rezn'mCldo-
P2)] (1317).

 

 

 

[R3111012(o--P2)2]+ (16) [Reznvale(o-P2)]' (17)
oxidations oxidations
Re(III) —-> Re(IV) Re2(II,III) —> Rez(III,III)

Re(o-P2)2° -> Re(o-P2)22+ (2 e- total) Re2(o-P2)0 _, Re2(o-P2)+ (1 e-)
_Ije(O-P2)22+ -) Re(o-P2)24+ (2 e_ total) Re2(o-P2)+ _) Rez(o-P2)2+

 

 

reductions reductions
Re(III) -> Re(II) Re2(II,III) —-) Re2(II,II)
_Rean -+ 320)

 

156

(a)

 

(b)

 

l l
+1.6 0.0 -l.6

Volts versus Ag/AgCl

Figure 29. Cyclic voltammogram of (a) [ReC12(o-P2)2][Re2C16(o-P2)] (16°17)
and (b) [ReC12(o-P2)2][BF4] in 0.1 M TBABF4/CH2C12 vs Ag/AgCl
at a Pt disk electrode.

157

exhibits four TTF phosphine-based oxidation processes and three metal-
based reductions, two of which would be expected to be fairly accessible,
namely Re(III) —> Re(II) and Re2(II,III) —> Re2(II,II), and one of which would
be much less accessible, namely Re(II) —>Re(I). The two TTF phosphine
ligands on the mononuclear cation, 16, undergo oxidations at the same
potential, therefore the coincidence of these processes leads to a total of 2 e'
being associated with these couples.

Obviously the only way one can assign the redox processes for the
individual ions in 16°17 is to prepare at least one ion separately with an
"innocent" counterion. In this vein, we have prepared and measured the
electrochemistry for [ReC12(o-P2)2][BF4]) in a 0.2 M TBABF4/CH2C12 solution
at a Pt disk electrode (Figure 29. The salt (16°[BF4]) exhibits couples at
E1/2(ox)1 = +0.75 V, E1/2(ox)2 = +1.14 V and E1/2(red)1 = +0.07 V, with an
irreversible reduction process located at E(p,c)1 = -1.02 V. The published data
for the related mononuclear Re(III) salt [ReC12(dppee)2]Cl, recorded on 0.1 M
TBAH/CHzClz solutions using a Pt bead electrode, include an oxidation fi'om
Re(III) to Re(IV) at ca. +1.6 V and two reductions corresponding to
Re(III)/Re(II) and Re(II)/Re(I) at -0.2 and ca. -1.4 respectively.26 Based on
these results, we can conclude that the mononuclear cation 16 is responsible
for the oxidations at E1/2(ox) = +0.67 V and E(p,a) = +1.05, as well as
reductions at E1/2(red) = +0.03 V and Em) = -1.12 V in the c.v. of 16°17.

These are assigned to the two oxidations of the o-P2 ligands and reductions

158

from Re(III) —-)Re(II) and Re(II) —> Re(I) respectively. The Re(III)/Re(IV)
couple for trans-[ReC12(dppbe)2][Cl] was reported to occur at +1.51 V in a 0.1
M TBAH/CH2C12 solution,26 which is beyond the 1.50 V scan range used for
[ReC12(o-P2)2]+. The remaining features in the cyclic voltammogram of
16°17 are E1/2(ox)2 = +0.50 V, E1/2(ox)2 = +0.31 V and E(p,c)2 = -0.79 V which
are assigned as two o-P2 oxidations and a reduction from Re2(II,III)
—> Re2(II,II) in the dinuclear anion. The oxidation processes for the
coordinated o-P2 ligands are shifted to more positive potentials relative to the
free ligand (El/2(OX)1 = +0.41 V, E1/2(ox)2 = +0.85 V), with those associated
with the cation occurring at the highest values. This shift to higher
potentials is indicative of strong metal-ligand interactions which leads to an
electron-withdrawing effect on the TTF substituents.

(6) Magnetic Properties.

(i) [ReC12(o-P2)2][Re2C13(o-P2)] (16°17). (a) Magnetic susceptibility.
The magnetic susceptibility measurements of 16°17 compound shown in
Figure 30 reveal a Curie paramagnetic behavior for the salt with a Curie
constant C = 0.395 and a temperature independent paramagnetism contri-
bution (TIP) (XTIP = 9.64 x 10‘3 emu/mol).35 This TIP behavior was previously
noted for a similar series of Re111 complexes, ReX3(PR2Ph)2 (X = Cl, Br; R =

Me, Et), although in these cases, mp was somewhat smaller (in the range

1.66 - 1.36 x 10'3 emu/mol).36 The anion [Re2C16(o-P2)]' is a mixed-valence

159

AER mo one? a firs 33 $63

385 2: s a a: 232333 ...8 is: M :83 ex 3 3:3 as 232383 .9,
88389 sex 33 as 81 3 ”A: 3.: _amssosa33-93635 as 3% 355332 .3 25mg

C: 0.53quth
com com omm com c2 2: an o

 

 

 

 

FLpp—prbp—hb_pblbp..—».r-bbbpb—..-» C
A .I
A m
m mm c
H Y
1
1“ I a VA
. ... L
H H )
1. H... m H m
J .
A .. n
1. 1 N
. .. M
. w .
A v m N w...
.. ..
U H (v1
1. . m
1. w md
1%--33114134414.

F"eff (HB)

05 3332—808

com com cmN ecu cm: 2: cm a

O up.ppPppp—thpbp-pphppppP-PPB—fhpr

 

oooooooooooooooooooooooooo
O
7. oo

0355

a -. Ba

0

o 0000

T I

 

.1 85

w 86
85

III]

H. 36
w 85
w 85

w 8.:

 

w uau<-q14«d.¢<q—*qda—ddq4_aq-14—1q44

mod

 

(lam/ma) tomx

160

compound with an overall d9 configuration and therefore should have an S =

1/2 ground state. Given that C = 0.395 for [Re2C16(o-P2)]- 17, we can
estimate peg to be ~1.77 1113. This value is in good agreement with data
obtained for similar compounds, such as [Re2C14(PMe2Ph)4][PF6], which
exhibits a moment of ~1.8 113 at room temperature,” and [R32X4(dppm)2][PFs]
(X = Cl, Br) which exhibit moments of ~1.5 113.38

(b) EPR specrosc0py. The EPR spectrum of [ReC12(o-P2)2][RezCle(o-P2)]
(16°17) in a 1:1 CH2C12/toluene glass at 4 K is shown in Figure 31. A
complex pattern is observed that is indicative of hyperfine coupling to the
185Re (I = 5/2) and 31P (I = 1/2) nuclei. The spectrum is centered at 2833 G (g

= 2.40). Given the complexity of the spectrum, exact g 1 and g“ values were

not able to be determined. Similar spectra have been reported for 1,3,6-
Re2C15(PMe3)3 and 1,2,7-Re2C15(PMe3)3.39

(ii) [ReC12(o-P2)2] [BF4] (16°[BF4]). The susceptibility measurements of the
separate mononuclear cation, 16, reveal a TIP (xnp = 10.7x 10'3
emu/mol) with an extrinsic paramagnetic (Curie) contribution being observed
at low temperatures. Assuming this impurity is an S=1/2 system, it can be
estimated that it is 10% of one spin 1/2. The value for mp agrees quite well
with the previously calculated value for 16° 17.

(iii) ReC12(o-P2)2 (18). The (15 compound, 18, contains the same ligand

system as 16 and is expected to possess one unpaired electron (S=1/2). The x

161

.m 3 B 3% 36353533 3 3 a... A: .45 23-93638:33.93534: B 888.3% mam .5 352m

R:

ooov ooom ooom coo“
_ _ _ _ _ _ _ _ com:

 

1 00m:

1_oov1

1.oom1

 

Inoom

.100?

Inoom

 

 

1.00m

 

162

own

111‘

0.: 235.8986?
can can com 03 2: on

l-rbhbpbbbebhhhPPbfih—DP>PrbbhbbhrP

  

YVIIIIYTYITYY'

 

 

ud-fi—q‘dq—adqd—quqd—qdi<—(dd~q——44|fil

 

IrrrrlrrrrwrrvrIrtr
H

.eaaéc Emfiouaméoa .8 2338583
.m> 9.38 M :88 Ex 39 98 0d 23.26388 .m> 9253.88 sex 38 5.9 .81va mo 33m .Nm mun—ma

(1.1mn x mm) .Lx
“err (“13)

Cd 333353.

 

 

omm com com com can 2: an o
o » prp — - PpLLP» » p p — . p p. — uh?» — p p pp — p p .b—
ooooooooooooooo So
7. H
H .12.; X
. ca
«1. _ . N o a W m.
H II on \a)
“I“ &.w0 I. 011 NCO m
. a I u
. I . N
U I 0.. w
T. .. - Lego u
. I I .
. I .
mi... I I O .
1441111AJ ‘ .4 — «q a 1d d u «d — dd 1 «411 «1 ~44 d 1 ”CO

 

 

163

 

025lmhi1l1111lirinliililiiixliiiili111
O

 

 

.l :5
I _
.I _
A 0.2 II :4
I L
20.15 ..l . u :3 (a:
8 .I eff C :3"
.— X “ t
o .
E 0'1 0 mol :2 9
>4 :0 _
005{% 31
1%000000000000000 :
0' l“‘17"'I"T‘I“"l""l""0'

 

0 50 100 150 200 250 300 350
Temperature (K)

Figure 33. Plot of peer (11B) and Xmol (emu) vs. temperature (K) of ReC12(o-
P2)2 (18).

164

versus T data follow a Curie law with a C = 0.392 and a xTIP = 9.34 x 10'3
emu/mol. This is in agreement with the presence of non-interacting S=1/2
ions (C=0.375 for S=1/2 and g=2). The moment at r.t. is ~ 4.9 113.

C. Reactions of M02[S(CH3)2]4C14 with o-P2.

(1) Synthesis

Reactions to yield products of the type M02X4L4 and MozX4(LL)2 are
well documented in the literature.2 Given the existence of M02X4(dppee)2 (X
= Cl, Br, I)41 and a-M02X4(dppb)2 (X = C1 or Br),428 the possibility of forming
M02X4(o-P2)2 species would appear to be promising. To this end, the reaction
of M02Cl4[S(CH3)2]4 with two equivalents of o-P2 was undertaken, and it was
discovered that the reaction is dependent on the solvent and the presence or
absence of air.

The use of acetonitrile results in an emerald green solution which
becomes dark brown over time and yields a green precipitate. When the
reaction is performed in air with CH2C12 as the solvent, however, a
homogeneous brown solution is obtained after stirring for approximately the
same length of time. This brown solution is also observed to form under
anaerobic conditions, but the reaction is slower and a precipitate forms. The
addition of CHzClz to the green precipitate from the reaction using
acetonitrile causes an immediate color change to brown. The varied results
obtained from difi'erences in the solvent and reaction conditions are not

surprising, given the previously documented reactions involving dppb, dppe,

165

and dpdt.‘12 Solution studies and solid state properties of the on and B isomers
of dpdt support the conclusion that the B-isomer is generally the
thermodynamically favored form, but that the a-isomer can be obtained in
solvents that take advantage of its low solubility. Similar behavior would be
expected for reactions aimed at the synthesis of MmX4(o-P2)2. The pr0posed
mechanism for the occurrence of both isomers from a precursor that contains
trans leaving groups (i.e. trans-M02X4L4) involves internal rotation of the M02
unit within the ligand fiamework.42d»43

Slow evaporation of solvent from the brown solution of CH2C12, in air,
yielded brown crystals, identified as MoC1202(o-P202) (19) by X-ray
crystallography. The formation of 19 is due to degradation of the o-P2 to the
phosphine oxide, most likely caused by moisture. Oxidations of this nature
are not uncommon with the tetrathiafulvalene phosphines, as the formation
of P402 from P4 has been observed to occur.44 Oxygen adducts have also
been commonly observed in the FAB-MS spectra of the homoleptic o-P2
complexes.44 Furthermore, quadruply bonded M024+ complexes are subject to

oxidative cleavage upon reaction with strong donor ligands.2

Ph2

Pph2

thP

Ph2

166

(2) Crystal Structure of MoC1202(o-P202) (19)

A PLUTO drawing of MoC1202(o-P202) (19) is provided in Figure 34,
while selected bond distances and angles are provided in Table 13. The
neutral compound is six-coordinate with axial chlorides and oxygen atoms
trans to the bis-phosphine oxide, o-P202, unit. The Mo-Cl distances of
2.412(3) and 2.330(3) A are comparable to 2.410(1) A, as found in
MoC12(dppb)242a and 2.3903(3) for MoC1202[OPCH2(C2H4OCH3)2]2.45 The
angles around the metal center O(l)-Mo(1)-O(2) = 7 8.4(4)°, O(3)-Mo(1)-O(4) =
98.6(7)°, Cl(1)-Mo(1)-Cl(2) = 165.7(2)°, and O(l)-Mo(1)-Cl(1) = 87.4(4)°,
indicate a highly distorted octahedral geometry, with the chlorides bent away
from the phenyl rings of the o-P202 ligand with Cl(1)-Mo(1)-Cl(2) = 165.7 (2)°.
Such a distortion from 180° is caused by repulsions from the bulky phenyl
groups, and has been reported for the related compound
MoClez[OPCH2(C2H4OCH3)2]2, with a C1(1)-Mo(1)-Cl(2) angle of 166.0(1)°.
The Mo(1)-O(1) and Mo(1)-O(2) distances of 2.091(11) and 2.214(10) A fall
outside of the values observed for MoC1202[OPCH2(C2H4OCH3)2]2 (2.149(4)
and 2.157(7) A). The Mo(1)-O(3) distance of 167(2) A is reasonable for a Mo-
O(oxo) bond, which are typically in the range 1.68(3)-1.77(3) A46 The
elongation of Mo(1)-O(2) can be attributed to the strong trans influence of the
terminal Mo-O(oxo) bond. The Mo(1)-O(4) distance is significantly longer at

2.114(9), and is closer to the terminal Mo-OHZ interaction reported for (p-

CH306H4NH)2M0216(H20)2 (2.188(11) = MO-O) and (p-CH3C6H4N)2M0216(1'120)2

167

P202) ' CH2C12 (19 ‘ CH2C12).

Bond Distances

Table 13. Summary of bond distances (A) and angles (deg) for MoC1202(o-

 

 

 

 

A B A-B (A) A B A-B (A)
Mo(l) 0(1) 2.091 (11) Mo(l) 01(1) 2.412(3)
Mo(l) 0(2) 2.214 (10) Mo(l) 01(2) 2.330 (3)
0(1) P(1) 1.433 (12) Mo(l) 0(3) 1.37 (2)
0(2) P(2) 1.434 (11) Mo(l) 0(4) 2.114 (9)
0(1) 0(2) 2.313 (5) 0(3) 0(4) 1.34 (2)
0(5) 0(3) 1.32 (2) 8(1) 0(2) 1.75 (2)
S(2) 0(1) 1.77 (2) 8(3) 0(5) 1.75 (2)
8(4) 0(3) 1.75 (2) 0(5) 0(7) 1.45 (2)

Bond Angles
A B C A—B-C (°) A B 0 A—B-C (°)
0(1) Mo(l) 0(2) 73.4 (4) 01(1) Mo(l) 01(2) 135.7(2)
0(3) Mo(l) 0(4) 93.3 (7) C(2) S(1) 0(3) 93.2 (7)
0(1) Mo(1) 01(1) 37.4 (4) 0(5) 8(3) 0(4) 933(3)
Mo(l) 0(1) P(1) 147.3(3) 0(5) 0(3) C(8A) 123.0 (14)
0(3) Mo(l) 0(1) 90.7 (7) 0(5) 0(3) C(8B) 124(3)
0(1) P(1) 0(2) 113.0(7) 8(3) 0(4) 8(4) 112.4(9)
P(2) 0(1) 0(2) 123.2 (13) S(1) C(3) S(2) 112.1(7)

168

 

Figure 34. PLUTO representation of MoClez(o-P202) (19).

169

(2.191(10) = Mo-O).47 Although attempts to identify remaining peaks in the
difference map have proven to be unsuccessful, the coordinated water
molecule would account for the unusually close Mo(1)-O(2) distance and the
O(3)-Mo(1)-O(4) angle being less than 102°. Cis-dioxomolybdenum complexes
exhibit angle widening caused by strong repulsions of the strongly bonded
terminal oxygen atoms.45 As the structure currently stands, the metal is
MoVI (do), however if 0(4) is actually a water molecule, the oxidation state
would be to MoIV (d2).

The angle between the planes defined as O(l)-Mo(1)-O(2) and 0(1)-
P(1)-P(2)-O(2) is 24.0(6)°. With respect to the TTF core, all distances and
angles are within normal ranges for the o-P2 unit, while the angles between
the plane S(1)-S(2)-C(3)-C(4)-S(3)-S(4) and the planes defined as S(1)-C(2)-
C(1)-S(1) and S(3)-C(5)-C(6)-S(4) are 28.7(4)° and 7.4(9)°, respectively. The
larger of the two bends follows the trend observed for other M(o-P2)
complexes such as [Rh(o-P2)2][BF4]2, [Ni(o-P2)2][BF4]2 (8), [Pt(o-P2)2][BF4]2
(11), [ReClz(o-P2)2]+ (16), and [Re2C13(o-P2)]' (17), where the bend occurs at
the sulfur positions closest to the phosphines.

(3) Spectrocscopic Characterization of MoC1202(o-P202) (19)

The 1H NMR spectrum of the green solid obtained from the reaction of
M02[S(CH3)2]4C14 with o-P2 in acetonitrile shows resonances due to dimethyl
sulfide and free o-P2. The singlet at 2.15 ppm is indicative of the methyl

protons of bound dimethyl sulfide. Resonances at 6 = 1.85 and 7.37 ppm are

170

due to the methyl and phenyl protons of the o-P2 ligand. The resonance at
1.95 ppm suggests the presence of an acetonitrile containing product, with
fast exchange occurring with the deuterated solvent. The 31P{1H} NMR
spectrum displays only a single signal, at -17.6, due to free o-P2. The
presence of a band at 600 nm in the electronic absorption spectrum supports
the presence of M02C14(NCCH3)4. Due to the close proximity of the
characteristic absorption bands of the 8—>5* transitions of M02C14[S(CH3)2]4
(595 nm) and MozCl4(NCCH3)4, (602 nm) it is not surprising that only a
single broad band is observed. Such a conversion to the solvated complex
should not be unexpected given the published synthesis of MozCl4(NCCH3)4
involves the reaction of M02Cl4[S(CH3)2]4 with acetonitrile at ambient
conditions for 12 hours.17

Analysis of the brown solution obtained from the same reaction
revealed very different results. The 1H NMR spectrum displays resonances
at 1.81, 1.84, and 2.13, with several broad signals between 7.2 and 7.6 ppm.
The set of broad resonances at lower fields can be assigned to the phenyl
protons of the o-P2 ligand. Likewise, the upfield resonances at 1.81 and 1.84
ppm are most likely due to two difi‘erent environments for the methyl protons
of o-P2. The resonance at 2.13 ppm can be assigned to the methyl protons of
unreacted SMe2 containing starting material. The 31P{1H} NMR spectrum
indicates the presence of at least two different environments of bound

phosphine. The resonance at 40.7 ppm is downfield shifted from the free

171

ligand by 59 ppm. This value is within the range observed for other Mo-P
complexes, and is characteristic of five-membered rings formed by chelating
phosphines.41a The other set of signals occurs further upfield as two sets of
doublets centered at -1.39 ppm. A pattern such as this indicates two different
phosphorus environments with PA-PB coupling. Assuming the two signals
centered at -O.64 result from PA coupling to P3, and the signals centered at
-2.71 ppm represent the coupling of P3 with PA, the coupling constants are
1JPA.pB = 17.1 Hz, and 1JpA.pB = 19.5 Hz. If the pattern is viewed as two
overlapping doublets, with the outer two (057 and -2.63 ppm) signals
originating from PA, and the inner two signals (-O.71 and -2.80 ppm)
originating from P3, the coupling constants are 1J1>A.1>B = 249.4 Hz, and
1JPA.PB = 251.8 Hz. While neither calculation provides PA-PB coupling
constants that are identical, the first interpretation is consistent with what is
expected for cis-oriented phosphines.48 The latter pattern produces coupling
patterns which are to large for cis-oriented phosphines, are more
characteristic of trans-oriented. Because of this ambiguity, a coordination
mode cannot yet be assigned. The small downfield shift from the free ligand
at ~18.7 ppm,8a indicates that the phosphorus nuclei may not be directly
bound to the metal but that they may be separated by a third atom as in the
case of 19. Another possibility is that they are not interacting with the metal
at all.

The NMR spectra from the reaction with CH2C12 as the solvent display

similar results. Reaction of M02[S(CH3)2]4C14 with o-P2 in CH2C12 under

172

anaerobic conditions produced a green-brown precipitate and a brown
solution. A 1H NMR of the solid obtained from this brown solution contains
resonances in two regions of the spectrum. The singlet at 1.85 ppm results
from the methyl protons of the NF ligand, while the broad set of signals
between 6.9 and 7.3 ppm are due to the phenyl protons. The resonance
occurring at 40.0 ppm in the 31P{1H} NMR spectrum is indicative of metal-
bound phosphine, and is equivalent to the resonance observed in the
spectrum of the brown solution from the reaction with acetonitrile. Addition
of CH2C12 to the green solid eventually leads to this same brown solution as
evidenced by 1H and 31P{1H} NMR spectroscopy.

4. Concluding Remarks

Reactions of phosphine-fuctionalized tetrathiafulvalenes with metal-metal
bonded complexes occur by several different reaction pathways, depending on
the redox properties of the metal-containing complex, the solvent system, and
the general reaction conditions. The TTF functionality is capable of reducing
transition metals to mixed valence complexes, and effecting non-redox metal-
metal bond cleavage. Although the backbone of the o-P2 ligand is similar to
ligands such as dppbe and dppee, the B-bridging mode of o-P2 has not yet
been observed. The lack of a B-isomer for M02X4(dppbe)2 has been attributed
to the rigidity of the ligand, which leads to an inability to bridge the
dinuclear unit.428 This is was not the case for the dinuclear rhenium

complexes, as both isomers were crystallograhically determined for X = Cl

173

and Br. Whether this same argument can be made for the expected
chemistry for o-P2 remains to be seen. Reactions involving the starting
material trans-M02Cl4[S(CH3)2]4 may eventually provide evidence for the B-
coordination mode. Given the tendency for the TTF phosphine ligands to
form phosphine-oxides however, it will be necessary to study these reactions

under much more stringent experimental conditions.

174

10.

List of References

Cotton, F. A.; Hong, B. Prog. Inorg. Chem., 1992, 40, 179.

Cotton, F. A.; Walton, R. A. Multiple Bonds Between Metal Atoms, 2nd
Ed., Clarendon Press: Oxford, 1993, and references therein.

Puddephatt, R. J. Chem. Soc. Rev. 1983, 99.

(a) Higgins, S. J .; Levanson, W. J. J. Chem. Soc., Dalton Trans. 1986,
317. (b) Gray, L. R.; Higgins, S. J .; Levanson, W. J .; Webster, M. J. J.
Chem. Soc., Dalton Trans. 1984, 1433. (0) Fox, M. A.; Chandler, D. A.
NATO ASI Ser. C. 1987, 214, 405. ((1) Gray, L. R.; Gulliver, D. J.;
Levanson, W. J.; Webster, M. J. J. Chem. Soc., Dalton Trans. 1983,
133. (e) Warren, L. F.; Bennett, M. A. Inorg. Chem. 1976, 15, 3126.

(a) Mahadevan, C.; Seshasayee, M.; Ramakrishna, B. L.; Manoharon,
P. T. Acta Crystallogr., Sect. C 1985, 41, 38. (b) Bennett, M. A.;
Robertson, G. B.; Rosalky, J. M.; Warren, L. F. ActaCrystallogr. Sect. A
1975, 31, 8136.

(a) Campbell, F. L., III.; Cotton, F. A.; Powell, G. L. Inorg. Chem.
1984, 23, 4222. (b) Cotton, F. A.; Dunbar, K. R.; Poli, R. Inorg. Chem.
1986, 25, 3700. (0) Campbell, F. L., III.; Cotton, F. A.; Powell, G. L.
Inorg. Chem. 1985, 24, 4384. (d) Cotton, F. A.; Dunbar, K. R.; Matusz,
M. Inorg. Chem. 1986, 25, 3641.

(a) Agaskar, P. A.; Cotton, F. A.; Derringer, D. R.; Powell, G. L.; Root,
D. R.; Smith, T. J. Inorg. Chem. 1985, 24, 2786. (b) Agaskar, P. A.;
Cotton, F. A.; Inorg. Chem. 1986, 25, 15.

