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University

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This is to certify that the

thesis entitled

SYNTHESIS OF GROUP IV IMIDO COMPLEXES SUPPORTED BY

'gDIKETIMINATE LIGANDS
presented by

Jie Fang

has been accepted towards fulfillment
of the requirements for

 

 

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l
l
M.S. degree in Chemistry \
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1

Major professor

 

Date 5/11/2001

 

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H . . , ... ”vi... Vt:F-EE.F .u . Iltllv .l E... r I t v E n! .EQEEEE in V‘Inp- fuBrlI-F... Ln, L

 

SYNTHESIS OF GROUP IV IMIDO COMPLEXES SUPPORTED BY
B-DIKETIMINATE LIGANDS

By

J ie Fang

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Chemistry

2001

ABSTRACT

SYNTHESIS OF GROUP IV IMIDO COMPLEXES SUPPORTED BY
B-DIKETIMINE LIGANDS
By

Jie Fang

In recent years, there has been considerable effort put forth in developing group 4
imido chemistry. Many research groups have focused on developing supporting ligands
with the major goal of tailoring chemical reactivity and properties.

B-Diketiminate ligands were used in this research, and a new ligand synthesis that
involves deoxygenation of monoketimines by Ti(NMe2)4 was devised for synthesizing B-
diketimines with bulky aryl groups.

A family of titanium imido complexes containing one or two B-diketiminate
ligands were synthesized. The synthesis of five-coordinate imido complexes containing
two B-diketiminate ligands was achieved for Ti and Zr. The sterically hindered ligand,
Dipnacnac, yielded (Bu‘N)Ti(Dipnacnac)Cl, a rare example of a four-coordinate group 4
imido complexes. I

The chloride in (Bu‘N)Ti(Dipnacnac)Cl could be readily replaced to form a new
Ti-E (E = element) bond. From this compound, (Bu‘N)Ti(Dipnacnac)(OTf),
(Bu‘N)Ti(Dipnacnac)(NMe2), (Bu‘N)Ti(Dipnacnac)Me were synthesized.

A reaction between Ti(NMe2)4 and C6F5nacnacH was discovered, wherein ortho
amination of each C6F5 group and fluoride abstraction yielded an unusual Ti difluoride
complex. Hydrolysis of this Ti complex gave the ketimine (2—NMe2-C6F5)nacnac in good

yield.

To my family and my parents

iii

ACKNOWLEDGMENTS

I would like to thank Professor Smith. He guided me step by step, which helped
me to learn about research and opened the door of organometallic chemistry. I appreciate
his help and patience as I wrote this thesis.

I also want to say thanks to Baixin, my former group member and undergraduate
classmate. He guided and helped me a lot on my research. I feel lucky to have this friend.
Also, other group members offered me a lot help, which was not limited to chemistry.
Especially, I want to express my appreciation to Jian-Yang.

I appreciate the help from Professor Odom. He inspired many ideas on the

research. Also, I appreciate the help of Dr. Ward and many others at MSU.

iv

TABLE OF CONTENTS

CHAPTER 1 ........................................................................................................................ 1
INTRODUCTION ............................................................................................................... l
A. Transition metal imido complexes ............................................................................. 1
Structural Features of Transition Metal Imido Complexes ......................................... 2
Synthetic Methods ....................................................................................................... S

B. Ti and Zr imido chemistry .......................................................................................... 5
Convenient syntheses for Ti and Zr imido complexes ................................................ 6

CH bond activation .................................................................................................... 7
Cycloaddition .............................................................................................................. 8

C. Ligand Considerations ................................................................................................ 9
B-Diketiminate ligands .............................................................................................. 1 1
Bibliography .................................................................................................................. 13
CHAPTER 2 ...................................................................................................................... 18
RESULTS AND DISCUSSION ....................................................................................... 18
Ligand Synthesis ........................................................................................................... 18
Synthesis of (Arnacnac)Ti(NBu')Cl and (Amacnac)Ti(NBu‘)Cl(Py) ........................... 20
Syntheses of L2M(=NR) through lithium salt metathesis ..... . ........................................ 2 6
Syntheses of LTi(=NR)Cl derivatives ........................................................................... 29
An unusual reaction between Ti(NMe2)4 and C6F5nacnacH ......................................... 33
Summary ....................................................................................................................... 37
Bibliography .................................................................................................................. 38

CHAPTER 3 ...................................................................................................................... 39

EXPERIMENTAL METHODS ........................................................................................ 39
General Methods and instrumentation .......................................................................... 39
Single Crystal X-Ray Structure Determination ............................................................. 40
Starting materials ........................................................................................................... 41
Synthesis ........................................................................................................................ 41
Bibliography .................................................................................................................. 55

APPENDIX ....................................................................................................................... 56

vi

LIST OF TABLES

Table 1. Selected bond lengths (A) and bond angles (°) for (Bu‘N)Ti(Dipnacnac)Cl (17).

................................................................................................................................... 22
Table 2. Selected bond lengths (A) and bond angles (°) for

(Bu‘N)Ti(Tolnacnac)Cl(PyBu‘) (18) ......................................................................... 24
Table 3. Selected bond lengths (A) and bond angles (°) for

(Bu‘N)Ti(TMFnacnac)Cl(PyBu‘) (19) ....................................................................... 25
Table 4. Selected bond lengths (A) and bond angles (°) for (DipN)Zr(Tolnacnac)2

(25) ............................................................................................................................ 29
Table 5. Selected bond lengths (A) and bond angles (°) for (Bu‘N)Ti(Dipnacnac)OTf

(26) ............................................................................................................................ 30

Table 6. Selected bond lengths (A) and bond angles (°) for (Bu‘N)Ti(Dipnacnac)(NMe2)
(27) ............................................................................................................................ 32
Table 7. 1H NMR (C6D6, BOOHZ) Chemical shift of Dipnacnac ligand in
(Dipnacnac)Ti(NBu‘)X (X = OTf, NMez, and Me) .................................................. 33
Table 8. Selected bond lengths (A) and bond angles (°) for (NMe;)Ti[(2-NMe2-

C6F4)nacnac]F2 (29) .................................................................................................. 35

vii

LIST OF FIGURES

Figure 1: Early known transition metal imido complexes .................................................. 2
Figure 2: VB descriptions of metal-imido linkages ............................................................ 4
Figure 3: Versatile synthons for titanium imido compound ............................................... 7
Figure 4: OH activation with a titanium imido complex ................................................... 8
Figure 5: Selected cycloaddition reactions of [Ti(NAr)(Me4taa)] ...................................... 9
Figure 6: Several supporting ligands used to support group 4 imido complexes ............. 1 1
Figure 7: Thermal ellipsoid plot (50% probability) of (Bu‘N)Ti(Dipnacnac)Cl (17). ...... 22

Figure 8: Thermal ellipsoid plot (50% probability) of (Bu‘N)Ti(Tolnacnac)Cl(PyBu')
(18). ........................................................................................................................... 23
Figure 9: Thermal ellipsoid plot (50% probability) of (Bu'N)Ti(TMFnacnac)Cl(PyBu')
(l9). ........................................................................................................................... 25
Figure 10: Thermal ellipsoid plot (50% probability) of (DipN)Zr(Tolnacnac)2 (25) ........ 28
Figure 1 1: Thermal ellipsoid plot (50% probability) of (Bu'N)Ti(Dipnacnac)(OTf) (26).
................................................................................................................................... 31

Figure 12: Thermal ellipsoid plot (50% probability) of (Bu‘N)Ti(Dipnacnac)(NMez) (27).

................................................................................................................................... 32
Figure 13: Thermal ellipsoid plot (50% probability) of (NMe2)Ti[(2-NMe2-

C6F4)nacnac]F2 (29) ................................................................................................. 35
Figure 14: Ligand (2-NMe2-C6F4)nacnac and its potential coordination with metal ........ 35

viii

LIST OF ABBREVIATIONS

Ar .................................................................................................................................... Aryl
Bu ................................................................................................................................. Butyl
BTBA ....................................................................... N ,N-bis(trimethylsilyl) benzamidinate
calcd ......................................................... ' ............................................................. calculated
C6F5nacnacH .................. 2-pentafluorophenylamino-4-pentafluorophenylimino-2—pentene
CCD ................................................................................................. Charge Coupled Devise
CN ...................................................................................................... Coordination Number
Cp .............................................................................................................................. (C5H5)‘
Cp* ......................................................................................................................... (C5Me5)‘
d ................................................................................................................................. doublet
decomp .............................................................................................................. decomposed
Dip .................................................................................................................... C6H3-2,6-‘Pr2
DipnacnacH ......................... 2-(2,6-iPr2-phenylamino)-4-(2,6-‘Pr2-phenylimino)-2-pentene
equiv ..................................................................................................................... equivalent
e' ............................................................................................................................... electron
Et ................................................................................................................................... Ethyl
i ......................................................................................................................................... iso
IR .............................................................................................................................. Infrared
L .................................................................................................................................. ligand
m .............................................................................................................................. multiplet
Me ............................................................................................................................... Methyl
mp. .................................................................................................................... melting point
NMR ....................................................................................... Nuclear Magnetic Resonance
o ..................................................................................................................................... onho
OTf ............................................................................................................................. triflate

ix

p ...................................................................................................................................... para

Ph ...................................................................................................... . ......................... Phenyl
Pr ................................................................................................................................. Propyl
py .............................................................................................................................. pyridine
s .................................................................................................................................. singlet
sept .............................................................................................................................. septet
t ..................................................................................................................................... triplet
taa ........................................................................................................... tetraazamacrocycle
tert .................................................. L ........................................................................... tertiary
THF ............................................................................................................. tetrahydrofuran

TFMnacnacH ........... 2-3,5-di-trifluoromethylamino-4-3,5-trifluoromethylimino-2—pentene
Tol .................................................................................................................................. tolyl
TolnacnacH .................................................... 2-(p-tolylamino)-4-(p-tolylimino)-2-pentene
TsOH .................................................................................................. p-toluenesulfonic acid
VB .................................................................................................................. Valence Bond

CHAPTER 1

INTRODUCTION

The chemistry of transition metal imido complexes has attracted considerable
interest and has experienced exceptional growth in recent years. Such compounds are of
interest as intermediates in organic syntheses as well as catalytically active species.1 A
substantial body of research has focused on the group 4 complexes.2 Terminal zirconium
imido complexes were reported in 1988,3'4 and terminal titanium imido complexes were
first structurally characterized in 1990.5’6 Group 4 compounds containing bridging imide
ligands are also well known.7‘l3 However, it is generally the terminal M=NR (M = Group
4 Metal, R = Organic fragment) linkage that demonstrates important chemical reactivity

3,4,14,15

such as C-H bond activation and N-C bond forming reactions with unsaturated

subtrates.4‘16'20
A. Transition metal imido complexes

Complexes containing metal-nitrogen multiple bonds are prevalent in transition
metal chemistry. Transition metal imido complexes have the general formula
M(=NR),,(L)m (R = alkyl or aryl group, L = ancillary ligand). They have received
significant attention in recent years because of their importance in a wide range of
applications that encompass industrial processes, catalysis, and some organic
transformations."21 The first transition metal imido complex to be prepared was tert—
butylimidotrioxo osmium (VIII) (compound 1 in Figure 1), reported by Clifford and

Kobyashi in 1956, and in 1962, the arylimido complex Re(=NPh)Cl3(PEt2Ph)2 was

described by Chatt and Rowe (compound 2 in Figure 1).22 Since then, numerous imido
complexes have been synthesized. In this section, the structural features and synthetic

methods to transition metal imido complexes will be described.

 

Bu Ph
l |
N N
/(l)|5\ PhEtzPIm..,. [LUNG
O/l \0 G” l ‘PEtZPh
0 Cl
1 2

Figure 1: Early known transition metal imido complexes

Structural Features of Transition Metal Imido Complexes

Terminal transition metal imido complexes can be considered to bond to a
transition metal with one 0' and either one or two 1: interactions. Limiting Valence Bond
(VB) descriptions of this interactionl are presented in Figure 2, where the hybridization
about the nitrogen and the metal-ligand bond order are suggested to impose certain
structural parameters on the imido ligand. In addition, three compounds are shown as
examples of the limiting VB structures in Figure 2.

