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PART I. SYNTHESIS OF AND CATALYSIS BY USING 1-DI-
METHYLAMINOMETHYLFERROCENE-Z-THIOE‘I‘HERS. PART II.

BIS (n 6—’+-CHLOROAN IS OLE )CHROMI UM

presented by

Robert V. Honeychuck

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PART I. SYNTHESIS OF AND CATALYSIS BY USING 1-DIMETHYL-
AMINOMETHYLFERROCENE-Z—THIOETHERS
PART II. BIS(n6-u-CHLOROANISOLE)CHROMIUM

By

Robert V. Honeychuck

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements

for the degree of
DOCTOR OF PHILOSOPHY

Department of Chemistry

1984

‘II

n...

 

ABSTRACT

PART I. SYNTHESIS OF AND CATALYSIS BY USING 1—DIMETHYL-
AMINOMETHYLFERROCENE-2-THIOETHERS
PART II. BIS(n6-4-CHLOROANISOLE)CHROMIUM

By
Robert V. Honeychuck

PART I
A number of previously unknown ferrocenyl thioethers

(n5-CSH5)Fe(nS-CSHB-l-CHZNMeZ-Z-SR), R = Me, Et, i-Pr.
i-Bu,‘i-pentyl, and Ph, have been made from dimethylamino-
methyl ferrocene via lithiation at the number 2 position

and subsequent reaction with RSSR. These compounds are
air-stable yellow solids which are easily produced in multi-
gram quantities and are separable on silica gel columns.

The iSOprOpyl derivative crystallizes directly from the reac-
tion mixture and requires no chromatography for purification.
The following techniques were used for characterization:

1H and 13C NMR. IR, MS, and elemental analysis. The deriva-
tives contain a plane of chirality causing NMR spectra

to exhibit separate peaks for diastereotOpic protons and
carbons. Methylene protons a to the nitrogen of the alkyl
derivatives give 1H NMR peaks which are widely separated.

The phenyl derivative shows these peaks closer together.

but the coupling constant remains the same at 13 Hz.

The ferrocenes are tertiary amines and thioethers and
thus act as bidentate ligands. The PdCl2 complex of (n5-
C5H5)Fe(n5-O5H3-1-CH2NMe2-2-S-i-Pr) was made and its potential
as a catalyst explored. The PdCl2 complex selectively
hydrogenates 1,3-cyclooctadiene to cyclooctene under hetero-
geneous conditions in CH2012 with H20 present. under homo-
geneous conditions in acetone with no H20 this reaction is
much faster. The PdCl2 complex isomerizes and hydrogenates
1,5-cyclooctadiene to cyclooctene under homogeneous condi-
tions in acetone.

PART II

A new Cné-arene)zchromium complex. bis(né-h-chloro-
anisole)chromium. has been prepared by metal vapor-ligand
cocondensation and characterized spectrosc0pically. This
compound exhibits some degree of air stability in the solid
state, unlike many bis(arene)chromium species. A metal
vapor reactor using resistive heating was built for this
work and is described. Attempts to make new complexes
bis(n6-h-bromoanisole)chromium and bis(n6-4-chloronitro-
benzene)chromium by metal vapor-ligand cocondensation are
detailed. Attempts to make the Grignard reagent of bis(né-

A—chloroanisole)chromium are also described.

For Fritz Hembach, Art DeLaurier. Julie Biernat,
Laurence LeGouge, Cynthia Hinds, Tom Dubovsky, Andy Bobrow,
Mark Leis, Dan Schaefer, Claudia Donase, John Albert,

Kathy Katovich. Dale Grover, Deirdre Weinberg, Mark Durbin,
Mike Zack, Elizabeth Kupfer, Tom Jaworski, Sue Kujawa.

Amy Matteson, Gabrielle Tazzia. Hojoon Kim, Janice Strait,
Mary Ann Sweetland, Tom Carlson, Karen Mausser, Steve Baker,

Linda Jackson, Dan Stouffer, and Silvia Blum,

and for

NARH and CLBK.

ii

ACKNOWLEDGEMENTS

I would like to express my deepest gratitude to Professor
Carl H. Brubaker, Jr. for his assistance and inspiration on
these projects.

I would also like to thank Dr. Donald G. Farnum,
Dr. Tomi T.-T. Li, Dr. Beth McCulloch, Lie-Hang Shen, and
Michael O. Okoroafor for countless discussions and helpful
suggestions, and Joseph M. Honeychuck, Ellen R. Honeychuck.
Armin J. Richter. and Mary S. Richter for support and love.

"Sine qua non."

iii

TABLE OF CONTENTS
Page

LI ST OF TABLES O O O O O O O O O O O O O O I I O O O O O Vii
LIST OF FIGURES. O O I O O O O O O .0 O O O O O O O I O OViii

PART I. SYNTHESIS OF AND CATALYSIS BY USING l-DIMETHYL-
AMINOMETHYLFERROCENE-Z-THIOETHERS . . . . . . . . 1

IN TROD UC TI ON C O O O O O I C O O O O O O O O O O O O O 2
EXPERIMENTAL O O O O O I O O O O O O I O O. I O I O O I 1 O

1-Dimethylaminomethyl-Z-methylthio-
ferrocene (1_6_, R=Me).............10

1-Dimethylaminomethyl-Z-ethylthio-
ferrocene(1_6gR=Et)ooococo-000.011

1-Dimethylaminomethyl-2-isoprOpylthio-
ferrocene (E, R=i-Pr) o o o o a o o o a o o .13

1-Dimethylaminomethyl-Zgi-butylthio-
ferrocene(1_6' R=i-BU) o o a o o o o a o o a 0114'

1-Dimethylaminomethyl-Z-i—pentylthio-

ferrocene (lg, R = i-pentyl) . . . . . . . . . .15
1-Dimethylaminomethyl-Z-phenylthio-

ferrocene (1_é, R: Ph) 0 o o a a o o o o o e o .17

1-Dimethylaminomethyl-Z-iSOpropylthio-
ferrocene palladium dichloride (12). . . . . . .18

Attempted hydrogenation of 1,3-cyclo-
octadiene with 11 in benzene at 1A.? psi
(Tab183913tentry)ooooooocoo-00.19

Attempted hydrogenation of 1,5-cyclo-
octadiene with iz_in methylene chloride
at 14.7 psi (Table 3, 2nd entry) . . . . . . . .19

iv

Attempted hydrogenation of 1,3-cyclo-
octadiene with 17 in toluene at 100

psi (Table 3, 3E3 entry) . . . . . . . .

Hydrogenation of 1,3-cyclooctadiene
with 11 in CHZCl2 at 99 psi (Table 3,

4th entry; Figure 22). a o o o o o o a o

Hydrogenation of 1,3-cyclooctadiene with

AZ in CH2012 at 101 psi (Figure 23). . .

Hydrogenation
17 in acetone

Hydrogenation
'17 in acetone

Isomerization-hydrogenation of 1,5-cyclo-

of 1,3-cyclooctadiene with

at 14.7 psi (Figure 24). .

of 1,3-cyclooctadiene with

at 61 psi (Figure 25). . .

OCtadiene With £20 a o o o o o o o o a 0

RESULTS AND DISCUSSION.

Ferrocenyl Sulfides 16 . . . . . . . .

Palladium Complex £2 a o o o o o o o x

Hydrogenation and Isomerization Using

Palladium Complex l2 0 a o o o o o a 0

PART II.
INTRODUCTION. . .
EXPERIMENTAL. . .

Bis(n6-4-chloroanisole)chromium (31)
Bis(n6-toluene)chrmmium (24. R = Me)

Attempted synthesis of bis(n6-1,3,5-
trimethylbenzene)chromium (38) . . .

Attempted synthesis of bis(n6-4-
bromoaniSOle)Chr0mium (22) e o a o o o o

Attempted synthesis of bis(n6-4-chloro-
nitrobenzene)chromium (49).

Attempted synthesis of bis(n6-4-chloro-
nitrobenzene)chromium (49).

V

methOd A.

BIS(n6-4-CHLOROANISOLE)CHROMIUM. . .

Method B.

Page

.19

.20

.21

.21

.22

.23
.23
.38

.42
.58
.65

.65
.66

.67

.67

.67

Page
Attempted synthesis of bis(n6-4-chloro-
nitrobenzene)chromium (49). Method 0. . . . . .68

Attempted synthesis of bis(n6-4-chloro-
nitrobenzene)chromium (49). Method D. . . . . .68

Attempted synthesis of bis(n6-4-
methoxyphenylmagnesium chloride)chromium
(fl) 0 O C O ‘0 O O O C O O C O O O O C O O O O O 68
RESULTS AND DISCUSSION. . . . . . . . . . . . . . . .70
APPENDIX 0 O O C O O O O O O O O I O C O O O O O O C O O O 81

BIBLIOGRAPHY I I O O O O O O O O O O O O O O O O O O O O O 97

vi

LIST OF TABLES
Table Page

1. Infrared modes of the unsubstituted ring of
compoundsl_6......................35

2. Metal-S, metal-N, and metal-Cl stretching modes
of several complexes. . . . . . . . . . . . . . . . . .40

3. Selective hydrogenation: initial attempts . . . . . . .43

4. Homogeneous selective hydrogenation of dienes
tomonoeneSopoooooooaoococoa000.052

vii

LIST OF FIGURES

Figure

1. Lithiation of dimethylaminomethylferrocene (l). .

2.

3.

9.
10.
11.
12.

13.

14.

15.
16.

Selected reactions of 1-dimethylaminomethyl-2-
lithiOferrocene I I I I I I I I I I I I I I I

Reaction of methyl disulfide with a t-butyl ester

enOl ate I I I I I I I I I I I I I I I I I I I

Reaction of methyl disulfide with bis(né-phenyl-

lithium)0hr0miumo o o o o o o o o o a o a o 0

Reaction of tetrais0pr0pylthiuram disulfide with

aryllithium species . . . . . . . . . . . . .

Reaction of.lithiated ferrocenes with disulfides.

Nucleophilic substitution leading to ferrocenes

with sulfur in the side chain . . . . . . . .

Introduction of sulfur to a ferrocene ring by
electrOphilic aromatic substitution . . . . .

Aminomethylation of methylthioferrocene . . .

Synthesis of new ferrocenyl thioethers $9 . .
1

1

250MHz HNMROflé9R=Etooeoooooo

250 MHz H NMR of 99, R = i-pentyl. . . . . .

Splitting pattern of SCH2 protons in 19, R =
l-pentyl...................

Broadband decoupled 13C NMR of 19, R = Et . .
Gated decoupled 13c NMR of lg, R = Et . . . .

Substituted ring 13C shifts in 19, R = Et, and 1.

viii

Page

. 2

.28
.30
.31
.33

Figure

17.

18.
19.

20.
21.
22.
23.
24.
25.

26.

27.

28.

29.

30.
31.

32.

34.

A portion of the infrared spectrum of 16, R =

i-Pr o a o o a o o a o a a o o a o a o o o o a o

 

Mass spectrum of 16, R = i-Pr. . . . . . . . . .

Synthesis of amine-thioether-palladium complex 31

Dimer i§ o o o o o o a o a I a a a o o o o o o o
Selective hydrogenation using (n-Bu)ZS . . . . .