(a) Fourmigué, M.; Batail, P. Bull. Soc. Chim. Fr. 1992, 12.9, 829. (b)
Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.; Bartley, S. L.;
Dunbar, K. R. J. Organomet. Chem., 1997, 52.9, 343.

Dunbar, K. R. J. Cluster Science 1994, 5, 125-146.

(a) Nocera, D. G.; Gray, H. B. J. Am. Chem. Soc., 1981, 103, 7349.
(b) Nocera, D. G.; Gray, H. B. Inorg. Chem., 1984, 23, 3686. (c)
Trogler, W. C.; Erwin, G. L.; Geoflroy, G. L.; Gray, H. B. J. Am. Chem.
Soc., 1978, 100, 1160. ((1) Chang, I.-J.; Nocera, D. G. J. Am. Chem.
Soc., 1987, 109, 4901. (e) Chang, I.-J.; Nocera, D. G. Inorg. Chem.,
1989, 28, 4309. (f) Partigianoni, C. M.; Chang, I.-J.; Nocera, D. G.

175

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

Coord. Chem. Rev., 1990, .97, 105. (g) Partigianoni, C. M.; Nocera, D.
G. Inorg. Chem., 1990,29, 2033.

Matsubayashi, G.; Yokoyama, K.; Tanaka, T., J. Chem. Soc. Dalton
Trans, 1988, 3060.

Munakata, M.; Kuroda-Sowa, T.; Masahiko, M.; Hirota, A; Kitagawa,
S., Inorg. Chem., 1995, 34, 2705.

Bousseau, M.; Valade, L.; Legros, J-P.; Cassoux, P; Garbauskas, M.;
Interrante, L. V., J. Am. Chem. Soc., 1986, 108, 1908.

(a) Dunbar, K. R. J. Am. Chem. Soc., 1988, 110, 8247. (b) Dunbar, K.
R.; Pence, L. E., Inorg. Synth. 1992, 29, 182.

Bernstein, S. N. ; Dunbar, K.R., Angew. Chem. Int. Ed. Engl., 1992, 31,
1360.

(a) Barder, T. J.; Walton, R. A. Inorg. Chem.,. 1982, 21, 2510. (b)
Barder, T. J .; Walton, R. A. Inorg. Synth., 1985, 23, 116.

San Filippo, Jr., J.; Sniadoch, H. J.; Grayson, R. L., Inorg. Chem.,
1974, 13, 2121.

SHELXTL v. 5., G. M. Sheldrick and Siemens Analytical X-Ray
Systems, Inc., 1995, 6300 Enterprise Lane, Madison WI. 53719.

MITHRIL: Integrated Direct Methods Computer Program, Gilmore, C.
J. J. Appl. Cryst. 1984, 17, 42.

Sheldrick, GM. SHELXL93. Program for the Refinement of Crystal
Structures. University of Gottingen, Germany, 1993.

SHELXTL v. 5.04, G. M. Sheldrick and Siemens Analytical X-Ray
Systems, Inc., 1997, 6300 Enterprise Lane, Madison WI. 53719.

Finniss, G.M.; Canadell, E.; Campana, C.; Dunbar, K. R., Angew.
Chem. Int. ed. Engl., 1996, 35, 2771.

Clérac, R. Ph. D. Dissertation, Université Bordeaux, 1., 1997.

Torance, J. B.; Scott, B. A.; Weller, B.; Kaufman, F. B.; Seiden, P. E.,
Phys. Rev. B., 1979, 19, 730.

176

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

Finniss, G.M.; Campagna, C.; Dunbar, K. R. manuscript in
preparation.

Esjornson, D.; Bakir, M.; Fanwick P. E.; Jones, K. S.; Walton, R. A.
Inorg. Chem., 1990, 2.9, 2055.

Bakir, M.; Fanwick, P. E.; Walton, R. A. Polyhedron, 1987, 6', 907.

(a) Jaecker, J. A.; Murtha, D. P.; Walton, R. A. Inorg. Chim. Acta.,
1975, 13, 21. (c) Barder, T. J .; Cotton, F. A.; Lewis, D.; Schwoltzer, W.;
Tetrick, S. M.; Walton, R. A. J. Am. Chem. Soc., 1984, 106', 2882. ((1)
Cotton, F. A.; Daniels, L. M., Inorg. Chim. Acta., 1988, 142, 255.
Anderson, L. B.; Bakir, M.; Walton, R. A. Polyhedron, 1987, 6‘, 1483.
(a) Bennett, M. J .; Cotton, F. A.; Walton, R. A. J. Am. Chem. Soc.,
1966, 88, 3 866. (b) Bennett, M. J .; Cotton, F. A.; Walton, R. A. Proc.
R. Soc., London, 1968, A303, 175.

Uzelmeier, C. E.; Fourmigué, M.; Grandinetti, G.; Dunbar, K. R.
manuscript in peparation.

(a) Cotton, F. A.; Dunbar, K. R.; Falvello, L. R.; Tomas, M.; Walton, R.
A. J. Am. Chem. Soc., 1983, 105, 206. (b) Cotton, F. A.; Jennings, J.
G.; Price, A. C.; Vidyasager, K. Inorg. Chem., 1990, 2.9, 4138.

Cotton, F. A.; Frenz, B. A.; Stults, B. R.; Webb, T. R. J. Am. Chem.
Soc. 1976, .98, 2768.

(a) Heyen, B. J .; Powell,G. L., Polyhedron, 1988, 7, 1207. (b) Heyen, B.
J .; Jennings, J. G.; Powell, G. L., Inorg. Chim. Acta., 1995, 22.9, 241.

Carlin, R. L.; Magnetochemistry, Springer: New York, 1986.

Gunz, H. P.; Leigh, G. J. J. Chem. Soc., 1971, 2229.

Prater, M. E.; Dunbar, K. R. unpublished results.

Costello, M. T.; Derringer, D. R.; Fanwick, P. E.; Price, A. C.; Rivera,
M. I.; Scheiber, E.; Siurek, III, E. W.; Walton, R. A., Polyhedron, 1990,
.9, 573.

Cotton, F. A.; Price, A. C.; Vidyasagar, K. Inorg. Chem. 1990, 29,
5143.

177

40.

41.

42.

43.

44.

45.

46.

47.

48.

Figis, B. N.; Lewis, J. Progr.Inorg. Chem., 1965, 6', 37.

Bakir, M.; Cotton, F. A.; Falvello, L. R.; Simpson, C. Q.; Walton, R. A.,
Inorg. Chem., 1988, 27, 4197.

(a) Bakir, M.; Cotton, F. A.; Cudahy, M.M.; Simpson, C. Q; Smith, T.
J .; Vogel, E. F.; Walton, R. A., Inorg. Chem., 1988, 27, 2608. (b)
Cotton, F. A.; Kitigawa, S., Inorg. Chem., 1987, 26, 3463. (0) Cotton,
F. A.; Kitagawa, S., Polyhedron, 1988, 7, 463. (d) Agaskar, P. A.;
Fanwick, P. E.; Fitch, III, J. W., Inorg. Chem., 1986, 25, 15.

Agaskar, P. A.; Cotton, F. A.; Deringer, D. R.; Powell, G. L.; Root, D.
R.; Smith, T. J., Inorg. Chem., 1985, 24, 2786.

(a) Fourmigue, M.; J arshow, S.; Batail, P., Phosphorus, Sulfur, and
Silicon, 1993, 75, 175. (b) Asara, J. M.; Uzelmeier, C. E.; Dunbar, K.
R.; Allison, J ., submitted to Inorg. Chem., 1997 .

Herbowski, A; Lis, T.; Deutsch, E. A., J. Organomet. Chem., 1993, 460,
25.

(a) Florian, L. R.; Corey, E. R., Inorg. Chem., 1968, 7, 723. (b) Cotton,
F. A.; Morehouse, S. M.; Wood, J. S., Inorg. Chem., 1964, 3, 1603. (0)
Cotton, F. A.; Wing, R. M., Inorg. Chem., 1965, 4, 872. (d) Atovmyan,
L. O.; Krasochka, O. N., J. Chem. Soc., Chem. Commun., 1969, 12, 649.
Brencic, J. V.; Segedin, P., Inorg. Chim. Acta, 1978, 29, L281.

Pregosin, P. S.; Venanzi, L. M., Chem. Br., 1978, 14, 276.

178

CHAPTER V

STEP-WISE SYNTHESIS OF METAL CONTAINING ARRAYS WITH

BI- AND TETRADENTATE TETRATHIAFULVALENE-PHOSPHINE
LIGANDS

179

1. Introduction

Our successful synthesis and isolation of the series [M(o-P2)2][BF4]2 (M
= Fe, Co, Ni, Pd, Pt) and [Rh(o-P2)2][BF 4] described in Chapter 2 illustrates
the feasibility of incorporating TTF into transition metal complexes through
the use of phosphine groups. Molecules such as these serve as models for
high molecular weight arrays that contain the tetradentate ligand P4 (2).1 In
this vein, recent work by Fox and coworkers demonstrated that mononuclear
complexes of the type [MCl(dppb)2][Cl] (M = Ni, Pd) could be used as models
for the synthesis of coordination polymers with
tetra(diphenylphosphino)benzene (tppb).2 The incorporation of TTF rather
than benzene as a substituent in such extended structures is an attractive
alternative due to its redox activity. As a backdrop for the proposed studies it
is important to note that functionalized TTF ligands have been used to bridge
mononuclear metal centers in several instances. For example, McCullough
and co-workers used the tetratbiolate ligand [TTFS4]4' as a bridging ligand
between mononuclear [TiCp2]2+, [TiCp*2]2+, and [Pt(PPh3)2]2+ groups.5 In
related work, Munakata et. al. demonstrated that
tetrakis(ethylthio)tetrathia-fulvalene [(EtS)4TTF], can act as a bridging
ligand between two CuX2 (X = Cl, Br) centers to give one- and two-
dimensional polymers.6

The rational design of arrays based on molecular precursors can be
achieved by a variety of methods, the simplest of which are one-step self-

assembly processes and stepwise bond formation.3 The methods described in

180

this chapter fall into the category of "stepwise bond formation", and are
related to what has been called the use of "complexes as metals/complexes as
ligands."3a»4 In this strategy, mononuclear or polynuclear metal-containing
complexes that possess labile ligands are used as the central coordination
"centers"; i.e. they become the transition metal, "M", in "MLn" complexes.
Labile ligands on these "building blocks" can be removed to form species with
open metal coordination sites ("complex metals") which can be ligated by
other metal complexes that possess donor sites ("complex ligands").3a Such a
stepwise method allows for good control over the shape and size of the
resulting "supermolecule." An advantage of this approach is the ability to
introduce specific building blocks in different steps, thereby allowing for the
placement of specific moieties at precise locations in the molecule.

In this chapter we describe the stepwise build-up of extended arrays
from mononuclear and dinuclear building blocks with o-P2 or P4 ligands. A
similar method was used by Fox et al., to form homo- and heterometallic
Oligomers using MClz(dppb) (M = Ni, Pd, Pt) and [Ni(dppb)(tppb)][BF4]2 as
molecular building blocks.2 Herein we report the rational synthesis of a
series of Pt, Pd, and Ni Oligomers with o-P2 and P4 ligands, with the
ultimate goal being to construct high molecular weight oligomeric materials

by design.

181

2. Experimental
A. Synthesis

Starting Materials and Reaction Procedures. Ortho-
[P(Cq;H5)2]2(CH3)2TTF,7 [P(C6H5)2]4TTF,3 and PtC12(NCC6H5)29 were prepared
according to published procedures. PdC12(NCC6H5)2 was purchased from

Aldrich Chemical Co., and NiC12°6H20 was purchased from Fisher Scientific.

Both reagents were used as received. Acetonitrile and methylene chloride
were distilled over 3 A molecular sieves, and ethanol was distilled over
Mg(OMe)2 under a nitrogen atmosphere. Diethyl ether was distilled over
sodium-potassium/benzophenone. Unless otherwise specified, all reactions
were carried out under an argon atmosphere by using standard Schlenk-line
techniques.
(1) Preparation of PtC12(o-P2) (20)

Samples of PtClz(NCC6H5)2 (0.103 g, 0.218 mmol) and o-P2 (0.139 g,
0.231 mmol) were loaded into separate flasks and dissolved in 5 mL of
acetonitrile and dichloromethane respectively. The TTF solution was
transferred into the flask containing the metal complex and stirred for 2 h,
producing a color change to red. The solution volume was then reduced by
one-half under reduced pressure, and copious amounts of EtzO were added to
precipitate an orange solid. The solid was washed three times with 5 mL of
EtzO and dried in vacuo; yield 0.147 g (78%). Single crystals were grown by

slow evaporation of an acetonitrile solution of 20. Anal. Calc’d for 20,

182

PthS4C32H26C12: C, 44.35; H, 3.02. Found: C, 45.21; H, 3.30. 1H NMR
(CD2C12) 8 ppm: -CH3, 1.90 (s); Ph-H, 7.58 (m), 7.86 (m). 31P{1H } NMR
(CD2C12) 5 ppm: 27.2 (s, 1th-p = 3640 Hz). IR (Nujol, cm'l): 693 (m, VaC-H). 526
(s, vcuc), 325 (m, vPec1), 303 (111, mm). C.V. (0.2 M CH2CMTBABF4, Pt
electrode vs Ag/AgCl): Em) = -0.49 V, E1/2(ox)1 = +0.7 0 V, E1/2(ox)2 = +1.14 V.
UV/Visible (CH3CN) Amax, nm (a, M'lcm‘l): 458 (1.6x103), 315 (2.5x104), 248
(2.8x104). FAB-MS (m/z): 867 (NF).

(2) Preparation of [Pt(o-P2)(NCCH3)2][BF4]2 (21)

PtC12(o-P2) (20) (0.065 g, 0.075 mmol) and AgBF4 (0.034 g, 0.175
mmol) were loaded into a 150 mL pear-shaped flask and treated with 10 mL
of acetonitrile. The reaction mixture was refluxed for 2 h to give to a red
solution and a white-gray precipitate. The mixture was allowed to cool, then
filtered through Celite on a Shlenk-line and reduced in volume by 50% under
vacuum. The red solution was treated with 30 mL of Et20 to aflord a red
precipitate which was separated fiom the liquid, washed three times with 20
mL of Et20 and dried in vacuo; yield 0.048 g (70%). 1H NMR (CD3CN) 5
ppm: -CH3, 1.90 (s); -NCCH3, 1.96 (s), 2.18 (s); Ph-H, 7.37 (br), 7.79 (br).
31P{1H } NMR (CD3CN) 8 ppm: 28.96 (s, 1Jp31> = 1646 Hz). IR (Nujol, cm'l):
2327 (m, var-.10), 2298 (m, VCEN), 1053 (s, VB-F), 689 (m, Vac-H).

(3) Preparation of Pt2Cl4(P4) (22)
P4 (2) (0.202 g, 0.224 mmol) and PtC12(NCC3H5)2 (0.203 g, 0.430 mmol)

were each dissolved separately in 5 mL of CH2C12 and the TTF solution was

183

added to the metal solution via cannula. After stirring for 24 h at r.t., a
highly insoluble yellow-orange precipitate was collected by filtration in air,
washed three times with 5 mL of Et20, and finally dried in vacuo; yield
0.256 g (81%). IR (Nujol, cm‘l): 1099 (8, v3.1“), 688 (m, v--c-H), 324 (m, vp301),
304 (m, th.c1).
(4) Preparation of [Pt2(P4)(NCCH3)4] [BF4]4 (23)

Quantities of AgBF4 (0.057 g, 0.293 mmol) and Pt2Cl4(P4) (20) (0.102 g,
0.069 mmol) were treated with 12 mL of acetonitrile and stirred under
refluxing conditions for 36 h. The mixture was allowed to cool, filtered
through Celite to remove AgCl, and reduced in volume by 50%. The yellow-
orange product was precipitated by the addition of Et20, filtered in air,
washed three times with 10 mL portions of Et20, and dried in vacuo; yield
0.081 g (64%). 1H NMR (CD3CN) 8 ppm: NCCHa, 1.97 (s); Ph-H, 7.64 (br),
7.78 (br). 31P{1H } NMR (CDaCN) 8 ppm: 19.5 (s, lJPt-P = 3845 Hz), 26.3 (s,
1th.p = 3421 Hz). IR (Nujol, cm'l): 2328 (m, was), 2286 (m, VCEN), 1055 (8, VB.
p), 690 (m, v=0.H). FAB-MS (m/z): CFssOsH added, 1927 (M+ =
[Pt2(P4)(CF3803) 4]”‘).
(5) Preparation of [Pt2(P4)(o-P2)2] [BF4]4 (24).
(i) Reaction of [Pt(o-P2)(NCCH3)2] [BF4]2 (21) with P4 (2). A solution of
P4 (2) (0.037 g, 0.039 mmol) in 5 mL of dichloromethane was added to a
solution of [Pt(o-P2)(NCCH3)2] [BF 4]2 (21) (0.058 g, 0.055 mmol) dissolved in

10 mL of acetonitrile. The resulting solution was stirred for 12 h and reduced

184

to ca. one-half of its original volume by vacuum techniques. The tan product
was isolated by the addition of 20 mL of Et20, washed repeatedly with Et20
until the liquid was clear, and dried under reduced pressure; yield 0.059 g
(75%). 1H NMR (CD3CN) 8 ppm: -CH3, 1.81 (s); Ph-H, 7.25 (m), 7.34 (m), 7.48
(m). 31P{1H} NMR (CDacN) 8 ppm: 32.94 (s, lJPt-P = 2365 Hz). IR (Nujol, cm:
1): 1054 (vim), 689 (won). C.V. (0.2 M CH2C12/TBABF4, Pt electrode vs
Ag/AgCl): E(p,c) = -0.89 V. UV/Visible (CH3CN) Amax, nm (e, M'1cm'1): 248
(1.1x105), 289 sh, 345 sh, 502 (3.5x103).
(ii) Reaction of [Pt2(P4)(NCCH3)4] [BF4]4 (23) with o-P2 (1). Solid
samples of [Pt2(P4)(NCCH3)4][BF4]4 (23) (0.050 g, 0.027 mmol) and o-P2 (1)
(0.036 g, 0.06 mmol) were treated with 10 mL of acetonitrile and stirred for
3 h at r.t. The resulting orange solution was decanted from any unreacted
solid, reduced to 3-5 mL under reduced pressure, and treated with 20 mL of
Et20 to afl'ord an orange precipitate. The liquid was decanted from the tan
solid which was washed 3 times with 20 mL of Et20, and finally dried in
vacuo; yield 0.047 g (61%). 31P{1H } NMR (CDaCN) 8 ppm: 32.94 (s, 1th.p =
2365).
(6) Preparation of PdC12(o-P2) (25)

Samples of PdC12(NCCsH5)2 (0.068 g, 0.178 mmol) and o-P2 (0.105 g,
0.175 mmol) were dissolved in 10 mL of CH2C12. The dark orange-red
solution was stirred for 12 h, reduced to ~3 mL under reduced pressure, and

treated with 20 mL of Et20 to precipitate a red solid. The solid was collected

185

by filtration in air, washed with copious amounts of Et20, and dried under
reduced pressure; yield 0.123 (91%). Anal. Calcd for 25, PdP2S4C32H26C12: C,
49.40; H, 3.37. Found: C, 49.86; H, 3.71. 1H NMR (CDC13) 8 ppm: -CH3, 1.88
(s); Ph-H, 7.51 (m, 8H), 7.57 (br, 12H), 7.59 (d), 7.82 (m), 7.86 (m), 7.89 (m).
31P{1H } NMR (CDC13) 8 ppm: 48.0 (8). IR (Nujol, cm'l): 687 (Vac-H), 515
(vcec), 324 (de.c1), 303 (de.(31). C.V. (0.2 M CH2C12/TBABF4, Pt electrode vs
Ag/AgCl): EN) = -1.04 V, E1/2(ox)1 = +0.71 V, E1/2 (ox)2 = +1.10 V. FAB-MS
(m/z): 778 (NP).

(7) Preparation of [Pd(o-P2)(NCCH3)2][BF4]2 (26)

In a 100 mL Schlenk-flask covered in aluminum foil, 0.100 g of
PdC12(o-P2) (25) (0.104 mmol) and 0.050 g of AgBF4 (0.257 mmol) were
treated with 10 mL of acetonitrile and stirred under refluxing conditions for 2
hours. The reaction mixture was allowed to cool to room temperature and
the mixture was filtered through Celite to remove AgCl. The red-brown
filtrate was reduced to 3-5 mL by vacuum techniques, and treated with 20
mL of Et20 to produce a red-brown precipitate. The liquid was decanted from
the solid which was washed 3 times with 20 mL of Et20 and finally dried in
vacuo; yield 0.090 g (90%). 1H NMR (CD3CN) 8 ppm: -CH3, 1.90 (s); -NCCH3,
1.96 (s), 2.15 (s); Ph-H, 7.68 (br), 7.90 (br). 31P{1H } NMR (CD3CN) 8 ppm:
50.72 (s). IR (Nujol, cm'l): 2322 (VCEN), 2294 (VCEN), 1055 (VB.F), 689 (v=0.H),

513 (v0-—-0).

186

(8) Preparation of Pd2C14(P4) (27)

Samples of PdC12(NCC3H5)2 (0.0815 g, 0.213 mmol) and of P4 (2) (0.102
g, 0.109 mmol) were treated with 5 mL of CH2C12, to give a green-brown
solution which was stirred for 24 h to give a brown precipitate. The solid was
isolated by filtration, washed 3 times with 5 mL of Et20, and dried in vacuo;

yield 0.119 g (87%). IR (Nujol, cm‘l): 687 (Ph), 322 (Vpd-c1), 299 (Vpd.c1). FAB-

MS (m/z): 647 (MZ+/2).
(9) Preparation of [Pd2(P4)(NCCH3)4][BF4]3 (28)

Solid samples of Pd2C14(P4) (27) (0.0602 g, 0.047 mmol) and AgBF4
(0.0447 g, 0.230 mmol) were treated with 12 mL of CH3CN and stirred under
refluxing conditions for 36 h. The mixture was allowed to cool, concentrated
to ~5 mL using vacuum techniques, and treated with 30 mL of Et20 to afl'ord
a tan precipitate. The solid was collected by filtration in air, washed 3 times
with 10 mL of Et20, and dried in vacuo; yield 0.045 g (47%). 1H NMR
(CDaCN) 8 ppm: NCCH3, 1.96 (s); Ph-H, 7.62 (m), 7.77 (m). 31P{1H} NMR
(CDaCN) 8 ppm: 50.9 (8). IR (Nujol, cm'l): 2333 (VCEN), 2298 (vcEN), 688 (v=0.
H). C.V. (0.2 M CH2C12/TBABF4, Pt electrode vs Ag/AgCl): E(p,c) = -1.04, V E1/2
(ox)1 = +0.71 V, E1/2 (ox)2 = +1.10 V.

(10) Preparation of Ni2C14 (P4) (29)

Solutions of P4 (2) (0.203 g, 0.216 mmol in 7 mL of CH2C12) and

NiC12°6H20 (0.100 g, 0.421 mmol in 5 mL of EtOH) were gently refluxed in

separate flasks. The flask containing the P4 solution was covered with

187

aluminum foil during the heating process to avoid light. While both solutions
were still warm, the P4 solution was added to the NiCl2/EtOH solution, and
the mixture was refluxed for 30 min. The resulting insoluble orange solid
was isolated by filtration in air, washed with copious amounts of Et20, and
dried under reduced pressure; yield 0.190 g (78%). Anal. Calc’d for 30,
Ni2P4S4C54H40C14: C, 54.04; H, 3.34. Found: C, 53.45; H, 3.28. IR (Nujol,
cm‘l): 689 (m, won), 366 (m, VNi-Cl), 338 (m, V5301). FAB-MS (m/z): 599
(MZ+/2).
B. X-ray Crystallography

The structures of the compounds PtC12(o-P2) (20) and Pt2Cl4(P4) (22)
were determined by application of general procedures that have been fully
described elsewhere.10 Crystal parameters and basic information pertaining
to data collection and structure refinement are summarized in Table 14.
Final full-matrix refinements on F2 were carried out with the use of the
SHELXTL version 5.0. structure solution package.11
(1) PtC12(o-P2)°CH3CN (20°CH3CN)
(i) Data Collection and Reduction. Single crystals of PtC12(o-
P2)°CH3CN (20°CH3CN) were grown by slow evaporation of an acetonitrile
solution of the compound. An orange parallelepiped of dimensions 0.20 x 0.20
x 0.14 mm3 was mounted on the tip of a glass fiber and secured with epoxy.
Data for 20 were collected on a Stoe IPDS diffractometer equipped with

monochromated MoKa radiation at 293 :1: 2 °C in a 0 range of 1.9 to 258°.

