2-tert-Butyl and 2-phenylphenylimido complexes of titanium(IV) and their olefin polymerisation activity

Article abstract of DOI:10.1039/b008232p

Reaction of 7 equivalents of tert-butylamine with TiCl₄ in hexane at 0 °C gave [TiCl₂(NCMe₃)(NH₂CMe₃)₂ ]₂ 1 which on thermalisation with 2,6-diisopropylaniline in toluene gave [TiCl₂(NC₆H₃Prⁱ_2- 2,6)(NH₂CMe₃₂]_x 2. Imido exchange of [TiCl₂(NCMe₃)(NH₂CMe₃)] _x. with o-toluidine or 2-tert-butylaniline and addition ofpyridine gave [TiCl₂(NC₆H_4- Me-2)(py)₃] and [TiCl₂(NC₆H₄CMe₃-2)(py)] ₃] which crystallised to give [TiCl₂(NC₆H₄Me-2)(py)₂] ₂ 3 and [TiCl_2-(NC₆H₄CMe₃-2)(py) ₂]₂ 4. 2-Phenylaniline and [TiCl₂(NCMe₃)(py)3] gave [TiCl₂(NC₆H₄Ph-2)(py)₂] ₂ 5 on crystallisation and reaction of (tert-butylaniline or 2-phenylaniline with [TiCl₂(NCMe₃)(tmeda)] gave [TiCl₂(₆H4CMe₃-2)(tmeda)] 6 and [TiCl₂(₆H₄Ph-2)(tmeda)]₂ 7. Complexes 1, 3, 4, 5, 6, and 7 were characterised by X-ray crystallography and the possibility of imdo ligand C-N bond rotation taking place analysed and compared with the NMR spectra. [TiCl₂(NCMe₃)(tmeda)] and MAO·(MeAlO)_n, polymerises ethylene at low pressure with low activity (3.2 g mmol^-1 h^-1 bar^-1), [TiCl₂(₆H₄CMe₃)(tmeda)] or [TiCl₂(NC₆H₄Ph-2)(tmeda)] and MAO gives a 4-fold increase in activity whereas propene is not polymerised but 1-hexene is. Heterogenisation by addition of [TiCl₂(NCMe₃)(NH2CMe₃)2]2 1 to tmeda-functionalised crosslinked polystyrene or imido exchange of [TiCl₂(NCMe₃)(tmeda)] with NH_2- functionalised crosslinked polystyrene gives supported complexes which do not polymerise ethylene at low pressure in the presence of MAO. The Royal Society of Chemistry 2001.