Selective hydrogenation of 1,3-cyclooctadiene in
CH7C12 at 25°C using Fc-Pd (91) (Table 3, 4th

entry) 0 o o o o o o o a o o o o o e o o o o o a

Selective hydrogenation of 1,3-cyclooctadiene in
CHZClz at 24°C USing FC'Pd (l1). 0 o a o o o o o

Selective hydrogenation of 1,3-cyclooctadiene in
acetone at 28°C and 14.7 psi using Fc-Pd (£1). .

Selective hydrogenation of 1,3-cyclooctadiene in
acetone at 27°C and 61 psi using Fc-Pd (11). . .

Olefinic region of 250 MHz 1H NMR of 1.3-cyclo-
octadiene (t0p), reaction mixture of Figure 25
(middle). and cyclooctene (bottom) . . . . . . .

Isomerization-hydrogenation of 1,5-cyclooctadiene
in acetone at 25°C and 61 psi using Fc-Pd (12) .

Possible mechanisms of the homogeneous selective
hydrogenation of 1,3-cyclooctadiene using complex

£1 a a o 0'. a a o a o o o o a o 0.0 o o a o o o

Hydrolysis of complex ll prior to heterogeneous
selective hydrogenation. . . . . . . . . . . . .

Synthesis of bis(né-benzene)chromium . . . . . . .

Bis(n6-arene)chromium compounds made by metal vapor-

ligand cocondensation. . . . . . . . . . . . . .
Reaction of biphenyl with Cr atoms . . . . . . .
Reaction of [2.21paracyclOphane with Cr atoms. .
Fluorinated bis(arene)chromium derivatives . . .

ix

Page

.36
~37
.38
.39
.43

.45

.46

.u7

.48

.50

.51

05“

.56
.58

.60
.61
.62
.63

Figure Page

35. Chromium complexes from metal vapor-ligand cocon-
densation using non-benzene ligands. . . . . . . . . .64

36. Complexes 99. 99, 49. and 4; . . . . . . . . . . . . .71
37. Synthesis of bis(n6-4-chloroanisole)chromium (32). . .72
38. Stainless steel electrodes . . . . . . . . . . . . . .73
39. Metal vapor reactor. . . . . . . . . . . . . . . . . .74

40. %SO)MHZ 1H NMR of bis(n6-4-chloroanisole)chromium
22 I I I I I I I I I I I I I I I I I I I I I I I I I77

41. Infrared spectrum of complex 91. . . . . . . . . . . .78

1+2. M358 SPeCtrlm 0f complex fl. 0 o o o o o o a o o o o 079

1

[+3-250MHZ HNMROfiéyR=Meoeoooooo0000082

44. Broadband decoupled 13c NMR of ;§, R = Me. . . . . . .83

.21

45. Gated decoupled 13c NMR of 19, = Me. . . . . . . . .84

46. 250 MHz 1H NMR of ;Q, R = l-Pr . . . . . . . . . . . .85
47. Broadband decoupled 13C NMR of 99, R = l-Pr. . . . . .86
48. Gated decoupled 13c NMR of 19- R = l-Pr. . . . . . . .87
49. 250 MHz 1H NMR of lg, R - i—Bu . . . . . . . . . . . .88
50. Broadband decoupled 13c NMR of 99. R = l-Bu. . . . . .89
51. Gated decoupled 13c NMR of Ag. R = i-Bu. . . . . . . .90

52. Broadband decoupled 13c NMR of 39, R = i-pentyl. . . .91
53. Gated decoupled 13c NMR of 19, R = i-pentyl. . . . . .92
54. 250 MHz 1H NMR of 99, R = Ph . . . . . . . . . . . . .93
55. Broadband decoupled 13c NMR of 39, R = Ph. . . . . . .94

56. Gated decoupled 13c NMR of ;§, R = Ph. . . . . . . . .95'
57. 1,1'-Bis(phenylseleno)ferrocene (49) . . . . . . . ...96

X

PART I. SYNTHESIS OF AND CATALYSIS BY USING l-DIMETHYL-
AMI N OME THYLFERROC ENE - 2 -THI OE THERS

INTRODUCTION

Since dimethylaminomethylferrocene's first appearance
in 1956,1 much effort has been expended on the reactions

of its lithiation product 9 (Figure 1). The chelating

 

<5:?2Im-2 (2'3“1' > QL,
é ' i "33:. ©2 '2

Figure 1. Lithiation of dimethylaminomethylferrocene (9).

effect of the lone pair of electrons on nitrogen directs
lithiation to the 2-position, giving 9 in high yield with
minimal 3- and 1'-contamination. The coordination chemistry
of 9 (Figure 2, available from 9 via nucleophilic substitu-
tion of chlorodiphenylphosphine) with chromium, molyb-
denum, tungsten, iron, and cobalt carbonyls has been
investigated.2 The ligand was bidentate with the group

VIB carbonyls, but monodentate through phosphorus with

Fe and Co. Compound 9 adds in Grignard fashion to carbonyl
species giving 3,3,4 and the addition products of acetyl-
ferrocene and acetaldehyde.5’6 Pyridine undergoes a nucleo-

2

Q3:
2 2%

 

 

Figure 2. Selected reactions of l-dimethylaminomethyl-Z-
lithioferrocene.

4

philic aromatic substitution to yield 9, whose CoX2 complexes
(X = Cl, Br, and SCN) have been studied.6

Marr et. al. have found that 9 reacts with paraform-
aldehyde and dimethylformamide giving 1-dimethylaminomethyl-
2-hydroxymethylferrocene and 1-dimethylaminomethyl-Z-formyl-
ferrocene, respectively.7 Several derivatives of these
compounds were reported. Trimethylchlorosilane reacts
with 9 to give 5,8 and 9 undergoes reaction with hexachloro-
ethane to give the 2-chloro compound.9 The latter reaction
involves lithium-halogen exchange followed by B-elimination
giving tetrachloroethylene. Tri-gébutyl borate reacts with
9 to yield, after hydrolysis, boronic acid 1,10 which is
an amino acid with the same prOperties as natural amino
acids: it has an isoelectric point and is soluble in aqueous
base and acid. More importantly, Z undergoes replacement
of the boronic acid portion with Cl, Br, and I using cupric
chloride, cupric bromide, and 12 as the reagents. Finally,
various quinones have been added to 9 giving the corresponding

keto alcohols, e.g.. 9.11

An excess of quinone was used,
and no evidence was found for addition of 2 molecules of 9
to the quinone.

Thus, there are a multitude of electrOphiles which will
react with lithioferrocene 9. There are also many lithiated
compounds which will react with disulfides.

The reaction of disulfides with anions has been known

for years, and involves electrOphilic rather than nucleOphilic

are

voov

guns
no.
u-.

3..
a.-

\v.

N9

5
sulfur. In organic chemistry, the reaction is used with
enolate anions to produce d-sulfenyl carbonyl species

(Figure 3), intermediates on the path to a,B-unsaturated

goof-l- “"8 sm
Moss». ’ > E::f~coz

Figure 3. Reaction of methyldisulfide with a E-butyl ester
enolate.

 

 

 

12-1“ In 1981, bis(né-benzene)chromium

carbonyl compounds.
was lithiated and the product reacted with methyl disulfide
(Figure 4).15 Thioether sandwich complex 9 acted as a chelating

agent with Mo(C0)4.

Li
Ct

@u @s...

Cr

@s...

Figure 4. Reaction of methyldisulfide with bis(né-phenyl-
lithium)chromium.

MeSSMe

\/

Cava's group has found that phenyllithium and a number
of lithiated aromatics react with tetrais0pr0pylthiuram

disulfide to give S-aryl-N,N-diisoprOpyldithiocarbamates

6

(99, Figure 5).16 The bulk of the isoprOpyl groups prevents
attack at the thione carbons, in contrast to the tetramethyl
analog. With tetraiSOprOpylthiuram disulfide replaced by
tetramethylthiuram disulfide, a major side product is the
thioamide. The authors hydrolyzed dithiocarbamates 19

to the thiols in high yield, so that the sequence repre-

sents a new synthesis of aromatic thiols.

 

NCESSCIIIN . > ArSfiN
‘I’ g 5 Te' ArLl . S
0

1

)_
>—

Figure 5. Reaction of tetraisopropylthiuram.disulfide with
aryllithium species.

17-19

Recently in these laboratories it was found that
lithioferrocene and 1,1'-dilithioferrocene react with
various disulfides to give thioethers and dithiocarbamates
(Figure 6). Other ferrocene derivatives with sulfur in

side chains have been made, but these were the products of

a nucleOphilic substitution in the side chain (Figure 7)

or electrophilic aromatic substitution (Figure 8). Reaction
of tetraalkylammonium iodide 99 (Figure 7) with sodium sul-
fide gave thioether l9 and disulfide 99.20 Sulfur was
introduced directly to a ferrocenyl ring via electrophilic

sulfonation (Figure 8).21 Sulfonic acid 94 was converted

to the sulfonyl chloride and then the thiol. The thiol

@

Fe

RSSR ' ©sn

.$

SCNRZ

<E§§E>S§NRZ

 

CC?“ @599

F‘ ;‘ Fe

/
R NCS-SCNR
@ 2....2 ©
_ _ S S

 

Figure 6. Reaction of lithiated ferrocenes with disulfides.

”29°” + Ph2c0H ph 2C0"
Fe ‘—————€> - Fe F. .
ll :2 2 Egg; 2

12 ll

Figure 7. Nucleophilic substitution leading to ferrocenes
with sulfur in the side chain.

 

(/

<::;:;> ‘ <;:;:;>-soan
0180 H
F: 3 Fe
@ A. ©
13

Figure 8. Introduction of sulfur to a ferrocene ring by
electrophilic aromatic substitution.

9
was converted to its methyl thioether. The methyl thioether
(92. Figure 9) was subjected to electrophilic substitution

22 All three possible

with bis(dimethylamino)methane.
monosubstituted products were obtained as was expected from

the activating nature of the methylthio group.

CF. 8M9 MeZNCH2 NMe2 \WQR NM ".2" :fisu.
‘2
§ HOAC >@ ©

@5114.

Fe

Figure 9. Aminomethylation of methylthioferrocene.

The lithiation procedure yielding 9 described above
offers a distinct advantage over electrOphilic substitution
in that only a single lithiation product is obtained.
Part I of this dissertation presents the reaction of a number
of disulfides with lithioferrocene 9 to give several new
ferrocene tertiary amine thioethers. The use of the PdCl2
complex of one of these amine thioethers in isomerization
and selective hydrogenation is also detailed.