188

Table 14. Summary of crystallographic data for PtC12(o-P2)°CH3CN
(20°CH30N) and Pt2C14(P4)°3CH3CN (22°3CH3CN).

 

 

20-CH3CN 22-30H3CN
Formula Pt01284P2N034H29 Pt2C1484P4N2C53H43
Formula weight 906.6 1586.2
Space group C2/c P2(1)/n
a, A 20.667(4) 9.0311(5)
b, A 20.003(4) 16.1894(9)
c, A 17.017(3) 22.8868(13)
a, deg 90 90
[3, deg 91.70(3) 96.1070(10)
7.de3 90 90
V, A3 7033.5(24) 3327.2(3)
Z 3 4
dcalc, g/cm3 1.714 1.599
a, om-I 4.493 4.619
Temperature, °C 20 i 2 -140 :L- 2
R18 0.027 0.053
szb 0.052 0.103
quality-of-fitc 0.886 1.055

 

1"R:ZIIFol-II-‘(~,||/2‘JFol,waZ = [ZwlFol - IFcl)2/2wlFol2]1/2; w = 1/o2(lFol).
Couahty-of-fit = [M Fol - I Fcl )2/(Nob5‘Nparamctcr)l ”2

189

Initial data indicated that the crystal belonged to a monoclinic system;
subsequent solution and successful refinement of the structure was carried
out in the 02/0 space group. Of the 27,300 reflections that were collected,
6803 were unique, and 5081 data were observed with I > 2.000(1). The data
were corrected for Lorentz polarization effects, and an empirical absorption
correction based on azimuthal w-scans near x = 90° was applied which
resulted in transmission factors ranging from 0.02 to 0.05.

(ii) Structure Solution and Refinement. The structure was solved by
direct methods and refined by full-matrix least squares refinement on F2. All
non-hydrogen atoms, except those associated with the solvent, were refined
anisotropically. Hydrogen atoms were not included in refinement. The final
refinement was based on 6803 reflections that were used to fit 400
parameters to give R1 = 0.0270 and wR2 = 0.0516. The goodness-of-fit index
was 0.886, and the maximum shift in the final difference map was 0.000 A
associated with H(8C). After the last least squares cycle, the mean shift/esd
was 0.000 and the highest peak in the difference Fourier map was 2.300 e'lA3
which is associated with the metal center.

(2) Pt2Cl4(P4)°3CH3CN°solvent (22°3CH3CN)

(i) Data Collection and Reduction. Single crystals of Pt2C14(P4)°
3CH3CN (22°3CH3CN) were obtained by loading a three-compartment,
fritted, electrochemical cell with an acetonitrile solution of PtC12(NCC3H5)2 in

one outer chamber, an acetonitile solution of P4 in the second outer chamber

190

and acetonitrile in the center chamber. Over the period of 2 days, orange
crystals formed in the center chamber and in the P4 chamber as the solutions
diflused together. An orange needle of dimensions 0.44 x 0.30 x 0.21 mm3
was immersed in perfluorinated ether, supplied by Prof. Larry Dahl of the
University of Wisconsin, and secured on to the tip of a glass fiber. Data for
22 was collected on a Siemens SMART/CCD area detector difi'ractometer

equipped with monochromated MoKa (A, = 0.71073) radiation. Initial data
indicated that the crystal belonged to a monoclinic system; subsequent
solution and successful refinement of the structure was carried out in the
P21/n space group. The data were collected at 13 :1: 2 °C in a 0 range of 1.9 to
258°. Of the 19,855 reflections that were collected, 7,711 were determined to
be unique, and 5,923 data were observed with I > 2.000(1). The data were
corrected for Lorentz polarization effects and an empirical absorption
correction based on azimuthal w-scans near 1 = 90° was applied.

(ii) Structure Solution and Refinement. The structure was solved by
direct methods and refined by full-matrix least squares refinement. The
position of the unique Pt atom was located by the XS program in
SHELXTL,11 and the remaining non-hydrogen atoms were located by a
series of alternating least-squares refinements on F2. All other non-
hydrogen atoms were refined anisotropically, with the exception of the
solvent molecules. The solvent atoms defined by atoms C(80), C(81), N(82),

C(91), and C(92) were defined as two disordered acetonitrile molecules

191

sharing a common nitrogen position; these were refined with a combined
occupancy of 1.0. Hydrogen atoms were placed in calculated positions. The
current refinement is based on 7,711 reflections that are being used to fit
318 parameters to give R1 = 0.0532 and wR2 = 0.1081. The goodness-of-fit
index is 1.098, and the maximum shift in the final difference map is
currently 0.138 A associated with N(91). The highest peak in the difference
Fourier map is 1.822 e'/A3 which is associated with the metal center, Pt(1).
3. Results and Discussion

The mononuclear complexes PdCl2(o-P2) and PtC12(o-P2) were
prepared in relatively high yields from the reaction of o-P2 (1) with
complexes of the type MC12(NCC6H5)2 (M = Pt (20), Pd (25)). Both compounds
exhibit redox chemistry involving the divalent metal center as well as the
TTF group. Infrared and UV-visible spectroscopies verify the presence of
bound chloride ion and the presence of a single o-P2 ligand. The reaction of
two equivalents of MC12(NCC3H5)2 with P4 (2) in CH2C12 or acetonitrile
affords the insoluble products M2Cl4(P4) (M = Pt (22), Pd (27)). Infrared
spectral analysis of 22 and 27 verify the presence of bound chloride ions and
the presence of P4. The analogous dinuclear complex of Ni can be obtained
under refluxing conditions fi'om the reaction of a dichloromethane solution of
2 and an ethanol solution of NiC12°6H20.

Reactions of 20, 22, 25, and 27 with stoichiometric amounts of AgBF4

lead to the precipitation of AgCl and the formation of soluble TTF-containing

192

 

products. The complexes [M(NCCH3)2)(o-P2)][BF4]2 [M = Pt (21), Pd (26)] and
[Mz(NCCH3)4(P4)][BF4]4 [M = Pt (23), Pd (28)] were characterized by 1H
NMR, 31P{1H} NMR, and infrared spectroscopies. Subsequent reactions of
two equivalents of 21 with P4 (2) or two equivalents of o-P2 (1) with 23 result
in the formation of the dinuclear complex [Pt2(o-P2)2(P4)][BF4]4 (24).

The structures of PtC12(o-P2) (20) and Pt2C14(P4) (22) were determined
by single crystal X-ray diffiaction methods. Crystal parameters and basic
information pertaining to data collection and structure refinement are
summarized in Table 14. Selected bond distances and angles for each
structure are listed in Table 17.

A. Preparation, Spectroscopy, and Redox Properties of MClz(o-P2) (M
= Pt (20), Pd (25))
(1) Synthesis

The reaction of MC12(NCC6H5)2 (M = Pt (21), Pd (26)) with o-P2 (1)
results in the formation of the red complex MC12(o-P2). The reaction is
performed with both reactants dissolved in CH2C12 in the case of 25, and with
a CH3CN solution of the metal precursor and a CH2C12 solution of 1 in the
case of 20. Displacement of benzonitrile for 1 is relatively sluggish, and the
reaction requires longer reaction times to ensure complete substitution.
These reaction procedures deviate from the typical method used to form
IVIX2(L-L) (M = Pt, Pd; L-L = dppee, dppb, dppe) compounds which usually

involves the use of [MX4]2'. The presence of two labile ligands allows for the

193

clean synthesis of the desired product, MC12(L-L), without the formation of
[l\/In(L-L)2]n+ which often occurs if one begins with the tetrachloridefl’l‘i-16

Both compounds are air stable and relatively insensitive to light in the
solid state, but in solution they are prone to decomposition if exposed to light
for extended periods of time (> 3 days). Such photochemical sensitivity has
been documented for numerous complexes of both metals.12 The
decomposition of these compounds is accelerated in the presence of
chlorinated solvents, most likely owing to the instability of the phosphine
ligand.13 Both complexes are soluble in nitriles, chlorinated solvents, and
acetone.
(2) 1H and 31P{1H} NMR Spectroscopic Studies

The 1H NMR spectra of 20 and 25 in CDC13 exhibit a series of
multiplets in the region 8 7.5 - 7.9 ppm due to the phenyl protons, and a
singlet at 8 ~19 ppm due to the methyl protons. The 31P{1H} NMR spectrum
of 20 shows a Pt satellite doublet centered at 27 .2 ppm (1th.p = 3640 Hz), in
accord with magnetically equivalent phosphorus nuclei. The downfield shift
of the signal fiom the fi'ee phosphine at -18.8 ppm7 indicates that the
phosphine is coordinated to the metal whereas the th-P value is indicative of
trans-disposed chlorides.16b Similar 31P{1H} NMR data were obtained for 25,
which exhibits only a single resonance at 8 +480 ppm. These shifts are
comparable to the reported values for other MC12(L-L) complexes of

palladium and platinum where L-L is a diphosphine chelate.15,17b The

194

I l L4 14 L 1 l 441

 

H

..1

O
N

(D
O
11

l

 

CD
O
l

‘

 

 

WrTjrrFffiltllleIIIIIIIIIIFIT

 

 

Coordination 31P NMR chemical shift
\1
O
l

 

Free ligand ”P NMR chemical shift

Figure 35. Correlation of 31P NMR coordination chemical shift A831P in
MC12(L-L) (M = Ni, Pd, Pt) complexes with the fi'ee ligand 31P ;
NMR chemical shift 831P.

 

195

 

increase in A831P [where A831P = 831P(complex) - 831P(ligand)] for the series
PtC12(o-P2) (20), NiC12(o-P2),7 and PdC12(o-P2) (25) follows the previously
observed trend for the chemical shifts of the compounds MC12(L-L) (M = Ni,
Pd, Pt; L-L = dppe, dippb,17 dppee”). A plot of the 831P chemical shifts of the
free ligands against A831P for the MC12(L-L) series that includes o-P2 (1)
reveals a linear relationship for 1, dippb, and dppe (Figure 35). The rigidity
of the ligand is thought to be the origin of the anomalous 31P NMR chemical
shifts for the dppee series of compounds.16b
(3) Infrared and Electronic Absorbance Spectroscopy

The infi'ared spectra of 20 and 25 display bands at ca. 690 and 520
cm'1 attributable to the ligand, 1. Modes at 300 and 320 cm'1 are in the
rangeexpected for the A1 + B1 VM-Cl stretching vibration, and agree well with
literature values for other square-planar complexes with chelating ligands.14
The electronic spectrum of 20 recorded in acetonitrile exhibits absorbances
attributable to the phenyl groups at 248 nm and the TTF moiety at 315 and
428 nm. The extinction coefficient, 8, for the phenyl chromophores in TTF-
phosphines is known to be approximately proportional to the number of
phenyl groups in the molecule, thus the e value of 2.8x104 is indicative of one
o-P2 (1) ligand (4 phenyl groups).7 The bathochromic shift for each TTF
absorption band in PtC12(o-P2) (20) relative to TTF indicates a weak
interaction with the phosphine, while the shift from 1 indicates strong metal-

phosphorus coordination, which serves to weaken the TTF-PR2 interaction.

196

mama H 0-5?
mvwm H .203

Hmvm H 0.53
00.30008 0:0:

.000”: .000 s 63:36: .2050 5 0 3 5:00:55 u a .0095 n. .5 .2050 e: 0 ..

00.50008 0:0:
mdm
00.30000: 0:0:
Nbdm

Qwv

05 00.00
50 0.00

05 0.0:
60.35de 020G

UQHSmwma mGOG

05 00.0 .05 00.0 :5 00.:

Umhzmwwe QGOS

:5 00.0 .05 00.0

5 0:.0 .5 00.: .5 00.:
05 00.0 :5 00.0 :5 00.0
.25 00.0 .50: ..5 00.0
.50 .5 :00 .5 00.:
:5 0:..0

.5 00.0 .05 00.0 .5 :0:

:5 00.0 .05 00.0 .05 00.:

Umafimmma QED:

:5 00.0 .05 00.0

0.50032 .00
50030000200550 .00
50:00:03: .00

0000:05002000500 .00

00.50000 .00
53.000200020060000 .00

4:400:4050205530 .00
53:00:03.: .00

 

000: n 2.5 :5 00.00 .5 0:.0 .5 00.: .00 00.: 0:400:00502000500 .:0
E0 .5 00.0
0000 u 3.5 05 0.00 .50: .5 00.0 .50 .5 00.: 000.5005: .00
0:» 00:30:00 $33500 :59 8:: 0.050000 £22 I: 05:09:00
£22 A3590 0.050000 £22 90

 

.350 00:30:88 :0.“ 0000 0500050000 522 90 0:0 3: .00 0.88806 .3 0308

197

.aNéN
00:00:88 :8 0:00 030000000000 0000.05 0:0 00:00.:0000 00:0,:0020 5000880030, 0:000 00 00:00::Sm

.3 0508

198

00008000 H .:< .0303 H00 .00.? Z 0 803.300 05030 0 .ZO0EU\0mm<mB 2 H0 8 0808080008
0 4003000 00 00800000.: 000-50000 0000 am 0 00 :03300 0:00EU\0mm<mB 2 N0 8 0808080008 00008080050200 0

 

dot/:3

000 00.25 000 .000 000
000 000

.Azm05 0000 .Azmo5 0000
emu-00$

000 00-005 000 .000 300
000

0:0 000 000 .005 000:
:zm05 0000.:zm05 0000
00-003 mom .00-003 0mm

0000:0002 .00
. 000+ n 00850000 .
00.:- u 0 .00 :3.0+ n 0050.0 0000:0000025000000 .00

0000:0000 .00

0:0-00.000002505000 .00
24+ H 0985005

 

0.0 0:0 .05 000 00.:- u 0.00.: :0.0+ n 005000: 0050000 .00
00.0 000
00.0000 000
05 000 . 0.05 000: 00000000 .00 000 .000. u 0.00 00005000000500. .00
000 000 .005 000:
00.005 0000.055 0000 00.0000000025000000 .00
00.05 000 .0005 000
05 000 .005 000: 0000:0000 .00
000 000 .005 000:
0E5 0000.005 3000 0000:00000ZX00-§0_ .:0
00.05 000 .0005 000 0.00 000 0:.:+ n 00550
000 000 .05 000 0.00:0 0:0 000 00.0- n 0.00 000+ n 00550 000.5000 .00
18 0.0: 0 5 a: 0...: 000000. 0550500

0.0000005 0000.05

0.50005 00>->D 0> > 0.0-50880300,. 0:000

 

<

199

(4) Electrochemistry

A cyclic voltammogram of PtC12(o-P2) (20) exhibits two accessible
reversible oxidation couples and one irreversible reduction couple. The
oxidations of the o-P2 (1) ligand are shifted to higher potentials relative to
the free ligand as expected. The first oxidation is shifted by +360 mV, and
the second oxidation is shifted by +426 mV. These values are similar to the
cyclic voltammetric data obtained for [Pt(o-P2)2][BF4]2 (11). The reduction
couple at -O.49 V in 20 could be a one-electron reduction to Pt(l), or a two-
electron process to Pt(O). The two-electron reduction is more commonly
encountered, but this process generally occurs at more negative potentials,
e.g. -1.71 V for PtClz(dppe).18 Given the larger bite angle of dppe versus dppb
and dppee,19 it would be expected that a change to an ethylene backbone
would result in a shift to more negative potentials for the metal reduction.
Electrochemical data for 25 are quite similar to 20, with reversible oxidations
attributable to the ligand occuring at +0.71 and +1.10 V, and an irreversible
reduction at -1.04 V (see Figure 36). Based on previous electrochemical
studies of [Pd(dppb)2][BF4]2, which exhibits a two-electron Pd(II)-Pd(0)
reduction at -O.99 V, the reduction processes in both 20 and 25 appear to be
more consistent with a one-electron reduction.19
B. Crystal Structure of PtClz(o-P2) (20)

Compound 20, whose ORTEP figure is shown in Figure 37 , is a slightly
distorted square planar molecule with a Pt ion ligated by cis chlorides and

one o-P2 ligand. The platinum atom and its four neighbors deviate from the

200

 

B(p,c) = '1.04 V

 

E1/2(ox)1 = +0.71 V

Em(OX)1 = +1.10 V

 

F l I I I l l
+1.6 +1.0 +0.5 0.0 -o.5 .1.0 -1.6

Volts vs. Ag/AgCl

Figure 36. Cyclic voltammogram of PdC12(o-P2) (25) in 0.2 M TBABF4 in
CHzClz.

201

 

 

Table 17. Selected Bond Distances (A) and Angles (deg) for PtClz(o-P2)
(20) and Pt2C124(P4) (22).

 

 

 

 

Atom 1 Atom 2 20 22
Pt(l) P(1) 2.2065(11) 2.219(2)
Pt(l) P(2) 2.2235(11) 2.212(2)
Pt(l) Cl(l) 2.3494(12) 2.356(2)
Pt(l) Cl(2) 2.347 6(12) 1.826(8)
P(1) 0(1)/C(2) 1.825(4) 1.312(12)
C(1) C(2) 1.336(6) 1.757(8)
C(l) S(1) 1.743(4) 1.321(17)
C(3) C(4)/C(3) 1.339(6)

C(5) S(3) 1.755(5)

C(5) C(6) 1.319(7)

C(5) C(7) 1.505(7)

Atom 1 Atom 2 Atom 3 20 22

P(1) Pt(l) P(2) 8875(4) 8885(8)
Cl(l) Pt(l) 01(2) 90.40(4) 91.67 (9)
P(1) Pt(l) C1(2)/Cl(1) 17 633(4) 177.17 (8)
P(1) C(1)/C(2) C(2)/0(1) 118.5(3) 119.3(6)
C(l) S(1) C(3) 94.4(2) 94.8(4)
C(4) 8(3) C(5) 95.5(2)

C(5) C(6) C(5) 128.0(5)

 

202

 

 

 

 

Figure 37. ORTEP representation of PtClz(o-P2) (20) with 50% ellipsoids
viewed from the (a) top and (b) side.

203

 

 

 

 

Figure 38. Packing diagram of PtClz(o-P2) (20).

204

best plane through the following atoms: Pt(l), 0.021(1); P(1), 0.069(1); P(2),
-0.083(1); C1(1), -0.075(1); C1(2), 0.067(2). This results in a dihedral angle
between planes P(1), P(2), Pt(l), and C1(1), C1(2), Pt(l) of 34°, which is nearly
identical to the bonding arrangement observed for NiBr2(o-P2),7 but which
differs from the planar geometry observed for PtC12(dppee),16b presumably
due to the increased rigidity of dppee versus other di-phosphine ligands.
Other angles in the molecule are within normal ranges, e.g. P(1)-Pt(1)-P(2) =
88.75(4)°, and Cl(1)-Pt(1)-Cl(2) = 90.40(4)°. The Pt—P bond distances of
2.2065(11) A and 2.2235(11) A are comparable to those found in the
analogous dppee compound [2.211(2) A], but significantly shorter than those
found in [Pt(o-P2)2][BF4]2 (11) (see Chapter 3). The Pt-Cl distances
2.3476(12) and 2.3494(12) A are slightly shorter than the equivalent
distances in the dppee complex 2.361(2) A.15b The C(1)-C(2) double bond
distance of 1.336(6) A in 20 is similar to that in free o-P2 (1) (135(3) A), and
not statistically different than 1.337 (6) A, which is expected for a standard
C=C double bond.20 A shorter distance would be expected if Pt-to-P 1t-
bonding is significant, as is the case with dppee.16b,21 The n-bonding would
also lead to complete coplanarity of Pt(l), P(1), P(2), C(1), and C(2), which is
not the case for 20 (rms deviation = 0.022 A).

The bond distances and angles within the TTF core are quite similar to
those found in the Pt-(o-P2) complex, 11. The largest difi'erence is found in

the C(1)-C(2) double bond distance of 1.336(6) A for PtC12(o-P2) (21) and

205

1.354(14) A for 11. This distance is highly dependent on the identity of the
metal, as can be seen from comparisons of the analogous distances in
NiBr2(o-P2) (125(1) A), [Ni(o-P2)2][BF4]2 (8) (1.328(12) A) [ReC12(o-P2)2]+ (16)
(134(2) A average) and [Re2C126(o-P2)]' (17) (138(2) A). Other notable
differences between 20 and 11 are the wider C-S-C angles of 94.4(2)° and
94.8(2)° within the phosphine-fuctionalized ring of the TTF in 20 as
compared to 92.6(4)° for the equivalent angles in 11. Also of importance is
the fact that the dithiole ring closest to the metal center is essentially planar
with an out-of-plane bend of only O.9(2)° between the planes C(1)-C(2)-S(2)-
S(1) and S(1)-S(2)-C(3)-C(4)-S(3)-S(4). The methyl-substituted dithiole ring
exhibits a bend of 7 .3(2)° between the planes S(1)-S(2)-C(3)-C(4)-S(3)-S(4) and
S(3)-S(4)-C(5)-C(6). This is quite different than the bis-(o-P2) complexes
discussed in Chapter 3 which exhibit out-of-plane bends in the rings closest
to the metal center, but which remain nearly planar at the outer dithiole ring
that contains the methyl groups. The planar nature of the phosphine-
fuctionalized fulvalene ring in 20 is believed to be partially due to electronic
efi'ects of the trans-halogens. This topic will be discussed in more detail in
Chapter 6. Another obvious factor that may influence the conformation of

the fulvalene rings is crystal packing forces. In [M(o-P2)2][BF4]2 [M = Ni (8),

Pt (11)] and [Rh(o-P2)2][BF4] the tendency to form close S---S intermolecular
interactions may facilitate the bending in the methyl-substituted dithiole

ring!)22 It is obvious from the packing diagram for 20 (Figure 38), that there

206

are no such short intermolecular stacking interactions. The molecules of

PtC12(o-P2) (20) pack in pairs, with adjacent molecules oriented in a head-to-

tail fashion, a situation that serves to minimize repulsions between the

phenyl rings. The closest distance between molecules is 11.08 A.

C. Preparation and Spectroscopic Properties of M2Cl4(P4) [M = Pt
(22), Pd (27), Ni (29)].

The reaction of two equivalents of MC12(NCC5H5)2 (M = Pd, Pt) with P4
(2) in CH2C12, acetonitrile, or a mixture of the two solvents yields precipitates
that are formulated as C12M(P4)MC12. The P4 molecule is not particularly
soluble in acetonitrile, thus the reaction is much slower in this solvent. The
use of CH2C12 requires that the reaction be protected from light due to the
instability of P4 (2) in chlorinated solvents over extended periods of time, and
the known photochemical reactivity of Pt complexes.12»13 The fact that the
reaction appears to require one day to go to completion (shorter reaction
times result in lower yields) may indicate a slow initial substitution of
nitriles, but more reasonably reflects a slow coupling process to form the
dimetal system.

The reaction of two equivalents of NiC12-6H20 in EtOH with a CH2C12
solution of 2 at elevated temperatures results in the precipitation of
ClzNi(P4)NiC12 (29). Highest yields are obtained when the reaction is
refluxed for an additional 30 min after combining the hot solutions. The hot

ethanol solution increases the solubilities of NiC12°6H20 and the hot CH2C12

207

solution of 2 prevents immediate precipitation of the reactants upon
combining the respective solutions. This strategy was also used in the
synthesis of NiX2(o-P2) (X = Cl, Br).7

D. Crystal Structure of Pt2Cl4(P4) (22)

Compound 22, shown in Figure 39, consists of two PtClz fragments
bridged by a P4 ligand. The geometry about the platinum centers is square
planar with negligible deviations. This strictly coplanar arrangement was
found for PtC12(dppee),16b but in 20 and NiBr2(o-P2)7 the molecules are
slightly distorted. The P-Pt-P angles are 88.85(8)° and the Cl-Pt-Cl angles
are 91.67(9)°. The trans relationships are P(1)-Pt(1)-Cl(1) = 177.17 (8)°, and
P(2)-Pt(1)-Cl(2) = 179.65(8)°. These metric parameters indicate a more ideal
arrangement than that observed in either 11 or PtC12(o-P2) (20). The Pt-Cl
distances (2.356(2) A) are in the expected range, and are similar to analogous
distances found in 20. The Pt-P distances of PtzCl4(P4) (22) are also similar
to those observed in 20, but slightly longer than those in 11 presumably due
to the different trans-influence of chlorides versus phosphines. The C(1)-C(2)
distance of 1.312(17) A is much shorter than the equivalent distance in both
11 and 20 as well as the free ligand 2. This distance is also shorter than an
idealized C=C double bond (1.337(6) A),20 but longer than the analogous
bonds in NiBr2(o-P2) and PtC12(dppee).7v16b This contraction of the bridging

double bond suggests some degree of Pt-P n- bonding enhancement, which is

208

C16
\ (a)
1 cf
:1
f . .
.r . Ptl
P g l f

(b)

 

Figure 39. ORTEP representation of Pt2C14(P4) (22) with 50% ellipsoids
viewed from the (a) top and (b) side.