In structure A, the sp2 hybridization of nitrogen yields an M=N double bond, with
one o and one 1: bond. The non-bonding lone pair on nitrogen makes a bent M-N-R
linkage. In the closed-shell formalism, the imido dianion [NR]2' acts as a four electron
(4e‘) donor. There are only a few examples of strongly bent imido complexes. Structure
A is expected only when the metal center cannot form a bond with the nitrogen lone pair.

This case occurs when a linear, triply bonded NR can cause the electron count of the

complex to exceed 18 electrons.23 Wilkinson & Hursthouse reported a tris(imido)
complex Mn(=NBu')3Cl.24 The Mn-N-C angles in this compound are very similar, and lie
in the range from 138.5(3)° to 141.8(3)°. The bending is consistent with a delocalization
of the bonding contributions required from the three imido functions for an 18-electron
manganese configuration.

The M-N-R moieties of most known transition metal imido complexes are close
to linear. This is consistent with sp hybridization at nitrogen. The M-N-R linkage could
be either structure B or structure C in Figure 2. In structure B, there are some restrictions

that prevent nitrogen from donating its lone pairs to the metal, thus it retains the one 0'
and one 7: double bond configuration. The restrictions could be symmetry imposed, or
due to a severe energy mismatch with the available metal orbitals. Bercaw and
coworkers25 reported the synthesis of the imido complex Cp'zTa(=NPh)H. They expected
a structure with a bent arrangement, because with a single Ta—M 1! interaction, tantalum
would achieve a closed-shell, l8-electron configuration. However, the X-ray structure
showed a nearly linear [177.8(9)°] Ta-N-Ph arrangement, with the phenyl group lying
nearly in the equatorial plane, indicating that the nitrogen is sp hybridized. The authors
suggested that steric interactions, which force the phenyl ring into the equatorial plane,
are responsible for sp hybridization at nitrogen. Hence a double [Ta=NPh] bond with a
lone electron pair localized in a nitrogen p orbital. Shortly thereafter, Jorgensen offered
supporting evidence for this description from extended Hiickel MO calculations.24

Most known transition metal imido complexes resemble structure C. Lone pair

p(1t) —> M(d) donation is very effective leading to a MENR bond order of 3. In contrast to

structures A and B, the imido dianion [NR]2‘ in structure C is a formal six electron (6e)

donor with 10 and 2n bonds to the metal. Structure C is found in many complexes

including octahedral mono(imido) complexes with do-d2 electronic configurations,
tetrahedral bis(imido) with dO-d2 electronic configurations, and d0 trigonal bipyramidal
bis(imides) with equatorial imides. As an example, the d0 imido complex Ti(NC6H3Me2-
2,6)(OC6H3Me2-2,6)2(Py)225 is shown in Figure 2. The linear M-N-C linkage shows an sp
hybridization of nitrogen, and the lone pair donation from nitrogen to titanium should be

described as an MENR triple bond.

Structure A B C

VB M: \ M=N—R MEN—R
' R
Hybridization N (spz) N (sp) N (sp)
[NR]2' 4e 4e' 6e'

N H N v
C11,. CPFI: ,
Examples I fin‘N C *vTa: pynciiiufi)
// ‘ , P \N 0' v
But/N But \Ph d Py
Angle l38.5(3)-141.8(3) 177.8(9) 180

Figure 2: VB descriptions of metal-imido linkages

Although structure C is a fairly accurate depiction of imido bonding for most
transition metal imido complexes, “M=NR” is a commonly used generic designation for

the metal imido group and is not necessarily an indication of the true bond order.

Synthetic Methods
Chemists have developed various methods for the synthesis of imido complexes.

21,2628 (2)

These include (1) a—elimination from amide ligands, Oxidative nitrene transfer

30.31

from arylazides29 and related species, (3) “Wittig-like” reactions between phosphin

23.32-36

imines and metal ligand double bonds (especially M=O), and (4) electrophilic

”’38 and diazenido ligands.39

. attacks on nitrido
Among the transition block elements, group 5-8 transition imido chemistry had
been reasonably well developed by the end of 19805. In contrast, well-defined derivatives

for group 4 did not appear until about this time."2 The current development of group 4

elements titanium and zirconium imido chemistry will be described in next section.

B. Ti and Zr imido chemistry

Although the first imido titanium complex Ti(=NSiMe3)C12(Py)2 was reported by
Burger and Wannagat40 as early as 1963 through Me3SiCl elimination from
Ti[N(SiMe3)2]Cl3, titanium imidos were still rare at the end of 19805. Terminal titanium
imido complexes were first structurally characterized in 1990.5 Since then, a number of
simple mononuclear, five- and six-coordinate titanium imido derivatives have been
reported.2 The first terminal Zi=NR functional groups were reported in 1988.3‘4 Since
then, many research groups have reported a range of new chemical reactivity. In this

section, many new developments in Ti and Zr imido chemistry will be described.

Convenient syntheses for Ti and Zr imido complexes

The Mountford group“42 reported the compound [Ti(NR)C12(L)n] (R=But or aryl;
L=py or NC5H£u‘-4; n=2 or 3) (Figure 3), which offers a general route to a series of
Ti=NR species. The tert-butyl imido complexes [Ti(NBu‘)C12(L)n] are readily obtained
from TiCl4, Bu‘NHz and the appropriate ligand(s). Analogous arylimido complexes
cannot be obtained directly from ArNHz and TiCl4, but arylamine/tert—butyl imide
exchange reactions of [Ti(NBu‘)Clz(Py)3] readily afford the desired complexes,
[Ti(NAr)Clg_(Py)3].42‘43 The utility of these complexes as synthons for new titanium imido
derivatives may partly be attributed to the imido ligand’s ability to stabilize higher
oxidation states by 1: donation. Hence, almost none of the anion metathesis reactions are
complicated by reduction of the Ti(IV) centers.

The easiest way to access Zr=NR complexes is by reacting 4 equiv of LiNHAr
with ZrCl4(THF)2 in THF / py, which yields Zr(=NAr)(NHAr)2(Py)2. This complex reacts
further with 1 or 2 equiv of Me3SiCl in THF / py to provide Zr(=NAr)(NHAr)Cl(Py)2

and Zr(=NAr)Cl2(Py)3 respectivelyf”4

Tier,

 

 

ii iii liii

Bu‘ II3U‘ Ilsu‘
|
H ITNl Cl- fi- —-Py
----Ti-.- c1--" “~-~ "'
Cl - Bl Py (
Bu‘Py/ ‘0 FY u Pr’ \a W ly\Cl
R4 /v
Rz’gms 2Q
N v R2 R6 R. R4 R6
R2 R,5 H N .................
"""""" c1---- .—-'Py “ Me H Me
Me Me Tl Cl Cl"“Ti"' Py Prl H Pr'
Pr‘Pr‘ PY I C] H H H
Py H Me H
H No2 H

Figure 3: Versatile synthons for titanium imido compound
(i) Bu'NH2(6 equiv), py-Bu'(2.2 equiv.)
(ii) Bu‘NH2(6 equiv), py(2.3equiv)
(iii) Bu‘NH2(6.3 equiv), py(4.lequiv)
(iv) aniline or substituted aniline
(v) 65°C, dynamic vacuum.

C-H bond activation

High-valent Ti and Zr imido complexes can activate C—H bonds. In 1991,
Wolczanski’s group'5 described the preparation and chemistry of highly reactive species
[Ti(NSiBu‘3)(NHSiBu‘3)2], which can activate C-H bonds of benzene. The reaction is
shown in Figure 4. The group also reported the selectivity in hydrocarbon activation
through the kinetic and thermodynamic investigations of reversible 1,2-RH-elimination

from (‘BugsiO)2(‘Bu3SiNH)TiR.45

 

 

 

 

 

Bu‘3SiHN Bugsm Bu‘3SiN
MeLi, EtzO
, ..-Ti—c1 > ..-Ti—0Et ' 5‘20 Ti— NHSiBu‘
Bu‘,SiHN\“" -ucr -MeH Bu‘gsiHN\\“‘ 2 3
Bu‘3SiHN BugsmN + 5‘20 Bu‘3SiHN
' C6D6 4- C606
Bu‘3SiN Bul3SiN Bu‘3SiN
\\ + Et20 \\ + C H \\
l . “Wu-Ti—OEt Ti— NH SiBu‘3 __6_D5___ ..--Ti—C6D5
Bu 3SIHN _ 5,20 W Bul3SiHN\\\\
Bu‘3SiDN Bu‘3SiDN 6 5 Bu‘3SiHN

 

 

 

 

Figure 4: C-H activation with a titanium imido complex

The Zr=N bond can activate the OH bonds of hydrocarbons through o-bond
metathesis. Bergman’s group reported C-H activation by using transient szZr=NR in
1988.31 At the same time, Wolczanski’s group reported that a highly reactive zirconium
imido complex, (Bu‘3SiNH)ZZr(=NSiBu‘3), effectively mediated the OH bond

. . 3
activation.

Cycloaddition

Titanium imido complexes also react with alkynes, isocyanates, and isocyanides
to produce [2+2] cycloaddition products.”48 For example, Mountford’s group49 studied
the cycloaddition reactions of the compounds [Ti(NR)(Me4taa)]with a range of organic
substrates. Figure 5 shows the cycloaddition reactions with isocynates, di-p-

tolylcarbodiimide and carbon dioxide.

 

I Ar
N I N
II II
..C'N T l ,C'
W TolN=C=NTol T;Ti:/N PhNCO Ph— N N- Tol
’N"Ti"N WN Ti-‘N
©~v ~ fi©:N

(VN‘ M

/;"" Tom.
if)

Tol

N
0.50
Ap'N'N-A

NO- "Ti’ ,N- \Né‘riiaN
Gk (v30

Figure 5: Selected cycloaddition reactions of [Ti(NAr)(Me4taa)]

Zirconium imido complexes undergo cycloaddition reactions with a wide range of
unsaturated organic molecules including alkynes, imines, and certain alkenes.47'50 Several
these reactions are believed to be important steps in catalytic transformations (e. g.

hydroamination and imine metathesis) mediated by imido compounds.

C. Ligand Considerations

By 1993, research showed that group 4 imido compounds could be isolated but
were relatively unreactive, or could be generated in situ and were extremely reactive.l In
recent years, there has been considerable effort put forth in developing supporting ligands
in transition metal imido chemistry, with a major goal being the tailoring of chemical
reactivity and properties.2 Supporting ligands are generally bulky in order to prevent

dimerization and to provide the necessary electronic stabilization to the metal center.

Studies utilizing a wide range of ligands have confirmed the influence of the ancillary
ligand environment on reactivity, but the accurate prediction of reactivity from a structure
remains a challenge. For group 4 metal imido chemistry, N-donor amide and N4
macrocyclic ligands have been developed, and some representative structures are shown
in Figure 6.

A class of ligand that has enjoyed widespread use across a range of transition
metal chemistry is “salen”-type Schiff bases D (Figure 6).5"52 The peripheral substituents
(i.e. R1, R2, R3) of these NzOz-donor ligands are readily modified, and their syntheses
from diamines and salicylaldehydes are typically straightforward. A few compounds with
group 4 imido chemistry have been reported, and investigations of these compounds are
still ongoing.53

OL-Diimines54 (E in Figure 6) can coordinate as a neutral bidentate ligands, but
most commonly they act as mono- or di-anionic moieties owing to their ability to accept

electron density into the 1:3 lowest unoccupied molecular orbital. This results in

shortening of the diimine CC and lengthening of the ON bonds in comparison to those
of the free ligand.”‘56

Amold’s group57 has explored several general classes of amindinate ligands
including linked bis(amidinates)58 and ferrocene-containing derivatives.59 An example is
the N,N-bis(trimethylsilyl) benzamidinate (BTBA) ligand (F) shown in Figure 6. This
ligand is particularly attractive because it is prepared easily and cheaply on a large scale.
Its complexes are nicely soluble and generally highly crystalline, and the ligand contains
excellent NMR spectroscopic handles. BTBA complexes are known for a wide range of

transition metals in various oxidation states.60

10

 

R N R NH
1': R
E
Ar
/
N
C‘
H
/
N
\
Ar
F G H

Figure 6: Several supporting ligands used to support group 4 imido complexes

The dianionic diamidoamine ligand [Me3SiN(CH2CH2NSiMe3)2]2' (NZNZ') (G in

Figure 6) has been used for imido group 4 chemistry.6| Like its diamidopyridine Nszy

62,63

analog, the NzN ligand can adopt a fac coordination geometry. Stable group 4 imido

compounds with this ligand were synthesized, and the structures have been reported.