This work represents an addition to the rich literature

of ferrocene chemistry.23'25

EXPERIMENTAL

Proton and 13C NMR's were obtained by use of a Bruker
WM 250 spectrometer in chloroform-d except where noted,‘with
TMS as internal standard. Infrared spectra were recorded
by use of a Perkin-Elmer 457 machine. Mass spectra were
obtained by means of a Finnigan 4021 instrument with INCOS
data system. Elemental analyses were performed by,Spang
Microanalytical Laboratory, Eagle Harbor, Michigan, and
Galbraith Laboratories, Knoxville, Tennessee. Gas chroma,
tography was done by using a Hewlett-Packard 5880A instrument.
Dimethylaminomethylferrocene was made by the standard method26
or was purchased. The hydrogenation substrate 1,3-cyclo-
octadiene was obtained from Columbian Carbon Co., and 1,5-
cyclooctadiene from Aldrich Chemical Co. The 1,4-isomer

27’28 Solvents were

was made via the existing method.
dried and distilled by standard methods.29 Hydrogenations
at 1 atm were followed by means of a barometer and manometer:
at greater than 1 atm a pressure bottle with gauge was used.
1-Dimethylaminomethyl-Z-methylthioferrocene (16, R = Me).
To a magnetically stirred 500 mL Schlenk flask with a rubber
septum were added 9.2 mL (0.046 mol) of dimethylaminomethyl-
ferrocene and 250 mL of dry ethyl ether under N2. Via
syringe, 32 mL (0.051 mol) of g-butyllithium (1.6 M in

10

11
hexane) was slowly added. After stirring for 12 yrs, 4.1 mL
(0.046 mol) of methyl disulfide was put in via cannula.
Four hours later, 100 mL of H20 was added, the mixture
was filtered, and the organic layer was separated, dried
over NaZSOu, and evaporated on the rotary evaporator.
Methyl disulfide was removed on a vacuum pump and the residue
was chromatographed on a 5 X 23 cm column of A1203, with
CH2012 as solvent. The first band gave the product as
brown crystals: yield 2.27 g (17 z); mp 165° dec; 1H NMR 6
2.27 (s, 3H, SCHB), 2.31 (s, 6H, NMeZ), 3.47 (d, J = 13 Hz,
1H, NCHZ), 3.73 (d, J = 13 Hz, 1H, NCHZ), 4.12 (s, 5H, 0
4.20 (m, 1H, H3, H4, H5), 4.35 (m, 1H, H3, H4, H5). 4.43
(m, 1H, H3, H4, H5); 130 NMR ppm (JCH) 20.2 (140.4, SMe),
44.2 (137.4, NMez), 56.6 (140.8, NCHZ), 68.0 (176.9, C
C4' 05), 70.0 (173.6, CSHS). 70.8 (176.7, 03, °4' 05).
71.9 (176.9, 03, C4’ C5), 83.6 (C1)’ 84.3 (02): IR (Nujol,
C31) 719, 805 (ring-H bend perpendicular to ring), 888,

5H5).

3,

946, 996 (ring-H bend parallel to ring). 1102 cm"1 (antisym-
metric ring breath); MS m/e (% RA) 44 (10, NMez), 47 (1,
SMe), 56 (15, Fe), 58 (15, CHZNMeZ), 65 (2, C5H5)' 121

(41, C

Fe), 231 (2, M+ - CH NMe 242 (44, M+ - SMe),

245 (37. M+ - NMez). 289 (89. M*).
1-Dimethylaminomethyl-Z-ethylthioferrocene (16, R = Et).
The lithioferrocene 9 was made as with 99, R = Me, using

8.1 mL (0.041 mol) of dimethylaminomethylferrocene, 100 mL
of ethyl ether, and 28 mL (0.045 mol) of g-BuLi. The flask

12
was cooled to 0° and 5.1 mL (0.041 mol) of ethyl disulfide
was added via cannula over 15 min. The suspension was
unchanged on warming to 25°, so 100 mL of hexanes was added
and the mixture was heated under reflux for 2 hrs. Distilled
water (100 mL) was added and the mixture was filtered. The
solid in the fritted glass funnel was washed with hexanes until
the washings were colorless. The organic layer from the fil-
trate was washed with 2 X 200 mL of H20, dried over N32504:
and reduced on the rotary evaporator. Excess disulfide was
removed on a vacuum pump. The residue was separated on a
5 X 24 cm column of alumina using hexanes/EtZO, giving the
product as golden crystals from the first band after 3
recrystallizations. Sublimation at 600-1080 gave the analyti-
cal sample of yellow crystals. Yield 5.60 g (45 %)3 mp

1

175° dec; H NMR 6 1.19 (t, 3H, ethyl CH3), 2.19 (s, 6H,

NMe 2.64 (m, 2H, ethyl CH2), 3.21 (d, J = 13 Hz, 1H,

2).
.NCHZ). 3.60 (d, J = 13 HZ, 1H,.NCH2), 4.09 (S, 5H, C5H5)'
4.16 (t, 1H, H3, Hu, H5), 4.32 (d, 2H, H3, H4. H5); 130

TWMR ppm (JCH) 14.8 (126.9, EtCH3), 30.7 (142.0, EtCHZ),

45.1 (133.9, NMez). 57.2 (131.7, NCHZ), 67.4 (169.9, 8.6,
<33, C4' 05), 69.8 (170.8, CSHS), 70.6 (179.9, 03, C4' 05),
'73.? (177.1, 8.0, C3, C4’ C5), 80.5 (C1), 87.0 (C2); IR
(Piujol, C31) 720, 808 (ring-H bend perpendicular to ring),
888, 946, 998 (ring-H bend parallel to ring), 1103 (antisym-
‘metric ring breath), 1178 (C-N stretch), 1264 cm'1 (alkyl

C-H bend); MS m/e (% RA) 44 (23, NMeZ), 56 (61, Fe), 58

I“

IV.

 

 

“m: .3 M» .5 «I. .x. a c. o( I . : t l a C u
. r . U .. a at I— I d .u . 7 .
2.. 2~ .. .. mu.» 0 «Pu 2.. 3. v z a a...» e. L IQW u. M. (4|... .01....

 

13

(76, CH NMe 65 (21, c ), 121 (100, FeCp). 242 (41, M+

2 2)' 5H5
- SEt), 259 (20, MI - NMez), 274 (4, M+ - Et), 303 (61,
M+). Anal. Calcd for C15H21FeNS: C, 59.41; H, 6.98; S,
10.57. Found: C, 59.61; H, 7.15; S, 10.48.
1-Dimethylaminomethyl-2-isoprOpylthioferrocene (161

R = i-Pr). Lithioferrocene 9 was made as with 99, R = Me,

 

using 16.3 mL (0.0823 mol) of dimethylaminomethylferrocene,
20 ml of ethyl ether, and 57 mL (0.090 mol) of g-BuLi.

The orange suspension was stirred at 25° for 12 hrs.
IsoprOpyl disulfide (13.1 mL, 0.0823 mol) was then added via
cannula over 0.5 hr. A voluminous yellow precipitate
appeared. After 1.5 hrs the reaction mixture was filtered
and washed with 100 mL of H20, then 200 mL of ether.

The red organic layer from the 2 phase filtrate was dried
over NaZSOI+ and reduced on the rotary evaporator to a red
oil. The oil was dissolved in 50 mL of CHZClZ, 25 mL of
hexanes added, and the CHZCl2 boiled off. Large brown prisms
appeared after 10 days at 25°. Two recrystallizations gave

1H NMR 6 1.15

8.22 g (31.5 %) of 1g, R = i—Pr: mp 82-830;
(d, J = 6 Hz, 3H, i—Pr CH3), 1.19 (d, J = 7 Hz, 3H,.1-Pr
<3H3), 2.18 (s, 6H, NMez), 3.02 (m, 1H, i-Pr CH), 3.14 (d,

J = 13 Hz, 1H, CH2), 3.61 (d, J = 13 Hz, 1H, CH2), 4.08

(s, 5H, C5H5), 4.16 (s, 1H, H3, H4, H5), 4.32 (s, 2H, H3,
H“, H5); 130 NMR ppm (JCH) 22.8 (128.8, g-Pr CH3). 23.6
(125.4, g-Pr CH3), 39.4 (148.4, g-Pr CH), 45.3 (134.3, NMeZ),

57.3 (132.5. CH2). 67.6 (179.5. 8.8. 03. 04' 05). 69.9

14
(178.0, CSHS), 70.9 (174.0, 03, C4' 05), 75.1 (185.0, 7.7,
03, C4' C5). 79.0 (01), 88.0 (02); IR (Nujol, KBr) 662
(C-S stretch), 815 (ring-H bend perpendicular to ring),
891, 998 (ring-H bend parallel to ring), 1018, 1103 (anti-
symmetric ring breath), 1180 (C-N stretch), 1260 (alkyl
C-H bend), 3095 cm"1 (ring-H stretch); MS m/e (% RA) 43

(32, i—Pr), 44 (8, NMeZ), 56 (26, Fe), 58 (28, CH NMe

2 2)!

+
65 (4, CSRE), 121 (52, C5H5Fe), 196 (9. M - CSHSFe),
242 (48, M - S-i—Pr), 259 (3, M+ - CHZNMeZ), 273 (23, M+
- NMez), 274 (24. M+ - 1-Pr). 302 (3, M+ - CH3), 317 (100,
M+). Anal. Calcd for C16H23FeNS: 0, 60.57: H, 7.31, s,
100100 Fode C, 60.54; H, 70h03 S, 10016.

1-Dimethylaminomethyl-2-i-butylthioferrocene (16,

R = i-Bu). The lithioferrocene 9 was made using the procedure

 

for 99, R = Me, and a 500 mL Schlenk flask with 250 mL

of Et20. After stirring for 6 hrs, 14.6 g (0.0823 mol)

of isobutyl disulfide was added via cannula. Nine hours
later, 100 mL of H20 was added and the mixture was filtered.
The solid remaining in the funnel was washed with 200 mL

of Et20. The organic layer of the filtrate was washed with
2 X 100 mL of H20, dried over NaZSOQ, and evaporated to a
red oil. Vacuum distillation gave 5 mL of isobutyl disulfide
and 5 mL of dimethylaminomethylferrocene in the receiver.
The pot material was chromatographed on a 5 X 11 cm column
of alumina with hexanes/CHZCIZ. The first band gave the
product as yellow crystals from CHZClZ/hexanes after 5 days.

Two subsequent recrystallizations and a sublimation at 870

15
gave the analytical sample: yield 12.0 g (43.9 %)3 mp 162-

1630 dec: 1

H NMR 6 0.94 (d, J = 7 Hz, 3H, l'Bu'CH3)' 0.99

(d, J = 7 Hz. 3H, i-Bu CH3). 1.77 (h, J = 7 Hz, 1H. 3° H),

2.19 (s, 6H, NMeZ), 2.45 (dd, J = 8 Hz, J = 12 Hz, 1H, SCHZ).

2.62 (dd, J = 6 Hz, J = 12 Hz, 1H, SCHZ), 3.20 (d, J =

13 Hz, 1H, NCHZ), 3.61 (d, J = 13 Hz, 1H, NCHZ), 4.09 (s,

5H, 05H5), 4.14 (t, 1H, H3, H4, H5), 4.30 (m, 2H, H3, H4.

R5), 130 NMR ppm (JCH) 21.8 (123.1, l-Bu CH3), 22.3 (126.8,

g-Bu CH3), 28.5 (125.7, i—Bu CH), 45.2 (132.0, NMez),

46.3 (132.0, i—Bu CH2), 57.3 (137.7, NCHZ), 67.5 (173.0,

03, °4' 05), 70.0 (170.4. CSHS), 70.6 (171.1, 03, °4' 05).

73.3 (173.6, 03, 04, 05), 81.9 (Cl), 87.1 (02); 1R (Nujol,

CsI) 718, 808 (rinng bend perpendicular to ring), 888,

945, 993 (ring-H bend parallel to ring), 1103 cm"1 (anti-

symmetric ring breath); MS m/e (% RA) 43 (8, i—Pr), 44

(11, NMez), 56 (45, Fe), 58 (48, CHZNMeZ), 65 (6, C5H5),

121 (86, CSHSFe, M+ - CSHSFe - S-i-Bu), 242 (97. M+- s-g-Bu),

331 (100, M+). Anal. Calcd for 0171125 FeNS: c, 61.63;

H, 7.61; S, 9.68. Found: C, 61.17; H, 7.69; S, 9.82.
l-Dimethylaminomethyl-Z-i-pentylthioferrocene (16,

R = i-pentyl). Lithioferrocene 9 was made as with 99, R

= Me, using 18.4 mL (0.0930 mol) of dimethylaminomethyl-

ferrocene, 250 mL of ethyl ether, and 64 mL (0.10 mol) of

Q-BuLi. The suspension was stirred for 6 hrs and 19.2 g

(0.0930 mol) of is0pentyl disulfide was added via cannula.
After 12 hrs 100 mL of H20 was added and the mixture filtered.