209

 

 

210

-ax13.

Figure 40. Packing diagram of PtzCl4(P4) (22) viewed down the a

supported by the coplanarity of the atoms involved (Pt(l), P(1), C(1), C(2),
P(2)).16b

Bond distances and angles within the TTF core of 22 are similar to
those observed for other TTF molecules. The S-C-S bond angles (94.8(4) and
95.0(4)°) are nearly identical to the equivalent bonds in the phosphine-
fuctionalized ring of 20. The C(3)-C(3)’ double bond distance is slightly
shorter, at 1.321(17) A, than the analogous distances in 11 (1.338(13) A) and
20 (1.339(6) A), and considerably shorter than the distance in 2 (1.362(13) A).
These metric parameters suggest the operation of electronic effects on the
TTF core for coordinated P4 molecules that are not operative for coordinated
o-P2 molecules. Also of note is the strict planarity of the TTF unit in the P4
(2) bridged ligand. The structure of 22 is the only TTF-phosphine molecule,
apart from NiBr2(o-P2), that does not exhibit appreciable out-of-plane
bending of the TTF core. Planar TTF substituents have been observed for all
TTF-phosphines that are trans to halogens; this will be discussed in more
detail in Chapter 6. The packing diagram for 22 is shown in Figure 40,
where it can be observed that there are no stacking interactions. As a result
of the bulky phenyl groups, the molecules are packed in a "staggered"
arrangement.
E. Reactions of MC12(o-P2) and M2Cl4(P4) (M = Pt, Pd, Ni) with

AgBF4

(1) Synthesis

211

Reactions of MC12(o-P2) and M2Cl4(P4) (M = Pt (21),(23); Pd (26),(28))
with the appropriate quantities of AgBF4 in refluxing acetonitrile results in
abstraction of the halides and formation of [M(NCCH3)2(o-P2)][BF4]2 and
[Mz(NCCH3)4(P4)][BF4]4 (M = Pt (21),(23); Pd (26),(28)). The reactions are
carried out under protection from light to prevent degradation of the
reactants and/or products. Experiments performed at different reaction
times and temperatures led to the conclusion that the highest yields are
obtained when the mononuclear reactants are refluxed for 2 h, but that
much longer reaction times are required for complete halide abstraction in
the dinuclear compounds. In the case of PtC12(o-P2) (20) and PdClz(o-P2)
(25), the reactants are soluble in chlorinated solvents, but only slightly
soluble in nitriles, while the opposite is true for the products. The dinuclear
compounds, 22 and 27 , are insoluble in most solvents, but the partially
solvated products are highly soluble in acetonitrile. These solubility
differences allow for ease of separation of reactants and products. It is
important to note that while 23 and 28 are air-stable, 21 and 26 decompose
in air, as signified by a color change fi'om red and red-brown to green. The
formation of a green solution is indicative of oxidation of the TTF core.

(2) Spectroscopic Studies

The infiared spectra of 21, 23, 26, and 28 display characteristic modes

at ca. 690 and 520 cm°1 for the phosphine ligand. Bands at ca. 2325 and

2290 cm'1 are assigned to the CsN stretch of coordinated acetonitrile. The

212

absence of v(M-Cl) features supports the conclusion that the halide
abstraction was successful. This is further supported by the presence of a
v(B-F) stretch at 1055 cm'l.

FAB-MS experiments performed on [Pt2(NCCH3)4(P4)] [BF4]4 (23)
reveals very little information due presumably to the high cationic charge on
the metal complex. In order to introduce a counterion that might serve to
reduce the cationic charge, triflic acid (HCF3S03, or HOTf) was introduced to
the matrix/analyte solution prior to analysis. The presence of triflate as a
weakly coordinating counterion with high molecular weight "super-
molecules" or "supramolecules" is well-documented in the independent work
of Stang and Hupp. The triflates appear to assist in the FAB-MS analysis of
cations with high charges.23 With triflate as a counterion, the species
[Pt2(P4)(OTf)2]+, [Pt2(P4)(OTf)2]+, and [Pt2"Pt2+“(P4)n°1](OTf)4]+ (n = 0 or 1).
are detectable. No peaks could be assigned to Pt2(P4)Cl4 (22) which further
supports the conclusion that abstraction of halides to give
[Pt2(P4)(NCCH3)4][BF4]4 (23) was successful. Clearly, FAB-MS will be a
useful tool in the characterization of multiply charged complexes such as 21,
26, and 28.1
(3) 1H and 31P{1H} NMR Spectroscopic Studies

The 1H NMR spectra of 21, 23, 26, and 28 in CD3CN display a series of

multiplets between 5 7.64 and 7 .78 ppm due to the phenyl protons of the

phosphine groups. All four compounds exhibit a sharp singlet at ca. 1.96 ppm

213

 

 

 

due to free acetonitrile which indicates some degree of lability of this ligand.
Complexes [Pt(o-P2)(NCCH3)2][BF4]2 (21) and [Pd(o-P2)(NCCH3)2][BF4]2 (23)
also display signals at 8 = 2.18 and 2.15 ppm respectively, that are assigned
to bound CH3CN. The presence of residual water in the deuterated solvent
used for the NMR spectra of 21 and [Pd2(P4)(NCCH3)4][BF4]4 (28) may serve
to mask this resonance in those cases. The singlet located at 1.90 ppm in the
spectra of 21 and 26 is due to the methyl protons of the o-P2 ligand. The
31P{1H} NMR spectra of 21, 23, 26, and 28 all display resonances that are
shifted downfield relative to the free ligand values (-18.8 ppm for 1 and -18.2
ppm for 2), which supports the formation of a five-membered ring through
metal coordination of the phosphorus atoms. Both Pd complexes (26 and 28)
display singlets at 6 = 50.7 ppm for 26 and 50.9 ppm for 28, indicating the
presence of only one type of coordinated phosphorus nucleus. The 31P NMR
spectrum of 21 displays a singlet at 29.0 ppm with Pt satellites, supporting
the presence of only one type of coordinated phosphorus nucleus with Ups? =
1646 Hz. The smaller 1th.p coupling for 21 (1646 Hz) relative to 20 (3640
Hz) is indicative of the presence of trans- nitriles rather than chlorides, and
follows the trend noted for PtC12(dppee) versus [Pt(DMF)2(dppee)][BPh4]2
(DMF = dimethylformamide).16b The 31P NMR spectrum of
[Pt2(P4)(NCCH3)4][BF4]4 (23) displays two singlets with Pt satellites at 6 =
19.5 and 26.3 ppm. The larger magnitude of the JPt-P coupling constants for

both resonances (3845 and 3421 Hz) suggests that the halogen abstraction

214

 

 

 

was incomplete, and trans-chloride ligands are still present in some form.
However, this is contradictory to the results of infiared and mass
spectroscopic analysis. Refluxing times in excess of 2 days result in metal
phosphorus bond cleavage and formation of [Pt(P4)]n[BF4]2n (31), as
evidenced by a 31P NMR resonance at 6 36.1 ppm (thr = 2361 Hz). The
larger coupling constant, relative to 21, is indictative of the phosphorus
groups being trans to each other. 8’22
F. Synthesis and Characterization of [Pt2(o-P2)2(P4)] [BF4]4 (24)
(1) Synthesis

The reaction of P4 (2) with two equivalents of [Pt(NCCH3)2(o-
P2)][BF4]2 (21) yields the dinuclear complex [Pt2(o-P2)2(P4)][BF4]4 (24). The
same product can be produced by substituting the CH3CN ligands in the
dinuclear complex [Pt2(NCCH3)4(P4)][BF4]4 (23) with o-P2 (1). The product is
very similar to the homo- and heterobimetallic complexes
W'(dppb)2(tppb)][BF4]4 (M, M’ = Ni, Pd, Pt) reported by Fox et al.1b
Complex 24 is stable in air, but demonstrates a tendency to decompose in
solution with prolonged exposure to light.

(2) Spectroscopic Characterization

The infrared spectrum of 24 exhibits a strong v(B-F) stretch for [BF4]'
at 1054 cm'l. Bands at 689 and 517 cm'1 are due to the phosphine ligand.
The absence of v(CEN) modes between 2200 and 2400 cm“1 suggests complete

substitution of CH3CN by the phosphine has occurred, but does not rule out

215

 

the possibility of residual coordinated CH3CN since these modes can be very
weak. Taube and Johnson have demonstrated that the frequency and

intensity of the CsN stretching vibration can be quite variable, and in some

cases even absent when coordinated nitrile is present.24

The electronic spectrum of [Pt2(o-P2)2(P4)][BF4]2 (24) recorded in
acetonitrile exhibits transitions at 248, 289 (sh), 345 and 502 nm. The
feature at 248 nm is assignable to the phenyl chromophores, while those at
345 and 502 nm arise from the TTF unit. Using the extinction coefficient, a,
for the phenyl chromophores in TTF-phosphines as a gauge to calculate the
number of phenyl groups in the molecule (o-P2 contains 4 phenyl groups and
e = 25,800), the e value of 1.1x105 is indicative of one P4 ligand (four Pth
groups) and two o-P2 ligands (two PPh2 groups each).7
(3) 1H and 31P{1H} NMR SpectroscOpic Studies

The 1H NMR spectrum of 25 contains the expected resonances in the
range 6 7.32 - 7 .48 ppm, assignable to the phenyl protons. The sharp singlet
at 1.81 ppm is due to the methyl-protons of the o-P2 ligands. Integration of
the signals results in a 20:3 ratio for the phenyl to methyl protons,
supporting the presence of 16 phenyl and 4 methyl groups. The 31P{1H} NMR
spectrum of 24 exhibits a singlet at 6 = 32.9 ppm with Pt satellites (th1) =
2365). The presence of only one signal shifted to lower fields relative to free
o-P2 or P4 indicates that the environments of the coordinated o-P2 and P4

ligands are too similar to be distinguished fi'om one another. Although the

216

 

 

 

coordinated phosphines of the P4 and o-P2 ligands in 24 are obviously not
equivalent, the environments of the phosphines are sufficiently similar
enough to render them magnetically equivalent. This is contradictory to
what was observed in the 31P NMR spectrum for [Pt2(dppb)2(tppb)][BF4]4,
which shows the bi- and tetradentate ligands to possess inequivalent
phosphines that exhibit a second order spectrum with one trans- and several
cis-coupling constants.2 The Pt-P coupling constant, Jpep, is in the expected
range for trans-phosphine ligands, and agrees well with [Pt(o-P2)2][BF4]2 (11)
and other [Pt(L-L)2]2+ complexes where L-L is a bis-phosphine ligand.2.15v16
(4) Electrochemistry

In the absence of electronic coupling, the electrochemistry of [Pt2(o-
P2)2(P4)][BF4]4 (24) would be expected to display two accessible one-electron
oxidation couples attributable to the P4 ligand and two superimposed one-
electron oxidation couples due to each o-P2 ligand. No separation of the one-
electron processes would be expected for the bidentate ligand, 1, based on
electrochemical data for the [M(o-P2)2]n+ series which revealed that the
ligands behave as isolated redox centers. Based on the cyclic voltammetry of
PtC12(o-P2) (20) at least one reduction couple may be expected for the metal
centers. The actual cyclic voltammogram of 24 is broad and relatively
featureless in the anodic region. An irreversible reduction couple is evident
at -O.89 V, which can be attributed to the previously described Pt(II)-Pt(I)
reduction process. Coulometry experiments have not been performed, thus

the exact nature of the process (one- or two-electrons) is undetermined. The

217

 

 

 

breadth of the signal may be a result of material depositing on the electrode
surface, a problem that has been observed with other metal-P4 complexes
(see Chapter 6). Another possibility is that communication between the TTF
units results in the superposition of several oxidation couples. Given the
results of the electrochemical studies for the [M(o-P2)2]’1+ series however, no
communication is expected between the phosphines of the o-P2 ligands.
Perhaps the shorter bridging C-C double bond (C(1)-C(2)) in the structure of
22 versus 20 is an indication that the electronic nature of the coordinated P4
ligand might be altered as compared to the o-P2 species. Even if this is the
case, the o-P2 ligands would still presumably act as isolated redox centers,
and overlapping couples should not be expected.
4. Concluding Remarks

The use of systematic synthetic procedures involoving polydentate
phosphine ligands to build extended materials with transition metal ions
allows for greater control over the resulting structure than typical cluster
synthesis methods. Fox and coworkers demonstrated that this methodology
works quite well using bis- and tetraphosphines as the ligand base.2 In the
present study the typically innocent organic backbone of the ligand is
replaced by TTF, which introduces added redox functionality and provides
the possibility of obtaining materials with interesting magnetic and
conducting properties. The syntheses of mononuclear and dinuclear metal
complexes containing only phosphine and chloride ligands proceeds with

relative ease and purity of product. The creation of vacant coordination sites

218

.5.8 .5 cm 22” <6 «.TmmzAvamm -83): mo mamfiamm mars- imam on: mcsoaoc 6.86:8 nosowmm .3. chum—m

.._.E ..EH.
H. I.

ssmx ”EuH

 

+vr

E 8.
68 E .28 E n E

a . . -

3502 i m

 

 

.. . m
+N 1 cm
A m < .2945
s fie E2 .38 E .88 E n 2 Em?

 

mmnm/ mama”

IMHE/Mzfl I Im_ €8En2
m

NE ”HEPH

 

E N
68 E .88 E u 2

 

 

£82 E E 28.x
- NE ..E m
+v
.; a. < .2946
Em»...

$8 Ez .98 E £8 E u 2

 

. E
a N
oVNmflM VI AU «EllesmoEoE. < .N o :8. 6.2 .N NEonoEoE < .m m/ \6
3m. Um” 2v Vnw N\ OWL/“WWW VI A WHEN—2H
E E «Asmeooszaz .H E
0\NE NE

219

by using reagents such as Ag+ to abstract one or more halides is a well
documented tool in synthetic chemistry, particularly in situations involving
small molecule reactivity.25 In the coordination polymers regime, such
complexes have been referred to as “complex-metals” due to the presence of
easily replaceable ligands which give rise to open coordination sites.3a These
complexes can then be used as building blocks for the formation of higher
nuclearity complexes with specifically engineered architectures. In the
present chemistry the halide abstraction step appears to be sluggish in the
case of the dinuclear complexes, and 31P NMR data indicate that some
partially halogenated impurities remain, especially in the platinum
chemistry. This is not too surprising given that Pt(II) is fairly inert. The
displacement of acetonitrile from partially solvated mononuclear-phosphine
complexes with P4 results in a coupling of the two mononuclear species to
form the dinuclear complex [Pt(o-P2)2(P4)][BF4]4 (22). The same product can
be obtained by reacting o-P2 with the partially solvated dinuclear complex,
[Pt2(NCCH3)2(P4)][BF4]4. The final step to form the all-phosphine product
[Pt2(o-P2)2(P4)]4+ has only been achieved with platinum, but it is reasonable
to believe that this can be extended to any metal for which MX2(o-P2) or
M2X4(P4) can be prepared.

While this chemistry does not strictly fall into the category of
"complexes as metals/complexes as ligands" due to the fact that thus far no
two metal-containing complexes have been combined to form a single

product, the potential for such chemistry exists. The complex

220

[Ni2(dppb)(tppb)][BF4]4 can be formed by in situ halide abstraction from
NiC12(dppb) with HBF4, followed by the addition of a stoichiometric amount
of the tetradentate- phosphine tppb.2 The fact that Pt2C14(P4) (20) and
Pd2C14(P4) (25) do not begin to form until after the first 30 minutes suggests
that the analogous product, MC12(P4), might be possible to obtain. The
formation could be rendered more favorable by the use of excess P4 and a
dilute solution of metal reactant. The preparation of such a complex opens
the possibility for the step-wise formation of highly extended structures with
precise control over the identity of the metal units (scheme 3). Such control
includes the formation of heterometallic complexes where more than one
metal can be included whose properties can be specifically chosen to produce
a desired outcome. This has been demonstrated by the use of

[Ni(dppb)(tppb)]2+ to form [NiM'(dppb)2(tppb)]4+, where M' = Pd or Pt.2‘=l

Ph.
CMe Ph P s 3 PC /Cl
I: H S1152: CMe Ph:PIS>_—<S lgl’f‘m —’ (3)
th th Cl 3 s Ph2 th
P\M / 2A,g+
KHZ]? IHI ISHSI} IHI
hz Ph2 Ph2 th

Another potential for this chemistry is the inclusion of magnetic metal
centers to form extended structures with unpaired electrons. A preliminary
report supports the successful synthesis of CoC12(o-P2) by a method
analogous to that used to prepare NiX2(o-P2).2‘6 Work in our laboratories

supports this report, and indicates that CoCl4(P4) can be similarly prepared.

221

Using cobalt (II) (S = 3/2) as an example, [002(o-P2)2(P4)][BF4]4, would be
expected to contain up to six unpaired electrons, barring strong
antiferromagnetic coupling through the ligand. If the phosphine groups serve
to restrict communication between metals in the chain, then molecules may
result with a large number of unpaired electrons. If the redox properties of
the TTF cores are exploited, the further possibility exists for adding three
unpaired electrons by one-electron oxidations of each ligand. The spin total
for the dimetal system could then be as high as nine unpaired electrons. The
use of [TCNQ]' as the counteranion instead of [BF4]' would introduce
additional radical species and allow the possibility of conduction through
stacked [TCNQP' (n = 0, 1) molecules. Given the potential for [Co(o-P2)2]2+
to bind two additional ligands, it may also be feasible to coordinate TCNQ
directly to the metal center (Figure 42), thereby forming multidimensional

arrays of metal and organic spins.

222

.1 H
NC/x ' _.\\\CN '—

 

/CO'\- ----- N E N S: is
“’2? 1’th (Iv-.4: T
N CN ------- -\- Co/

(A
m
\
/

*‘d
:r
to
*U
"U
"U
z:-
N)

 

 

Ph2P Pth 0&0 >———(
H c — o thP\m/PPh2

N --------- Co

5 \

Potential Conduction Band H

Figure 42. Schematic showing the potential coordination of [TCNQ]n' (n =
0, 1) to "[C02(o-P2)2(P4)]m+" (m = 4, 6, 7).

223

10.

11.

12.

List of References

Asara, J. M.; Uzelmeier, C. E.; Dunbar, K. R.; Allison, J., Inorg.
Chem., 1998, 37, 1833.

(a) Fox, M. A.; Chandler, D. A. Adv. Mater. 1991, 3, 381-385. (b)
Wang, P.-W.; Fox, M. A. Inorg. Chem., 1994, 33, 2938-2945. (c) Fox,
M.; Chandler, D. A., NATO Adv. Studies Sers., 1987, 214, 405.

(a) Balzini, V.; Campagna, S.; Denti, G.; J uris, A.; Serroni, S.; Venturi,
M. Acc. Chem. Res, 1998, 31 , 26. (b) Carter, F. L.; Siatkowski, R. E.;
Wohltjen, H., Eds., Molecular Electronics Devices, North-Holland:
AMsterdam, 1998. (c) Lehn, J-M. Supramolecular Chemistry, VCH:
Weinheim, Germany, 1995. (d) Balzini, V.; De Cola, L.,
Supramolecular Chemistry, Kluwer: Dorecht, The Netherlands, 1992.
(e) Véigtle, F. Supramolecular Chemistry, Wiley: Chichester, UK,
1993. (f) Stang, P. J ., Olenyuk, B. Acc. Chem. Res, 1997, 30, 502. (g)
Moore, J .S. Acc. Chem. Res, 1997, 30, 402.

(a) Campagna, S.; Denti, G.; Serroni, S.; Ciano, M.; Balzini, V. Inorg.
Chem., 1992, 31, 4251. (b) Serroni, S.; Denti, G. Inorg. Chem., 1992,
31 , 4251.

McCullough, R. D.; Belot, J. A. Chem. Mater., 1994, 6', 1396.

Gan, X.; Munakata, M.; Kuroda-Sowa, T.; Maekawa, M.; Misaki, Y.
Polyhedron, 1995, 14, 1343.

Fourmigué, M.; Batail, P. Bull. Soc. Chim. Fr., 1992, 12.9, 829.

Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.; Bartley, S. L.;
Dunbar, K. R. J. Organomet. Chem., 1997, 52.9, 343.

Uchiyana, T. Bull. Chem. Soc. Jap., 1981, 54, 181.

(a) Bino, A.; Cotton, F. A.; Fanwick, P. E. Inorg. Chem. 1979, 18, 3558.
(b) Cotton, F. A.; Frenz, B. A.; Deganello, G.; Shaver, A. J. Organomet.

Chem. 1973, 50, 227.

SHELXTL v. 5.04, G. M. Sheldrick and Siemens Analytical X-Ray
Systems, Inc., 1997, 6300 Enterprise Lane, Madison WI. 53719.

Cotton, F.A.; Wilkinon, G. Advanced Inorganic Chemistry, 3rd Ed.,
Wiley & Sons, New York, 1972.

224

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

Fourmigué, M., personal communication.

(a) Sanger, A. R. J. Chem. Soc., Dalton Trans.., 1977, 1971. (b)
Hudson, M. J .; Nyholm, R. S.; Stiddard, M. H. B. J. Chem. Soc. (A),
1968, 40.

Champness, N. R.; Levason, W.; Preece, S. R.; Webster, M.; Frampton,
C. S. Inorg. Chim. Acta, 1996, 244, 65.

(a) Jarrett, P.S.; Sadler, P. J. Inorg. Chem., 1991, 30, 2098. (b)
Oberhauser, W.; Bachmann, C.; Briiggeller, P. Inorg. Chim. Acta,
1995, 238, 35.

Liu, S-T.; Chen, J-T.; Peng, S-M.; Hsiao, Y-L.; Cheng, M-C. Inorg.
Chem., 1990, 2.9, 1169.

Davies, J. A.; Staples, R. J. Polyhedron, 1991, 10, 899.

Miedaner, A.; Haltiwanger, R. C.; DuBois, D. L. Inorg. Chem., 1991,
30, 417 .

Handbook of Chemistry and Physics, 63rd Ed., CRC, Clevelend Ohio,
1982-1983, F-200.

Calligaris, M.; Carturan, G.; Nardin, G.; Scrivanti, A.; Wojcicki, A.
Organometallics, 1983, 2, 865.

Uzelmeier, C. E. ; Founigué, M.; Smucker, B.; Grandinetti, G.; Dunbar,
K. R., manuscript in preparation.

(a) Whiteford, J. A.; Rachlin, E. M.; Stang, P. J. Angew. Chem. Int.
Engl., 1996, 35, 2524. (b) Slone, R. V.; Yoon, D. I.; Calhoun, R. M.;
Hupp, J. T. J. Am. Chem. Soc., 1995, 117, 11813.

Johnson, A.; Taube, H. J. Indian. Chem. Soc., 1989, 66, 503.

(a) Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc., 1971, .93, 2397. (b)
Shapley, J. R. Schrock, R. R. J. Am. Chem. Soc., 1969, 91, 2816. (c)
Green, M.; Kuc, T. A.; Taylor, S. H. J. Chem. Soc. (A), 1971, 2334. (d)
Haines, L. M.; Singleton, E. J. Chem. Soc., Dalton Trans, 1972, 1891.
(e) Haines, L. M. Inor. Nuc. Chem. Lett., 1969, 5, 399. (f) Haines, L.
M. Inorg. Chem., 1970, .9, 1517.

Fourmigué, M.; Jarchow, S.; Batail, P. Phosphorus, Sulfur, Silicon,
1993, 75, 175.

225

CHAPTER VI

ASSEMBLY OF OLIGOMERIC SYSTEMS FROM HOMOLEPTIC

PLATINUM GROUP NITRILE COMPLEXES AND

TETRAKIS(DIPHENYLPHOSPHINO)TETRATHIAFULVALENE (P4)

226

1. Introduction

The preparation of the mononuclear M-(o-P2) complexes described in
Chapter III led us to become interested in the use of the tetradentate ligand
(PPh2)4TTF (P4) for the preparation of the analogous extended species. The
presence of four phosphine groups on the TTF unit Opens up the possibility
for chelating metal centers on both sides, as observed in the molecular
structure of Pt2C14(P4) (22). Based on the reactions of the o-P2 ligands it can
be expected that P4 will react in a similar fashion, resulting in the
preparation of coordination polymers.