B-Diketiminate ligands

A In this research, B-diketiminate ligands (H in Figure 6) were used. Applications of
B-diketiminate ligands to imido metal complex have been limited despite several

attractive features. First, they can be prepared in high yields from cheap and readily

ll

available building blocks, 2,4-pentanedione and primary amines. Second, the steric and
electronic properties of the B—diketiminate ligands can be altered through appropriate
choices of amine and B-diketone used in their syntheses. Lastly, this ligand family can
provide kinetic stability while maintaining several accessible oxidation states at the metal
since they generally bind as monoanionic ligands.

Diketiminate ligands have been known for a long time, and early investigations
involved spectroscopic studies of transition metal complexes.64456 In addition to our

67-74
rk,

group’s wo several groups have recently used the ligands to carry out

stoichiometric and catalytic reactions.”83

12

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(1)

(2)
(3)

(4)

(5)

(6)

(7)
(8)

(9)
(10)

(11)

(12)

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(14)

(15)

(16)

Wigley, D. E. In Progress in Inorganic Chemistry, Vol 42, 1994; Vol 42, pp 239-
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17

CHAPTER 2

RESULTS AND DISCUSSION

Ligand Synthesis
Syntheses of various B-diketiminate ligands were of interest. The general route is

from 2,4-pentanedione, through two steps of amine condensation catalyzed by p-
toluenesulfonic acid (Scheme 1).1 However, relatively few examples of unsymmetrically
substituted ketiminate ligands are known, and most involve reactions of more basic alkyl
amines with arylketinines."2 For arylamines, the procedure in scheme 1 is complicated by
reversible amine condensations, which can lead to mixtures. Hence, we attempted to

devise routes to unsymmetrically substituted ligands.

Scheme 1:
H Ar Ar\ H Ar
/ \ /
(1) O TsOH o N/ TsOH
M + ArNH2 ——. ——_. v
/ ATNHZ
Ar

 

18

Our group previously found that Ti(NMe2)4 deoxygenation of monoketiminate
complexes, which is thermodynamically driven by formation of T102.3 For example, two
equiv of 4-(p-methylphenylamino)-3-pentene-2-one (3) react with 1 equiv of Ti(NMe2)4
to afford colorless 2-Dimethylamino-4-p-tolylimino-2-pentene (11) in 80% yield after
standard workup. With a TsOH mediated reaction, the secondary dimethylamino group

could be replaced by primary arylamines, thus TolnacnacH (7) was prepared in about

52% yield (Scheme 2).
Scheme 2:
H M
o \N/T01 Me\ / e /Toi

I N N
2/“\/|\ + T1(NM62) ——> 2 /J\)l\ + Tio2
ll

3
2ArNH2
TsOH

Ar H To]
2 N N '10 7
M Ar:

4% 12

After this encouraging result, we designed a new in situ reaction route. To avoid
isolation of 11, we replaced dimethylamino unit at the outset by reacting Ti(NMe2)4 with
two equiv of an aryl amine, and then we reacted the titanium intermediate(s) with 4-
amino-3-pentene-2-one to synthesize the desired B-diketiminate ligand (Scheme 3). The

result was what we expected, simplifying the syntheses of ligands with bulky aryl groups.

19

For example, after Ti(NMe2)4 and p-toluidine were stirred in toluene for 8 hours, 4-(2,6-
di-iso-propylphenylamino)-3-pentene-2-one (4) was added and the mixture was refluxed.
The desired unsymmetrically substituted ketiminate ligands 12 was obtained after the
workup.

Scheme 3:

Ar'\ H Ar
3 N/ \N/

["TuNAr'); ——» M , "no,

Ti(NM62)4 + ZAI',NHZ

 

Synthesis of (Amacnac)Ti(NBu')Cl and (Amacnac)Ti(NBu‘)Cl(Py)

The B-diketiminate ligands are all readily converted to the corresponding lithium
salts (14, 15 and 16) in excellent yields through reaction 'with butyl lithium in
toluene/pentane. Filtration and evaporation of volatile materials give products suitable for
use without the need for additional purification. Mountford’s group“’5 reported that the
compound Ti(=NBu‘)C12(PyBu')2 (13), which is inexpensive and readily prepared, is an
excellent starting material in titanium imido chemistry since the tert-butyl pyridine and
chloride ligands are usually easily substituted. Therefore, compound 13 was examined as
a source of the titanium imido fragment.

The syntheses of B-diketiminate titanium imido chloride complexes were
achieved by reacting 13 with lithium salts 14, 15 and 16 respectively, where a chloride

and one or two tert-butyl pyridine ligands are replaced by the Amacnac group. The

20

chemistry is summarized in Scheme 4, and full spectroscopic and analytical data are

listed in Chapter 3.

Scheme 4:

D'P\ NL/ \ ND/

_|_

 

 

Dip\
Tol
MU ; Null”... Ti \

A g NI Cl

H Tol\ N/Li\ N/Tol Tol\ N
C'Illt Ti" "\ucnlpyBu +M T01 : Nmu... Tr ""PyBu
PyBu A (- N’ c1
T01 18

13 l
N

TFM

TF/|\/LTFM T0] > N""'""|I|‘r"|1PyBu
C. N C1
TFM
19
Yr;Y (5 G

TFM

 

“(2%:

3'?

Reaction of 13 with 14 in toluene at 70 0C for 16 hours resulted in an orange
solution. Standard workup and crystallization from toluene/pentane at —30 °C gave
(Bu‘N)Ti(Dipnacnac)Cl (17) in 66% yield. The NMR spectra for 17 in CDC13 indicate
mirror symmetry in solution. Diffraction-quality crystals of 17 were grown at —30 0C
from a saturated pentane solution. Details of data collection, processing, and structure
resolution are given in the Appendix. The molecular structure is shown in Figure 7, and

selected bond lengths and angles are given in Table 1.

21

C(32)

canytr m2"
C(33) (/75/ C(25) C(20) (I, ‘)
C(30) 4 C(29) ‘3’.
%3 III?
j 4 C(19) (‘g C(22)
" ' N13) 3 (E’fg €901
cams: Q) (4%
”(10) 0‘1"“(3‘15) T ‘ )"8’\ C27) (*3
m9) '3 ’ 1
‘ " ‘ (6) <3

   

C(28)
C(14) CM) e7)
. C(S)
1““ )0112)
i
(5 (1)
« C(13)

Figure 7: Thermal ellipsoid plot (50% probability) of (Bu‘N)Ti(Dipnacnac)Cl (17).

Table 1. Selected bond lengths (A) and bond angles (°) for (Bu‘N)Ti(Dipnacnac)Cl
(17).
Bond Lengths (A) Bond Angles (°)
N3—Ti-N1 1.695(2) N3-Ti-Nl 106.39(9) N2-Ti-C1 l 1579(6)
N3-Ti-N2 2.0292(18) N3'Ti‘N2 1 124300)

 

Tm 2.031(2) N1-Ti-N2 9383(8) Ti-N3-C30 171.3(2)
Ti—Cl 2.3268(7) N3-Ti-Cl 113. 17(8)
N3—C30 1.460(3) Nl—Ti-Cl 1 1336(6)

 

(Bu‘N)Ti(Dipnacnac)Cl (17) has a four-coordinate TiIV center which possesses a

distorted tetrahedral geometry. The Ti=Nimmc bond length [1.695(2) A] lies in the middle

22

of the range of values (ca. 1.67-1.73 A) usually found for this linkage.“ The angle
subtended at the imido nitrogen atom [Ti—N3-C30] is 171.3(2)°.

The Dipnacnac ligand in 17 has the di—iso-propyl substituents on the 2- and 6-aryl
positions. We were interested in probing the effects of changing the aryl ring substituents
on the properties of titanium imido derivatives. Thus, we also investigated chemistry with
less hindered Tolnacnac ligand.

The lithium salt 15 reacted with compound 13 in toluene to afford brown
Ti(NBu‘)(Tolnacnac)Cl(PyBu') (18) in 44% recrystallized yield. Formation of a five-
coordinate titanium with one tert-butylpyridine in 18 reflects the reduced steric demands
of the Tolnacnac ligand relative to Dipnacnac ligand.

A view of the molecular structure of (Bu‘N)Ti(Tolnacnac)Cl(PyBu‘) (18) is shown

in Figure 8, and important bond lengths and angles are listed in Table 2.

   
   

'I -
C131) (4 C(23)
\ ,//\\>
e“) 0125) 0121) (1470122)
[‘0‘29’ 75‘ C(20)
C130) (44‘
(i “ 1'4” "1 N13)

01321231 (3‘2
0117) C C127) V

(M‘Cl
v C17) (8’ q

(\( , 4 )\\\-\
0161 (4' 95? 1),?)

(guns) 8,
(«01“IA
C(16) C(13) ‘\\\2l\‘ C19) 0112)
)
C(14) “0111)
a. ’\
0(5)”? LC11)

Figure 8: Thermal ellipsoid plot (50% probability) of
(Bu'N)Ti(Tolnacnac)Cl(PyBu') (18).

23

Table 2. Selected bond lengths (A) and bond angles (°) for
(Bu'N)Ti(Tolnacnac)Cl(PyBu‘) (18)

 

 

Bond Lengths (A) Bond Angles (°)
Ti-N 3 1.685(5) N 3-Ti—N1 104.8(3) N 3-Ti-N4 100.5(3)
Ti-N 1 2.067(6) N 3-Ti-N 2 l 10.4(3) N1-Ti-N4 154.0(2)
Ti-N2 2.076(5) N1-Ti-N2 83.6(2) N2-Ti-N4 82.4(2)
Ti-N4 2.228(6) N3-Ti-Cl 1 l 1.6(2) N4-Ti-Cl 84.28(16)
Ti-Cl 2.376(2) N l-Ti-Cl 91 .53(17)
N 3-CQ 1.455(9) N 2-Ti-Cl 137.55( 17) Ti-N3-C20 171.6(5)

 

 

Compound 18 has the titanium in a square pyramidal geometry with the near-
linear tert-butylimido ligand in the apical position. The titanium-imido nitrogen bond
distance of 1.685(5)A also falls in the typical range of 1.67-1.73 A. The two Ti-N bond
lengths for the ligand are statistically identical, averaging 2.072 A.

Lithium salt 16 was also tried to perform the reaction. Under the same condition,
the orange compound (Bu‘N)Ti(TFMnacnac)(PyBu‘)Cl (19) was formed in 53% yield.
Compound 19 was obtained with a five-coordinate titanium. The molecular structure of
19 and some importantbond lengths and bond angles are shown in Figure 9 and Table 3
respectively.

Similar to that of 18, the structure of 19 shows a square pyramidal geometry. The
titanium-imido nitrogen bond distance is almost identical to that of 18. The angle of
168.5(7)o at the imido nitrogen atom (Ti-N6-C24) is nearly linear and consistent with a
Ti—N triple bond. The titanium-imido nitrogen bond distance is experimentally identical

to that in compound 18.

24

 

Figure 9: Thermal ellipsoid plot (50% probability) of
(Bu'N)Ti(TMFnacnac)Cl(PyBu') (19).

Table 3. Selected bond lengths (A) and bond angles (°) for

(Bu'N)Ti(TMFnacnac)Cl(PyBu‘) (19)

 

 

Bond Lengths (A) Bond Angles (°)
Ti 1-N6 1.684(8) N6-Til-N3 104.1(3) N3-Ti1-N5 156.2(3)
Ti 1-N3 2.1 19(7) N6—Ti1-N4 109.8(3) N4-Ti 1 —N5 86.1(3)
Ti l-N4 2.084(7) N6-Ti-N5 99.5(3) N4-Ti1-C12 139.5(2)
Ti 1-N5 2.255(7) N6-Ti-C12 110.6(3) N5-Ti 1 -C12 85.2(2)
Ti 1-C12 2.380(3) N3-Ti 1 -N4 83.4(3)
N6-C24 1.483( 12) N3-Ti 1 -C12 89.0(2) Ti 1 -N6-C24 168.5(7)

 

 

In an attempt to prepare an arylimido analog of (Dipnacnac)Ti(NBu‘)Cl, the NMR

reaction between 17 and toluidine was examined in a toluene-d3 solution. The exchange

required forcing conditions. Nevertheless, a clean conversion occurred within 1 hour at

150 °C (Scheme 5).