16
The organic layer from the filtrate was dried over NaZSOQ
and evaporated to a red oil. A vacuum distillation at 35-650
at this point gave 3 mL of red liquid in the receiver.
Crystallization was induced in the pot with CH2C12/hexanes.
The product was recrystallized twice, dissolved in CHZClz,
deprotonated with 1 % aqueous Na2C03, and chromatographed
on a silica gel column with CHZClz/MeOH. The product was
obtained as yellow crystals: yield 10.2 g (31.7 %)3 mp 1750

dec; 1

H NMR 6 0.85 (d, J = 7 Hz, 3H, i-pentyl CH3), 0.86

1.65 (h, J = 7 Hz, 1H, i-pentyl CH), 2.19 (s, 6H, NMeZ),

2.59 (ddd, J

gem 12 Hz, JVic = 7 Hz, J

gem 12 HZ’ Jvic vic
3.17 (d, J = 13 Hz, 1H, NCHZ), 3.62 (d, J = 13 Hz, 1H,
NCHZ), 4.08 (s, 5H, C5H5)' 4.14 (t, 1H, H3, H4, H5), 4.30

(d, 2H, H3, H4, H5); 130 NMR ppm (JCH) 22.1 (119.7. i-pentyl

vic 8 Hz, 1H, SCHZ),

2.70 (ddd, J 7 Hz, J 8 Hz, 1H, SCHZ),

CH3), 22.4 (119.5, 9-pentyl CH3), 27.2 (125.6, i-pentyl CH),
35.1 (138.5. i—propyl-CHZ), 38.6 (128.0. SCHZ). 45.2 (129.9,
NMeZ), 57.3 (136.3, NCHZ), 67.4 (177.4, 03, op, 05). 69.9
(170.8, C5H5), 70.7 (184.1, 03, 04' 05). 73.6 (177.5. 03.

04' C5). 81.2 (C1). 87.2 (02); IR (Nujol, CsI) 720, 810
(ring-H bend perpendicular to ring), 888, 947. 995 (ring-H
bend parallel to ring), 1103 cm"1 (antisymmetric ring breath);
MS m/e (% RA) 56 (17, Fe), 53 (19, CHZNMeZ). 65 (3. C5H5).

+
121 (20, FeCp, M+ - FeCp - S-i-pentyl). 153 (3. M - FeCp -

+

irpentyl), 242 (15, M+ - S-l-pentyl), 274 (2, M - g-pentyl),

17

301 (2, M+ - NMeZ), 345 (20. M+). Anal. Calcd for C18H27FeNS:
C, 62.61: H, 7.88; S, 9.28. Found: C, 62.82; H, 8.07;
S. 9.42.

1-Dimethylaminomethyl-Z-Lhenylthioferrocene (16, R =
phenyl). Lithioferrocene 9 was made using the procedure for
_1_6_, R = i-Pr, and a 1000 mL Schlenk flask with 250 ml of
ethyl ether. After stirring for 8 hrs, a solution of 18.0 g
(0.0823 mol) of phenyl disulfide in 250 mL of Et20 was
added via cannula. Sixteen hours later, 100 mL of H20 was
added. The mixture was filtered and filtrate's organic layer
was dried over Na280,+ and reduced to a red oil on the rotary
evaporator. The oil was deprotonated with 1 % aqueous NaZCO3
and chromatographed repeatedly on silica gel with CHZClz/MeOH,
then benzene/Etzo, until an analytical sample was obtained.
The product was exceedingly difficult to purify and the yield
given ropresents that of the analytical sample, a yellow

solid. Yield 0.030 g (0.10 %); mp 66-68°; 1

H NMR 6 2.02
(s, 6H, NMeZ), 3.40 (d, J = 13 Hz, 1H, 110112), 3.46 (d, J
== 13 Hz, 1H, NCH2), 4.16 (s, 5H, CSHS), 4.32 (t, 1H, H3,
II“, H5), 4.46 (m, 1H, H3, Ha, H5), 4.51 (m, 1H, H3, H4.
Its). 6.98-7.17 (m. 5H, Ph); 130 NMR ppm (JCH) 45.0 (132.6,
runez), 56.7 (134.5. CH2). 69.0 (176.9. 03, °4' 05). 70.3
(176.2, C5H5). 71.3 (175.2. 03. Cu. 05). 75.6 (179.8. 03.
C4’ CS)’ 76.4 (C1)' 87.6 (C2). 124.8 (157.5, para C).
126.2 (161.4, meta C), 128.4 (154.3, ortho C), 140.1 (sub-

stituted phenyl C); IR (neat) 690 (out-of-plane phenyl C-H

18
bend), 740 (out-of—plane phenyl C-H bend), 820 (C5H5 ring-H
.bend perpendicular to ring),1000 (05H5 ring-H bend parallel
to ring), 1025, 1104 (antisymmetric 05H5 ring breath), 1176
(C-N stretch), 1260 (alkyl C-H bend), 1375 (methyl C-H bend),
1480 (phenyl C-C stretch), 1580 (phenyl C-C stretch), 2760,
2810, 2940 (alkyl C-H stretch), 3050-3100 cm'1 (phenyl

C-H stretch): MS m/e (% RA) 56 (43, Fe), 58 (32, CH NMez),

2
121 (78, C5H5Fe), 242 (94, M+ — SPh). 351 (92, M+).' Anal.
Calcd for C19H21FeNS: C, 64.96; H, 6.03; S, 9.13. Found:
C, 65.27: H, 5.87: S, 9.14.

1-Dimethylaminomethyl-2-isopropylthioferrocenekpalladium

dichloride (17). A 125 mL Erlenmeyer flask with a stir bar
was placed in a 100° oil bath. To this was added 1.00 g
(0.00307 mol) of KZPdClu in 75 ml of H20. A solution of
0.973 g (0.00307 mol) of 99, R = i-Pr, in 45 mL of acetone
was added dr0pwise over 15 min. The mixture was heated 10
minutes and left overnight at 25°. Filtration and washes
with 20 mL of H20 and 10 mL of hexanes gave fine brown crystals
of the product. yield 0.902 g (59.6 z), mp 165—167°, IR
(Nujol, CSI) 300 (Pd-S, Pd-Cl stretch), 331 (Pd-S, Pd-Cl
stretch), 469 (Pd-N stretch), 718, 814 (ring-H bend perpen-
dicular to ring), 992 (ring-H bend parallel to ring),
1103 (antisymmetric ring breath), 1168 (C-N stretch):
MS m/e (% RA) 43 (41,‘9-Pr), 44 (55. NMeZ), 56 (21, Fe),
), 106 (2, Pd), 121 (26, C

.58 (18, CHQNMez), 65 (24, 0 Fe),

. 5H5 5H5
196 (4, M+ - C5H5Fe - PdClz). 242 (15, M+ - S-i-Pr - PdClZ),

273 (6, M+ - NMe — PdClZ), 274 (7, M+ - g-Pr - PdClz),

2

19
317 (20, M+ - PdClZ).

Attempted hydrggenation of 1y3-cyclooctadiene with 17
in benzene at 14.7 psi (Table 31 let entry). Ferrocene-
palladium complex AZ (0.040 g, 0.000081 mol), benzene
(100 mL), and Red-Al (1 mL, 0.003 mol, 3.4 M in toluene)
were added to a 250 mL Schlenk flask with stir bar on a
1 atm hydrogenation line. Less than half of the catalyst
went into solution. The system was evacuated and filled
several times with H2. Ten minutes passed during which no
H2 adsorption by the catalyst was observed. Via syringe
1.00 mL (0.00815 mol) of 1,3-cyclooctadiene was added. No
hydrogen was absorbed in the next 36 hrs.

Attempted hydrogenation of 1,5-cyclooctadiene with 17~
in methylene chloride at 14.74psi (Table 3, 2nd entry).
Ferrocene-palladium complex 91 (0.040 g, 0.000081 mol),
CHZCl2 (150 mL), Red-Al (0.50 mL, 0.0017 mol, 3.4 M,in
toluene), and 1,5-cyclooctadiene (1.00 mL, 0.00815 mol)
were added under Ar to a 250 mL Schlenk flask with stir
bar on a 1 atm hydrogenation line. The system was evacuated
and filled several times with H2. No H2 uptake was observed
in 12 hrs. The system was evacuated and filled with Ar
and 1.99 mL (0.0000811 mol) of 02 was added via syringe.

The catalyst was stirred for 12 hrs and then the system was
evacuated and flushed with H2. No H2 was absorbed in 18 hrs.

Attempted hydrogenation of 1,3-cyclooctadiene with 17

.151 toluene at 100 psi (Table 3, 3rd entry). Ferrocene-

Palladium complex 92 (0.010 g, 0.000020 mol), toluene (500 mL),

I

20
Red-Al (1.0 mL, 0.0034 mol, 3.4 M in toluene), and 1,3-
cyclooctadiene (1.00 mL, 0.00815 mol) were placed in a 1000 mL
Schlenk flask with a magnetic stirring bar under argon on
a 1 atm hydrogenation line. The system was evacuated and
filled several times with H2. No H2 uptake was observed in
20 hrs, so complex 91 (0.010 g, 0.000020 mol), Red-Al (1.0
mL, 0.0034 mol), 1,3-cyclooctadiene (1.00 mL, 0.00815 mol),
and the 1 atm reaction mixture (9.0 mL) were placed in a
100 mL pressure bottle with a pressure gauge and stir bar.
The bottle was evacuated and filled several times with
H2 to a pressure of 100 psi. No H2 uptake was seen in 3
hrs at 30°.or 12 hrs at 95°.

Hydgogenation of 1,3-cyclooctadiene with 17 in CH29l_2
at 99 psi (Table 3, 4th entry: Figure 22). Ferrocene-palladium
complex 91 (0.010 g, 0.000020 mol), methylene chloride
(10.0 mL), and 1,3-cyclooctadiene (1.00 mL, 0.00815 mol)
were added to a 100 mL pressure bottle with a pressure
gauge and stir bar. The bottle was evacuated and filled
several times with H2 to a pressure of 99 psi. Uptake began
in 30 minutes and slowed after absorption of 0.00815 mol
of H2. The initial turnover rate was 33 mol/mol Pd-hr.

This reaction was later shown to be contaminated by H20.

Hydrogenation of 1,3-cyclooctadiene with 17 in CH2_C__12
at 1019psi (Figure 23). Ferrocene-palladium complex 91
(0.010 g, 0.000020 mol), methylene chloride (9.0 mL), and
1,3-cyclooctadiene (1.00 mL, 0.00815 mol) were added to a

21

100 mL pressure bottle with a pressure gauge and stir bar.
The bottle was evacuated and filled several times with H2
to a pressure of 101 psi. No H2 uptake was observed in
27.4 hrs, so 0.0036 mL (0.00020 mol) of H20 was added and
the bottle was refilled with H2. Uptake began immediately
and slowed after absorption of 0.00815 mol of H2. The initial
turnover rate was 27 mol/mol Pd-hr.