It has been theorized that the introduction of transition metal ions into
a conjugated polymer chain will create a partially-filled band, possibly
leading to intrinsic conductivity.1 The preparation of polymers requires two
characteristics.2 First, the redox-active centers (inorganic, organic, or a
combination of the two) must be oriented to permit strong interactions, often
requiring close spatial proximity and similar crystallographic and electronic
environments for the units. Second, the polymers must be partially oxidized
or reduced (forming mixed-valence species) to permit free charge transfer
along the chain.3

Thus far, eflorts to produce conducting or semiconducting coordination
polymers have met with varied success. Some of these include metal
coordination polymers of tetrathioxalate,4 dihydroxybenzoquinone,5 and
benzodithiolene.‘5 In considering our own approach, the molecule that bears

the most resemblance to P4, from a coordination perspective, is

227

tetrakis(diphenylphosphino)benzene (tppb).7 In this chapter, the chemistry of
P4 with divalent metal ions is reported and the results discussed in light of
the potential of these compounds to form Oligomers/polymers.

A. Synthesis

Starting Materials and Reaction Procedures. The compounds
[P(C6H5)2]4TTF,8 [Rh2(NCCH3)1o][BF4]4,9 Ni(CF3803)21° and [M(NC-
CH3)x][BF4]2 (M = Ni, Co, Fe,11 Pd,12 x = 6; M = Pt,13 x = 4) were prepared
according to published procedures. Acetonitrile, and methylene chloride were
distilled over 3 A molecular sieves. Diethyl ether, hexanes and toluene were
distilled over sodium-potassium/benzophenone. Unless otherwise specified,
all reactions were carried out under an argon atmosphere by using standard
Schlenk-line techniques.

(1) Reaction of [Rh2(NCCH3)1o][BF4]4 with P4: Formation of

[Rh(P4)] [BF 4] (30)

3.8 mL of a stock solution P4 (0.2089 g, 0.222 mmol) in 11.5 mL of
CHzClz was added to an CH3CN solution of [Rh2(NCCH3)1o][BF4]4 (0.308 g,
0.319 mmol, 10 mL), which led to an immediate darkening of the orange
solution. After stirring for 24 h, the solvent was removed under vacuum and
the residue redissolved in 3 mL of CH3CN. The solution was treated with 30
mL of Et20 and filtered in air, to yield a tan solid which was washed with
additional Et20 and dried in vacuo; yield 0.185 g (7 4% on [Rh(P4)][BF4]). 1H

NMR (CD2C12) 6 ppm: 25 °C: Ph-H, 7.28 (m, T1 = 0.72(2)s), 7.06 (m, T1 =

228

0.76(3)s); 0 °C: 7.24 (m), 7.05 (m); -35 °C: 7.07 (m). 31P{1H} NMR (CD2C12) 6
ppm: 25 °C: 51.0 (d, lJRh-P = 34 Hz). C.V. (0.1 M CH3CN/TBAPF6, Pt electrode
vs Ag/AgCl): E1/2(ox)1 = +0.76 V, E1/2(ox)2 = +1.12 V. UV/Visible (CH3CN)
lmax, nm (a, M'lcm'l): 387 (8.1x103), 310 (3.4x104), 266 (3.8x104). GPC (1.00
mL/min, THF, 254 nm): 20.65 min., 22.00 min retention.

(2) Reaction of [Mn(NCCH3)n][BF4]2 (M = Pt, n = 4; M = Pd, Co, Fe, Ni,

11 = 6) with P4.

(i) Formation of [Pt(P4)]n[BF4]2n (31). 5 mL of a stock solution of P4
(0.300 g, 0.319 mmol) in 15 mL of CH2C12 was added to an CH3CN solution of
[Pt(NCCH3)4][BF4]2 (0.057 g, 0.107 mmol, 10 mL) which caused a darkening
of the orange solution. After stirring for 24 h, the solution was treated with
20 mL of Et20 and filtered in air, to yield an orange solid which was washed
with copious amounts Et20 and dried in vacuo; yield 0.109 g (78% for
[Pt(P4)][BF4l2). 1H NMR (CD3CN) 6 ppm: 25 °C: Ph-H, 7.23 (br), 7.44 (br),
7.73 (br); 0 °C: 7.20 (br), 7.44 (br), 7.74; -15 °C: 7.20 (br), 7.43 (br), 7.73 (br); -
35 °C: 7.20 (br), 7.40 (br), 7.71 (br). 31P{1H } NMR (CDaCN) 6 ppm: 36.1 (s,
1th-p = 2361 Hz). IR (Nujol, cm'l): 689 (m, won), 1054 (br, VB-F). UV/Visible
(CH3CN) km“, nm (e, M'lcm'l): 406 (5.5x103), 238 (6.6x104).

(ii) Formation of [Pd(P4)]n[BF4]2n (32). Solutions of 0.116 g of
[Pd(NCCH3)6]BF4]2 (0.221mmol) in 6 mL of CH3CN and 0.207 g (0.220 mmol)
of P4 in 5 mL of CH2C12 were prepared in separate flasks. Upon addition of

the phosphine solution to the metal complex, a color change from orange to

229

brown ensued. The solution was stirred for 12 h before being reduced to 5
mL and treated with 50 mL of Et20, which gave a brown precipitate. The
mixture was filtered in air, and the solid was washed with copious amounts
of EtzO before being dried in vacuo; yield 0.243 g (90% for [Pd(P4)][BF4]2).
Anal. Calcd for 32, PdP4S4C54H4o: C, 53.12; H, 3.31. Found: C, 53.67; H, 3.69.
1H NMR (CD3CN) 6 ppm: 25 °C: Ph-H, 7.13 (m, T1 = 2.23(5)s), 7.20 (m, T1 =
1.99(3)s), 7.44 (br, T1 = 1.98(3)s); 0 °C: 7.13 (br), 7.19 (m), 7.43 (br); -15 °C:
7,14 (m), 7.17 (m), 7.42 (br); -35 °C: 7.16 (m), 7.42 (br). 31P{1H} NMR (CD3CN)
6 ppm: 44.2; (solid) 6 ppm: 42.6. IR (Nujol, cm'l): 525 (s, vc=c), 670 (m, won),
1049 (br, VB-F). UV/Visible (CH3CN) Xmax, nm (e, M'1cm°1): 337 (4.1x104).
FAB-MS (in HCF3803, m/z): 1194 ([Pd(P4)(CF3S03)]+), 1601
([Pd2(P4)(CF3SO:3)3]+), 2945 ([Pd3(P4)2(CF3SOs)5]+), 3890 ([Pd3(P4)3(CF3-
sos)5]+), 4294 ([Pd4(P4)3(CF3S03)7]+).

(iii) Formation of [CO(P4)]n[BF4]2n (33). 0.046 g (0.096 mmol) of
[CoH(NCCH3)6][BF4]2 and 0.101 g (0.107 mmol) of P4 were dissolved in 10 mL
CH3CN and 10 mL CH2C12, respectively. Upon addition of the phosphine
solution to the cobalt complex, the reaction mixture immediately turned dark

green. The reaction mixture was stirred overnight, concentrated to a volume
of ~ 5 mL, and treated with Et20 (20 mL) to give a green precipitate. The

solid was isolated by decanting the solution, washed several times with Et20,
and dried in vacuo; yield 0.056 g (51% for [Co(P4)] [BF4]2) . 1H NMR (CD3CN)

6 ppm: broad and unresolved. 31P{1H } NMR (CDgCN) 6 ppm: none observed.

230

EPR (1:1 toluene/acetonitrile, -140°C): g z 2.21. magnetic moment, peg (pg),
1T: 2.05 at 5 K, 5.00 at 340 K.

(iv) Formation of [Fe(P4)]n[BF4]2n (34). 0.051 g of [Fe(NCCH3)6]BF4]2
(0.107 mmol) and 0.105 g (0.112 mmol) of P4 were loaded into a Schlenk-
flask and treated with a combination of 5 mL of CH2C12 and 10 mL of
CH3CN, which produced a red solution. The solution was stirred for 3 days
before being treated with 40 mL of Et20 to afford a red precipitate; the liquid
was decanted, and the solid was washed 4 times with 5 mL portions of Et20.
The solid was dried under vacuum; yield 0.094 g (75% for [Fe(P4)][BF4]2). 1H
NMR (CD3CN) 6 ppm: 6.90 (br), 7.27 (m), 7.34 (m), 7.59 (br). 31P{1H } NMR
(CD3CN) 6 ppm: 53.6 (s), 73.8 (s).

(v) Formation of [Ni(P4)]n[BF4]2n (35). 0.051 g of [Ni(NCCH3)6]BF4]2
(0.107 mmol) and 0.104 g (0.111 mmol) of P4 were loaded into a Schlenk-
flask and treated with a combination of 5 mL of CH2C12 and 10 mL of
CH3CN, to yield a green-brown solution. The solution was stirred for 1 week
before being reduced to 5 mL under vacuum. The solution was treated with
50 mL of Et20 to afford a green precipitate, the liquid was decanted, and the
solid was washed 4 times with 10 mL portions of Et20. The solid was finally
dried under vacuum; yield 0.050 g (41% for [Ni(P4)][BF4]2. 1H NMR (CD3N) 6
ppm: -CH3 1.90 (s, 6H); Ph-H, 7.05 (br), 7.23 (m), 7.25 (br). 31P{1H} NMR

(CDsN) 6 ppm: 41.7. IR (Nujol, cm'l): 689 (m, won) 503 (s, vc=c), 1020 (br, VB-

F)-

231

(3) Reactions with excess P4

(i) [Rh2(NCCH3)1o][BF4]4. Solutions of 0.226 g of P4 (0.240 mmol) and
0.056 g of [Rh2(NCCH3)1o][BF4]4 (0.058 mmol) were prepared separately by
dissolving the solids in 10 mL of CH2C12 and 10 mL CH3CN respectively. The
phosphine was then slowly added to the metal complex 5 mL at a time,
causing the solution to change from orange to dark brown. After stirring for
several hours, the volume of the solution was reduced by application of a
vacuum to ~5 mL. An orange-brown solid precipitated from the solution
following the addition of 50 mL of toluene. The product was recovered by
decanting the orange liquid and washing the solid 5 times with 10 mL of
toluene to remove unreacted ligand. Finally, the solid was collected by
filtration in air and washed with copius quantities of Et20, and dried in
vacuo. 31P{1H} NMR (CDaCN) 6 ppm: -18.2 (s), 50.3 ((1)

(ii) [Pdn(NCCH3)6][BF4]2. CH2C12 (15 mL) was added to a mixture of
[PdII(NCCH3)6][BF4]2 (0.022 g (0.05 mmol) and (thP)4TTF (0.103 g 0.11
mmol), which dissolved the phosphine but left the palladium complex
undissolved. After stirring for several minutes, an equal amount of
acetonitrile was added which led to dissolution of the metal-complex and a
color change from orange to dark red-orange. The solution was stirred
overnight, reduced to dryness by vacuum, and washed several times with
excess amounts of toluene to remove unreacted ligand. Due to the difficulty in

preventing loss of solid, the washings were saved in a separate flask. Both

232

flasks were reduced to dryness by reduced pressure, washed with Et20, and

dried in vacuo. 1H NMR (CD3CN) 6 ppm: Ph-H, 7 .23 (m), 7.70 (pentet).

31P{1H} NMR (CD3CN) 6 ppm: 44.0 (s), 43.7 (s), -17.1 (s).

3. Results and Discussion

A. Preparation and Characterization of [M(P4)]n[BF4]xn ( M = Rh, x =
1; M = Pt, Pd, Co, Fe, Ni, x = 2) (30-35)

(1) Synthesis

The reaction of [Rh2(NCCH3)1o][BF4]4 with four equivalents of the
tetradentate ligand P4 results in the formation of a product, formulated as
[Rh(P4)]n[BF4]n (31) based on the stoichiometry of the reaction. The reaction
proceeds by sacrificing two equivalents of TTF-phosphine in order to reduce
both d7 metal centers. This is evidenced by the formation of a green solution,
indicative of TTF cation formation. The reaction proceeds very similarly to
the synthesis of [Rh(o-P2)2][BF4],14 with the exception of the use of CH2C12 as
a solvent due to the low solubility of P4 in nitriles.

Similar reactions involving mononuclear metal precursors such as
[M(NCCH3)n][BF4]2 (M = Pt, 11 = 4; M = Pt, Pd, Fe, Co, Ni, 11 = 6), proceed
without the redox chemistry observed in the formation of 30. The loss of
nitriles appears to be quite rapid in mononuclear cases, as judged by the
immediate color changes. The loss of acetonitrile is more dificult to gauge in
the case of Rh due to the color changes caused by oxidation of the TTF

moieties. The reaction conditions are quite similar to those used by Fox

233

and co-workers in the formation of long chain oligomers using
tetrakis(diphenyl-phosphino)benzene (tppb).7 In contrast to the insoluble
products obtained by Fox, the products are highly soluble in most organic
nitrile and chlorinated solvents, as well as acetone. Increased solubility may
be a result of the high charge associated with complexes 30-35, but given that
the charges are the same for 31, 32, 35 and for complexes of Ni“, Pdn, and
Pt11 with tppb, this does not explain the difference in solubilities. Unlike
their mononuclear analogs, [Ni(o-P2)2][BF4]2 (8) and [Co(o-P2)2][BF4]2 (9) , 33
and 35 are air-sensitive, and decompose to an unidentified species.
Complexes 31 and 32 are air stable and 32 is resistant to decomposition after
heating at 80°C for 24 h. The complexes have been characterized by NMR,
infrared, and electronic absorption spectroscopies. EPR and magnetic
susceptibility studies of the paramagnetic CoII complex have also been
conducted. Elemental analysis of [Pd(P4)]n[BF4]2n (32) is in excellent
agreement with a 1:1 formulation, while FAB-MS spectrometry contains
mass ion peaks attributable to trinuclear species when triflic acid is used
with the medium.15

(2) Spectrosopic Characterization

(i) NMR Spectroscopic Studies. The NMR spectral properties of 30-35 A
closely resemble those observed for their mononuclear, M-(o-P2),
counterparts. The 1H NMR spectra of 30-35 in CDaCN exhibit a series of

multiplets in the region 6 = 7 .2 - 7 .7 ppm due to the phenyl protons. The

234

31P{1H} NMR spectra of the PdII (32) and NiII (35) complexes each contain a
single resonance at 6 =44.2 and 41.7 ppm respectively. The downfield shift of
the signal from the free phosphine at -18.2 ppm is a result of five-coordinate
ring stabilization, and indicates that the phosphine is chelated to the metal
center.8’16 Compounds 30 and 31 each exhibit splitting patterns
characteristic of coupling with an I = 1/2 nucleus. The 31P spectra of
[Pt(P4)]n[BF4]2n (31) contain a singlet at 6 = 36.1 ppm with satellites (th-p =
2361 Hz) due to the 33% abundance 195Pt. 103Rh is 100% abundant, which
explains the doublet observed in the 31P NMR spectra of 30 at 51.0 (JRh-P =
134 Hz). These data support that there is only one environment for the
phosphorus nuclei in these complexes, and that they are metal-coordinated.
[Co(P4)]n[BF4]2n (33) exhibits no observable resonances in its 31P{1H} NMR
spectrum, and only broad signals in the 1H spectrum, which indicates a
paramagnetic complex.

The presence of an 31P NMR signal for [F9(P4)]n[BF4]2n (33) indicates
that it is a diamagnetic product, with the metal behaving as a low-spin, d6,
FeII center similar to [Fe(o-P2)2][BF4]2 (12). Compound 33 contains two
signal patterns in its 31P{1H} NMR spectrum, both of which are downfield
shifted relative to flee ligand. The singlet at 53.6 ppm is in the same range
as the other P4 complexes described above, indicating that it is a homoleptic
phosphine. The second signal observed at 6 = 7 3.8 ppm is at considerably

lower fields than other complexes of o-P2, a fact that may indicate the

235

presence of coordinated fluoride in some form.17 This has also been reported
for 12 and confirmed by 19F NMR spectrosc0py. Similar experiments are
warranted for 33.

As stated previously, the above data support one environment of
coordinated-phosphine in solution. If one considers the structures of the
predicted long-chain products, this would is not be expected. In long chain
oligomers, there must be both linking groups and end groups. These two
different environments would be expected to exhibit very different chemical
shifts in 31P NMR spectra. For the reactions described here there are two
different possibilities for end groups: phosphines and nitriles which would be
trans to phosphines. In either case, two 31P NMR signals would be expected,
namely one in the region of the observed spectra for the internal phosphorus
nuclei of the chain, and one for the phosphorus nuclei closest to chain
termination. The latter signal would be expected to occur upfield from the
internal phosphines, but downfield from the free ligand signal. This was the
observation for the tppb coordination polymers mentioned previously. End-
group analysis of these oligomers by 31P NMR spectroscopy led to estimated
chain lengths of 37i7 for Ni, 50:1:10 for Pd, and 23i5 for Pt.

Given the absence of of 31P NMR resonances for 30-35 other than those
predicted for internal phosphines (with the exception of [Fe(P4)]n[BF4]2n)
other options must be considered. One possibility is that a dynamic process
occurs in solution causing the phosphines to reversibly coordinate to the

metal. This would lead to an averaged signal and a broadening of the

236

terminal phosphines. To check for this, variable temperature 31P NMR
studies were performed on 30 and 32 in CD2C12 between 20 and -80 °C. The
resulting spectra revealed no change with decreasing temperature. To
further explore possible fluxionality, the solid state 31P NMR spectra of
[Pd(P4)]n[BF4]2n (32) were measured on a Varian-400 MHz spectrometer with
the idea that end groups would be detected. The resulting spectrum

exhibited a singlet at 6 = 42.7 ppm, which supports the conclusion that a

fluxional process is not present.

Another NMR method used to obtain a qualitative size comparison of
two similar molecules is measuring the spin-lattice (Tl) relaxation time.
Nuclei in an NMR experiment are in a sample. The vibration and rotation of
nuclei within a sample creates a complex magnetic field, called the lattice
field. Some components of the lattice field can interact with nuclei in the
higher energy state, and cause them to lose energy, returning to the lower
state. T1 is the average lifetime of nuclei in the higher energy state. Larger
molecules tend to undergo a greater degree of vibrations and rotations, thus
causing a shorter T1 relaxation time. By comparing the T1 values of similar
molecules, such as [Pd(o-P2)2][BF4]2 (10) and [Pd(P4)]n[BF4]2n (32), or [Rh(o-
P2)2][BF4] and [Rh(P4)]n[BF4]n (30) we can obtain a qualitative estimation of
the difference in size between the two molecules. Measurements of the T1
relaxation times of the phenyl protons of 10 and 32 showed both molecules to

exhibit relaxation times on the order of 2 seconds. This indicates that there

237

is little size difference between the two molecules, supporting that 32 is not a
long chain oligomer or polymer. Similar observations were made when
comparing the Rb complexes, with both molecules exhibiting T1 values on
the order of 0.7 seconds.

(ii) Infrared and UV-Visible Spectroscopy. The infrared spectra of 31,
32, and 35 display bands at ca. 690 and 520 cm:1 attributable to the C-_-.-C and
H-CuC out-of-plane bends of the phenyl rings of the phosphine groups.18

Strong bands at ca. 1050 cm“1 are due to the B-F stretch of the [BF4]‘ groups.
The absence of absorptions at higher wavenumbers (ca. 2300 cm°1) supports
complete displacement of acetonitrile, but is not conclusive given that the
frequency and intensity of the CaN stretching vibration can be quite variable,
and in some cases even be absent when coordinated nitrile is present.18 The
electronic spectra of 31 and 32 recorded in acetonitrile exhibit transitions
attributable to the phenyl groups between 238 and 266 nm, and the TTF at
310-407. The overlap of certain features renders wavelength assignments
dificult, and accounts for the absence of certain key transitions in 31 and 32.
Fourmigé and co-workers reported that the extinction coefficient, a, for the
phenyl chromophores in TTF-phosphines is approximately proportional to the
number of phenyl groups in the molecule, where s = 2.5x104 is indicative of
four phenyl rings.8 Applying this value leads to an estimation of eight phenyl

rings, or one P4 ligand for 30, and two P4 units for 31. In the case of 31, such

238

a formulation would require dangling phosphines, but given the 31P NMR
spectrum this is not a possibility. 1

(iii) Magnetic Susceptibility and EPR Spectroscopic Studies of
[CO(P4)]n[BF4]2n (33). Figure 43 shows the measured molar magnetic
susceptibilities (x), corrected for diamagnetisim, and the corresponding
effective magnetic moment (peg), from 5 to 320 K for [Co(P4)]n[BF4]2n (33).
Studies revealed the magnetic susceptibility of 33 is similar to its
mononuclear analog, [Co(o-P2)2][BF4]2 (9). The 11.5 range of 5.00 “B at 320 K,
to 2.05 1.113 at 5 K is in good agreement with a high-spin, S = 3/2 Co(II)
molecule, with pseudo-octahedral geometry (see Chapter I).19 The moment
observed at higher temperatures is a result of the large spin-orbit coupling
contribution to the expected peer (spin-only) value of 3.87 1113. At temperatures
below 20 K one populates the doubly-degenerate S = 1/2 ground.

EPR measurements of 33 were first carried out in CH3CN/toluene (1:1)
glasses at 121 K. Spectra of 33 display a broad signal at g = 2.21. This
spectrum is similar to that observed for 9 in similar media, and suggests the
metal center is a four-coordinate S = 1/2 molecule, a result that is in direct
conflict with the observed magnetic moment in the solid state. In contrast to
the spectra of 9, compound 33 does not exhibit hyperfine splitting. These
discrepancies between the solid state magnetic measurements and EPR

spectra from solutions have yet to be resolved.

239

 

 

 

 

 

0.12 d 141 11114 111 111l1111l111ll1 1L4 ii;14 _5
0 ‘I I . :
0.1:“ - . ' :
g 2. I I :4
0.08“. I. Z
P I .I' I ueff . m:
g I. I. :3 g
V— 0'06: . ' ' Xmol : ’5
a 3’. L2 w
. __ V
N 0.04: . _
I 0 I
. I—
o.02— 0.... _ 1
: 0 g o o o o o . . . . :
O I I 1' [I 111] 17ft] II T I l 1 11 I [1 I r TITTWI O

0 50 100 150 200 250 300 350
Temperature (K)

Figure 43. Plot of 11.3 (1113) and Xmol (emu/mol) vs. temperature (K) of
[00(P4llnIBF4lzn (33)-

240

(iv) Electrochemistry of [Rh(P4)]n[BF4]n (30). Cyclic voltammetry data
for 30 show two reversible oxidation couples at +0.76 and +1.12 V due to the
accessible oxidations of the TTF moieties. Shifting of the couples by +0.30
and +0.21 V from the fiee P4 molcecule indicates strong interactions with the
metal ions. These potentials are within the range that was found for [Rh(o-
P2)2][BF4] and NiX2(o-P2) (X = C1, Br).14v8 We note that the breadth of the
signal may be a result of material depositing on the electrode surface. This
problem has been observed for 31 and 32 also, and in those cases no well-
defined couples were visible in the voltammograms. Another possibility is
that communication between the TTF units results in the superposition of
several oxidation couples. Electrochemical studies of the [M(o-P2)2]n+ series
points to no communication of the phosphines through the metal, but the
shorter bridging C-C double bond (C(1)-C(2)) in the structure of PtzCl4(P4)
(22) versus PtC12(o-P2) (20) suggests that the electronic nature of the
coordinated P4 ligand does not follow the same pattern.

(v) Fast Atom Bombardment Mass Spectrometry. Currently the most
accurate method of determining molecular weight is Mass Spectrometry
(MS). A problem which arises with MS is the high charge associated with
these structures. For compounds such as 31-35 the charge is +2 for each
metal center. In the gas phase, fragmentation occurs such that charges are
generally minimized. Consequently, highly charged complexes are quite

difiicult to characterize.

241

 

 

 

Studies performed on [Pd(P4)]n[BF4]2n (32) by Dr. John Allison and
John Asara in conjunction with our laboratories reveal peaks attributable to
the formation of polynuclear species.15 The addition of triflic acid (HOTf) to
the matrix/analyte allowed for the isolation of peaks representing
[Pd(P4)(OTf)]+ (m/z = 1194), [Pd2(P4)(OTf)3]+ (m/z = 1601), [Pd3.(P4)3(OTf)5]+
(m/z = 2945) ]+), [Pd3(P4)3(CF3-803)5]+ (m/z = 3890), and [Pd4(P4)3(CF3803)7]+
(m/z = 4294). Stang and coworkers are using triflate as a counterion for the
FAB-MS characterization of a series of supermolecular inorganic structures
with charges ranging fiom 4-8 by utilizing triflate as a counterion.20 While
the potential size of metal-P4 oligomers is too large to measure by standard
FAB-MS techniques, new techniques such as Electrospray (ES) and Mass
Assisted Laser Desorption Ionization (MALDI) MS may be useful for
obtaining the parent ion peaks of extremely large inorganic species formed in
solution by an extremely soft bombardment method.