Scheme 5:

+ £5

. N . N
DIP- I1 DIP. 11
Nmuu-Ti —©—NH2 NIm....Ti
C. I \Cl NI \
0
”(mp 150 C, C7D8 Dip

17 20

‘1

C1

The pyridine adduct of 20 was easily prepared from lithium salt Li(Dipnacnac)
(l4) and (NTol)TiC12Py3 (21). The desired products could be synthesized from the imido
complex and lithiated B-diketimine ligands. For example, compound 21 was reacted with
14 in toluene for 16 hours at 70°C. After standard workup procedure, the brown
compound (TolN)TiDipnacnacCle2 (22) was obtained in 63% yield. With the success of
this reaction, a series of arylimido titanium compounds were analogously synthesized

with this route.

 

Scheme 6
Cl” II? Dip‘N/ l\N'D 1p T0] Nllllln-u-fiiflspy
h. .M‘ +
P641418) M A L 1(9) c1
Py Dlp
21 14 22

Syntheses of L2M(=N R) through lithium salt metathesis

We tried to coordinate a second B-diketiminate ligand to titanium by further

lithium salt metathesis. Addition of 14 to a stirred toluene solution of

26

(Bu‘N)TiC12(PyBu‘)2 (13) gave compound 17 and unreacted 14. Since steric factors may
prevent incorporation of the second dipnacnac ligand, analogous reactions with 15 were
examined. However, the desired product Ti(=NBu‘)(Tolnacnac)2 could not be obtained.
Surprisingly, two equiv of 16 reacted with 13 afforded the yellow compound
(Bu’N)Ti(TFMnacnac)2 (23) in 62% yield (Scheme 7). A singlet methane proton in the

1H NMR spectrum and only one singlet in the 19F NMR suggest a C2v-symmetric

 

SIYUCtUI'C.
Scheme7
’11
TFM, ,Li. .TFM
Clllllm-TiuulluPyBut 2 N N1'FM\I\J1;1....'I~|i,,,,:NTFM
Buth/ \Cl + M
13 16 TFM23

\r%—+ W/TO
Tol~ it -T01 T01 Tol’No,1

Cl 2 NUN : T°'\ v =N

Pym, 'ZlI'JBY+ M A N I

N
1% \Tol

25

 

24 15

We also tried the syntheses of zirconium compounds because zirconium has a
bigger atomic radius. The complex (DipN)ZrC12Py2 (24)8 was chosen as the starting
material.

Two equiv of 15 were dissolved in toluene, and the solution was added drOpwise
to a toluene solution of 24. The yellow-orange compound (DipN)Zr(Tolnacnac)2 (25) was
obtained in 70% yield (Scheme 7). The solid-state structure of compound 25 is shown in

Figure 10 and selected bond lengths and bond angles are listed in Table 4.

27

Compound 25 has a five-coordinate er center in a distorted trigonal—bipyramidal
arrangement with an approximately linear arylimido ligand (174.95(7)°) occupying an
equatorial coordination site. The Zr—Nimido bond length (1.854(2) A) is within the range of
known alkyl- and aryl—substituted imido ligands for Zirconium complexes (1.83-1.88
A).6‘8'l3 The nitrogens of each B-diketimine ligand occupy both axial and equatorial I
coordination sites, where the averaged axial Zr-Nngand bond distances (2.60 A) are longer

than the averaged equatorial Zr-Nngand bond distances (2.35 A).

90142)

   

C(4\) C140 4“.
(11“: I/ ‘
// “' 1‘44,

'9’ ) (6’))
f“ )‘. I}

‘ 3
C138 .‘ 014 10147) (80 0148101171’1

  

(.1, 135) \1) "6)
C(36) Q. (34) (”1511501 c1181q’1151
3 \\\\“ C 91
()3) C(37) C1331 C1131 / 9 C‘ 3’ "
. W Zr 9’ 6% V1511 \\\\

  
 

§ v.
\ N12) (1‘

.\\ I//
5

  
  

N14) ”In “ ‘
'3’ C(31)
2V 61‘)

“(313(25): $26 0127)
12% 141

‘1; (5)

C120)

‘3’” 111

Figure 10: Thermal ellipsoid plot (50% probability) of (DipN)Zr(Tolnacnac)2 (25).

28

Table 4. Selected bond lengths (A) and bond angles (°) for (DipN)Zr(Tolnacnac)2

 

 

(25)
Bond Lengths (A) Bond Angles (°)
Zr-Nl 2.2447(19) NS-Zr-Nl ll7.72(8) Nl-Zr-N4 8993(7)
Zr-N2 2.259(2) N5-Zr-N2 9862(8) N2-Zr-N3 91.04(7)

Zr-N 3 2.228(2) N5-Zr-N3 1 1634(8) N2-Zr-N4 160.30(7)
Zr-N4 2.261(2) N5-Zr-N4 101 .08(8) N 3-Zr-N4 8033(7)
Zr-NS 1.854(2) N1-Zr-N2 8080(7)

N5-C39 1.395(3) N1-Zr-N3 125.94(8) Zr-NS-C39 174.95( 17)

 

 

Syntheses of LTi(=NR)Cl derivatives

Compounds 17, 18, and 19 provide good entries to potentially interesting
imidotitanium compounds by exchanging the chloride ligand. As shown in Scheme 8,
compound 17 reacts with 1 equiv silver triflate at room temperature to afford the orange
compound (Bu‘N)Ti(Dipnacnac)(OTf) (26) in 72% yield. Since triflate is usually a better
leaving group than chloride, compound 26 may exhibit interesting reactivity. Compound
26 has a similar 1H NMR spectrum to 17. Therefore, the triflate is almost certainly bound
in solution. ORTEP diagram of complex 26 is shown in Figure 11. In Table 5, some

selected bond lengths and bond angles are listed.

29

Scheme 8

Jr

Dip\ fil
N""""Ti

g N’ \Cl
Dip 17

I AgOTf LlNMe2 L‘CH3
Dip\ II) 4)’
N""""Ti\ Dip W
C. N’

O.S//O

\
' N NM"... '
.. Dlp Tl
- . \ \
DIP O CF3 \1\Illm..rl~|i\ / (- N’
26 L N’ N\ Dip
Dip 28
27

The structure of 26 has a distorted pseudo tetrahedral symmetry similar to
chloride 17. The angle subtended at the imido nitrogen atom [Ti-N3—C30] is 177.0 (5)”,
which is slightly more linear than in 17 [(171.3(2)°], and the Ti=Nimjdc bond length
[1.680(5) A] is slightly shorter than that of 17 [1.695(2) A]. These data may reflect a

somewhat higher degree of n-interaction between Nimido and Ti in 26.

Table 5. Selected bond lengths (A) and bond angles (°) for (Bu‘N)Ti(Dipnacnac)OTf

 

 

(26)
Bond Lengths (A) Bond Angles (°)
Ti-N3 1.680(5) N3-T1-N1 108.0(2) N2-Ti-Ol 116.3(2)
Ti-Nl 1 993(6) N3-T1—N2 108.4(2) Ti-Ol -S 163.7(3)
Ti—N2 2.006(5) N1-Ti-N2 94.8(2)
Ti—Ol 1.982(4) N3-Ti-Ol l 13 .7(2) Ti-N3—C30 177.0(5)
N3-C30 1.458(7) Nl—Ti-Ol 113.9(2)

 

 

30

C(25) (111—. (13)
C124)

s“ 1201 34/1321 _. \ |\,
(l, 07‘ ‘11). (7% ‘1’", «' '\\\
' C12 1 4,1301 C112)

(91
, , C13

11 ’5 N12)
C1221 6:13 C118 (1')”

C 4) C18)

        

111')!“
Y 1271

”a 129)

015)

Figure 11: Thermal ellipsoid plot (50% probability) of (Bu‘N)Ti(Dipnacnac)(OTf)
(26).

31

 

  
   

CA C(16)
{17) C141 Cm
' 1. .
M215 V (Q N?) __\
111 \
VV,C(34) $9 0‘2)
-1“ N111
35’ “1501321 016) /
Q C171
1, C1331 c1121
C1251 1‘51.“ 119 0‘9)
‘. C181
(26) l C1141
C K
(C(13)

Figure 12: Thermal ellipsoid plot (50% probability) of (Bu'N)Ti(Dipnacnac)(NMez)
(27).

Table 6. Selected bond lengths (A) and bond angles (°) for
(Bu‘N)Ti(Dipnacnac)(NMe2) (27)

 

 

Bond Lengths (A) Bond was (°)
Ti-N4 1.703(4) N4-Ti-Nl 113.8(4) N2—Ti-N3 114.7(4)
Ti-Nl 2.047(9) N4-Ti-N2 113.2(4)
Ti—N2 2.080(9) N1—Ti-N2 92.64(14) Ti-N4—C32 176.2(9)
Ti—N3 1.922(4) N4-Ti~N3 108.4406)
N4-C32 1.430(6) N1-Ti-N3 113.6(4)

 

 

The amide derivative (Bu‘N)Ti(Dipnacnac)(NMez) (27) was prepared by

metathesis between 17 and Li(NMez) in 62.4% yield. The 1H NMR spectrum showed two

32

N-CH3 resonances at 3.93 ppm and 2.61 ppm, respectively. It is not clear whether
restricted Ti-N bonds have steric or elctronic origins. The solid-state structure from single
crystal X-ray diffraction on 27 is shown in Figure 12 and some important bond lengths
and bond angles are listed in Table 6.

A Ti-C derivative was also synthesized by metathesis route. Chloride 17 reacted
cleanly with methyl lithium at room temperature, and the yellow, crystalline
(Bu‘N)Ti(Dipnacnac)Me (28) was obtained in 88% yield after workup. Although the
solid-state structure was not determined, the 1H NMR data for 28 are consistent with a
structure similar to those of the compounds 26 and 27 (Table 7).

Table 7. 1H NMR (C5D6, 300HZ) Chemical shift of Dipnacnac ligand in
(Dipnacnac)Ti(NBu‘)X (X = OTf, NMez, and Me)

 

 

 

 

 

 

 

 

 

 

 

 

 

Compound (Dipnacnac) (Dipnacnac) (Dipnacnac)
Ti(NBu‘xort) (26) Ti(NBu')(NMe2) (27) Ti(NBu‘)Me (28)
Backbone (1H) 4.81 4.94 4.86
Methane of petane (6H) 1.51 1.53 1.56
Bond to 1,3-C 1.71 (6H) 1.44 (6H) 1.60 (6H)
of isopropyl group 1.37 (6H) 1.20 (6H) 1.42 (6H)
(24H) 1.30 (6H) 1.13 (6H) 1.19 (6H)
0.92 (6H) 0.85 (6H) 1.07 (6H)
Bond to 2-C of 3.11 (2H) 3.61 (2H) 3.36 (2H)
isopropyl group (4H) 3.02 (2H) 2.83 (2H) 3.14 (2H)

 

An unusual reaction between Ti(NMe2)4 and C6F5nacnacH

Previously, Our group14 and Collins’ group'5 had examined reactions between

various B-diketiminate ligands and Ti(NMez)4. Scheme 9 shows the general scheme for

these reactions.

33

 

Scheme9
1“”
H
Ar‘N’ \N’Ar \Ti/
An / \ ,Ar
N N

U + Ti(NMe2)4
A/K M

The general scheme 9 holds for many different B-diketiminate ligands. However,

MezN NMCz

 

'1' HNMCz

when we used the highly fluorinated ligand C6F5nacnacH for the reaction, an unusual
dark red compound (NMe2)Ti[(2-NMe2-C6F4)nacnac]F2 (29) was formed in 93% yield
(Scheme 10). 1H NMR spectrum in benzene-d6 exhibits four sharp singlets and three
multiplets between 1.48 ppm and 3.51 ppm. Each resonance integrates as three protons
against the B-diketiminate ligand backbone resonance. The typical chemical shift of the
backbone hydrogens ranges from 5 ppm to 6 ppm. In this case, the resonance was

observed at 5.09 ppm. The 19F NMR spectrum showed ten fluorine resonances.