Hydrogenation of 1,3-cyclooctadiene with 17 in acetone
at 14.7Apsi (Figure 24). Ferrocene-palladium complex 91
(0.010 g, 0.000020 mol), acetone (9.0 mL), and 1,3-cyclo-
octadiene (1.00 mL, 0.00815 mol) were added to a 100 mL
round-bottomed magnetically-stirred flask on a 1 atm hydrogena-
tion line with a mercury manometer. The system was evacuated
and filled several times with H2 to 1 atm. Uptake began
after the red solution became cloudy and brown. The turnover
rate in the linear region was 1.9 mol/M01 Pd-hr. Product
analysis at the end of reaction showed 0 % 1,3-cyclooctadiene,
100 % cyclooctene, and 0 % cyclooctane.

fiyggogenation of 1,3-cyclooctadiene with 17 in acetone
at 61 psi (Figure 25). Ferrocene-palladium complex 92
(0.010 g, 0.000020 mol), acetone (9.0 mL) and 1,3-cycloocta-
diene (1.00 mL, 0.00815 mol) were added to a 100 mL pressure
bottle with a pressure gauge and stir bar. The bottle was
evacuated and filled several times with H2 to a pressure
of 61 psi. Uptake began immediately and slowed after absorp-

tion of 0.0055 mol of H2. The initial turnover rate was

22

422 mol/M01 Pd-hr. Product analysis at the end of reaction
showed 6.5 % 1,3-cyclooctadiene, 72.4 % cyclooctene, and
‘ 21.1 % cyclooctane.

Isomerization-hydrogenation of 1,5-cyclooctadiene with
17 (Figure 27). Ferrocene-palladium complex AZ (0.010 g,
0.000020 mol), acetone (9.5 mL), and 1,5-cyclooctadiene
(0.50 mL, 0.0041 mol) were added to a 100 mL pressure bottle
with a pressure gauge and stir bar. The bottle was evacuated
and filled several times with H2 to a pressure of 60 psi.
Uptake began immediately and ceased after absorption of
0.0025 mol of H2. The initial turnover rate was 9.0 mol/M01 Pd-hr.
Product analysis at the end of reaction showed 17.0 %
1,5-cyclooctadiene, 10.2 % 1,4-cyclooctadiene, 10.0 %
1,3-cyclooctadiene, 52.4 % cyclooctene, and 10.4 % cyclo-

octane.

RESULTS AND DISCUSSION
Ferrocenyl Sulfides 99

Several ferrocenyl tertiary amine thioethers 99, R =
Me, Et, i-Pr, i-Bu, l-pentyl, and Ph, have been synthesized
for the first time (Figure 10), via reaction of lithio-
ferrocene amine 9 with the apprOpriate disulfide. These
compounds are yellow solids which are soluble in polar
solvents such as methylene chloride, acetone, and chloroform,
and insoluble in nonpolar solvents such as hexane.
Dimethylaminomethylferrocene was lithiated using the
procedure of Marr (Figure 1).8 A hexane solution of g-BuLi
was used. The g-BuLi was not titrated, although a procedure
for this is available.36 Instead, good results were obtained
by use of 1.1 nominal equivalents of g-BuLi. Tetramethyl-
ethylenediamine is not necessary or desirable here. It
is used in the lithiation of benzene and ferrocene.37
Rausch's group has isolated ferrocenyllithium38 in the
solid state. Aminoferrocenyllithium 9 was not isolated here
but rather was prepared fresh for each reaction.

Figure 11 shows the 250 MHz 1

H NMR of 99, R = Et.
The most striking feature of this spectrum is the large

shift (0.39 ppm) between the 2 diastereot0pic protons of
23

24

Li
F ""02

8853 > FI::M92
.1_6.

@A

IN

R: Me, Std-Pr, l-Bu,
l-pentyl, Ph

Figure 10. Synthesis of new ferrocenyl thioethers 99.

25

.pm 1 x .mm mo msz m
o p u a
a

 

 

ems 6mm .HH oasmaa

 

a a 13%

 

 

 

26

the aminomethylene group in the 0 3-4 region. By contrast,
the methylene protons of the ethylthio group at 0 2.64,
although diastereot0pic, appear overlapped. The large shift
between aminomethylene protons has also been exhibited in

O Inver-

1-dimethylaminomethyl-Z-diphenylphosphinoferrocene.3
sion of the pyramidal N of 99, R = Et, is faster than the
NMR time scale at this temperature, so the nitrogen methyls
appear as a singlet at 6 2.19. Assignments of the substi-
tuted ring protons H3, H4, and H5 have not been made since

1H NMR studies31-33 have shown that a single

a number of
substituent may deshield or shield position 2 and-5, and

may deshield or shield positions 3 and 4, in any combination
relative to ferrocene. Finally, Rosenblum and Woodward34

have shown that there is free rotation about the Fe-Cp

ring axis in ferrocenes. The barrier to rotation in ferrocene
is only about one third that of the 2 methyls in ethane.35
Thus, the unsubstituted CSHS ring appears as a singlet at

0 4.09.

The 250 MHz 1

H NMR of 99, R = i-pentyl is given in
Figure 12. Several points can be made about this spectrum.
The iSOpentyl methyls appear as 2 doublets due to their
diastereot0pic relationship to each other. This is remark-
able in that they are 5 atoms removed from the chiral plane39
of the molecule. The peaks in the 6 2.5-2.8 region are due
to the SCH2 protons. Their splitting pattern is given in

diagrammatic form in Figure 13. Two singlets are split into

27

43189;. n a now .3 msz : or: 6mm .3 Resume

H

O.— O.N 6.0 0* e

uu‘dd‘d—ddqddddud_qdd44

 

D

as

:

 

 

 

 

 

 

 

 

 

 

28

 

 

 

 

 

 

 

 

 

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2.52'

2.60

2.68

6 2.78

2 protons in 16, R =

i-pentyl.

Figure 13. Splitting pattern of SCH

29

doublets by a vicinal coupling constant of 8 Hz (t0p), into
doublets again by a vicinal constant of 7 Hz (middle),
and into more doublets by a large geminal coupling constant
of 12 Hz (bottom). The total number of peaks should be
2(23) = 16. The actual number is 15 due to overlap of the
central peaks.

Typical broadband and gated decoupled 13C NMR spectra
(those of 99, R = Et) are presented in Figures 14 and 15.
All of the peaks in Figure 14 are singlets except those at
77.1 ppm downfield of TMS. This is a triplet due to the CDCl3
solvent, with the nuclear spin of deuterium = 1. The com-
pound in Figure 14 has a C1 symmetry due to planar chirality
but contains no diastereot0pic carbons. Suitably substituted
derivatives do contain diastereot0pic carbons, however,
which absorb at different chemical shifts (see, for example,
Figure 50 in the Appendix). Assignments in Figure 14 were
made with the help of the gated decoupled spectrum in Figure
15. A gated decoupled spectrum utilizes a pulse sequence
which yields accurate, reproducible coupling constants
without sacrifice of Nuclear Overhauser Enhancement; the
result is a coupled spectrum with intense peaks.l+°’l+1
Methyls appear as quartets in Figure 15, methylenes as
triplets, methines as doublets, and substituted ring carbons
as singlets. The four rightmost peaks in Figure 14 are thus
assigned, right to left, to Et CH3, Et CH2, NMeZ, and NCHZ.

.As in the proton spectrum, the NMe2 carbons are equivalent

30

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2 ca 8 3 S 8 2. 8 8 sea
a1-.1.--1-_----..---l---..--1.l-.1-.----D--1-.--.-_----.-114411--.-.--_----.-.--a-

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<9

 

 

31

2.

 

 

 

 

 

N9

.8 u m. .fl .8 msz o? coaasoooc cocoa .3 933m

¢ 8 En.—

 

 

 

 

 

 

32

due to fast inversion and appear as singlets.

The peaks at 80.5 and 87.0 ppm are due to substituted
ring carbons C1 and C2 respectively. These assignments
are firm and are based on the following observations:
1) the gated decoupled spectrum reveals the 2 peaks as
singlets (substituted carbons), 2) these peaks are the
weakest in the spectrum due to the long spin-lattice relax-

42 3) the more deshielded

ation time of substituted carbons,
carbon is directly attached to a heteroatom, and 4) the up-
field peak in Figure 15 is split by long-range coupling

from CH2 and is therefore broader and less intense than the
downfield peak. The 2 peaks in Figure 14 are just barely
above the baseline: their size can be increased by use of

a longer relaxation delay (at expense of the acquisition time).
Figure 14 was obtained with a relaxation delay of 1.0 sec.

The unsubstituted ring is easily assigned to the intense
peak at 69.8 ppm, but carbons 3, 4, and 5 are.more difficult.
For this purpose the data in Figure 16 on 99, R = Et, and
9 are presented. Assignments in 9 are unequivocal and have
been established by selective spin-spin proton decoupling.“3
Assignments of C3, °4’ and 05 in 99, R = Et, are tentative.

The ethylthio group exerts an inductive effect on C2
in 99, R = Et, causing its shift to be downfield of that of
the corresponding carbon in 9 (87.01> 70.0). The other
orderings are easily explained using the inductive H-polar-

ization c0ncept.1°2’1°3 The Cz-S dipole (positive at C2,

negative at S) causes H-polarization of the C4-C3 and

33

67.4 87-0

3
- 2
4stt 70.6Q‘set
5 7 _ 80.5
T ""92 37 Fe NMe2

1_6,R=Et

 

Figure 16. Substituted ring 130 shifts in 99, R = Et, and 9.

34

C5-C1 bonds (positive at C4 and C5, negative at C3 and C1).
Hence the relative chemical shifts of 99, R = Et, and 9
(C1 in 99, R = Et, 80.5 < 83.9; C3, 67.4 < 67.8; C4, 70.6>'
67.8: 05, 73.7 > 70.0).

As stated above, these assignments for C3, C4, and
C5 must be viewed as tentative at this time. In addition,
it is incorrect to extrapolate 13C data to 1H data. In

some cases the chemical shift ordering is the same, but in

ferrocenylaldehyde, for example, the carbon order is C3>C2,’+4

whereas the proton order is H2>H3.31'33
The 2 most important peaks in the infrared spectra

of derivatives 99 are presented in Table 1. These compounds

46

obey the "1000, 1100 rule" which states that ferrocenes

containing an unsubstituted ring will have 2 peaks, one near

1

1000 cm“ due to C-H_bend parallel to the ring, and another

near 1100 cm'1 due to an antisymmetric ring-breath. The

remainder of the IR assignments were made by using the avail-

45-48

able literature; some of these peaks appear in the

infrared spectrum of 99, R = 9-Pr, given in Figure 17.

1

Absorptions near 890 cm- would be indicative of 1,2

(as Opposed to 1,3) disubstitution, but these are too weak
to be diagnostic. The 1,2/1,3 analysis using peaks in this
region is most successful with acetyl, alkyls, and aryls

48-51

as substituents but is not as useful with 2-substituted

dimethylaminomethylferrocenes.52 The spectra are those
of tertiary amines and thus lack peaks in the 3400 cm-1

region associated with N-H stretching in primary and secondary

35

Table 1. Infrared modes of the unsubstituted ring of com-

 

 

poundsl99.
R 9, cm'1
Me 996, 1102
Et 998, 1103
i-Pr 9989 1103
i-Bu 993! 1103
i-pentyl 995. 1103
Ph 1000, 1104

 

1

amines. Sulfides have a C-S stretch near 660 cm- which

is usually too weak to be of use; this is the case with
compounds 99.