(3) Proposed Cyclic Oligomers.

The appearance of only one signal in 31P NMR spectra for 30-35 points
to either a long chain polymer, where the number of bound phosphorus atoms
outnumber the terminating phosphorus to such a high degree that the
unbound signal is lost in spectrum baseline, or to the presence of a cyclic
structure that renders all phosphorus environments equivalent. If one
recalls the molecular structures of [Rh(o-P2)2][BF4],14 [Ni(o-P2)2][BF4]2 (8),
and [Pt(o-P2)z][BF4]2 (11), all three contained out-of-plane bends between 27

and 32° at the bound dithiole ring of the TTF ligand. The bending occurs at

242

 

the sulfur positions closest to the metal bound phosphorus atoms. Given the
angle of the deformations (~30°), and the extrapolation that bending occurs
in both dithiole rings of the fully functionalized P4, the linking of six
[M(P4)]n+ units would result in a total bend for an “all-boat” conformation of
360°.

(i) Molecular Visualization. In order to visualize such a structure,
the SPARTAN21 program was used on a Silicon-Graphics workstation to
minimize the "M(P4)" fragments using the SYBYL forcefield from Tripos,
Inc.;22 these were then used to build the [Ni(P4)6]12+ hexamer depicted in
Figure 44. The resulting core measures an average distance of ~14 A from
hydrogen to hydrogen across the diameter. Although this is not a rigorous
molecular mechanics analysis, the results suggest that the structure is
possible on steric grounds.

(ii) Gel Permeation Chromatography. GPC is a common technique
in organic polymer chemistry for establishing molecular weight distributions
against a standard such as polystyrene.23 The longer the retention time on
the column, the smaller the size of the polymer chains. When the Rb
compounds of o-P2 and P4 (30) were simultaneously passed down a GPC
column, the elution time difference on the column was indiscernible (~ 20
min). The low resolution indicated that the P4 complex is not in the range of
the typical polymers that are separated on that column (>100,000 g/mole),
and it also suggests that there is minimal difference between the o-P2 and P4

structures on a logometric scale of the column. In order to best utilize this

243

 

Figure 44. Molecular model of the proposed cyclic hexamer [Ni(P4)s]12+.

244

technique a column with greater resolution for low molecular weight
polymers must be used. Although this will not give absolute molecular
weights, the column can be calibrated with smaller arrays of known
molecular weight that contain the P4 and/or P2 ligand. These studies are
ongoing in our laboratories.

(iii) Variable Temperature 1H NMR Spectrscopy. In the proposed
cyclic oligomer structure, there is an expected difference between the 1H
NMR signals of the phenyl groups directed towards the interior of the ring
and those on its exterior. To probe this diffference, variable temperature 1H
NMR measurements were made on [Rh(P4)]n[BF4]n (30), [Pd(P4)]n[BF4]2n

(32), and [Pt(P4)]n[BF4]2n (31). While 30 and 31 showed no significant

changes to the spectra, 32 exhibited coalescence of two multiplets at 7 .13 and
7 .20 ppm (at 25 °C) to a broad resonance at 7.16 ppm at —35 °C. Beyond this
change, the phenyl resonances remained broad and relatively featureless,
limiting more detailed assignment of the spectra. Despite the difficulty in
obtaining detailed information, the changes in the 1H NMR spectra of 32
demonstrates that further studies are warranted.
B. Reactivity of [Rh2(NCCH3)1o] [BF4]4 and [PdH(NCCH3)6] [BF4]2 with
excess P4.

In order to attempt end-group analysis on the [BF4]- products,
reactions were carried using excess P4 in the hopes that the additional

ligands will cap metal terminated positions. This is the same procedure used

245

for the analysis of the tppb coordination polymers.7 Reactions of
[Rh2(NCCH3)1o][BF4]4 and [PdU(NCCH3)6][BF4]2 with excess P4 were carried
out under identical conditions to the methods used for the synthesis of 30 and
32 in order to keep other experimental changes at a minimum. 31P NMR
spectral studies of the products reveal very different results for the two
systems. The 31P NMR spectrum of the product obtained from the reaction
with Rh is identical to that of 30, with the addition of a singlet at -18.2 due to
free phosphine. This indicates that the use of a non-stoichiometric amount of
ligand has no effect on the final product. Similar reactions with
Pd11(NCCH3)6][BF4]2 as the metal precursor produced a product(s) which
exhibits three distinct singlets in its 31P NMR spectrum. The signals at 6 =
44.0 and 43.7 ppm are very near the observed signal in the spectrum of
[Pd(P4)]n[BF4]2n (32) (44.2 ppm). The third signal is at much lower chemical
shift values, near the expected position of free P4. This would indicate at
least two difierent environments for coordinated phosphine, and supports the
presence of end-capped phosphine at -17.1 ppm. Integration of the area
under these peaks provides a roughly 2:1:2 ratio.
3. Concluding Remarks

Reactions between solvated precursors, such as [Rh2(NCCH3)1o][BF4]4
and [Mn(NCCH3)n][BF4]2 (M = Pt, 11 = 4; M = Pd, Co, Fe, Ni, n = 6), and the
tetradentate TTF-phosphine ligand, P4 result in the formation of soluble

products formulated as [M(P4)] n[BF4]xn (M = Rh, x = 1; M = Pt, Pd, Co, Fe,

246

 

Ni, x = 2). These complexes exhibit 31P NMR spectra typical of a single
environment for the phosphorus nuclei, with all phosphines being metal-
bound. The appearance of one resonance at all temperatures points to either
(1) the presence of an extremely high molecular weight polymer or (2) the
adoption of a structure that places all of the P atoms in the same
environment. One possible structure is the formation of cyclic oligiomers.
Bends in the molecular structures of the mononuclear model compounds,
[M(o-P2)]2[BF4]m (M = Rh, m = 1; M = Pt, Ni, m = 2), support this theory.

The preferred method for elucidating the molecular structure of the P4
complexes is single crystal X-ray diffraction. Unfortunately attempts to grow
crystals of 30-35 have not been successful. Possible causes for this are the
size of the cavity for the proposed hexamer, and the number of counterions
associated with such a species. In order to grow crystals, a favorable packing
situation must occur. The open cavity poses a problem due to the void space
that must be filled in order to stabilize a the structure. The use of
polyoxometallates such as [TBA]6[MO7024] could serve to pack this cavity, as
well as to reduce the number of counterions required to balance the
molecular cation. Preliminary studies indicate that addition of
polyoxometallates to solutions of a typical P4 complex results in oxidation of
the TTF unit. Such a reaction would be expected to lead to ring-opening due
to forced planarity on at least one of the ligands. To circumvent this
problem, other non-redox active anions are currently being investigated,

including [Fe(CN)e]4'.

247

10.

11.

12.

13.

14.

15.

16.

List of References

Gooding, R. D.; Lillya, C. P.; Chien, J. C. W. J. Chem. Soc., Chem.
Commun. 1983,15. '

Marks, T. J. Angew. Chem., Int. Ed. Engl. 1990, 29, 857.
Wang, P.-W.; Fox, M. A. Inorg. Chem. 1994, 33, 2938.

Reynolds, J. R.; Lillya, C. P.; Chien, J. C. W. Macromolecules, 1987, 20,
1184.

Wrobleski, J. T.; Brown, D. B. Inorg. Chem. 1979, 18, 2738.

Dirk, C. W.; Bousserau, M.; Barrett, P. H.; Moraes, F.; Wudl, F.;
Heeger, A. J. Macromolecules, 1986, 19, 266.

Wang, P.-E.; Fox, M. A. Inorg. Chem. 1994, 33, 2945.
Fourmigué, M.; Batail, P. Bull. Soc. Chim. Fr. 1992, 12.9, 829.
Dunbar, K. R.; Pence, L. E. Inorg. Synth. 1992, 2.9, 182.

Dixon, N. E.; Lawrance, G. A.; Lay, P. A.; Sargeson, A. M.; Taube, H.
Inorg. Chem. 1984 23 2940.

Hathaway, B. J .; Holah, D. G.; Underhill, A. E., J. Chem. Soc., 1962,
2444.

Thomas, R. R.; Sen, A., Inorg. Synth., 1989, 26, 128.

DeRenzi, A.; Panunzi, A.; Vitagliano, A., J. Chem. Soc., Chem.
Commun., 1976, 47.

Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.; Bartley, S. L.;
Dunbar, K. R., J. Organomet. Chem., 1997, 52.9, 343.

Asara, J. M.; Uzelmeier, C. E.; Dunbar, K. R.; Allison, J. Inorg. Chem.,
1998, 37, 1833.

Carlin, R. L.; van Duyneveldt, A. J. Magnetic Properties of Transition
Metal Compounds, Springer: New York, 197 7 .

248

17.

18.

19.

20.

21.

22.

23.

(a) Honeychuck, R. V.; Hersh, W. H. Inorg. Chem. 1987, 26', 1826. (b)
Honeychuck, R. V.; Hersh, W. H. Inorg. Chem. 1989, 28, 2869. (c)
Lundquist, E. G.; Folting, K.; Hoffman, J. C.; Caulton, K. G.
Organometallics, 1990, 9, 2254. (d) Fernandez, J. M.; Gladysz, J. A.
Inorg. Chem., 1986, 25, 2672.

Silverstein, R. M.; Bassler, G. C.; Morrill, T. C. Spectrometric
Identification of Organic Compounds, 4th Ed. John Wiley & Sons:
1981.

Johnson, A.; Taube, H., J. Indian. Chem. Soc., 1989, 66', 503.

Whteford, J. A.; Rachlin, E. M.; Stang, P. J. Angew. Chem., Int. Ed.
Engl. 1996, 35, 2524.

SPARTAN 5.0, Wavefunction Inc., 18401 Von Karman Ave., Suite 370,
Irvine, CA. 92612, USA.

SYBYL 6.4, Tripos Inc., 1699 South Hanley Road, St. Louis, MO,
63144, USA.

(a) Peckham, T. J .; Massey, J. A.; Edwards. M.; Manners, I.; Fousher,

D. A. Macromolecules, 1996, 29, 2396. (b) Wood, B. R.; Semlya, J. A.;
Hodge, P. Polymer, 1996, 38, 191

249

CHAPTER VII

CONCLUSION

250

The results presented in this dissertation establish the use of
tris(2,4,6-trimethoxyphenyl)phosphine as an excellent supporting ligand for
the stabilization of various metal complexes. The mononuclear Rh(I)
complex, [Rh(nz-TMPP)2][BF 4] (3) was prepared from the reaction of the
Rh(II) species [Rh(n3-TMPP)2][BF4]2 with Con2 in the presence of a
methylating agent. The formation of 3 marks the first such series of
homoleptic-phosphine complexes that spans three oxidation states, namely
Rh (1, II, III). Dealkylation of 3 by addition of a nucleophile results in the
formation of the unstable neutral species, Rh1(TMPP)(TMPP-0) (4).
Although considered sterically bulky, the TMPP ligand is quite flexible as
evidenced by the variety of fluxional and isomerization processes that have
been observed for its metal complexes.1 The ability to change coordination
modes makes it possible to access different oxidation states of a metal center
while maintaining the same ligand set. At room temperature, solutions of 3
and 4 decompose to [RthI'MPP)(TMPP-0)][BF4]2 and ax,ax-[Rhm(TMPP-
O)2][BF4]. The chemical relationship between the known rhodium-TMPP
complexes studied in our laboratories is illustrated in Figure 14. Rather than
forcing a particular geometry on the metal center, the ligand adjusts to the
available coordination sites and the electronic requirements of the metal
center. This ability is readily apparent when one examines geometry

changes in going from Rh(I) to Rh(II) in the structure of [Rh1(n2-

TMPP)2] [BF4] - [Rhnm 3-TMPP] [BF4] 2 (3' [Rhnm 3-TMPP] [BF4]2).

251

The combination of both hard and soft donor groups in a phosphine
ligand leads to an ability to stabilize a metal atom in a variety of
coordination geometries and oxidation states. The availability of cis-disposed
phenoxide groups on Co(TMPP-O)2 renders it able to act as an inorganic
"ligand," as has been shown in the stabilization of the bimetallic complexes
C12Co(TMPP-O)2 and ClenCo(TMPP-O)2.1d The formation of the
hexanuclear cluster, [CoIIu3OH)(u-OH)3{CoH-n3TMPP-O)2}3][BF4]2 serves as
additional evidence for the use of Co(TMPP-O)2 as a "synthon" for the
preparation of polynuclear metallic complexes.

The functionalization of TTF with phosphine groups has been shown to
be an excellent route into the synthesis of "hybrid" inorganic/organic
compounds.2 The preparation of [M(o-P2)2][BF 412 (Ni, Co, Pd, Pt, Fe), from
the reaction of the appropriate fully-solvated precursor with ortho-
Me2(PPh2)2TTF (o-P2) demonstrates the ability of these phosphines to
coordinate to a host of different transition metals. Each of the complexes
described in this study exhibit electrochemically accessible redox processes
associated with both the TTF and the metal center. The molecular structures
of members of this series show deformations in the TTF unit, which serves to
allow for intermolecular interactions of ~3.5 A between the TTF moieties of
neighboring molecules. The result is a one-dimensional arrangement. The
accessibility of the TTF oxidation pathway has been demonstrated by

chemical oxidation of [Rh1(o-P2)2][BF4]. The stabilization of [Con(o-

252

P2)2][BF4]2 illustrates the potential for incorporating a paramagnetic center
with the organic donor molecule. The salt, [ReC12(o-P2)2][Re2C15(o-P2)]
(16-17), contains the first documented dinuclear complex of the formula, a-
M2X6(LL) (where LL is a chelating, bidentate ligand), and serves as evidence
for an intermediate mixed-valence redox state in the formation of a-Re2C14(L-
L)2 compounds. Further study in the regime of metal-metal bonded
chemistry is needed to determine whether a bridging mode (B) for o-P2 will be
possible. The ethylene bridge of o-P2 renders it similar to the skeleton of the
dppee and dppb ligands. The ethene derivative has been shown to engage in
both a- and B- type coordination,3 but to date the dppb has only been reported
in the a- mode.4 This may be a result of the restrictions placed on the ethene

linkage by ring cyclization. If this is the case, similar problems would be
expected for o-P2.

Systematic build-up of extended arrays has been achieved from
reactions of o-P2 and (PPh2)4TTF (P4) with MC12(NCC6H5)2 (M = Pt, Pd) and
NiClz. The incorporation of halide atoms as terminating ligands allows for
access to open coordination sites by abstraction of [Cl]: with [Ag]+. The
resulting solvated sites can then be replaced with additional phosphine
groups to yield, for example, [Pt2(P4)(o-P2)2][BF4]4 (24). It is of interest to
extend this series to Co and Mn analogs because incorporation of two
paramagnetic metal centers with up to three TTF units leads to the

possibility for forming complexes with 9 unpaired electrond for [(o-

253

P2)Co(P4)Co(o-P2)]7+ and 13 unpaired electrons for the MnII derivative. The
observation that the TTF cores in [M(o-P2)2][BF4]2 act as isolated redox
systems provides the basis for expecting molecules with a large number of
unpaired electrons. The reaction of P4 with [M(NCCH3)X][BF4]2 (M = Pt, x =
4; M = Ni, Co, Pd, Fe, x = 6) or [Rh2(NCCH3)1o][BF4]4 results in the
spontaneous assembly of compounds formulated as [M(P4)]n[BF4]2n or

[Rh(P4)]n[BF4]n. The 31P{1H} NMR spectral properties of these complexes are

not in accord with straight chain oligomers. Resonances are observed for
only metal-bound phosphorus environments with no end groups being
detected. By using the bis-(o-PZ) complexes as structural models for the
analogous P4 compounds, it can be surmised that deformations in the
neutral-TTF cores are also occurring in solution. Based on this hypothesis,
one proposed structure type that is being considered is a cyclic oligomer.
While the cyclized structure is a possibility for neutral TTF cores, oxidation
of the units will result in strict planarity, thereby eliminating the potential
for ring formation. If so, the reaction of [P4]'+ with the solvated precursors
ofi'ers the potential for forming long chain polymers which may exhibit

interesting magnetic properties by themselves, but with the additional

possibility for conductive properties upon the incorporation of [TCNQ]" as

the counterion.

254

List of References

(a) Dunbar, K. R.; Quillevéré, A.; Sun, J.-S. Inorg. Chem., 1994, 33,
2598. (b) Dunbar, K. R.; Sun, J.-S. J. Chem. Soc. Chem. 00mm, 1994,
2387. (c) Sun, J.-J.; Uzelmeier, C. E.; Ward, D. L.; Dunbar, K. R.
Polyhedron, 1998 in press. (d) Quillevéré, A.; Uzelmeier, C. E.; Sun,
J.-J.; Dunbar, K. R. manuscript in preparation. (e) Haefner, S. C.;
Uzelmeier, C. E.; Dunbar, K. R. manuscript in preparation.

(a) Fourmigué, M.; Batail, P. Bull. Soc. Chim. Fr. 1992, 129, 829. (b)
Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.; Bartley, S. L.;
Dunbar, K. R. J. Organomet. Chem., 1997, 52.9, 343. (c) Asara, J. M.;
Uzelmeier, C. E.; Dunbar, K. R.; Allison, J., Inorg. Chem., 1998, in
press.

Anderson, L. B.; Bakir, M.; Fanwick, P. E.; Walton, R. A. Polyhedron,
1987, 6, 1483.

Esjornson, D.; Bakir, M.; F anwick, P. E.; Jone, K. S.; Walton, R. A.
Inorg. Chem., 1990, 2.9, 2055.

255

APPENDICES

256

APPENDIX A

PHYSICAL MEASUREMENTS

257

APPENDIX A

PHYSICAL MEASUREMENTS

1. Infrared Spectroscopy Infrared spectra in the 4800-400 cm1 range
were recorded on a Nicolet 740 FT-IR spectrophotometer. Spectra in the far-
IR range (600-50 cm°1) were recorded on a computer controlled Nicolet 750
FT-IR spectrophotometer equipped with a TGS/PE detector and silicon beam
splitter at 2.0 or 4.0 cm'1 resolution. Solid state spectra were measured as
Nujol mulls between CsI plates.

2. NMR Spectroscopy 1H NMR spectra were measured on either a Gemini
300-MHz, Varian 300-MHz or Varian 500-MHz spectrometer. Chemical
shifts were referenced relative to the residual proton impurity of the
deuterated solvent: d2-methylene chloride, 5.32 ppm; d3-acetonitrile, 1.93

ppm; d6-acetone, 2.04 ppm; d1-chloroform, 7.24. 13C{1H} NMR spectra were

recorded on a Varian 300-MHz spectrometer operating at 75.43 MHz or on a
Varian 500-MHz spectrometer operating at 125.72 MHz. Signals were
referenced relative to the 13C solvent resonance. 19F NMR spectra were
recorded on a Varian 300-MHz spectrometer operating at 282.23 MHz.
Signals were referenced relative to an external standard of trifluorotoluene.
31P{1H} NMR spectra were obtained on a Varian 300-MHz spectrometer
operating at 121.42 MHz or on a Varian 500-MHz spectrometer operating at

202.37-MHz. Chemical shifts were referenced relative to an external

258

standard of 85% H3PO4. Positive chemical shifts are reported downfield
relative to H3PO4.

3. EPR Spectroscopy X-band EPR spectra at temperatures above 90 K
were obtained using a Varian E4 spectrometer. Spectra below 90 K were
measured on a Bruker ES-300-E spectrometer equipped with an Oxford
Instruments EPR-900 Continuous Flow Cryostat.

4. Electronic Absorption Spectroscopy Electronic absorption spectra
were measured on a Hitachi U-2000 spectrophotometer.

5. Electrochemistry Electrochemical measurements were performed by
using an EG&G Princeton Applied Research Model 362 scanning potentiostat
in conjunction with a BAS Model RXY recorder. Cyclic voltammetric
experiments were carried out at 22i2°C using 0.1 M tetra-n-butylammonium
tetrafluoroborate (TBABF4) as a supporting electrolyte, unless otherwise
noted. Measurements were typically made at a scan rate of 200 mV/s using a

platinum disk working electrode and a Ag/AgCl reference electrode. E1/2

values, determined as (Ep,a+Ep,c)/2, were referenced to a Ag/AgCl electrode
and are uncorrected for junction potentials.

6. Magnetic Susceptibility Variable temperature and field magnetic
susceptibility measurements were carried out on a Quantum Design model
MPMS Superconducting Quantum Interference Device (SQUID) housed in
the Physics and Astronomy Department at Michigan State University. The

operating field was typically 1000 G and the temperature range 2 - 300 K.

259

7. Mass Spectrometry Fast Atom Bombardment (FAB) mass spectrometry
studies were performed on a JEOL HX double-focusing mass spectrometer
housed at the National Institutes of Health / Michigan State University Mass
Spectrometry Facility.

8. Elemental Analysis Elemental analyses were performed at either

Galbraith Laboratories, Inc., or Desert Analytics, Tucson, AZ.

260

APPENDD( B

STRUCTURAL ANALYSIS OF FUNCTIONALIZED

TETRATHIAFULVALENES

261

APPENDIX B

STRUCTURAL ANALYSIS OF FUNCTIONALIZED

TETRATHIAFULVALENES

1. Introduction

Organic molecules such as tetrathiafulvalene (TTF) and its derivatives
are important precursors in the design of new conducting, optical and
magnetic materials. These planar molecules can be readily oxidized to yield
radical cations which, when associated with suitable electron acceptors such
as 7,7 ,8,8-tetracyanoquinodimethane (TCNQ), form segregated stacks that

allow for electrical conductivity due to the overlap of their n-orbitals.1 These

donor molecules have also been observed to form donor-acceptor salts with
large metal-based cluster anions that exhibit remarkably variable pr0perties,
differences that are attributed to the size and shape of the organic donor and
inorganic acceptors, as well as their redox properties. The magnetic and
conductive properties of these salts are highly dependent on subtle changes
in the packing of these structures in the solid state.2 The discovery of a new,
less stable, polymorph of TTF which crystallizes in what has been
characterized as "chains", rather than stacks, indicates that interactions that
are singled out as "important" or "dominant" may vary.3 Recently,
Fourmigué and Batail have shown that unsymmetrical methyl-TTF

derivatives such as 3,4-dimethyltetrathiafulvalene can be used to prepare a

262

series of multidentate TTF-phosphine ligands, including 3,4-dimethyl-3'4'-
bis(diphenylphosphino)tetrathiafulvalene (1)4 The structures of 1, 2, and 36
have been undertaken in order to compare the geometrical features with
those of related TTF derivatives and structures of the ortho-P2 ligand and its
metal complexes.5

2. Experimental

A. X-ray Crystallography

(1) ortho-(CH3)2TTF (36)

(i) Preparation, Data Collection and Reduction. The synthesis of (36)
was carried out according to methods previously published by Lerstrup,
Johannsen and Jargensen.6 Crystals were obtained by dissolving the product
in a minimum volume of hot toluene, allowing the solution to slowly cool to
room temperature, followed by chilling at 258 K for 12 hours. An orange
crystal of dimensions 0.68 x 0.60 x 0.29 mm3 was secured on the tip of a glass
fiber with Dow Corning silicone grease and placed in a cold N2(g) stream.
Least-squares refinement using 24 well-centered reflections in the range 4 S.

26 _<_ 24° indicated that the crystal was consistent with a monoclinic crystal

system. The data were collected at -110 i 1 °C using the (1)-26 scan technique
to a maximum 26 value of 47°. Of the 2950 measured reflections, 1481 were

independent. An empirical absorption correction based on azimuthal scans of

three reflections with x near 90° was applied which resulted in transmission

263

factors ranging from 0.770 - 0.543. The data were corrected for Lorentz and
polarization effects.

(ii) Structure Solution and Refinement. The structure was solved in the
space group P21/n using the MITHRIL7 and SHELXL 938 structure solution
programs and refined by full-matrix least-squares refinement on F2.9 The
final full-matrix least-squares refinement was based on 1481 reflections that
were used to fit 118 parameters to give R1 = 0.0354 and wR2 = 0.0851. The
goodness-of-fit index was 1.068, and the maximum shift in the final
difference map was 0.000 A associated with H(7B). After the final least
squares cycle, the mean shift/esd was 0.000 and the highest peak in the
difference Fourier map was 0.32 e'/A3 which is associated with C(3). All non-
hydrogen atoms were refined with anisotropic displacement parameters.
Methyl and aromatic hydrogen atoms were placed in calculated positions.