 

Scheme 10
F NMCZ

H 4 F/II’O Med

C6F5 . N / \ N .C6F5 .Ti|\\N\
, 1.1. MezN V VF ,
+ Ti(NMez)4 ——-> | A? + HNMez
N F4
10 29

To help assign the NMR data, an X-ray diffraction experiment was performed on
single crystals of 29 (Figure 13). In Table 8, the selected bond lengths and bond angles

are listed.

34

 

Figure 13: Thermal ellipsoid plot (50% probability) of
(NMez)Ti[(2-NMez-C5F4)nacnac]Fz (29)..

Table 8. Selected bond lengths (A) and bond angles (°) for
(NMe2)Ti[(2-NMez-C6F4)nacnac]F2 (29)

 

 

 

Bond Lengths (A) Bond Angles (°)

Ti-Nl 2.140(3) NS-Ti-Nl 175.55(13) N1-Ti-F6 90.54( 10)

Ti-N2 2.055(3) N5-Ti-N2 100.04(13) N2-Ti-N3 155.62(12)

Ti-N 3 2.350(3) N5—Ti-N3 104.26(12) N2-Ti-F5 99.26(l 1)

Ti-N5 1.911(3) NS—Ti—FS 89.81(12) N2—Ti-F6 93.5 1(1 1)

Ti-F5 1.846(2) N5-Ti-F6 9253(11) N3-Ti-F5 82.8800)

Ti-F6 1.818(2) Nl-Ti-N2 82.97(12) N3-Ti—F6 83.58(10)
N1 -Ti-N3 72.89(l l) F5-Ti-F6 166.41 ( 10)
N1-Ti-F5 86.46(10)

 

The ORTEP diagram shows a distorted octahedral geometry with two trans fluoride
ligands. The B-diketimine ligand C6F5nacnac has been aminated twice through ortho C-F
activation at each pentafluoro phenyl group (Figure 20). Three out of four nitrogens in

the (2-NMe2-C6F4)nacnac ligand coordinate to the central titanium, and inequivalent (2-

35

NMez-C6F4) are evident by 1H and 19F NMR. With five sites of the six-coordinate

compound 29 accounted for, the last coordination site is occupied by a dimethylamide.

M62
NMcz N
9:1 1:375 .g ,.< 131
N N ___. N N
M M

C6F5nacnac (2-NMe2-C6F4)nacnac

(2-NMe2-C6F4)nacnacH

/ l \ M62 M

NM62 M62 N N62
N F \ / I:4
F 4 F4
N N N N

M .2 “62 M

CN 2 3 4
Figure 14: Ligand (2-NMez-C6F4)nacnac and its potential coordination with metal

Hydrolysis of compound 29 afforded the ligand (2-NMe2-C6F4)nacnacH (30) in
90% yield. The ligand 30 has interesting possibilities as a 2-4 coordinate ligand with a

valence of —1 (Figure 14).

36

Summary

In this project, a new method for synthesizing unsymmetrical diketminate ligands
from an arylketimine, Ti(NMe2)4 and an arylamine has been developed. This may be
useful for preparing complexes where standard acid catalyzed reactions give mixtures.

A series of four and five-coordinate Ti and Zr imido complexes were prepared
with one or two diketiminate ligands. For Ti, a series of compounds with the formula
(Dipnacnac)Ti(NBu‘)X (X = OTf, NMez, and Me) were prepared from
(Dipnacnac)Ti(NBu‘)Cl.

Finally, the fluorinated ligand C6F5nacnacH undergoes an ortho C-F activation at
each C6F5 group to give a novel Ti compound, which hydrolyzes to give the new

ketamine (2-NMe2-C6F4)nacnacH.

37

Bibliography

(1)
(2)

(3)

(4)

(5)

(6)

(7)
(8)

(9)

(10)

(11)

(12)

(13)

(14)

(15)

Qian, B. X.; Ward, D. L.; Smith, M. R. Organometallics 1998, 17, 3070-3076.

Qian, B. X.; Scanlon, W. J.; Smith, M. R.; Motry, D. H. Organometallics 1999,
18, 1693-1698.

Kakaliou, L.; Scanlon, W. J.; Qian, B. X.; Baek, S. W.; Smith, M. R.; Motry, D. H.
Inorg. Chem. 1999, 38, 5964-5977.

Blake, A. J.; Collier, P. E.; Dunn, S. C.; Li, W. S.; Mountford, P.; Shishkin, O. V.
J. Chem. Soc. Dalton Trans. 1997, 1549-1558.

Dunn, S. C.; Batsanov, A. S.; Mountford, P. J. Chem. Soc. Chem. Commun. 1994,
2007-2008.

Wigley, D. E. In Progress in Inorganic Chemistry, Vol 42, 1994; Vol 42, pp 239-
482.

Mountford, P. J. Chem. Soc. Chem. Commun. 1997, 2127-2134.

Amey, D. J.; Bruck, M. A.; Huber, S. R.; Wigley, D. E. Inorg. Chem. 1992, 31,
3749-3755.

Walsh, P. J .; Hollander, F. J .; Bergman, R. G. J. Am. Chem. Soc. 1988, 110, 8729-
8731.

Bennett, J. L.; Wolczanski, P. T. J. Am. Chem. Soc. 1997, 119, 10696—10719.

Bai, Y. N.; Roesky, H. W.; Noltemeyer, M.; Witt, M. Chem. Ber. Reel. 1992, 125,
825-831.

Profilet, R. D.; Zambrano, C. H.; Fanwick, P. E.; Nash, J. J .; Rothwell, I. P. Inorg.
Chem. 1990, 29, 4363-4364.

Zambrano, C. H.; Profilet, R. D.; Hill, J. E.; Fanwick, P. E.; Rothwell, I. P.
Polyhedron 1993, 12, 689-708.

Scanlon, W. J. Master Thesis, Michigan State University 1998.

Rahim, M.; Taylor, N. J.; Xin, S.; Collins, S. Organometallic. 1998, 17, 1315-
1323.

38

CHAPTER 3

EXPERIMENTAL METHODS

General Methods and instrumentation

All manipulations, excluding ligand preparations, were carried out under an
atmosphere of dinitrogen or argon using standard Schlenk-line or dry-box techniques.
Dinitrogen and argon were purified by passing through columns of MnO supported on
silica.

Solvents (excluding deuteriated solvents) were freshly distilled over
sodium/benzophenone ketyl (toluene, pentane, ether and THF) or over calcium hydride
(methylene chloride) and were saturated with dinitrogen before use. Chloroform-dl,
bezene-d6, toluene-d3 were dried over activated 3A sieves, and vacuum transferred.
Dichloromethane-dz was dried over activated 4A sieves, and vacuum transferred.
Chloroform-d1 and dichloromethane-dz were stored under dinitrogen in air-free flasks in
the dry-box. Bezene-d6 and toluene-d8 were stored in air-free flask over a sodium mirror
in dry-box.

Elemental analyses (C, H, N) were performed on a Perkin Elmer CHN 2400
Series II CHNS/O at the chemistry department of Michigan State University. The
following NMR spectrometers were used: Varian Gemini-300, Inova—3OO or VXR-300.
IH (300 MHz) and 13C (75 MHz) NMR spectra were referenced to the chemical shift of
the residual proton and '3C signals of the deuterated solvents. ”F (288 MHz) NMR

spectra were referenced to neat CFC13 (5 0 ppm) as an external standard. Uncorrected

39

melting points of crystalline samples in sealed capillaries (under a dinitrogen atmosphere)

were reported as ranges.

Single Crystal X-Ray Structure Determination

Unless otherwise noted, all crystals were considered to be air sensitive and were
collected by filtration and coated with Paratone-N. A suitable single crystal was selected
and mounted onto a glass fiber (with Paratone-N). The crystal was then transferred to the
goniometer of a Siemens SMART CCD diffractometer using Mo K), radiation (it:
0.71073 A). Data frames were collected as 30-second exposures at 173K. The initial cells
were calculated from three sets of 20 frames. All data sets were collected over a
hemisphere of reciprocal space. SAINT was used to integrate 1025 frames and to
generate the raw file. Final unit cell parameters were obtained by least-squares
refinement of strong reflections obtained. Absorption correction and time decay were
applied to the data by SADABS. The non-hydrogen atoms located by using SHELXS and
refined using.

Calculations were based on F2 data. Unless noted otherwise, all non-hydrogen
atoms were refined using anisotropic displacement parameters and all hydrogen atoms
were placed in calculated positions and refined as riding models. Three of the parameters
are defined below.

GOF = [21111183 — F.2121/(n - p11”

where n is the number of reflections and p the total number of parameters refined.

R1 = ZIIFOI — IFCIIIZIFOI

wR2 = [1:[w(F,2 — F.2121/2[w(F02)2]]”

4O

Starting materials

Common chemicals were purified by established procedures. The compounds
(Bu‘N)TiC12(PyBu‘)2,' (Bu'N)TiCl3Py3,2 (TolN)TiClzPy3,2 (DipN)ZrC12Py2,3 Ti(NMe3)4,4
and Zr(NMe2)44 were prepared according to the literature procedures.

2,4-pentanedione, 2,6-diisopropyl aniline were distilled prior to use. p-Toluidine

was sublimed and AgOTf was recrystallized from ether before use.

Synthesis
4-(p-Methylphenylamino)-3-pentene-2-one (3)5 In a 500 mL round bottom

flask, 2,4-pentanedione (40 g, 0.4 mol) and freshly sublimed p-toluidine (42.8 g, 0.4 mol)
were dissolved in 300 mL toluene. A Dean-Stark apparatus was used to azetropically
remove water. The mixture was heated at 130 °C for eight hours to give a brown solution.
All the toluene was removed by a rotary evaporator and the subsequent brown oil was
diluted with hexane. The hexane solution was put into —30 °C freezer for overnight. The
yellow crystallized material was collected by suction filtration (61.3 g, 81.5%). mp 67—
68 °C. 1H NMR (CDC13, 300 MHz) 5 12.38 (br, s, 1H), 7.12 (d, 2H), 6.97 (d, 2H), 5.18
(s, 1H), 2.32 (s, 3H), 2.07 (s, 3H), 1.94 (s, 3H). 13C {'H} NMR (CDC13, 75 MHz) 6
195.8. 160.6, 135.9, 135.4, 129.5, 124.7, 97.10, 29.03, 20.81, 19.68.
4-(2,6-Di-iso-propylphenylamino)-3-pentene-2-one (4)5 A 250 mL round
bottom flask was charged with 2,4-pentanedione (40 g, 0.40 mol), TsOH-H20 (0.46 g,
2.5 mmol), and 2,6-diisopropyl aniline (47 g, 0.27 mol). The mixture was heated with a
minimum amount of toluene in a Dean-Stark apparatus for eight hours. After removing

the solvents, the mixture was vacuum distilled (105 °C / 0.01 mmHg) to give a pale

yellow ketoamine which solidified upon standing overnight (65 g, 93%). mp 49-51 °C.

41

1H NMR (CDC13, 300 MHz) 5 12.06 (8, br, 1H), 7.26 (m, 1H), 7.15 (d, 2H), 5.18 (s, 1H),

3.00 (sept, 1H), 2.09 (s, 3H), 1.18 (d, 6H), 1.60 (s, 3H), 1.12 (d, 6H). ”c1011 NMR
(CDC13, 75 MHz) 5195.9, 163.2, 146.2, 133.4, 128.2, 123.5, 95.53, 29.03, 28.41, 24.54.
2261,1910.

4-(3,5-Di-trifluoromethylamino)-3-pentene-2-one (5) A 100 mL round-bottom
flask was charged with 2,4-pentanedione (0.75 g, 7.5 mmol), 3,5-di-
trifluoromethylaniline (1.15 g, 5.0 mmol) and TsOH-H20 (0.02 g, 0.1 mmol). Dry
toluene 50 mL was added to the flask and a Dean-Stark apparatus was used to
azetropically remove water. The mixture was heated at 130 °C for eight hours to give a
brown solution. All the volatiles were removed by rotary evaporator. The subsequent
brown oil was vacuum distilled (75 °C / 0.01 mmHg) to give pale yellow oil which
solidified upon standing overnight. (1.45 g, 93%). mp 45-48 °C. 1H NMR (CDC13, 300
MHz) 6 12.68 (s, 1H), 7.60 (s, 1H), 7.49 (s, 2H), 5.29 (s, 1H), 2.10 (s, 3H), 2.06 (s, 3H).
'3c {‘H} NMR (CDC13, 75 MHz) 5197.73, 157.74, 147.67, 132.67, 123.37, 121.06,
1 18.02, 100.09, 29.40, 19.84. 19F NMR (CDC13, 288MHz) 6 —63.7 1.