The mass spectrum of 99, R = 9—Pr, is given in Figure
18 and is typical of the series. It shows peaks of high
relative abundance due to 9-Pr, Fe, CHZNMeZ, CSHSFe' M+ -
S-9-Pr, and a molecular ion which is also the parent peak.

In addition to these fragments, peaks consistent with the

less abundant isotOpes SuFe, 57Fe, and 3°S were present.

36

5me u m .Ifl mo 85.30QO consumed. 23 mo 203.8% < .2 ouswam

 

 

 

 

 

 

 

 

use
com com . coop com.
_ _ _ q _ _ — _
«o—zz
TNUV
1 _ _ a a _ _
e. 3 a. c. o a ad

E:

37

.hmnw u m .WM we gunpommm mmms .mH mpswflm

mm w 2.4 5mg,» 2...”... a 7m 3.4 ”u can am"... .34. 2.... q. :

 

 

 

k—Pbb-hphh-OEFL_DbP_ aban—rbrb—rPFLb-bb_nDLPbL”Lbhhynbm-I—mhLb~bEkFl~Ithh.b.P-IhflPPP‘Pfiob-h—l—P»bmh*h. —tbLF
...n ..|. 2.... I ,... _ — ‘u . ...I. « — 4 I‘d“ .u. o — —
F9“: -..‘ .l .2. . fl , Hv—flwv 1}... ‘ h a unit...“ .. n»... — .4

l

L Y
. .0‘
alipsl.

I; I

1 urn. I aim,

 

 

L 4
I

Em: _ g .1 m. .9”:
mm mam me; 53 a: . mg 92 mm mm. a... mu:
_ . ‘

~rr<n .kmq-$.J.“—muu1m mum
=_ ma 9%

 

 

 

 

 

 

 

 

v.3: L [9.9:

38
Palladium Complex l1

Palladium complex 12 was made by using the same pro-
cedure as for g-methylthioaniline.53 An acetone solution of
the ferrocene was added dr0pwise to a hot aqueous solution
of potassium tetrachloropalladate (Figure 19). The acetone
boiled off and the product precipitated immediately as fine
brown crystals. The product l2 did not have a molecular ion
in its mass spectrum. This was expected based on previous
findings from this laboratory.19 The mass spectrum had
fragments consistent with those of the starting material
gg, R = i—Pr. That the product was different from the
starting material was established based on clearly defined
melting points: lg, R = i—Pr; 82-830; 12, 165-1670. S-
Dealkylation was not observed here as with similar complexes.5u
The elemental analysis of £1 supports its structure rather
than that of various dimers similar to ;§ (Figure 20), for
example, with Pd-N chelation only. It is not likely that
a Pd-S bond is not formed when the amine thioether reacts

2+

with KdeClu. Low spin d8 ions, e.g. Pd , form strong 6

bonds with soft ligands such as thioethers and also dw-dw

8-<

K PdCl
F0 NMCZ 2 4

acetone ' Nie‘Me
© H20

L6, R: i-PI‘ , l2

 

V

Figure 19. Synthesis of amine-thioether-palladium complex 12.

39

CH3 Cl $H3

l I
©CH2-N—Pd —T—CH2—@
I I

© ©

Figure 20. Dimer l§.59

bonds by donation of electron density to 8.57 The w-acceptor
capacity of thioethers, although somewhat lower than that of

58'60”61 is still substantial.

3° phosphines or arsines,
Complex l1 gave an elemental analysis with carbon outside
the t O.ht% range. ‘This is consistent with other results
obtained recently on similar amine-thioether-palladium and
amine-selenoether-palladium complexes.55

Chromatography of 11 on silica gel left a gray deposit
distributed throughout the column. The complex did not give
a simple 1H NMR spectrum. Deposition of a black precipitate
began immediately on dissolution in chlorofonm-d.

The metal-S, metal-N, and metal-Cl stretching modes
of several complexes including 12 are given in Table 2.
Metal-S bands are often weak and occur in a region similar
to metal-Cl bands. Consequently the absorptions at 300 and

331 cm"1

in $7. have been assigned to Pd-S and/or Pd-Cl
stretches. Metal-N stretches occur at a higher frequency

so the 469 cm'1 peak is assigned to Pd-N. These assignments
are tentative since in complex molecules of low symmetry

more than one fundamental mode often contributes to a given

40

Table 2. Metal-S, metal-N, and metal-Cl stretching modes
of several complexes.

 

1 Stretching

 

Compound 3, cm" mode Ref.
ll 300 Pd-S, Pd-Cl This work
331 Pd-S. Pd-Cl
#69 Pd-N
Et 273 Pd-Cl 56
g 316 Pd-Cl
s" \PdCl 349 Pd'S
\_S/ 2 396 Pd-S
1
Et
thioether- 280-u00 M-S 57
metal
complexes
unidentate 370-500 M-N 57
amine-
metal

complexes

 

41
peak.58
The reader is directed to reference 62 for more infor-

mation on ferrocene-palladium complexes.

42

Hydrogenation and Isomerization Using

Palladium Complex $2

Hydrogenation by homogeneous catalysts is a well-deveIOped
discipline.63 Of the many known complexes, those of Group
VIII metals with amines and sulfides have been used with
varying degrees of success. In 1967 PtClZ(SPh2)2 was found
to be selective for the hydrogenation of dienes to monoenes

in the presence of SnClZ.64

Treatment of PdCl2 or'NaZPdCl4
with tertiary amines resulted in an active selective catalyst.65
The same was true of PdCl2 when treated with 2,2'-bipyridine

and NaBHu.66 Palladium chloride and thioethers gave complexes
which, upon reduction by diisobutylaluminum hydride, were
selective catalysts.67 The thioether-rhodium complex
RhClB(SEt2)3 hydrogenates maleic acid, provided maleic acid
68-71

is present in excess. Finally, RuClB(PhS-n_-Pr)3 has

been synthesized and is inactive in catalytic hydrogenation.72
In view of the selective hydrogenation activity of amine-

palladium and thioether-palladium complexes when treated with

hydride reducing agents66’67 (Figure 21), a number of similar

procedures were tried by using ferrocene-palladium complex

$2 and NaH2A1(OCH2CHZOCH3)2 in various solvents at various

temperatures and pressures (Table 3). All of the hydrogena-

tions with reducing agent present failed. Pretreatment of

Pd complexes with 02 has given increased rates of hydrogena-

tion.73’7u Treatment with 02 here (Table 3, 2nd entry)

did not. When the reducing agent was left out in a blank

43

/
2 2) (i-Bu)2A1H (:3

3) H2,(:)

Figure 21. Selective hydrogenation using (n-Bu)28.

PdCl

 

Table 3. Selective hydrogenation: initial attempts. Red-Al
NaH2A1(OCHZCHZOCH3)2. COD = cyclooctadiene..

 

Conditions , Result

 

11, PhH, Red-Al, 14.7 psi, 25°, 1,3-COD No H2 uptake
12, CHZClZ’ Red-Al, 14.7 psi, 25°, 1,5-COD, No H2 uptake

1 . toluene, Red-Al, 100 psi, 95°. 1,3—COD No H uptake
2

11, CH2012, 99 psi, 25°, 1,3-COD, Figure 22 One double
bond hydro-
genated

 

an

experiment, however, hydrogen uptake was observed (Table 3,
4th entry; Figure 22). This experiment was repeated with
carefully distilled CHZCl2 (Figure 23). The horizontal

part of Figure 23 shows that before H20 was added the system
was inactive. Therefore the solvent in the initial success-
ful experiment (Figure 22) was contaminated by water. After
10 mol of HZO/mol of 11 was added in Figure 23, a black
precipitate appeared and 1,3-cyclooctadiene was hydrogenated
to cyclooctene, but only at a slow rate. The complex also
forms an active heterogeneous system in acetone at 1 atm
(Figure 2b). The original red solution became cloudy after
36 hrs and H2 uptake began. The selectivity was excellent
(0 % diene, 100 % monoene, and O % alkane) but the rate was
again low (1.9 mol/mol Pd°hr).

Hydrogenation of 1,3-cyclooctadiene became conveniently
fast in acetone at 61 psi (Figure 25). This is a homogeneous
system with no H20 or reducing agents and reaction proceeds
at a useful rate (#22 mol/mol Pd-hr). As time passed the
red solution became brown but remained homogeneous. Most
of the product at the end of reaction was cyclooctene, but
some cyclooctane was present.

The compounds present after each of the above reactions
were 1,3-cyclooctadiene, cyclooctene, and cyclooctane.

The (diene + monoene):alkane ratio was determined by gas
chromatography, the two peaks being separated typically

by more than 1.1 minutes. The dienezmonoene ratio was

45

 

 

 

 

 

 

100 P ' . FC-Pd, CH2C12 . 1 .B'CODO H2
turnover rate . 33 ”01
Inn Hrhr
+
——1»————
1 I L l l 1

hrs
Figure 22. Selective hydrogenation of 1,3-cyclooctadiene
in CHZClZ at 25°C using Fc-Pd (11) (Table 3,

4th entry).

46

   
 
    

100 10 mol H20 added

psi

80— Fc-Pd, c3202,
1.3-COD, H2

 

turnover rate - 27
deFM-hr

W3-

 

60 1 1 1 l l l
O 12 24 36 48 60 72

I":
Figure 23. Selective hydrogenation of 1,3-cyclooctadiene
in CHZClZ at 24°C using Fc-Pd (l1).

 

47

 

 

 

 

.032 —
Fc-Pd, acetone, 1,3-C00,.H2, 1 atm
‘ mol
. turnover rate '_ 1.9 m-
.03
moles
H2
.028 -
.026 *—
1 L . 1

“0240 100 zoo 300 400

hrs
Figure 24. Selective hydrogenation of 1,3-cyclooctadiene in
acetone at 28°C and 14.7 psi using Fc-Pd (11).

48

.ANMV vmrom mcflms awn H was m
ecovoom aw mcoflcMPoooaohoum.H mo Coapmsowonwzn m>wmwmawm .mm onswam

 

 

 

VN ON .5:
or up w
a _ _ a .4 ,fl _ d a _ w a MW on
[0*
3..
[Om
2.2 .2. .
Hal NNV I much LO>OE$H
N: .aeu-n.2 .oeeeee. .ea-ud
.LOQ

 

49

1H NMR, as illustrated in Figure 26. The

determined by
central Olefinic protons of the diene appear near 6 5.8,

and the outer protons near 5.6. The Olefinic protons of the
monoene are near 6 5.6. The ratio of monoene to diene is

therefore given by

monoene _ A5.6 - A5.8
diene - A5.8

 

where A = area. In the case of Figure 26, the ratio was

monoene _ 91.8
diene _ 8.2

which with the GC data gave diene:monoene:alkane = 6.5 :
72.4 : 21.1.
Complex 12 isomerized and hydrogenated 1,5-cyclooctadiene
(Figure 27) according to the scheme:
1 ,5-COD—> 1 ,4-COD 9 1 ,3-COD-) cyclooctane
The isomerizations were slow compared to the hydrogenation,

as evidenced by the relative rates of Figures 25 and 27:

c-
N

Rat625 ='_2_ = 47

Rate27 9.