(2) ortho—(CH3)2[(C6H5)2P]2TTF (1)

(i) Preparation, Data Collection and Reduction. Compound 1 was
prepared by following the procedure outlined by Fourmigué and Batail et al.2
Crystals were obtained by concentration, of a solution of 1 in a mixture of
acetonitrile and toluene. An orange crystal of dimensions 0.12 x 0.12 x 0.23
mm3 was secured on the tip of a glass fiber with Dow Corning silicone grease
and placed in a cold N2(g) stream. Least-squares refinement using 12 well-
centered reflections in the range 6 S 26 S 19° indicated that the crystal was

consistent with a monoclinic crystal system. The data were collected at -110

264

i 1 °C using the (1)-26 scan technique to a maximum 26 value of 50°. Of the
5477 measured reflections, 5201 were independent and 933 were found with
I>2o(l). An empirical absorption correction based on azimuthal scans of two
reflections with x near 90° was applied which resulted in transmission factors
ranging from 1.00 - 0.412. The data were corrected for Lorentz and
polarization effects.

(ii) Structure Solution and Refinement. The structure was solved in the
space group P21/c using the MITHRIL7 and SHELXL 938 structure solution
programs and refined by full-matrix least-squares refinement on F2.9 R(int)

and R(o) were determined to be 0.273 and 0.755, respectively. All non-

hydrogen atoms were refined with anisotropic displacement parameters.
Methyl and aromatic hydrogen atoms were placed in calculated positions and
were not refined. Phenyl groups were restrained with C=C distances of 1.39
A and C-C-C angles of 120.0°, and C(5)-C(7) and C(6-C(8) distances were
refined to be equivalent, resulting in distances of 1.49(2) A for C(5)-C(7) and
1.48(2) A for C(6)-C(8). The final full-matrix least-squares refinement is
based on 5183 reflections that are used to fit 297 parameters to give R1 =
0.0974 and wR2 = 0.2284. The goodness-of-fit index was 0.990, and the
maximum shift in the final difference map was 0.070 A, which is associated
with H(7 C). After the final least squares cycle, the mean shift/esd was 0.030
and the highest peak in the difference Fourier map was 0.58 e'IA3 which is

associated with S(4).

265

 

 

(3) [(C6H5)i
(i) Prepar
was carried
01.5b Crystz
of hot toll
temperatur
secured on
placed in :

centered re

consistent 1
°C using th
measured
empirical a
With 7. hear
from 1.000
efieCts.

(ii) Stru.
the SpaCe g1.
programs a]
and R(c) We
matrix leas.

llSed to fit

 

(3) [(C6H5)2P]4TTF (2)

(i) Preparation, Data Collection and Reduction. The preparation of 2
was carried out according to methods previously published by Fourmigué et
al.51) Crystals were obtained by dissolving the product in a minimum volume
of hot toluene and then allowing the solution to slowly cool to room
temperature. An orange crystal of dimensions 0.42 x 0.39 x 0.29 mm3 was
secured on the tip of a glass fiber with Dow Corning silicone grease and
placed in a cold N2(g) stream. Least-squares refinement using 20 well-

centered reflections in the range 6 S 26 S 16° indicated that the crystal was

consistent with a triclinic crystal system. The data were collected at -110 i 1
°C using the (1)-26 scan technique to a maximum 26 value of 55°. Of the 4683
measured reflections, 2277 were found to be greater than 3o(I). An
empirical absorption correction based on azimuthal scans of three reflections
with x near 90° was applied which resulted in transmission factors ranging
from 1.000 - 0.487. The data were corrected for Lorentz and polarization
effects.

(ii) Structure Solution and Refinement. The structure was solved in
the space group P-l using the MITHRIL7 and SHELXL 933 structure solution
programs and refined by full-matrix least-squares refinement on F2.9 R(int)
and R(o) were determined to be 0.00 and 0.116, respectively. The final full-
matrix least-squares refinement was based on 4683 reflections that were

used to fit 438 parameters to give R1 = 0.0945 and wR2 = 0.2417. The

266

.Comcab: “BELZOEBNRCQE - _OEEEHNMBi .755: TE - _OE _wnm.

 

 

x: 38 SE 82.23 8.3-8286
8.3 $8 89o same
3: :58 38.8 LE
SS 33 mm: 9.863% 4:3 38
«we. 8% SE .33 83:: .oz
3 - E. om - a. S. a. .33 .3 .35... ._8 33
E E. a. N
882 $83 $5.33 .4 .>
5.3.8 682.8 8.8 m3 s
$82.: $8.82 82.8 E3 .8
69...: 32.8 8.8 E3 .5
883.2 $58.2 $39: .a .0
238.2 @843 883.3 4 5.
A883 3823.: 83: < .s
Tm 22mm 5:5 98% 693m
emommwcovm vmmfimmmOmm vmmmmwO Niaaaorm
.563 E 3

 

2:. .8

EEE..._Eafifivfifovsss .68

Eeeasmovéfiio .SE

Ema

.2838 . A8 .2838 . msvaflnmaoz
oEgaEmoH—Smio

.3 6369

267

goodness-of-fit index was 1.037, and the maximum shift in the final
difference map was 0.031 A associated with H(52). After the final least
squares cycle, the mean shift/esd was 0.019 and the highest peak in the
difference Fourier map was 1.05 e'/A3 which is associated with C(31). All
non-hydrogen atoms were refined with anisotropic displacement parameters.
Methyl and aromatic hydrogen atoms were placed in calculated positions. A
molecule of toluene was found to reside on a center of inversion. The toluene

was modeled with restraints on the CC distances within the ring, as well as
on the C~~C distances between alternating C atoms of the ring (e.g.

C(54)°--C(52)). Occupancies were refined such that the two independent
toluene fragments were assigned an occupancy of 0.5 for a total of 1.0.
2. Results and Discussion
A. Molecular Structure of ortho-(CH3)2TTF (36)

ORTEP drawings of ortho-(CH3)2TTF (36) are represented in Figure
45, while a packing diagram of 36 can be found in Figure 46. Selected bond
distances and angles are provided in Table 19. The central core [S(1)-S(2)-
C(3)-C(4)-S(4)-S(3)] of the title molecule is nearly planar with a maximum
deviation of 0.016(2)° for C(3), and a RMS deviation of 0.001. The dihedral
angles between planes C(5)-C(6)-S(4)-S(5) and S(3)-S(4)-C(4)-C(3)-S(1)-S(2) is
O.60(13)°, while the angle between planes C(1)-C(2)-S(2)-S(1) and S(1)-S(2)-
C(3)-C(4)-S(4)-S(3) is 1.88(16)°. This is in contrast to the analogous dihedral

angles in the neutral and cationic TTF crystal structures, where both

268

 

 

 

Table 1 9-

 

 

Table 19. Selected bond distances (A) and Angles (deg.) for ortho-(CH3)2TTF
(36) and ortho-(CH3)2[(C6H5)2P]2TTF (1).

 

 

 

 

Atom 1 Atom 2 36 1
C(1) C(2) 1.308(5) 135(3)
C(3) C(4) 1.340(4) 138(3)
C(5) C(6) 1.338(4) 137(3)
C(5) C(7) 1.500(5) 1.49(3)
C(1) S(1) 1.743(4) 1.71(2)
C(3) S(1) 1.765(3) 1.77(2)
C(5) S(3) 1.755(3) 1.77(2)
C(4) 8(3) 1.753(3) 1.7 3(2)
P(1) C(1) 1.88(2)
P(1) C(11) 1.840(13)

Atom 1 Atom 2 Atom 3 36 1

C(1) S(1) C(3) 94.42(17) 94.8(10)
S(1) C(3) S(2) 114.27(17) 115.2(12)
S(3) C(4) S(4) 113.89(17) 114.1(15)
C(5) S(3) C(4) 96.14(15) 94.4(13)
8(3) C(5) C(6) 127.0(3) 114.0(15)
P(1) C(1) C(2) 119.0(15)
C(1) P(1) C(11) 100.7(8)
P(1) C(11) C(12) 122.7(9)

 

269

H1

H2

Figure 45.

 

s3 C7 gm
‘ .
C4 l/ C5 H7C
N“) C6
./ (IslSC
34 £9 8‘0
C8 H8B
. H8A

ORTEP representation of ortho-(CH3)2TTF (36) with 50%

ellipsoids.

270

fulvalene rings exhibit the same out-of-plane-bend. For the neutral
tetrathiafulvalene the value is 21° for both 5-membered rings,10 whereas for
cationic TTF the corresponding dihedral angles between the planes are 22°.11
Bond distances and angles within the TTF-core of 36 are comparable to other

TTF molecules. The C=C bond at the center of the molecule is 1.340(4) A,
and S---S distances within the molecule are 2.967(2) A for S(1)-"S(2) and
2.945(1) A for S(3)-~-S(4). It should be noted that this value for the central
C=C distance is equivalent to the neutral TTF (1.349(3) A), but shorter than
that found in the cationic TTF (1.369(4) A). The bond lengths of the external
carbons in 36 are 1.308(5) A for C(1)=C(2) and 1.338(4) A for C(5)=C(6). This
lengthening of C(5)=C(6) renders it indistinguishable from C(3)=C(4).
Another manifestation of the presence of methyl substituents is differences in
the S~--C distances. The 5-membered ring that contains the methyl groups
exhibit S---C distances that are essentially all equivalent, but on the opposite
side of the molecule, the sulfur to bridging-carbon distances are longer than
the sulfur to exterior-carbon bond lengths by 0.024 (4) A.

Typically, neutral TTF stacks in a parallel orientation to the b axis
with intermolecular SmS contacts of 3.62 A; the TTF cation in TTF-TCNQ
also stacks parallel to the b axis, but with a much shorter TTFH'IVI‘F distance
of 3.47 A.11 In contrast, 36 "dimerizes" into stacked pairs. These pairs (TTF-
TTF'; symmetry code C) 1-x,-y,-z) pack with significantly longer

intermolecular contacts of 3.932(2) A, and furthermore align themselves in

271

 

 

 

 

 

Figure 46. Packing diagram of ortho-(CH3)2TTF (36) viewed down the a-

axis.

272

ahead-to-tail fashion, as clearly indicated in the packing diagram depicted in
Figure 46. This distance is significantly greater than twice the van der
Waals radius of sulfur (3.6 A).13 Adjacent pairs are approximately
perpendicular to each other, with a dihedral angle of 83.03(4)° [between
planes S(1)-S(2)-C(3)-C(4)-S(4)-S(3) and S(1)"-S(2)"-C(3)"-C(4)"-S(4)"-S(3)";
symmetry code (") 0.5-x,-0.5+y,-0.5-z]. This orientation results in one of the
hydrogens, H(2), of the unsubstituted fulvalene ring system for each molecule

pointing towards the S(4)ii p-orbital of a molecule in an adjacent pair. The

C(2)-S(4)" intermolecular distance is 4.46(1) A, which is greater than the
sum of the van der Waals radii of carbon and sulfur (3.55 A), indicating no
significant interaction is present.

B. Molecular Structure of ortho—(CH3)2[(C6H5)2P]2TTF (1)

A PLUTO drawing of ortho-(CH3)2[(C6H5)2P]2TTF (1) is represented in
Figure 47, and a packing diagram is in Figure 48. Selected bond distances
and angles are provided in Table 19. Due to the poor refinement of 1, high
esd values associated with the bond distances and angles of the structure
make accurate comparisons to 36 difficult. There are, however, certain
differences that are worth pointing out. Bond distances and angles within
the fulvalene rings of 1 remain similar to those observed in 36.12 Most
notable is the lengthening of C(5)=C(6) [137(3) A], making it nearly equal to
C(3)=C(4) [138(3) A]. This is the same effect caused by the addition of

methyl rings in 36. It is interesting to note that there appears to be very

273

 

 

 

Figure 47. PLUTO diagram of ortho-(CH3)2[(C6H5)2P]2TTF (1) with inset
side view.

274

 

n,
D) Gad
E1... 31m.
. up

 

 

 

Figure 48. Packing diagram of ortho-(CH3)2[(C6H5)2P]2TTF (1) viewed down

the a-axis.

275

little affect on the other ring system due to the presence of the phosphine
substituents. The C(1)=C(2) distance of 135(3) A is ~.0.03 A shorter than the
other C=C bonds in 1, just as the unsubstituted C=C bond in 36 is ~0.03 A
shorter than the central C=C bond and the C=C bond containing the methyl
substituents. At first glance the C=C distances all appear to be elongated in
1 relative to 36, but that may be an artifact of the poor refinement. The
geometry about the phosphorus atoms is that of the unusual distorted
tetrahedron, with angles of 100.7 (8) - 104.9(9)°, and average P-C distances of
~1.837 A about P(1) and ~1.864 A about P(2).

The most notable difference between the molecular structures of 1 and
36 is the out-of-plane bend located at S(3) and S(4) of the methylated dithiole
ring. The dihedral angles between planes [C(5)-C(6)-S(4)-S(3)] and [S(1)-
S(2)-C(3)-C(4)-S(3)-S(4)] is 23.0(7)°, while the angle between planes C(1)-C(2)-
S(2)-S(1) and S(1)-S(2)-C(3)-C(4)-S(4)-S(3) is 7.9(6)°. While both these values
are certainly larger than those observed in the precursor compound, 36, the
methylated ring is the more distinct in its deviation from planarity. Given
the TTF core is neutral in the case of 1, it is not surprising that the fulvalene
rings are non-planar, but it is quite different than what has been seen in the
previously structurally characterized metal complexes containing trans-
phosphines. In all other bis-(o-PZ) structures, the out-of-plane bend occurrs
at the sulfur positions in the ring containing the phosphines, with the
methylated ring exhibiting a much smaller bend. While the driving force for

the bend in the metal complexes may be able to achieve the close

276

intermolecular S---S contacts, there are no such interactions in the structure
of 1. The packing diagram 1, shown in Figure 48, reveals a motif where
steric interactions serve to isolate the individual molecules from one another.
The bend in the methyl-substituted dithiole ring appears to be due to its

proximity to the phenyl rings of the adjacent o-P2 molecule. This packing

arrangement results in the closest intermolecular S---S distance being 5.17 A.

Apart fiom the location of the out-of-plane bend, the structure of 1 is
very similar to the metal-ligand complexes previously discussed.4»5 As
expected, the P(1)-C(1) of 1 is longer in the free ligand than in the metal
complexes by as much as ~0.11 A {[Rh(o-P2)2][BF4]}.5b The C=C distances
within the TTF core are all generally smaller than those in 1, with the
exception of the external C=C [equivalent to C(1)-C(2) in 1] distance in the
phosphine-funtionalized ring of [Rh(o-P2)2][BF4.].5b The most extreme case of
this contraction is NiBr2(o-P2), which has a C(50)-C(51) distance of 125(1)
A.4 The angles within the methyl-substituted ring remain essentially
unchanged between the free and coordinated ligand. The C-C-S and S-C-S
angles within the phosphine-functionalized ring are slightly tighter in the
coordinated ligand than in 1, indicating some affect on the ring caused by the
phosphorus donation.
C. Molecular Structure of [(C6H5)2P]4TTF (2)

An ORTEP drawing of [(C6H5)2P]4TTF (2) is represented in Figure 49,

and a packing diagram is in Figure 50. Selected bond distances and angles

277

are provided in Table 20. Because the center of the molecule rests on a
center of inversion, the two fulvalene rings are symmetry related. Bond
distances and angles within the ring are similar to those reported in previous
TTF structures. The C-S distances range from 1.744(7) A for S(2)-C(3) to
1.782(7) A for S(1)-C(1). These are slightly elongated relative to free TTF
(1.729(2) - 1.756(2) A),10 and 36 (1.743(4) - 1.767(3) A), but within errors for
the phosphine-substituted ring of 1 (1.70(3) - 1.7 7(2) A). The external and
internal C=C distances are indistinguishable at 1.358(9) A for C(1)=C(2), and
1362(13) A for C(3)=C(4). The geometry about the phosphorus continues to
be distorted with C-P-C angles ranging fiom 101.5(3)° to 104.5(3)°. Unlike 1,
The fulvalene rings of 2 are nearly planar, with an out-of-plane bend of 365°
between the dihedral planes C(1)-C(2)-S(1)-S(2) and S(1)-S(2)-C(3)-C(3)'-S(1)'-
S(2)‘ (symmetry code C) = 2-x, 1-y, 1-z). The individual five-membered rings
in question are planar with a maximum deviation of 0.007(4) for C(1), and
0.001(6) for C(3). The RMS deviation for the two planes are 0.005 and 0.000,
respectively. The packing diagram in Figure 50 shows that 2 packs in

slightly off-center "stacks", where only one fulvalene ring for each adjacent

molecule overlaps with intermolecular S-o-S distances of 8.15 Such an

extended distance precludes the presence of any significant interactions

between molecules, as would be expected given the bulky phenyl groups.
Comparison of 2 with PtzCl4(P4) (21), shows difierences reminiscent of

what was observed for 1 and its own metal complexes. Due to the retention

278

Table 20. Selected bond distances (A) and Angles (deg) for [(CsH5)2P]4TTF

 

 

 

 

(2)-

Atom 1 Atom 2 2
C(1) C(2) 1.358(9)
C(1) S(1) 1.782(7)
C(2) S(2) 1.7 44(7)
C(3) S(1) 1.752(6)
C(3) S(2) 1.755(7)
C(3) C(3) '1.362(13)
P(1) C(1) 1.804(7)
P(2) C(2) 1.841(8)
P(1) C(11) 1.842(8)

Atom 1 Atom 2 Atom 3 2
C(1) S(1) C(3) 95.5(3)
C(2) S(2) C(3) 95.6(3)
S(1) C(3) S(2) 114.8(4)
S(1) C(3) C(3) '122.7(7)
P(1) C(1) C(2) 122.3(6)
P(2) C(2) C(1) 122.2(5)
C(1) P(1) C(11) 101.8(3)
P(1) C(11) C(12) 121.6(6)

 

279

 

C o
A, ,1: I]:
C43 ‘”
C45 ‘ /
C42 0* 1
C4 2.. A
C Ck
C41 \--
C36
P ‘ C31 P2 0 ' 2)
C3 C32 :- $2 “ ‘
C34 ‘0 ,_
C 3 9 C3
\
~r
KA"
€‘ §n
‘ fi " “‘0
~o
1’
n .2
"I”, .
‘ 1:4, .
(ft
0

Figure 49. ORTEP representation of [(C6H5)2P]4TTF (2) with 50% ellipsoids.

280

 

 

 

fa _
if f
..4. f (2?»

.f '
. Q , .
. . fig! 3%?) ”2

+80

6
d .23
Q

Figure 50. Packing diagram of [(CsH5)zP]4TTF (2).

281

of symmetry from 1 to 21, the fulvalene rings are equivalent, with C=C
distances slightly elongated in the case of the free ligand. The P-C distances
are longer in the free ligand, as expected, with no difference in the C-S-C
angles. The C-C-S angles tighten by 1° upon coordination of the phosphine,
indicating that while there may be some effect from the phosphorus donation,
it does not seem as great as in the case of 1.
3. Concluding Remarks

The series (CH3)x[(C6H5)2P]4-xTTF represents a unique series of ligands
capable of coordinating directly to metals centers to yield a variety of
structural types. Single crystal X-ray studies of the free ligands and their
methyl-substituted precursors indicate that the additional R groups have a

pronounced effect on the orientation of the molecules within the crystal

lattice. These steric effects also dictate elongated intermolecular S~~~S
distances, which indicate that they will most likely not exhibit the typical
conducting properties exhibited by most other TTF-based molecules. In the
case of o-P2 (2), the steric effects of the phenyl groups appear to cause an out-
of-plane bend in the methyl-substituted fulvalene ring not previously
observed in this series of compounds. Comparisons between the free and
bound ligands reveal small changes in the structure of the TTF core, possibly

caused by the donation of the phosphorus atom to the metal center.

282

 

10.

11.

12.

List of References

Ferraris, J.; Cowan, D. 0.; Walatka, V.; Perlstein, J.H., J. Am. Chem.
Soc., 1973, .95, 948.

(a) Melby, L.R.; Harder, R.J.; Hertler, W.R.; Mahler, W.; Bensen, R.E.;
Mochel, E.E., J. Am. Chem. Soc., 1962, 84, 3374. (b) Kistenmacher, T.;
Phillips, T. E.; Cowan, D.O., Acta Cryst. C., 1974, B30, 763.

Ellern, A.; Bernstein, J.; Becker, J.Y.; Zamir, S.; Shahal, L., Chem.
Mater., 1994, 6, 1378.

Fourmigué, M.; Batail, P., Bull. Soc. Chim. Fr., 1992, 12.9, 29.

(a) Uzelmeier, C. E.; Fourmigué, M.; Grandinetti, G.; Dunbar, K. R., 1997
In preparation. (b) Fourmigué, M.; Uzelmeier, C. E.; Boubekeur, K.;
Bartley, S. L.; Dunbar, K. R., J. Organomet. Chem., 1997, 52.9, 343.

Lerstrup, K.; Johannsen, I. & Jorgensen, M. Synth. Met., 1988, 27, B9.

Gilmore. C. J. MITHRIL. Computer Program for the Automatic
Solution of Crystal Structures fiom X-ray Data. Department of
Chemistry, University of Glaskow, Scotland, 1983.

Sheldrick, G. M. SHELXL93. Program for the Refinement of Crystal
Structures, 1993, University of Gottingen, Germany.

North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Cryst., 1968, A24,
351.

Cooper, L. B.; Kenney, N. C.; Edmonds, J. W.; Nagel, A.; Wudl, F.;
Coppens, P., J. Chem. Soc. Chem. Commun., 1971, 889.

Bondi, A., J. Phys. Chem., 1964, 68, 441.

Uzelmeier, C.E.; Fourmigué, M.; Dunbar, K.R., Acta Cryst. C., 1998,C54,
in press.

283

 

APPENDIX C

SYNTHESIS OF [Bu4N]2[Re2Cls] FROM
RHENIUM-CONTAINING LABORATORY RESIDUES.

284

APPENDIX c

SYNTHESIS OF [Bu4N]2[Re2Cls] FROM

RHENIUM-CONTAINING LABORATORY RESIDUES.

1. Introduction

The precious metal content compounds used in our laboratories has
sufficient value to make recovery an attractive prospect. Even though
recovery, recycling, and reuse of laboratory chemicals may no! be an
economical option in many laboratories, hazardous waste regulations and
economic incentives make it an option that should be continually assessed.
In particular, the expense of many metals make this a useful process for use
by inorganic chemists. Currently there are established methods for the
recovery of silver and mercury from laboratory residues.1 The metal values
in spent catalysts or solutions that contain such noble metals as platinum,
palladium, rhodium, and ruthenium are almost always worth recovering.
While the recovery procedures for small quantities of platinum, palladium,
and rhodium are reported in the literature, the chemistry of these metals is
sufficiently distinct that no general procedure is applicable.2

Due to the extent of research being carried out with rhenium
compounds in our laboratories, and our accumulation of a large quantity of
rhenium-containing residues, it became useful to investigate a method for

reclaiming rhenium in a form that could be used to prepare a common

285

starting material for dinuclear rhenium chemistry, namely [Re2C13]2‘.
Currently, the only reported method for recovering rhenium residues involves
the work-up of nitron hydrogen perrhenate precipitates and various solutions
of rhenium-sulfur complexes which can be recovered as K[ReO4] and
[NH4][ReO4].3 Described in this section is a new method for the recovery of
rhenium residues, which ultimately results in the formation of [(n-
Bu)4N]2[R92C16].
2. Experimental
A. Synthesis

All reactions were carried out in air unless otherwise stated. KCl was
purchased from Columbus Chemical Industries, reagent grade nitric acid was
purchased from Olin Corporation at 69% purity, and [TBA] [Br] was
purchased from Strem Chemicals. All starting materials were used as
received. All rhenium-containing residues were kept isolated from all other
metal waste, and was stored in clean, empty reagent bottles until time of use.
(1) Preparation of KreO4 from Rhenium-Containing Residue.

Rhenium residues were combined into a 1 L round bottomed flask,
such that the volume never exceeded 750 mL, and subsequently reduced in
volume by roto-evaporation with heating at 60°C. This process was
continued until the liquid volume had been sufficiently minimized. The
remaining residue was washed into a 500 mL glass crystallizing dish using

low boiling solvents such as acetone and hexanes to complete the transfer.