4-(Pentafluorophenylamino)-3-pentene-2-one (6) A 250 mL round bottom flask
was charged with 2,4-pentanedione (11 g, 0.11 mol), TsOH-H20 (0.3 g, 1.6 mmol), and
pentafluoroaniline (14.2 g, 0.078 mol). Dry toluene (50 mL) was added to the flask and a
Dean-Start apparatus was used to azetropically remove water. The mixture was heated at
130°C for ten hours to give a yellow solution. All the volatiles were removed by rotary
evaporator leaving a yellow solid, which was washed with pentane (20 mL). Colorless
crystals formed after recrystallization overnight from pentane/MeOH at -30 °C. (16.50 g,

80.3%). mp 83—85 °C. lH NMR(CDC13, 300 MHz) 611.84 (s, 1H), 5.34 (s, 1H), 2.05 (s,

42

3H), 1.79 (s, 3H). l3C1111} NMR(CDC13, 75 MHz) 6197.97, 159.80, 145.10, 141.75,
139.42, 138.12, 136.06, 114.41, 99.41, 29.01, 18.59. ”P NMR (CDC13, 288MHz) 6—

146.63, -156.94, -162.48.
2-p-Tolylamino-4-p-tolylimino-2-pentene (TolnacnacH) (7)

METHOD 15: A toluene solution of compound 3 (41.0 g, 0.38 mol), TsOH-H20

 

(72 g, 0.38 mol), p-toluidine (40.7 g, 0.38 mol) was charged in 500 mL round bottom. A
Dean-Stark apparatus was used to azetropically remove water. The mixture was heated at
130 °C for 24 hours. After the mixture was cooled to room temperature, it was diluted
with ether (40 mL) and washed with aqueous base (100 mL, 18.7% NaOH). After
separation from the ether layer, the aqueous layer was back extracted with ether (2 x 20
mL). The combined organics were dried over magnesium sulfate, filtered, and ether was
removed using a rotavap. The resultant oil was diluted with 30 mL hexanes, and cooled
to —30 °C overnight to induce crystallization. The pale yellow diketimine was obtained
after filtration. The product was washed with cold hexane and then dried in vacuo (87 g,
82.4 %).

METHOD 26: A 50ml round bottom flask was charged with compound 11 (216
mg, 1.0 mmol), TsOH-H20 (190 mg, 1.0 mmol), p-toluidine (107mg, 1.0mmol). The
mixture was stirred with 20 mL toluene in Dean-Stark apparatus in an oil bath heated at

130 °C for 24 hours. After the mixture was cooled to room temperature, it was diluted

with ether (25 mL) and washed with aqueous base (30 mL, 20% NaOH). After separated
from the organic layer, the water phase was back extracted with ether (2 x 10 mL). The

combined organic phase was dried over MgSO4. The solvent was removed by vacuum.

43

Yellow analytically pure compound was obtained by recrystallization from Hexane. (146
mg, 52.5%).

METHOD 3: To a stirred solution of Ti(NMe2)4 (224 mg, 1.0 mmol) in toluene
was added a toluene solution of p-toluidine (214 mg, 2.0 mmol). The solution quickly
turned from yellow to dark red. After 8 hours stirring, compound 3 (378 mg, 2.0 mmol)
was added, and the mixture was refluxed 24 hours. A yellow solution with orange
precipitate was formed. After filtration, the solvent was removed under vacuum and gave
a yellow solid. (453 mg, 81.5%) Samples thus prepared were sufficiently pure ('H NMR
spectroscopy) to use in further reactivity studies. mp 67—70 °C. 1H NMR (CDC13, 300
MHz) 5 12.62 (s, br, 1H), 7.07 (d, 4H), 6.84 (d, J = 8.1 Hz, 4H), 4.83 (s, 1H), 2.31 (s,
6H), 1.98 (s, 6H). 13C {H} NMR (CDC13, 75 MHz) 6 159.5, 143.1, 132.6, 129.2, 122.6,
96.80, 20.76, 20.60.

2-2,6-Di-iso-propylphenylamino-4-2,6-di-iso-propylphenylimino-Z-pentene
(DipnacnacH) (8) A 250 mL round bottom flask was charged with compound 4 (34 g,
0.13 mol), TsOH-H20 (22.6 g, 0.13 mol), and 2,6-diisopropyl aniline (23 g, 0.13 mol).
The mixture was stirred with a minimum amount of toluene in a Dean-Stark apparatus in
an oil bath heated at 170 °C for 24 hours. After the mixture was cooled to room
temperature, it was diluted with ether (100 mL) and washed with aqueous base (100 mL,
12.7% KOH). The water layer was separated from the organic layer, and the water phase
was back extracted with ether (20 mL). The combined organics were dried over MgSO4.
Colorless, analytically pure compound was obtained by recrystallization from
hexane/MeOH (43.4 g, 80%). mp 138—140 °C. 1H NMR (CDC13, 300 MHz) 5 12.12 (3,

br, 1H), 7.12 (m, 6H), 4.86 (s, 1H), 3.11 (sept, 4H), 1.71 (s, 6H), 1.20 (d, 12H), 1.11 (d,

12H). '3c1'H} NMR (CDC13, 75 MHz) 5 161.18, 142.44, 140.69, 125.06, 123.00, 93.18,
28.17, 24.20, 23.22, 20.74.
2-3,5-Di-trifluoromethylamino-4-3,S-trifluoromethylimino-2-pentene
(TFMnacnacH) (9) A 100 mL round bottom flask was charged with compound 5 (1.33
g, 4.3 mmol), 3,5-di-trifluoromethylani1ine (0.979 g, 4.3 mmol) and TsOH-H20 (0.813 g,
4.3 mmol). Dry toluene (50 mL) was added to the flask and a Dean-Stark apparatus was
used to azetropically remove water. The mixture was heated at 150 °C for 24 hours. After
the mixture was cooled to room temperature, it was diluted with ether (20 mL) and
washed with aqueous base (50 mL, 1.0% KOH). After separated from ether layer, the
aqueous layer was back extracted with ether (2 x 10 mL). The combined organics were
dried over MgSO4. A brown solid was formed after removal of the ether under reduced
pressure. Colorless analytically pure compound was obtained by crystallization from
hexane/MeOH at -30°C. (1.76 g, 78.0%). mp 126-128°C. 1H NMR (CDC13, 300 MHz) 6
12.51 (s, 1H), 7.56 (s, 2H), 7.34 (s, 4H), 5.04 (s, 1H), 2.02 (s, 6H). l3(21'111 NMR
(CDC13, 75 MHz) 6160.35, 146.79, 132.44, 125.06, 122.33, 116.95, 99.93, 20.96. l9F
NMR (CDC13, 288Hz) 5 -63.49. Anal. Calcd for C21H14N2F12: C, 48.29; H, 2.70; N,
5.36. Found: C, 48.32; H, 2.57; N, 5.32.
2-Pentafluorophenylamino-4-pentafluorophenylimino-2-pentene

(C6F5nacnacH) (10) A 250 mL round bottom flask was charged with compound 6 (3.0 g,
96.5 mmol), pentafluoroaniline (22.1 g, 96.5 mmol) and TsOH-H20 (0.813 g, 4.3 mmol).
Dry toluene 150 mL was added to the flask and a Dean-Stark apparatus was used to
azetropically remove water. The mixture was heated at 150 °C for 24 hours. After the

mixture was cooled to room temperature, it was diluted with ether (40 mL) and washed

45

with aqueous base (80 mL, 10% N aOH). After separated from ether layer, the aqueous
layer was back extracted with ether (2 x 10 mL). The combined organics were dried over
MgSO4. A dark brown solid was formed after removal of the ether under reduced
pressure. Colorless analytically pure compound was obtained by recrystallization from
hexane/MeOH overnight at -30 °C. (17.86 g, 42.9%). mp 85-86 °C. 1H NMR (CDC13,
300 MHz) 5 12.06 (s, 1H), 5.18 (s, 1H), 1.93 (s, 6H). 13(3 {1H 1 NMR (CDC13, 75 MHz) 5
164.28, 142.96, 139.67, 136.27, 120.00, 99.21, 20.90. 19F NMR (CDC13, 288Hz) 5 —
149.23, -160.84, -163.31. Anal. Calcd for C17H8N2F102 C, 47.46; H, 1.87; N, 6.51. Found:
C, 47.23; H, 1.87; N, 6.47.

2-Dimethylamino-4-p-tolylimino-2-pentene (11) To a stirred solution of
Ti(NMe2)4 (3.150 g, 0.014 mol) in toluene was added a toluene solution of freshly
prepared 3 (5.32 g, 0.028 mol). The solution changed from yellow to dark red quickly.
After heatin g and reflux for 24 hours, precipitate formed. After filtration, the solvent was
removed under vacuum to give dark red solid. Colorless crystals formed in saturated
pentane solution at —80 °C for 24 hours (4.88 g, 80.4%). mp 31-33 °C. 1H NMR (CDC13,
300 MHz) 5 7.04 (d, 2H), 6.63 (d, 2H), 4.75 (s, 1H), 2.86 (s, 6H), 2.45 (s, 3H), 2.77 (s,
3H), 1.84(s, 3H). 13c {'H} NMR (CDC13, 75 MHz) 5 165.39, 154.10, 150.17, 130.43,
128.88, 120.03, 97.32, 39.36, 22.31, 20.46, 16.15.

Li(Dipnacnac) (14) A pentane (200 mL) solution of freshly recrystallized
compound 8 (21.1 g, 50 mmol) was treated with a hexane solution of "BuLi (2.5 M, 20
mL, 50 mmol) at 0 °C with stirring in 30 minutes. The mixture was heated to reflux for
one hour, giving a homogeneous pale yellow solution. The volume of solution was

concentrated to about 20 mL during which time colorless compound crystallized. After

46

being cooled to —30 °C, the solid was collected by filtration (19.9 g, 93%). mp 158—160
°c (decomp). 1H NMR (C61), 300 MHz) 5 7.18 (m, 6H), 4.86 (s, 1H), 3.09 (sept, 4H),
1.80 (s, 6H), 1.17 (d, 12H), 1.15 (d, 12H). 13c1'H} NMR (c613,, 75 MHz) 5164.0, 149.2,
140.7, 123.4, 123.3, 93.01, 28.21, 24.08, 24.02, 23.35. Anal. Calcd for LiC29H41N2: C,
82.04; H, 9.73; N, 6.60. Found: C, 82.63; H, 9.64; N, 6.65.

Li(Tolnacnac) (15) A solution of compound 7 (20 g, 72 mmol) in pentane (350
mL) was treated with a hexane solution of "BuLi (45 mL, 1.6 M, 72 mmol) with stirring
at 0 °C. After the addition, the stirring was maintained for another 10 minutes at that
temperature. The mixture was allowed to warm to room temperature and was stirred for
another two hours. The volume of the yellow mixture was reduced to about 250 mL.
Yellow compound was collected by filtration under nitrogen (18 g, 88%). mp 185-187
°C. 1H NMR (C6D6, 300 MHz) 5 6.91 (d, 4H), 6.61 (d, 4H), 4.67 (s, 1H), 2.15 (s, 6H),
1.79 (s, 6H). 13(3 {'H} NMR (C613,, 75 MHz) 5 165.6, 151.4, 131.2, 129.6, 124.3, 95.49,
23.08, 20.87. Anal. Calcd for L1C19H21N22 C, 80.26; H, 7.44; N, 9.85. Found: C, 80.18;
H, 7.15; N, 9.50.