O

The isomerization-hydrogenation is a homogeneous reaction.
In order to assess its effectiveness as a selective
hydrogenation catalyst, complex 12 is compared to previous
homogeneous Pd catalysts in Table 4. The initial rates
have been normalized as much as possible by dividing by the
number of moles of Pd and the pressure. The catalyst in
this work and that of the 2nd entry (PdCl2 complexed by

undecylamine, reduced by diisobutylaluminum hydride, and

.Asopponv mcovoooaoho cam .Amauuwsv mm mhsmwm eo

 

 

 

caspxfla soapoMou .Agopv osmfiUMPoooHozoum.H mo msz ma am: omm mo sowwmu oHsHmoHo .om on:Mwm
ad ad Eu 9» e
_ _ J _

 

 

 

 

a j}

 

5o

 

 

51

 

 

 

 

Isanerization-hydrogenation:

60- Fc-Pd, acetone, 1.5-COD, H2
turnover rite - 9.0 mol Pd-hr

58-

psi

56+

54 .—

52 " Q.—

l L 1 L 1 l 1 1 4 I
50 0 40 so 120 160
In:

Figure 27. Isomerization-hydrogenation of 1,5-cyclooctadiene
in acetone at 25° and 61 psi using Fc-Pd (£1).

52

 

ozoaumxon
ms --- ususaop +~pa we -oaesous.fi HHoo.o
mo nu: msmsaop cum mm mampmomfl mm.mnme.m
so 0mm usesaou sea mm moonm.H aa.m
xuos
mane III oCOPmom +Ncm mm GOOIM.H No.0

 

.mem e>apaee< ese>aom Asses 00 .e messeupsm sud.ms.ea Hos\aos
mess asaeasH

 

.zppso pmuam one 2H cow: was Nd xoamsoo .mmdo op omno Sosa zgm> mccmwfiq
.osmavmpoooaozo u 900 .moCooCoa op mocofiu mo cowpmsoMouuhs o>flpomaom mzomComoEo: .3 mamas

53

hydrolyzed)67 have rates of the same order of magnitude
with 1,3-cyclooctadiene. The 3rd (catalyst = PdCl2 complexed

by trialkylamines)65 and 4th (catalyst = (thPCHZPPh2)PdC12)73
entries are not as comparable to this work as the 2nd entry.
As has been pointed out,73 rates and selectivities are affected
most by substrates, and to a smaller extent by ligands,
oxidation state of the metal, and solvents. iWith this in
mind, the catalyst in this work appears to be at least as
fast as the amine catalyst in entry 3. and 3 orders of magni-
tude faster than the chelating bisphosphine in entry 4.

Figure 28 presents a mechanistic scheme for the homo-
geneous selective hydrogenation of 1,3-cyclooctadiene using
11, This scheme accounts for 2 observations: 1) that the hydro-
genation proceeds in acetone but not methylene chloride, and
2) that 1.3- cyclooctadiene is hydrogenated much faster than
cyclooctene.

Complex 11 dissolves completely in dry CHZClZ’ forming
a red solution. This solution is, however, catalytically
inactive since H2 is unable to oxidatively add to Pd. When
12 is dissolved in acetone, acetone replaces the amine.

That the N-Pd bond and not the S-Pd bond breaks is supported
by the mechanism of the Grignard cross-coupling reaction of
the PdCl2 complex of a similar ferrocenyl tertiary amine
thioether,55 in which N-Pd bond breakage is a necessary
prerequisite to N-Mg bond formation. Catalysts for hydro-

genation, dimerization, and carbonylation tend to be low

| c:
Pd/

I \H
c:

23.

 

Figure 28. Possible mechanisms of the homogeneous selective
hydrogenation of 1,3-cyclooctadiene using complex
1]. Fc- = 2-dimethylaminomethylferrocenyl.

55
valent complexes stabilized by soft, polarizable ligands
such as thioethers.63 Also, the transition metal hydrides
formed subsequently in Figure 28 can exist only if they are

stabilized by a n acceptor.64

Sulfur is a n acceptor and
nitrogen is not.

Hydrogen is able to add to 12 in contrast to 12. The
hydrogenation therefore proceeds in acetone. Complexation l
of the diene and olefin insertion give 6 complexg21..'Atithis 1
point rearrangement could give 22 or complexation to the t
second double bond could give 22. The cycle 12, 22, 21,
22, 12 is the less probable cycle. The energy requirements
for each step would be similar whether 1 or 2 double bonds
were present, so the monoene would be hydrogenated as easily
as the diene. The other cycle (22, 21, 22, 22) is more likely.
It contains 2 steps (21922 and the subsequent step) which
are impossible in the hydrogenation of the monoene. If
either of these steps is rate-determining it could explain
why the diene is hydrogenated faster. The rate-determining
step in this type of reaction may involve a hydrido-metal-
olefin complex such as 22.64

It should be pointed out that the hydrogenation of
cyclooctene could proceed by a route analagous to the 1st
cycle (1 , 22, 21, 22, 12), which is similar to an accepted
route involving Wilkinson's catalyst.75 Also, the possibil-

76

ity of binuclear catalysis in the diene hydrogenation

has not been ruled out.

56
One explanation of the heterogeneous reactions of Figures
22 and 23 is presented in Figure 29. The quaternary ammonium
salt may precipitate and act as the catalyst, or a Pde
hydroxide species dissociated from the thioether may be the

precipitate. Hydrolysis as in Figure 29 has been previously
67

observed.

 

Figure 29. Hydrolysis of complex 12 prior to heterogeneous
selective hydrogenation.

PART II. BIS(n 6-4-CI-[L.OROANISOLE)CHROMIUM

IN TRODUC TI ON

There are a number of useful methods available for the

synthesis of n-bis(arene)chromium complexes, including the

Grignard synthesis,u5 the Fischer-Hafner aluminum synthesis,77

78-80

and Fischer-Hafner variations. These methods cannot . a

 

be used, however, when the arene rings contain substituents h
with lone pairs of electrons. Some of the Grignard reagents
are impossible to make, and in the Fischer-Hafner-type
reactions, either the substituent withdraws too much electron
density from the ring, or the heteroatoms complex with
the Lewis acid present in each case. Alkylarenes are
dealkylated and isomerized under Fischer-Hafner conditions.
For alkylated arenes and arenes with heteroatom substituents,
chromium vapor-ligand cocondensation must be employed.
In a cocondensation reactional'au (illustrated for

bis(benzene)chromium in Figure 30) metal vapor is produced

 

>: Cr

. .
@ + Cr atoms 196 c

Figure 30. Synthesis of bis(né-benzene)chromium.

58

59 .

in a high vacuum. Chromium is easily vaporized and a resistive-
ly heated tungsten filament or boat is generally used,
although electron gun setups are available. An organic
compound (the ligand) is vaporized at the same time by slow
admission through an addition funnel (liquids) or resistive
heating (solids). The metal and ligand vapors are cocondensed
on the flask walls, which are kept near ~196°C by liquid
nitrogen. The flask contents are subsequently warmed and
the products removed.

Many'bis(né-arene)chromium derivatives have been made
by metal vapor-ligand cocondensation. Some of these are
presented in Figure 31 and include 1,1'-disubstituted com-

86 86

pounds Q, R = H.85 Me, Et, CEO-Ph,87 F, Cl, OMe, COZMe,

88

NMeZ, PPh2,89 and SiMe 9O dodecamethyl substituted 22,86

3.
bis(n6-naphthalene)chromium (2_§),91 and bis(n6-1,4-difluoro-
benzene)chromium (22).86 Elschenbroich and Heck have
discovered that the reaction of biphenyl with chromium atoms
gives monometallated compound 22, dimetallated compound 22,
and a.small amount of dimetallated compound 22 with side-
by-side chromium atoms (Figure 32).92 The unusual [2.2]para-
cyc10phane derivatives 21 and 22 (Figure 33) have also been
made.93

A series of fluorinated bis(arene)chromium compounds
22 (and the 2 and g_isomers) has been made (Figure 34) and

studied by 19F NMR.9u The results showed that the electron-

withdrawing effect of the Or is similar to the effect of

60

R _
R = H, Me, Et, CiC-Ph, F, Cl, OMe, CO Me,

Cr 2

@n NMeZ, PPh2, SiMe3

a

fit
@2—

£5.

 

Figure 31. Bis(n6-arene)chromium compounds made by metal
vapor-ligand cocondensation.

61

Ph-Ph + Cr atoms -—€> Cr

IN
+ (I)

Q-é}
.-@> #

Figure 32. Reaction of biphenyl with Cr atoms.

62

Cr atoms

u

@

(‘9

Figure 33. Reaction of [2.23paracy010phane with Cr atoms.

63

R.F + Cr atoms ———> 8":

Figure 34. Fluorinated bis(arene)chromium derivatives.

64
4 fluorines together.
Other compounds besides benzene derivatives have been
condensed with chromium vapor. These include cyclOpenta-

86 2,6-dimethyl-

diene, giving chromocene ( 4, Figure 35),
pyridine, giving pyridine sandwich compound 22,95 and PFB'
giving complex 22.85

This portion of the thesis describes the synthesis

and characterization of a new bis(né-arene)chromium com- I

pound, the metal vapor system used, and attempts to make

 

other bis(arene)chromium species.

N<::>>

<3?
e ~22 .

Figure 35. Chromium complexes from metal vapor-ligand
cocondensation using non-benzene ligands.

EXPERIMENTAL

Proton NMR's were obtained by use of a Bruker WM 250
spectrometer in benzene-d6 or chloroform-d, with TMS as
internal standard. Infrared spectra were recorded by use
of a Perkin-Elmer 457 machine. Mass spectra were obtained
by means of a Finnigan 4021 instrument with INCOS data
system. Elemental analyses were performed by Spang Micro:
analytical Laboratory, Eagle Harbor, Michigan.

Bis(n6-4-chloroanisole)chromium (37). Chromium chips
(1.8 g, 0.035 mol) were placed in a B12B.O4OW conical tung-
96

sten basket connected to the electrodes. The flask was
evacuated and surrounded by liquid nitrogen. After the
chromium was degassed at a low voltage setting, metal vapor
was produced at 40 amps, 7 V AC. Over a period of 3 hrs,

50 mL (0.41 mol) of 4-chloroanisole was added through an
addition funnel equipped with high vacuum stopcocks. After
reaction, the liquid N2 was removed, excess arene was pumped
away, and the electrodes were replaced with a cold finger
under a strong flow of Ar. The product was sublimed twice
under high vacuum giving 22 as brown crystals: yield 0.31 g

(6.0 % based on Or evaporated): mp 47-48 0C: 1

H NMR (benzene-d6,
TMS) 6 3.14 (s, 6H, CH3). 4.38 (d, 4H, J = 5.2 Hz, ring H),

4.63 (d, 4H, J = 5.2 Hz, ring H): IR (Nujol, CsI plates)

462 (asymmetric Cr-ring stretch or ring tilt), 615, 792,

65

66

989, 1025, 1060 (C-H deformation), 1173 (c-c stretch), 1225
(c-o stretch), 1515 om‘1, MS m/e (% RA) 52 (29, Cr), 99,
101 (60, 20, 5-chloro-1,3-cyclopentadienyl cation), 107
(4, CéHuOCHB), 127, 129 (55, 18, ClC6H40). 142, 144 (100,

+
32. 0106H4OCH3)' 194, 196 (5, 2, M - ClC6HuOCH3), 336, 338

L),

(2, 1, M+): UV (1.9 x 10‘ M in cyclohexane) A 317 nm.

max

Anal. Calcd for Cl4H14ClZCrO : C, 49.87; H, 4.19: Cl, 21.03.