286

Once filled to half capacity, the dish was heated on a hot plate to boil 03
additional solvents and volatiles, which resulted in the formation of a sticky
black residue. This process was repeated several times until all the residues
were contained in the crystallizing dish. The dish was left to stand several
days in a vacuum hood to further dry the residues, which left a crusted black
solid on top, with some sticky residues beneath. This residue was scraped
from the dish and transferred to a new container.

An amount of concentrated HN03 (~150-200 mL) was added to an
empty 400-500 mL beaker, which was secured in an oil bath over a hot plate.
Approximately 20 g of dried rhenium residues were carefully added to the
acid. Upon introduction of the metal-containing solid, the acid began to
bubble vigorously. The mixture was stirred occasionally with a spatula.
When the bubbling appeared to subside, the mixture was heated to a
temperature near 90°C. After 12 h, the hot liquid was separated from the
undissolved black solid by filtration through a large fritted glass funnel.
Care should be taken during the reaction of the residues with acid, and
during the filtration of the hot mixture, as noxious NO; fumes are produced.
This liquid was returned to the oil bath, and 1020 mL of a saturated
aqueous solution of K0] was added to the acid.I The mixture was heated for
an additional hour, with occasional stirring, and the hot liquid was carefully
decanted into a new flask, using a minimum of hot water to complete the

transfer. The solution was allowed to cool to room temperature, affording a

287

 

 

tan precipitate. This solid was isolated by decanting the liquid back into the
previous flask, using cold water to wash the solid. The flask containing the
liquid was returned to the oil bath, re-heated to ~90°C to reduce the volume,
and additional black rhenium-residues were added to the solution. It may
also be necessary to add additional HN03 (~75 mL total over the course of
these procedures). The procedures were then carried out from the point
following the addition of KCl (1'). This was repeated numerous times until no
additional black residues could be dissolved by the acid, or if no additional
tan precipitate was formed upon cooling. In either case the liquid was
transferred back to the crystallizing dish, heated to a black solid, and
combined with the previously collected rhenium residue.

The tan solid that was collected was washed with acetone over a
Buchner funnel, dried, transferred into a new flask, treated with deionized
water, and finally heated to near boiling in an oil bath. A minimal amount of
additional water was added with stirring to dissolve the solid. The hot
solution was filtered through a Buchner funnel, and allowed to cool to room
temperature, after which time an off-white crystalline solid was observed to
form. The solid was isolated by filtration, and the recrystallization
procedures were repeated 3 additional times, until the product appeared to be
fairly pure by infrared spectroscopy. The final white microcrystalline solid
was dried under reduced pressure. Recovery rate = ~ 2.0 - 3.0 g per hour.

Total recovered quantity: ~13.0 g (with not all reactants being exhausted).

288

I.R. (Nujol, cm'l): 914 (vRao, [ReO4]'), 316 , 304 ([ReO4]'); (Impurities): 1261,
1050, 723, 522, 482, 363.
(2) Metathesis of KReO4 to form [(n-Bu)4N] 2ReO4

A sample of the impure K[ReO4] (10.00 g) was loaded into a 600 mL
beaker and treated with 300 mL of millipore water.4 The mixture was
heated, with stirring, in order to fully dissolve the solid. To this hot solution
was added an aqueous solution of [TBA][Br] (13.481 g, 0.042 mol; 100 mL),
which led to the formation of a white precipitate. The mixture was cooled in
an ice bath, and then filtered to collect the solid. The solid was washed with

cold water, then a 2:1 Et201EtOH solution followed by Et20, and finally

dried under reduced pressure. Crude yield = 7.853 g. I.R. (Nujol, cm'l): 904
(mac), 801, 324 ([12604]); (Impurities): 1055, 521,480.
(3) Synthesis of [(n-Bu)4N]2[Re2Cls]

The procedures for the preparation of [(n-Bu)4N]2[Re2Clg] were
followed according to the method of Barder and Walton.5 The synthesis was
carried out using 3.028 g (9.310 mmol) of the [Bu4N][ReO4] produced from the
above procedures. Upon rotoevaporation of the final solution, a brownish-
yellow residue was present along with the expected blue-green solid. This
impurity was removed from the desired product by washing the product with
EtOH and Et20. The final product was recrystallized from 300 mL of a 20:1
mixture of MeOH and HCl, collected by filtration, washed with Et20, and

dried in vacuo. Yield = 1.657 g (47%).

289

3. Results and Discussion
A. Preparation and Characterization of [(n-Bu)4N]2[Rezcls] from
Rhenium-Residues.

Rhenium-containing waste from our laboratories are typically
combined and stored in various containers awithout contamination with
other metal-containing wastes. Volatile organic solvents can be removed by
rotoevaporation with mild heating. The application of further heat assists in
the elimination of higher boiling volitiles, such as acids, and eventually yields
a black solid. Reaction of this black solid in concentrated HN 03 with aqueous
KCl gives a tan solid upon cooling. This tan solid can be recrystallized from
water to yield a crystalline solid identified as K[ReO4] contaminated with
remaining miscellaneous impurities. The infrared spectrum of the solid (Fig.

51) reveals a strong band at 914 cm'1 which is due to the 1239.0 stretch of

[ReO4]'. The presence of additional bands in the spectrum indicate the
presence of a mixture. In particular, the band at 363 cm'1 indicates the
presence of a product which may contain Re-Cl groups. Reactions of
rhenium compounds with HNOs, H2804 and bromine water are known to
result in the formation of "perrhenic" acids by oxidation of the metal to it's
lowest oxidation state, namely ReVII (do). The addition of KCl serves to
introduce potassium as a cation, thus making the perrhenate anion insoluble

and therefore easily extracted from water or acetone. This solubility

290

o.cow

b

5

omo«

.32: 2.: E :32? mg :2me cmuwmfiéwm one 63:me
m558:8-83:m€ .«o 3382 as... 89a vmfimano $.03“va 95am: mo 85.50QO 3.8.9: :3 ouzwmh

4
3
be

 

 

 

 

 

 

 

can cam

 

cu

‘AAAA‘AJLAALI

rUYUIlllUIIAIIIYTIIII
8

 

 

 

 

 

—-_4 Ar“ A‘J'Alu-A‘A‘h'

IlllfiliuTrIrilllrl‘lw

 

A...

n.~h

if

d .0

o
d
v.

n««

 

 

a.h««

291

 

differe]

are m0

precipi
separa
52) re‘
feature
480 CH

have b

cm'l, w

m)

Prepare
Walton
reportec
.VeHow-k
reaction
lead to b
4. Con
T
1ElbOratO

the fie]

difference can be used to eliminate any polar impurities; those that remain
are most likely neutral rhenium containing compounds such as RezO7.
Metathesis of KreO4 with aqueous (n-Bu)4NBr which leads to the
precipitation of [(n-Bu)4N]ReO4 and serves as an additional step in the
separation of impurities. An IR spectrum of the [(n-Bu)4N]ReO4 product (Fig.
52) reveals a much cleaner sample than the K[ReO4]. Loss of the broad

feature at 723 cm'l, and a decrease in the intensity of the bands at 521 and

480 cm'1 (relative to [ReO4]‘), provide evidence that some of the impurities

have been removed. This is further demonstrated in the region below 400

cm°1, where only the band associated with the vas of [ReO4]' can be observed.

The use of the [TBA] [ReO4] obtained from the rhenium waste in the
preparation of [(n-Bu)4N]2[Re2C18] by procedures published by Barder and
Walton5 results in a high-purity product, but in much lower yields than those
reported in the literature. The greatest visible difference is the presence of a
yellow-brown residue following concentration of the benzoyl chloride/ethanol
reaction solution. This may be a result of Re-O containing impurities that
lead to by-products.

4. Concluding Remarks
The preparation of salts containing [R82C13]2’ from rhenium-containing

laboratory residue is a cost-effective process for research groups working in

the field of. dirhenium metal-metal bonds. Aldrich lists K[Re04] at

292

 

 

 

124.2

:20.

.32: m5 5 :39? mm common teammfiéwm 23. .2663 955855
-8532: .«o .3958“ 93 89a vofigao «Ommmzxsmé: 235: .«o 85.50on wouwacm .Nm mun—mum

o.oov

 

N.vo

r.o~

 

 

 

v. .OG

 

fi.00u
com com

 

 

 

 

 

 

or .owu

 

 

-.NJ1.N.VN«

293

approximately $4.78/g for a 25g sample (the least expensive quantity
available).6 For the procedure outlined above the materials costs are as
follows: $4.7 0/500 g for KCl and $9.00/7 lb for HNOa. Given the approximate
quantities of each material used, the final price is 30.09/10 g of KCl and
$0.77/2.7 5 mL of HNOs, or a total cost of $0.86. Given the low yield of both
the metathesis and [Re2C18]2' synthesis, it can be estimated that less than
25% of the "K[ReO4]" was pure. Considering the cost of K[ReO4], as listed
by Aldrich, it would cost ~$15.54 to purchase 3.25 g of K[ReO4] whereas it

cost $0.86 to produce roughly the same amount using the described method

294

List of References
Prudent Practices for Disposal of Chemicals from Laboratories, 6th ed.,
National Academy Press, Washington, D.C., 1983, 44.

Handbook of Preparative Inorganic Chemistry, 2th ed., Brauer, G., Ed.,
Academic Press, New York, 1965, 1560.

Handbook of Preparative Inorganic Chemistry, 2th ed., Brauer, G., Ed.,
Academic Press, New York, 1965, 1476.

Millipore water was obtained from the Biochemistry Department at
Michigan State University.

Barder, T. J .; Walton, R. A., Inorg. Synth., 19??, 28, 332.

1996-1997 Aldrich Catalog, Aldrich Chemical Company, Milwaukee,
W.I., 1192.

295

APPENDIX D

31P{1H} NMR ANALYSIS FOR PtCl(TMPP)(TMPP-0)

296

 

v,

 

f2

f:

S:

APPENDIX D

31P{1H} NMR ANALYSIS FOR PtCl(TMPP(TMPP-0)

1. Introduction

Earlier work from our laboratories had shown that homoleptic TMPP
compounds of RN, RhII and RhIII exhibit interesting redox chemistry and that
they undergo reversible small molecule reactions based on the ability of the
ether groups to dissociate.1 Given these promising results, it was logical to
extend these studies to Pd(II) and Pt(II)2 which are known to be useful in
catalytic applications when weakly bonded ligands are involved.5’03kv4‘6 In
addition, polydentate ligands such as TMPP with steric requirements that
favor octahedral coordination may enforce this geometry on metals for which
six coordination is rarely observed",8 In spite of the considerable interest, a
fairly limited number of such compounds have been studied.3

31P NMR spectroscopy has been used extensively as an important
spectroscopic tool for the characterization of phosphine complexes due to the
31P nucleus bearing a spin of 1/2 and being 100% abundant.9 Although the
specific theory pertaining to the chemical shift values for organometallic
phosphine complexes is not well understood, 31P NMR data are extremely
useful for establishing spectroscopic "fingerprints" and trends which can be
used for distinguishing related compounds. Coupling constants are

particularly useful, owing to the fact that the 2J(31P, 31P) for trans phosphines

297

 

 

 

are mu
metal ‘
pattern
the geo
2. Exp
A. Syr

f‘
J

accordi
carried
softwar
3. Res
A. 31p{

(TM

room te

are incl

33% ab

Sate flit,

 

 

are much larger than those for cis phosphines.9c The addition of a transition
metal with I = 1/2, such as 195Pt or 106Rh introduces additional splitting
patterns due to strong coupling with 31P, which provides more information on
the geometry of the complex.

2. Experimental

A. Synthesis and Physical Methods.

The preparation of PtCl(TMPP)(TMPP-O) (37) was carried out
according to the literature procedure.2 Spin-simulation experiments were
carried out by using the LAME program which is included in the VNMR
software package.

3. Results and Discussion
A. 31P{1H} NMR Simulation and Interpretation for PtCl(TMPP)-
(TMPP-O) (37).

A 31P{1H} NMR spectrum of PtCl(TMPP)(TMPP-0) in acetonitrile-d3 at
room temperature exhibits an ABX second-order pattern with satellites that
are indicative of two inequivalent phosphorus atoms coupled to 195Pt (I = 1/2,
33% abundance)”11 Successful simulation of this spectrum was obtained by
first simulating the ABX splitting pattern, thereby producing the expected
satellite positions, followed by simulation of the AB PA-PB splitting pattern.
These two spectra were overlayed with the approximate parent-to-satellite

intensity ratio, which led to chemical shift values of PA, 6 = -20.48 ppm , PB, 5

= -26.39 ppm and coupling constants of 1J(Pt-PA) = 3212 Hz, 1J (Pt-PB) = 2993

298

Hz and 2J(PA-PB) = 561 Hz (Figure 53); the large magnitude of 2J(P.».-PB) is
common for trans phosphine ligands. These NMR data are in accord with the
molecular geometry depicted in Figure 54 wherein one neutral TMPP ligand
is coordinated in an n1 fashion and a demethylated TMPP group is bound as
an n2- P,O ligand with trans P atoms, a phenoxide O and a Cl- ion in a square

plane. These data are supported by the observed 1H NMR spectrum?
4. Concluding Remarks

Our identification of 37 as containing both an nl-TMPP and a 112-
TMPP—O ligand indicates that, unlike most other P,O chelates reported in the
literature, the TMPP ligand appears to be sufficiently flexible to adopt a
myriad of bonding modes. This point is well-demonstrated by the observed
hapticity changes of TMPP from monodentate in 37 to bidentate in
Pd(TMPP-0)2 (7), Pt(TMPP-O)2,2 and [Rh(TMPP)2][BF 4] (3) to tridentate in
[Pd(TMPP)2] [BF412.2" [Rh('I'MPP)2l[131-“4h.1b and [Rh(’1‘MPP)2][BF4]3,1**'b and
even 112-n3 in [Cos(u2-OH)3(p3-OH){Co(TMPP-0)2}3][BF4], (8).12 The ability of
TMPP to change hapticity in order to stabilize a given complex allows for
reversibility of substitution reactions, which is generally not possible with
complexes that undergo dissociative loss of a ligand such as phosphine. This
attribute has been proven to be useful in the reversible reactions of [Rh(n3-

TMPP)2 2+ with small molecules such as CO and isocyanides?

299

”(Pam X 'Imrr)
r”) W)

 

21(PAP3)

 

(a)

 

 

Ll l_Jl 11 ll

 

 

 

 

 

- i I A." __ _J g _-_.—H U b—N L—JJLALA 4‘ A
f V Y 1 V 7 fi Y j Y V v v 1 fir 1 v v I f V v 1 ‘ v v v v I fir 1 fi’ 1
-1° -15 '20 ’25 -3° '35 ’

Figure 53. Calculated (a) and experimental (b) room temperature 31P{1H}
NMR spectra of PtCl(TMPPXTMPP-O) (37) in acetonitrile-d3.
The 1:3 satellitezparent' intensity ratio resulting fiom the 33%
abundance of 195Pt is not drawn to scale in spectrum (a).

300

 

Figure 54. Illustration of PtCl(TMPP(TMPP-O) (37).

301

(1).

(2).

(3).

(4).

(5).

(6).

(7).

List of References

(a) Dunbar, K. R.; Haefner, S. C.; Pence, L. E. J. Am. Chem. Soc. 1989,
111, 5504. (b) Dunbar, K. R.; Haefner, S. C.; Bender, C. J. Am. Chem.
Soc. 1991, 113, 9540. (c) Dunbar, K. R.; Haefner, S. C.; Swepston, P. N.
J. Chem. Soc., Chem. Commun. 1991, 460. (d) Dunbar, K. R.; Haefner,
S. C. Organometallics 1992, 11, 1431. (e) Haefner, S. C.; Uzelmeier, C.
E.; Dunbar, K. R., manuscript in preparation.

(a) Sun, J -S.; Uzelmeier, C.E.; Ward, D.L.; Dunbar, K.R., Poyhedron,
1998, in press. (b) Dunbar, K. R.; Sun, J .-S. J. Chem. Soc. Chem.
Comm., 1994, 2387.

(a) Anderson, G. K.; Kumar, R. Inorg. Chem. 1984, 23, 4064. (b)
Braunstein, P.; Matt, D.; Dusausay, Y. Inorg. Chem. 1983, 22, 2043. (c)
Podlahova, J .; Kratochvil, B.; Langer, V. Inorg. Chem. 1981, 20, 2160.
(d) Empsall, H. D.; Johnson, 8.; Shaw, B. L. J. Chem. Soc., Dalton
Trans. 1980, 302. (e) O'Flynn, K. H. P.; Mc Donald, W. S. Acta Cryst.
1977, B33, 194. (i) Anderson, G. K.; Corey, E. R.; Kumar, R. Inorg.
Chem., 1987, 26, 97. (g) Alcock, N. W.; Platt, A. W. G.; Pringle, P. G. J.
Chem. Soc. Dalton Trans, 1989, 2069. (h) Reddy, V. V. S.; Whitten, J.
E.; Redmill, K. A.; Varshney, A.; Gray, G. M. J. Organomet. Chem.,
1989, 372, 207. (i) Braunstein, P.; Matt, D.; Dusausoy, Y.; Fischer, J.;
Mitschler, A.; Ricard, L. J. Am. Chem. Soc., 1981, 103, 5115. (i)
Lindner, E.; Schrieber, R.; Kemmler, M.; Schneller, T.; Mayer, H. A.
Chem. Matter. 1995, 7, 1951. (k) Lindner, E.; Schrieber, R.; Schneller,
T.; Wegner, P.; Mayer, H. A. Inorg. Chem. 1996, 35, 514.

(a) Peuckert, M.; Keim, W. Organometalics 1983, 2, 594.(b) Huang, Q.;
Xu, M.; Qian, Y.; Xu, W.; Shao, M.; Tang, Y. J. Organomet. Chem. 1985,
287, 419. (c) Keim, W.; Behr, A.; Hoffmann, B.; Kowaldt, F. H.;
Kiirschner, U.; Limbacker, B.; Sistig, F. Organometalics 1986, 5, 2356.
(d) Klabunde, U.; Ittel, S. D. J. Molec. Catal. 1987, 41 , 123.

(a) Schrock, R. R.; Osborn, J. A. J. Am. Chem. Soc. 1976, 98, 2134. (b)
Davies, J. A.; Hartley, F. R.; Murray, S. G. Inorg. Chem. 1980, 19, 2299.
(c) Sen, A.; Lai, T. W. Organometalics 1982, 1, 415.

Boeré, R. T.; Montgomery, C. D.; Payne, N. C.; Willis, C. J. Inorg. Chem.
1985, 24, 3680.

(a) Blake, A. J .; Gould, R. O.; Lavery, A. J .; Schrbder, M. Angew. Chem.
Int. Ed. Engl. 1986, 25, 274. (b) Wieghardt, K.; Kiippers, H. -J.; Raabe,

302

 

 

(8).

(9)

(10). <

(11).

(12). C

 

(8).

(9)

(10).

(11).

(12).

E.; Kruger, C. Angew. Chem. Int. Ed. Engl. 1986, 25, 1101. (c) Blake, A.
J .; Holder, A. J .; Hyde, T. L; Roberts, Y. V.; Lavery, A. J .; Schréider, M.
J. Organomet. Chem. 1987, 323, 261. (d) Grant, G. T.; Sanders, K. A.;
Setzer, W. N.; VanDerveer, D. G. Inorg. Chem. 1991, 30, 4053. (e) de
Groot, B.; Hanan, G. S.; Loeb, S. J. Inorg. Chem. 1991, 30, 4644.

Blake, A. J.; Crofts, R. D.; de Groot, B.; Schrbder, M. J. Chem. Soc.
Dalton Trans. 1993, 485.

(a) Davies, J .A., The Chemistry of the Metal-Carbon Bond, Hartley,
F.R., Ed., Wiley-Interscience: New York, 1982, 880. (b) Pregosin, P.S.;
Kunz, R.W., NMR Basic Principles and Progress, Springer-Verlag,
Heidelberg, 1979, 55. (c) Collman, J.P.; Hegedus, L.S.; Norton, J .R.;
Finke, R.G., Principles and Applications of Organotransition Metal
Chemistry, Univ. Science Books, Mill-Valley, 1987, 7 2.

(a) Comprehensive Coordination Chemistry; Wilkinson, G.; Gillard, R.
D.; McCleverty, J. A., Eds; Pergamon Press: Oxford, England, 1987; vol
5; chap. 52 and references therein.

(a) Jones, C. E.; Shaw, B. L.; Turtle, B. L. J. Chem. Soc., Dalton Trans.
1974, 992. (b) Empsall, H. D.; Shaw, B. L.; Turtle, B. L. J. Chem. Soc.,
Dalton Trans. 1976, 1500. (c) Empsall, H. D.; Heys, P. N.; Shaw, B. L.
J. Chem. Soc., Dalton Trans. 1978, 257.

Quillevéré, A.; Uzelmeier, C. E.; Sun, J.-S.; Dunbar, K. R., manuscript
in preparation.

303

APPENDIX E

COMPILATION OF 31P{1H} NMR SPECTRAL DATA

304

APPENDIX E

Table 19. COMPILATION OF 31P{1H} NMR SPECTRAL DATA

 

Compound Chemicala JM-1> J pA.pB
Shift Hz Hz
(1) o-P2 -18.8 (s) — —
(2) P4 -18.2 (s) _ -
(3) [RhIG‘MPPflHBM 17.6 (d)b 158 -
(4) RhI(TMPP)(TMPP-O) 20.0 (dd)b 162 22

10.3 (dd)b 162 22

(5) ax,ax-[Rh111(n3-TMPP-O)2][BF4] 35.5 (aa)» 153 —
(6) [C03(u2-OH)3(p3-OH)(uz-n3-TMPP-O)6[BF4]2 not measured
(8) [Nin(o-P2)2] [BF4]2 42. 1(d) — —
(9) [0011(0-P2)2l [BF4l2 not observed
(10) [PdH(o-P2>21[BF412 43.0 (s) — -
(11) [PtH(o-P2)2][BF4]2 35.8 (d) 2355 (Pt-P) —
(12) [Fe11(o-P2)2] [1317.12 56.1(s) — —
75.5 (s) - -
(13) [NiH(o-P2)2][03SCF3]2 46.6(s) — —
(14) [RhH(o-P2) 213311.13 paramagnetic - not observed
(15) Product of [Rh2(NCCH3)1o][BF4]4 + 4 P1 paramagnetic -

not observed

(16) [RemC12(o-P) 2]+ not observed

305

(17)
(18)
(19)
(20)
(21)
(22)

(23)

(24)
(25)
(26)
(2 7)
(28)
(29)
(30)
(31)
(32)
(33)

(34)

(35)

Compound

[Reznv IIICl(;(o-P)]'
ReHC12(o-P) 2
MOWC12(o-P202)(O)(HzO)
PtHCl2(o-P2)

[Pt1 I (0-P2)(NCCH3)2][BF4]2
Ptznv IICl4(P4)

[Pt2H’H(P4)(N C CH3)4] [BF4]4

[Ptzn’n(P4)(0-P2) 2] [BF4l 4
PdHClz(0-P2)
[Pd(NCCH3)2(0-P2)l[BF4] 2
Pd2H’ IIC14(P4)

[Pd2H.H(P4)(NCCH3 4] [BF4l4
Niznanl4(P4)

[RhI(P4)]n[BF4],,

[PtII(P4)],,[BF4]2,,
[PdII(P4)]n[BF4]2n
[CoH(P4)]n[BF4]2,.
[FeH(P4)ln[BF4]2a

[NiH(P4)]n[BF4] Zn

306

Chemicala J M-P J papa
Shift Hz Hz

paramagnetic - not observed
not measured
40.7 (s)C 19.7 —
27 .2 (d)c 3640.4 —
29.0 ((1) 1646.0 -

not measured

19.5 (d) 3845.5 —
26.3 ((1) 3420.9 —
32.9 ((1) 2365.8 —
48.0 (s)‘1
50.7 (s)

not measured
50.9 (s)

not measured
51.0 (d) 134
36.1 (d) 2361 —

44.2 (s) — —
paramagnetic - not observed
53.6 (s) — —
73.8 (s) — -

41.7 (s) — -

 

Compound

 

Chemicalal J M-P J PA-PB
Shift Hz Hz
(37) PtCl(TMPP)(TMPP-O) -20.5 3212 561
-26.4 2993 561

 

O"

9.0

Chemical shift reported in CD3CN relative to 85% H3PO4 unless noted
otherwise.

Chemical shift reported in deg-acetone.
Chemical shift reported in CD2C12.
Chemical shift reported in CDC13.

307