Li(TFMnacnac) (16) To a stirred solution of freshly recrystallized compound 9
(3.49 g, 6.69 mol) in toluene was added hexane solution of nBuLi (1.6 M, 4.2 mL, 6.69
mmol) at 0°C in 30 minutes. The solution was then heated at 55°C for one hour, forming
a yellow solution. The solvent was removed under vacuum to afford a yellow solid. The
yellow solid was washed with pentane and then dried in vacuo. (3.02 g, 85.6%). Samples
thus prepared were sufficiently pure (1H NMR spectroscopy) to use in further reactivity

studies. mp 157-160 °C. lH NMR (C6D6, 300 MHz) 5 7.54 (s, 2H), 6.99 (s, 4H), 4.61 (s,

1H), 1.49 (s, 6H). 13(:1‘H} NMR ((261)., 75 MHz) 5 166.90, 155.14, 132.48, 125.73,

47

124.32, 116.16, 96.99, 22.95. ”P NMR (C613,, 288Hz) 5 —63.07. Anal. Calcd for
LiC21H13N2F12: C, 47.74; H, 2.48; N, 5.30. Found: C, 47.87; H, 2.53; N, 5.17.

Li(Cngnacnac) (31) To a stirred solution of freshly recrystallized compound 10
(641 mg, 1.49 mmol) in pentane was added a hexane solution of nBuLi (2.5 M, 0.6 mL,
1.49 mmol) at 0 °C over 30 minutes. The solution was then warmed to room temperature
and stirred overnight to give a yellow precipitate. The mixture was allowed to stand at —
30 °C for 24 hours. The yellow solid was obtained after filtration. The product was
washed with cold pentane and then dried in vacuo. (474 mg, 73%). Samples thus
prepared were sufficiently pure (1H NMR spectroscopy) to use. lH NMR (C6D6, 300
MHz) 54.60 (s, 1H), 1.51 (s, 6H). l3C{1H} NMR (C6D6, 75 MHz) 5170.97, 143.16,
140.11, 136.54, 127.23, 100.68, 23.53. ‘91: NMR (C6D6, 288Hz) 5 —154.98, -163.80, -
164.34.

(Bu‘N)Ti(Dipnacnac)Cl (17) To a stirred solution of (Bu‘N)TiC12(PyBu')2 (3.69
g, 8.02 mmol) in toluene, a toluene solution of compound 14 (3.40 g, 8.02 mmol) was
added dropwise. After addition, the mixture was heated at 70 °C for 16 hours. After
filtration, the solvent was removed under vacuum to give a brown solid, which was
washed with pentane two times to give yellow solid after drying in vacuo. (3.02 g, 66%).
Samples thus prepared were sufficiently pure (1H NMR spectroscopy) to use. An
analytically pure, X-ray quality crystalline sample was obtained from a saturated

pentane/toluene solution at —30 °C. mp 230-233 °C (decomp). 1H NMR (CDC13, 300

MHz) 5 7.17 (m, 6H), 5.30 (s, 1H), 3.22 (sept, 2H), 3.15 (d, 2H), 1.91 (s, 6H), 1.58 (d,

6H), 1.41 (d, 6H), 1.22 (d, 6H), 1.06 (d, 6H), 0.49 (s, 9H). '3C1'H} NMR (c1303, 75

MHz) 5167.83, 144.81, 142.18, 140.62, 126.51, 125.05, 123.60, 94.14, 72.46, 30.90,

48

28.69, 28.40, 26.47, 24.33, 24.05, 23.97, 23.92. Anal. Calcd for TiC33H50N3Cl: C, 69.28;
H, 8.81; N, 7.35. Found: C, 69.15; H, 9.04; N, 7.33.

(Bu‘N)Ti(Tolnacnac)(PyBut)Cl (18) To a stirred solution of Bu'NTiC12(PyBu‘)2
(1.298 g, 2.82 mmol) in toluene, a toluene solution of compound 15 (0.801 g, 2.82 mmol)
was added dropwise. After addition, the mixture was heated at 70°C for 16 hours. After
filtration, the solvent was removed under vacuum to give a dark brown solid, which was
recrystallized from saturated pentane/toluene overnight at —30 °C gave a brown
crystalline compound. (0.71 g, 44.4%). mp 80-82 °C. 1H NMR (C6D6, 300 MHz) 5 8.64
(br, s, 4H), 6.98 (br, s, 4H), 6.81 (m, 4H), 5.06 (s, 1H), 2.12 (s, 6H), 1.87 (s, 6H), 0.97 (s,
9H), 0.96 (s, 9H). 13C {'H} NMR (C6D6, 75 MHz) 5150.69, 149.51, 133.57, 129.69.
129.00, 125.56, 122.92, 120.78, 98.16, 71.56, 34.45, 31.55, 30.17, 22.66, 22.51, 20.91.

(Bu'N)Ti(TFMnacnac)(PyBu')Cl (19) To a stirred solution of
(Bu‘N)TiC12(PyBu‘)2 (200 mg, 0.435 mmol) in toluene, a toluene solution of the
compound 16 (230 mg, 0.435 mmol) was added dropwise. The solution turned brown
from yellow and some precipitate formed. The mixture was heated at 70 °C for 16 hours.
After filtration, the solvent was removed under vacuum to give an orange solid. After
washing with pentane two times, yellow solid was dried in vacuo. (185 mg, 52.6%).
Samples thus prepared are sufficiently pure (1H NMR spectroscopy) to use. An
analytically pure, X-ray quality crystalline sample was obtained from a saturated
pentane/toluene solution at —30 °C. mp 174-177 °C. 1H NMR (C6D6, 300 MHz) 5 8.41

(br, s, 2H), 8.35 (m, 2H), 7.77 (br, s, 1H), 7.50 (br, s, 1H), 7.13 (m, 2H), 6.67 (m, 2H),

4.91 (s, 1H), 1.53 (s, 3H), 1.45 (s, 3H), 0.92 (s, 9H), 0.74 (s, 9H). l3C1 1H 1 NMR (c613,,

75 MHZ) 5178.49, 163.81, 153.36, 150.32, 146.26, 132.03, 128.37, 128.05, 127.73,

49

126.76, 126.13, 121.67, 118.76, 100.15, 72.77, 34.91, 30.87, 29.84, 22.71, 14.26. 19F
NMR (CDC13, 288Hz) 5 -61.83, -62.08. Anal. Calcd for TiC34H35N4F12Cl: C, 50.35; H,
4.35; N, 6.91. Found: C, 50.27; H, 4.39; N, 6.92.

(NTol)Ti(Dipnacnac)Cle2 (22) To a stirred solution of (TolN)TiC12Py3 (127
mg, 0.28 mmol) in toluene, a toluene solution of compound 14 (119 mg, 0.28 mmol) was
added dropwise. After addition, the mixture was heated at 70 °C for 16 hours. After
filtration, the filtrate was concentrated under vacuum and pentane was added to a
saturated the solution. Dark brown crystals formed after standing at —30 °C overnight.
(121 mg. 63.0%). mp 184-187 °C. 1H NMR (CDC13, 300 MHz) 5 8.46 (d, 2H), 7.11 (m,
3H), 7.03 (m, 2H), 6.77 (m, 3H), 6.70 (m, 3H), 6.44 (m, 2H), 5.35 (s, 1H), 3.76 (sept,
2H), 3.20 (sept, 2H), 2.02 (s, 3H), 1.75 (s, 6H), 1.45 (d, 6H), 1.19 (d, 6H), 1.12 (m, 12H).
13c {'H} NMR (CDC13, 75 MHz) 5166.95, 160.88, 150.63, 147.48, 142.94, 142.28,
136.76, 130.26, 128.55, 126.73, 124.70, 124.38, 123.90, 123.30, 98.66, 29.16, 28.05.
25.28, 24.77, 24.58, 20.98. Anal. Calcd for TiC41H53N4Cl: C, 71.86; H, 7.80; N, 8.18.
Found: C, 70.57; H, 7.87; N, 8.13.

(Bu‘N)Ti(TFMnacnac)2 (23) To a stirred solution of (Bu‘N)TiC12(PyBu‘)2 (146
mg, 0.317 mmol) in toluene, a toluene solution of the compound '16 (335 mg, 0.634
mmol) was added dropwise. The solution turned brown from yellow and some precipitate
formed. The mixture was heated at 70 °C for 16 hours. After filtration, the solvent was
removed under vacuum to give the yellow solid. After washing with pentane two times,
yellow solid was dried in vacuo. (228 mg, 62.0%). Samples thus prepared are sufficiently
pure ('H NMR spectroscopy) to use. An analytically pure, X-ray quality crystalline

sample was obtained from a saturated pentane/toluene mixed solution at —30 °C. mp 165-

50

167 °C. 1H NMR (CDC13, 300 MHz) 5 7.56 (s, 4H), 7.17 (s, 8H), 5.012 (s, 2H), 2.00 (s,

12H), 0.52 (s, 9H). l3C{lH} NMR (CDC13, 75 MHz) 5 164.02, 151.07, 131.96, 125.41.
121.17, 118.38, 101.74, 77.20, 31.00, 23.39. 19F NMR (CDC13, 288Hz) 5. -61.45. Anal.
Calcd for TiC46H35N5F24: C, 47.56; H, 3.04; N, 6.03. Found: C, 47.45; H, 2.97; N, 5.62.

(DipN)Zr(Tolnacnac)2 (25) To a stirred suspension of (DipN)ZrC12Py2 (502 g,
1.04 mmol) in toluene, a toluene solution of compound 15 (593 mg, 2.08 mmol) was
added dropwise. Stirring continued overnight. After filtration, the solution was
concentrated under reduced pressure. Pentane was added to the saturated solution.
Yellow-orange crystals formed upon standing at -30 °C for 24 hours. (598 mg, 70%) mp
232-235 °C. ]H NMR (C6D6, 300 MHz) 5 7.00 (d, 2H), 6.94 (d, 8H), 6.82 (d, 8H), 6.77
(m, 1H), 4.87 (s, 2H), 3.94 (sept, 2H), 2.00 (s, 12H), 1.90 (s, 12H), 1.02 (s, 6H), 1.00 (s,
6H). l3C{'H} NMR (c613,,75 MHz) 5 164.01, 146.91, 141.66, 133.65, 129.72, 125.45,
121.57, 100.25, 27.84, 24.21, 23.70, 20.68. Anal. Calcd for ZrC50H59N5: C, 73.12; H,
7.24; N, 8.53. Found: C, 73.22; H, 7.36; N, 8.31.

(Bu'N)Ti(Dipnacnac)OTf (26) To a stirred solution of compound 17 (0.58 g, 1.0
mmol) in toluene, an ether solution of AgOTf (0.26 mg, 1.0 mmol) was added dropwise.
A white precipitate was formed spontaneously. Stirring was continued for an hour,
yielding to give an orange solution. The solution was filtered. The solvent was removed
under vacuum, and then washed by pentane for two times. The off-white solid was dried
in vacuo. (0.497 g, 71.5%). Samples thus prepared were sufficiently pure (1H NMR
spectroscopy) to use. An analytically pure, X-ray quality crystalline sample was obtained

from a saturated petane/toluene solution at —30 °C. mp 202-205 °C (decomp). 1H NMR

(C6D6, 300 MHz) 5 7.12 (m, 6H), 4.81(s, 1H), 3.11 (sept, 2H), 3.02 (sept, 2H), 1.71 (d,

51

6H), 1.51 (s, 6H), 1.37 (d, 6H), 1.30 (d, 6H), 0.92 (d, 6H), 0.58 (s, 9H). '3c1'H} NMR
(C6D6, 75 MHz) 5 168.08, 145.11, 142.48, 140.29, 131.09, 127.48, 124.46, 123.98.
92.76, 74.04, 30.93, 29.71, 28.65, 25.84, 24.37, 24.15, 23.61, 22.74. 19F NMR (C6D6,
288Hz) 5. —78.17.

(Bu‘N)Ti(Dipnacnac)(NMe2) (27) To a stirred solution of compound 17 (275
mg, 0.48 mmol) in toluene, LiNMez (25 mg, 0.49 mmol) was added slowly. After
addition, the mixture was stirred overnight. After filtration, the solvent was removed
under vacuum to afford a brown solid. An off-white crystalline compound formed
through recrystallization from saturated pentane solution at —30 °C.(272 mg, 62.4%) mp
>260 °C. 1H NMR (C6D6, 300 MHz) 5 7.15 (m, 6H), 4.94 (s, 1H), 3.93 (s, 3H), 3.61 (sept,
2H), 2.83 (sept, 2H), 2.61 (s, 3H), 1.53 (s, 6H), 1.47 (d, 6H), 1.44 (d, 6H), 1.20 (d, 6H),
1.13 (d, 6H), 0.85 (s, 9H). 13c1‘H} NMR (C6D6, 75 MHz) 5 167.23, 144.91, 142.28,
141.38, 126.18, 123.86, 123.28, 96.06, 52.90, 40.11, 32.55, 28.74, 28.45, 25.62, 24.60.
24.34, 24.23, 24.20, 2411. Anal. Calcd for TiC35H56N4: C, 72.38; H, 9.72; N, 9.65.
Found: C, 71.94; H, 9.78; N, 9.39.