2
Found: C, 49.68; H, 4.26; Cl, 20.94.

Bis(q6-toluene)chromium (24, R = Me). Freshly cut
chromium chips (1 g, 0.02 mol) were placed in a B12B.06OW
conical tungsten basket connected to the electrodes. The’
flask was evacuated and placed in a Dewar flask of liquid
nitrogen. Degassing was done at 2.1 V, 24 A, and metal vapor
produced at 9 V, 64 A for 2.0 hrs, during which time 41 mL
(0.39 mol) of toluene was added. The product was sublimed
as usual giving 1.7 g (37 % based on Or evaporated) of 22,

R = Me, with a proton NMR spectrum identical to that previously
reported.86

Attempted synthesis of bis(n6-1,3,5-trimethylbenzene)-
chromium (38). An SZOA-.OO5W tungsten boat96 was fixed to
the electrodes using set screws. Chromium chips (0.511 g,
0.00983 mol) were placed in the boat. The system was evacuated
and the flask was cooled with liquid nitrogen. Exiting
cooling water became hot when the potential was 8 V.

Through the addition funnel 15 mL (0.11 mol) of 1,3,5-tri-

methylbenzene was added over a 3 hr period. When the liquid

 

 

an.

67
nitrogen was removed it was apparent that no metal had
evaporated.

Attempted synthesis of bis(q6-4-bromoanisole)chromium (39).

 

Chromium chips (1.2 g, 0.023 mol) were placed in a B12B.O4OW
conical tungsten basket connected to the electrodes. The
flask was evacuated and surrounded by liquid N2. The chromium
was degassed and metal vapor was produced at 40 amps. Over
a period of 3 hrs, 30 mL (0.24 mol) of 4-bromoanisole
was added. Afterwards the liquid N2 was removed, excess
arene was pumped away, and the electrodes were replaced with
a cold finger. Nothing appeared on the cold finger after
sublimation for 36 hrs at 250 and 12 hrs at 100°.

Attempted synthesis of bis(n6-4-chloronitrobenzene)-
chromium (40). Method A. Chromium chips (1.76 g, 0.0338

 

mol) were placed in a B12B.O4OW tungsten basket. The rest
of the procedure was similar to that for 22, except that

the solid ligand (mp 83°) was kept in the liquid state with
heating tape. The ligand clogged the inlet tube early in
the addition. No product was obtained on sublimation of the
reaction mixture.

Attempted synthesis of bis(n6-4-chloronitrobenzene):
chrmmium(40). Method B. In this case 1.7 g (0.033 mol)
of chromium chips, and 20.0 g (0.127 mol) of 4-chloronitro-
benzene in 32 mL of diethylene glycol dimethyl ether were
used. The ligand inlet tube did not clog, but evaporation

of the solvent left the ligand at the bottom of the tube

68

in a ball. Chromium continued to evaporate for 30 minutes
after addition of the ligand, during which time the ball of
ligand disappeared. Removal of solvent and excess arene
with the vacuum pump gave a black tar which did not sublime.

Attempted synthesis of bis(q6-4-chloronitrobenzene)-
chromium (40). Method C. Chromium chips (1.5 g, 0.029 mol)
were placed in a B12B.04OW tungsten basket. A solution of
20.0 g (0.127 mol) of 4-chloronitrobenzene in 32 mL of
diethylene glycol dimethyl ether was placed in the bottom
of the flask with a stirring bar and the flask was immersed
in Dry Ice/is0pr0pyl alcohol. Chromium vapor was condensed
into the stirred solution for 4 hours. The rate of Cr evapor-
ation was slow. No product was obtained on workup.

Attempted synthesis of bis(n6-4-chloronitrobenzene)-
chromium (40). Method D. A stainless steel crucible was
suspended from the ligand inlet tube. In it was placed
18.5 g (0.117 mol) of 4-chloronitrobenzene. Chromium was
evaporated from a B12B.O40W basket. The ligand melted and
evaporated quickly 35 minutes after the chromium began‘to
vaporize. Chromium was evaporated for 10 more minutes then
stOpped. No product was obtained on sublimation. Brief
exposure of the reaction mixture to air did not result in
formation of a cationic complex.

Attempted synthesis of bis(n6-4-methoxyphenylmagnesium
chloride)chromium (41). In a 3-necked 200 mL round-bottomed

 

flask under Ar with a condenser, addition funnel, and stirring

69

bar was placed 0.032 g (13 X 10'1“t

mol) of Mg turnings, Com-
plex 22 (0.204 g, 6.07 X 10'“ mol) in 100 mL of ether was
placed in the addition funnel. The complex was added slow-
ly to the magnesium. No reaction occurred at 250 or with
gentle heat.' Addition of Mg activated by reaction with
bromobenzene caused no change. A change of solvent to

THF, then to dimethoxyethane, did not produce any visible

reaction.

RESULTS AND DISCUSSION

A stationary metal vapor system including water-cooled
electrodes and a Pyrex flask was designed and built for this
work. To assess the effectiveness of this system in metal
vapor-ligand cocondensation, known complex bis(né-toluene)-
chromium (22, R = Me, Figure 31) was made. The electrodes
were modified to accept tungsten boats in an attempt to
circumvent the problem of chromium chips falling through the
basket. The synthesis of bis(n6-1,3,5-trimethylbenzene)-
chromium (22, Figure 36) using a boat was then tried.

The new complex bis(n6-4-chloroanisole)chromium (22, Figure
37) was successfully made using a tungsten basket and char-

1H NMR, IR, MS, UV, and elemental analysis.

acterized by
Efforts to make 22,(the bromo analog of 22) and nitro deriva-
tive 22 were unsuccessful. Chloro compound 22 did not form
Grignard reagent 21 at 250 or 350 in ether, THF, or dimethoxy-
ethane.

The electrodes designed for this work are shown in
Figure 38. The flask with electrodes and addition funnel
in place is shown in Figure 39. The system consists of
electrodes, a rubber O-ring, and a Pyrex flask. The electrodes
are of stainless steel throughout except the c0pper blocks,
plastic insulator, and solder. They are made from a round
3/8 inch plate through which three 1/4 inch tubes are inserted.
Two of the tubes are silver-soldered to the plate: the
third is insulated from the plate by a plastic ring.

70

71

no...»
Q MeO—@—er .1

22

 

02N—.—cn MeO-.—MgCl

Cr Cr
.411 ' ‘
' 41

Figure 36. Complexes 22, 22, 40, and 41

 

72

 

 

Cr

lWeO-<E§§E>PCH

21

Figure 37. Synthesis of bis(n6-4-chloroanisole)chromium

(3__).

. .1960 Mew-.0!
MeO©CI + c: atoms >

73

 

 

 

 

 

 

 

 

(0000

 

 

 

 

6:“? .

Figure 38. Stainless steel electrodes.

m0

 

 

 

vacuum

l~ IT

 

 

 

 

 

 

 

 

 

Figure 39. Metal vapor reactor.

75

The plastic-steel interfaces are made vacuum tight with
epoxy glue. The center ligand inlet tube is fitted with
an 18/9 socket joint for connection with the addition funnel.
Sixteen holes (4 X 4) are drilled in the bottom inch of the
inlet tube. The two side tubes are water-cooled with inner
1/8 inch tubes. A 3/8 X 1/2 X 1/2 inch copper block with a
hole for the heating element is attached to the bottom of
each side tube. An O-ring groove is cut into the underside
of the 3/8 inch plate. The flask is made with a commercially
available 75 mm inside diameter O-ring joint and has a test
tube-shaped bottom of 120 mm diameter. A side arm with a
high vacuum 8 mm stOpcock provides for evacuation of the reactor.
Other nonrotating systems similar to this have been previous-
ly described.82’83'97

Bis(toluene)chromium (22, R = Me) was made using the
new metal vapor system. A tungsten basket of 0.060 inch
diameter wire was used. A large amount (1700 mg) of product
was obtained but two problems became apparent: 1) chromium
chips fell‘through the basket, making accurate yield deter-
. minations difficult, and 2) the current requirement for this
large diameter wire was high. The limiting factor at high
currents in the system was the melting temperature of the
epoxy glue.

To correct the first problem 2 grooves were made in the
copper blocks of the electrodes so a tungsten boat could be

attached. However, the current required was too high and

(i.

'l\

rn

n1

L10

*4.

cf

76

no metal evaporated in an attempted synthesis of hexamethyl
derivative 22.

The second problem was corrected in the successful
synthesis of bis(n6-4-chloroanisole)chromium (22) using
a tungsten basket of 0.040 inch diameter wire. The 250
MHz proton NMR of 22 (Figure 40) was done in a sealed NMR
tube in benzene-d6. This compound is air-sensitive in
solution and decomposes in chloroform-d. The spectrum shows
the expected ring proton doublets (J = 5.2 Hz) of this
AA'XX' system and a methyl singlet. The ring protons appear
upfield of their uncomplexed position due to reduction
of electron density in the ring w orbitals upon complex

98 That deoxygenation of the

formation or to other effects.
ether linkage has not occurred is shown by the presence of
a C-O stretch at 1225 cm'1 in the IR (Figure 41). The
infrared also shows an asymmetric Cr-ring stretch or ring
tilt99 at 462 cm'l. The base peak in the mass-spectrum
(Figure 42) is due to 4-chloroanisole (m/e 142) and there
is a peak at m/e 144 of the correct relative abundance (32)
due to 37C1. The compound exhibits molecular ions at m/e
336 and 338. A metal to ligand (4e2ée>4e2u) charge transfer
band at 317 nm in cyclohexane solution is present in the
UV spectrum.

Like many bis(arene)chromium complexes compound 22

is air-sensitive. However, the presence of the electronega-

tive Cl and O retards oxidation so that 22 may be left

77

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exposed to air for short periods in the solid state without
significant decomposition.
The bromo analog of 22 is 22. It has been previously

100 that bromobenzene fails to form a w complex with

found
Cr atoms, the product being CrBrB. In accordance with this,
no 22 could be found after cocondensation of 4-bromoanisole
with chromium.

The metal vapor reactor here is best suited for liquid
ligands. The solid ligand used in the attempted syntheses
of bis(4-chloronitrobenzene)chromium (22) created problems.
Four methods were used: 1) addition of hot liquid ligand,

2) addition of a diglyme solution of the ligand, 3) conden-
sation of chromium vapor into a cold diglyme solution of the
ligand in a procedure similar to that described by Kfindig

101 and evaporation of the ligand from a stainless

and Timms,
steel crucible inside the flask. These reactions failed
for a variety of reasons, mostly related to failure of the
ligand to mix evenly with Cr atoms.

Finally, chloro derivative 22 did not form Grignard
reagent 21 under a variety of conditions. The magnesium

turnings failed to give any visible reaction. Addition of

Mg activated by reaction with bromobenzene did not help.

 

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96
Infrared spectral data for 1,1'-bis(phenyl-

seleno)ferrocene (22, Figure 57)

This compound was made by Mr. Lie-Hang Shen. IR
(Nujol, CsI) 466 (antisymmetric ring-Fe stretch), 493 (anti-
symmetric ring tilt), 685 (out-of-plane phenyl C-H bend),
729 (out-of-plane phenyl C-H bend), 820 (C-H bend perpendicular

to Cp ring), 1010, 1150, 1575 cm‘1 (phenyl c-c stretch).

<::;:;>-SePh

Fe
SePh

Figure 57. 1,1'-Bis(phenylseleno)ferrocene (22).

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