(Bu‘N)Ti(Dipnacnac)Me (28) To a stirred solution of compound 17 (1.21 g, 2.1
mmol) in toluene, an ether solution of LiMe (1.3 mL, 1.6 M, 2.1 mmol) was added
dropwise at —50 °C. After addition, the mixture was allowed to warm to room
temperature. After two hours, the mixture was filtered and the filtrate was concentrated.
Yellow compound was crystallized after 24 hours at —30 °C. (1.029 g, 88.2%). mp 201-
203 °C (decomp) 1H NMR (C6D6, 300 MHz) 57.15 (m, 6H), 4.86 (s, 1H), 3.36 (sept,
2H), 3.14 (sept, 2H), 1.60 (d, 6H), 1.56 (s, 6H), 1.42 (d, 6H), 1.19 (d, 6H), 1.07 (d, 6H),

0.90 (s, 9H), 0.76 (s, 3H). '3C1'H) NMR (C6D6, 75 MHz) 5167.78, 145.29, 142.07,

52

141.02, 126.56, 124.05, 123.87, 93.38, 70.03, 32.40, 28.84, 28.58, 27.44, 26.48, 24.39,
24.30, 23.93, 23.86. Anal. Calcd for TiC34H53N3: C, 74.02; H, 9.68; N, 7.62. Found: C,
73.42; H, 10.03; N, 7.47.

(NMe2)Ti[(2-NMe2-C6F4)nacnac]F2 (29) To a stirred solution of Ti(NMe2)4
(1.257 g, 5.61 mmol) in pentane, was added compound 10 (2.413 g, 5.61 mmol) toluene
solution dropwise at —50 °C. The solution changed from yellow to dark red
spontaneously. The mixture was warmed to room temperature and stirred overnight. The
volatile materials were removed under vacuum. Then product was crystallized from a
saturated pentane/toluene solution at —30 °C to give dark red crystals. (3.19 g, 93.4%) mp
170-173 °C. 1H NMR (CDC13, 300 MHz) 5 5.09 (s, 1H), 3.51 (s, 3H), 2.90 (s, 3H), 2.77
(s, 3H), 2.75 (s, 3H), 2.69 (m, 3H), 2.51(m, 3H), 1.66 (m, 3H), 1.48 (s, 3H) . 13C {'H}
NMR (CDC13, 75 MHz) 5 168.10, 166.74, 146.67, 145.42, 143.44, 142.10, 140.78,
138.70, 137.49, 135.41, 134.47, 132.89, 132.08, 130.67, 105.07, 50.55, 49.49, 47.59.
42.63, 34.41, 22.69, 21.84, 14.20. ”P NMR (CDC13, 288Hz) 5 -143.62, -146.88, -148.65,
-149.39, -157.79, -159.31, -161.55, -162.10, -163.57, -167.21. Anal. Calcd for
TiC23H25N5F10: C, 45.33; H, 4.14; N, 11.50. Found: C, 44.94; H, 4.04; N, 10.55.

(2-NMe2-C6F4)nacnacH (30) Compound 29 (220 mg, 0.36 mmol) was dissolved
in an ether/1120 mixture, and stirred for 10 minutes in air. After separation from the ether
layer, the aqueous layer was back extracted with ether two times. The combined ether
fractions were dried over MgSO4. The solvent was removed by rotavap to give a yellow
solid. Off-white crystals were deposited from a saturated pentane solution after standing

at —30 °C overnight. (155 mg, 89.6%). mp 77-80 °C. 1H NMR (CDC13, 300 MHz) 5

11.97 (s, 1H), 5.037 (s, 1H), 2.739 (s, 12H), 1.854 (s, 6H). 13c {'H} NMR (c1303, 75

53

MHz) 5 162.83, 146.33, 142.95, 139.48, 136.43, 131.58, 126.23, 97.68, 42.98, 20.70. 19F

NMR (CDCl3, 288Hz) 5 -149.63, -150.45, -162.59, -l64.26.

54

Bibliography
(1) Dunn, S. C.; Batsanov, A. S.; Mountford, P. J. Chem. Soc. Chem. Commun. 1994,
2007-2008.

(2) Blake, A. J.; Collier, P. E.; Dunn, S. C.; Li, W. S.; Mountford, P.; Shishkin, O. V.
J. Chem. Soc. Dalton Trans. 1997, 1549-1558.

(3) Amey, D. J.; Bruck, M. A.; Huber, S. R.; Wigley, D. E. Inorg. Chem. 1992, 3],
3749-3755.

(4) Bradley, D. C.; Thomas, L. M. J. Chem. Soc. 1960, 3857-3861.
(5) Qian, B. X.; Ward, D. L.; Smith, M. R. Organometallics 1998, 17, 3070-3076.

(6) Kakaliou, L.; Scanlon, W. J.; Qian, B. X.; Baek, S. W.; Smith, M. R.; Motry, D.
H. Inorg. Chem. 1999, 38, 5964-5977.

55

APPENDIX

X-ray Data structure collection parameters

56

Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group

Cell

a (A)

b12511

c (A)

01(°)

B (°)

X (°)

Volume (A3)

Z

d (calc.) (Mg/m3)
Abs. coef. (mm‘l)

F (000)

Crystal size (mm)
26 range (°)
Index ranges

Reflections
collected
Independent
reflections
Refinement method

Data / restraints /
parameters

GOF / F2

Final R indices
[1>26(1)l

R indices (all data)

Largest diff. peak
and hole (e A3)

TMFnacnacH (9)

C21H14F12N2
522.34
173(2)
0.71073
Triclinic

P-I

8.3746(17)
8.5077(17)
16.900(3)
7709(3)
7750(3)
6559(3)
1058.2(4)
2

1.639
0.172

524
0.34 x 0.26 x 0.21

2.50 to 28.30

-10 <=h <=11
-10 <= k<=11
-20 <=l<=21
9062

4837 [R(int) =
0.0412]
Full-matrix least-

squares on F 2
4837 / O / 321

0.996

R1 = 0.0569, wR2
= 0.1237

R1 = 0.1327, wR2
= 0.1486

0.368 and -0.318

(Bu‘N)Ti(Dipnacnac)
Cl (17)

C33H50C1N 3T1

572.1 1
173(2)
0.71073
Monoclinic

P2(I )/n

10.3135(2)
27.56620( 10)
12.4202(2)
90

106.8840

90
3378.90(9)

4

1.125

0.356

1232
0.21x 0.16 x 0.10

1.48 to 28.18

-13 <= h <=13
-36 <= k<= 36
-15<=l<=16
29415

7965 [R(int) =
0.0448]
Full-matrix least-

squares on F 2
7965 / 0 / 343

1.130

R1 = 0.0568, wR2 =
0.1583

R1 = 0.0859, wR2 =
0.1741

0.883 and —0.492

57

(Bu‘N)Ti(Tolnacnac)
(PyBu‘)Cl (18)
C32H43C1N4Ti
567.03

173(2)

0.71073

Triclinic

P-I

12.362(3)
13.428(3)
13.672(3)
6859(3)
8590(3)
7330(3)
2022.3(7)
3

1.624
0.459

1056
0.26 x 0.16 x 0.13

1.60 to 28.53

-16 <= h <=16
-17 <= k <=17
-18<=l<=17
24432

9525 [R(int) =
0. 1269]
Full-matrix least-

squares on F2
9525 /0 / 417

0.997

R1: 0.1171, wR2 =
0.3099

R1 = 0.2658, wR2 =
0.3802

2.265 and —0.791

Empirical formula

Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group

Cell

21181

b11111

c (A)

01(°)

13 (°)

11 (°)

Volume (A3)

Z

d (calc.) (Mg/m3)
Abs. coef. (mm'l)

F (000)

Crystal size (mm)
26 range (°)
Index ranges

Reflections
collected
Independent
reflections

Refinement method

Data / restraints /
, parameters

GOF / F2

Final R indices
11>20(1)]

R indices (all data)

Largest diff. peak
and hole (e A3)

(Bu‘N)Ti(TFMnacna
c)(PyBu‘)Cl (19)
C34H35C1F12N4Ti

81 1.01

173(2)

0.71073

Monoclinic

P2( I )/c

9.3094(19)
14.324(3)
27.812(6)
90
9132(3)
90
3707.8(13)
4

1.456
0.393

1656
0.31 x 0.26 x 0.10

1.46 to 28.63

-12 <= h <= 12
-19 <= k <= 18
-37 <=l<= 35
42794

9047 [R(int) =
0.1414]
Full-matrix least-
squares on Fa

9047/0/423

1.459

R1: 0.1648, wR2 =
0.4541

R1 = 0.2355, wR2 =
0.4742

1.596 and —0.842

(Bu'N)Ti(Dipnacnac)
OTf (26)

C34H50F3N3035Ti

685.73
173(2)
0.71073

Tetragonal
P-42(1)c

l9.429(3)
l9.429(3)
19.991(4)
90

90

90
7547(2)

8

1.207
0.331

2912
0.16 x 0.18 x 0.21

2.04 to 28.38

-25 <= h <= 25
-25 <= k <= 25
-25 <2 1 <= 26
87259

9259 [R(int) = 0.331]

Full-matrix least-
squares on F2
8259 / 0 / 419

1.658

R1 = 0.1017, wR2 =
0.0693

R1: 0.2561, wR2 =
0.0768

0.567 and —0.556

(DipN)Zr(Tolnac
nac); (25)
C50H59stl‘

821 .24

173(2)

0.71073
Monoclinic
P2(I)/n

1 1.167(2)
19. 194(4)
21.749(4)
90
100.86(3)
90

4578.2( 16)
4

1.191
0.278

1736
0.34 x 0.23 x

1.43 to 28.23

-14 <= h <=14
-11<= k <=25
-28 <=l<= 27
28559

10702 [R(int) =
0.0521]
Full-matrix least-
squares on F 2
10702 / 0 / 518

0.954

R1 = 0.0424, wR2
= 0.0847

R1 = 0.0922, wR2
= 0.0983

0.292 and -0.390

Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
Cell

a (A)

b (A)

c (A)

01 (°)

B (°)

X (°)

Volume (A3)

Z

d (calc.) (Mg/m3)
Abs. Coef. (mm'l)
F (000)

Crystal size (mm)
26 range (°)
Index ranges

Reflections
collected
Independent
reflections
Refinement method

Data / restraints /
parameters

GOF / F2

Final R indices
[I>26(I)]

R indices (all data)

Largest diff. peak
and hole (6 A3)

(Bu‘N)Ti(Dipnacnac)
(NMez) (27)

C35H56N4Ti
580.74
173(2)
0.71073
Monoclinic
P2(I)

9.4329(19)
19.798(4)
10.299(2)
90

1 1320(3)
90
1768.0(6)
2

1.091
0.269

632
0.51x 0.16 x 0.13
2.06 to 28.45

-12 <= h <= 12
-25 <= k<= 25
-13 <=l<= 13
21251

831 1 [R(int) = 0.0959]

Full-matrix least-
squares on F8
8311 / 1 / 371

0.771

R1 = 0.0703, wR2 =
0.1941

R1: 0.1599, wR2 =
0.2598

0.977 and -0.316

59

(NM62)T1[(2'NM82'
CsF4)nacnac]F2 (29)

(323142513101‘15'1'i
609.38

173(2)
0.71073
Monoclinic
P2(1)/n

13.0595(9)
9.4528(6)
21 .1353(14)
90

99.71 1(2)
90

2571 .7(3)

4

1.574
0.428

1240
0.40 x 0.26 x 0.23
1.71 to 28.27

-17 <= h <= 16

. —10<=k<= 12

-27 <= 1 <= 21
16039

6081 [R(int) = 0.0998]

Full-matrix least-

squares on F2
6081 /0 / 352

0.880

R1 = 0.0549, wR2 =
0.1288

R1 = 0.1548, wR2 =
0.1536

0.536 and -0.400

_‘ ”—3, . ._