Full text of DOI:10.1039/b008232p

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2-tert-Butyl and 2-phenylphenylimido complexes of titanium(IV)
and their olefin polymerisation activity
Alastair J. Nielson,*a Mark W. Glennyb and Clifton E. F. Rickardb
a Chemistry, Institute of Fundamental Sciences, Massey University at Albany,
Private Bag 102904, North Shore Mail Centre, Auckland, New Zealand
b Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland,
New Zealand
Received 12th October 2000, Accepted 20th November 2000
First published as an Advance Article on the web 15th January 2001
Reaction of 7 equivalents of tert-butylamine with TiCl4 in hexane at 0 ЊC gave [TiCl2(NCMe3)(NH2CMe3)2]2 1 which
on thermalisation with 2,6-diisopropylaniline in toluene gave [TiCl2(NC6H3Pri2-2,6)(NH2CMe3)2]x 2. Imido exchange
of [TiCl2(NCMe3)(NH2CMe3)]x with o-toluidine or 2-tert-butylaniline and addition of pyridine gave [TiCl2(NC6H4-
Me-2)(py)3] and [TiCl2(NC6H4CMe3-2)(py)3] which crystallised to give [TiCl2(NC6H4Me-2)(py)2]2 3 and [TiCl2-
(NC6H4CMe3-2)(py)2]2 4. 2-Phenylaniline and [TiCl2(NCMe3)(py)3] gave [TiCl2(NC6H4Ph-2)(py)2]2 5 on crystallisation
and reaction of tert-butylaniline or 2-phenylaniline with [TiCl2(NCMe3)(tmeda)] gave [TiCl2(NC6H4CMe3-2)(tmeda)]
6 and [TiCl2(NC6H4Ph-2)(tmeda)]2 7. Complexes 1, 3, 4, 5, 6, and 7 were characterised by X-ray crystallography and
the possibility of imdo ligand C–N bond rotation taking place analysed and compared with the NMR spectra. [TiCl2-
(NCMe3)(tmeda)] and MAOؒ(MeAlO)n, polymerises ethylene at low pressure with low activity (3.2 g mmolϪ1 hϪ1
barϪ1), [TiCl2(NC6H4CMe3)(tmeda)] or [TiCl2(NC6H4Ph-2)(tmeda)] and MAO gives a 4-fold increase in activity
whereas propene is not polymerised but 1-hexene is. Heterogenisation by addition of [TiCl2(NCMe3)(NH2CMe3)2]2
1 to tmeda-functionalised crosslinked polystyrene or imido exchange of [TiCl2(NCMe3)(tmeda)] with NH2-
functionalised crosslinked polystyrene gives supported complexes which do not polymerise ethylene at low pressure
in the presence of MAO.
Since our work on the reaction of TiCl4 and tert-butylamine1
which showed that an imido ligand was generated and not two
amido ligands,2 the reaction has been used to produce com-
pounds for vapour deposition3,4 and the precursor to the com-
plex [TiCl2(NCMe3)(py)3] which has generated an extensive and
unique chemistry.5 We have taken renewed interest in the
reaction as addition of N,N,NЈ,NЈ-tetramethylethylenediamine
(tmeda) to the reaction mixture gives [TiCl2(NCMe3)(tmeda)]
cleanly and in high yield.1 The crystal structure shows a 5-co-
ordinate monomeric complex with cis-orientated dichloro
ligands3 similar to that found in both [TiCl2(NPh)(tmeda)] and
[(TiCl2)2{trans-NC(Me)(Me)CN}],6 and does not have the
imido-bridged dimeric structure we originally proposed.1 In
Fig. 1 Molecular structure of complex 1; without H atoms and with
view of the prominence of cis-dichloro ligands in catalysis
involving the 16-electron complexes [TiCl2(Cp)2]7 and [TiCl2-
(OAr)2],8 the dichloro ligands in the 14-electron tmeda imides
are an attractive prospect for homogeneous catalysis and the
imido and other nitrogen donor ligands present opportunities
for heterogenisation. We have also been interested in using
phenylimido ligands substituted in the 2 position with a tert-
butyl or phenyl group to influence regiospecifically sections of a
complex when imido ligand C–N bond rotation is impeded.9 We
report here the results of studies directed towards an under-
standing of these features in the titanium imide system.
key atoms labelled.
bridging imido structure has been proposed.3 Although the
orange complexes are crystalline the crystal quality has gener-
ally been found to be poor. In addition, the reaction apparently
does not go to completion in solution as amine hydrochloride is
sometimes produced as the reaction medium is removed.10 In
the present work a reaction of TiCl4 and 4 equivalents of tert-
butylamine in CH2Cl2 initiated at Ϫ78 ЊC and then allowed to
warm to room temperature gave an orange complex which
analysed close to the formulation [TiCl2(NCMe3)(NH2-
CMe3)2]2ؒ5 Me3CNH3Cl. Poor quality X-ray data were
obtained for a crystal of the sample but this did show the pres-
ence of amine hydrochloride in the unit cell. From a reaction
using 7 equivalents of tert-butylamine in hexane at 0 ЊC a sam-
ple analysing as [TiCl2(NCMe3)(NH2CMe3)2] was obtained
which gave crystals suitable for X-ray crystallography.
Results and discussion
When TiCl4 is treated with an excess of tert-butylamine in
benzene solution an orange crystalline solid can be obtained
which depending on the degree of drying corresponds to the
formulation [TiCl2(NCMe3)(NH2CMe3)3] or [TiCl2(NCMe3)-
(NH2CMe3)2].3 Osmometric molecular weight determinations
of the tris-amine complex indicate a trimer for which a cyclic
The structure (Fig. 1) shows the complex is a chloro-bridged
dimer with terminal imido ligands conforming to the formu-
lation [TiCl(µ-Cl)(NCMe3)(NH2CMe3)2]2 1. This solid state
232
J. Chem. Soc., Dalton Trans., 2001, 232–239
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b008232p

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Table 2 Selected bond lengths (Å) and bond angles (Њ) for [TiCl2-
(NC6H4Me-2)(py)2]2 3
Table 1 Selected bond lengths (Å) and bond angles (Њ) for [TiCl2-
(NCMe3)(NH2CMe3)2]2 1
Ti–N(1)
Ti–N(3)
Ti–Cl(2)
N(1)–C(1)
1.695(2)
2.662(2)
2.4639(6)
1.470(3)
Ti–N(2)
Ti–Cl(1)
Ti–Cl(2Ј)
2.264(2)
2.4332(6)
2.8142(6)
Ti–N(1)
Ti–N(3)
Ti–Cl(2)
N(1)–C(11)
1.711(2)
Ti–N(2)
Ti–Cl(1)
Ti–Cl(2Ј)
2.230(2)
2.3788(6)
2.7123(6)
2.220(2)
2.4529(6)
1.385(3)
Ti–N(1)–C(1)
N(1)–Ti–N(3)
N(1)–Ti–Cl(1)
N(3)–Ti–Cl(1)
N(2)–Ti–Cl(2)
Cl(1)–Ti–Cl(2)
N(2)–Ti–Cl(2Ј)
Cl(1)–Ti–Cl(2Ј)
Ti–Cl(2)–TiЈ
164.4(2)
102.2(1)
98.8(1)
159.1(1)
156.3(1)
91.7(1)
76.6(1)
84.3(1)
100.2(1)
128.3(1)
N(1)–Ti–N(2)
N(2)–Ti–N(3)
N(2)–Ti–Cl(1)
N(1)–Ti–Cl(2)
N(3)–Ti–Cl(2)
N(1)–Ti–Cl(2Ј)
N(3)–Ti–Cl(2Ј)
Cl(2)–Ti–Cl(2Ј)
Ti–N(2)–C(5)
104.8(1)
86.9(1)
87.8(1)
98.7(1)
85.4(1)
176.7(1)
74.8(1)
79.8(1)
131.2(1)
Ti–N(1)–C(11)
N(1)–Ti–N(3)
N(1)–Ti–Cl(1)
N(2)–Ti–Cl(2)
N(3)–Ti–Cl(2)
Cl(1)–Ti–Cl(2)
N(3)–Ti–Cl(2Ј)
Cl(1)–Ti–Cl(2Ј)
Ti–Cl(2)–TiЈ
170.4(2)
93.2(1)
97.8(1)
93.1(1)
86.1(1)
161.3(1)
86.7(1)
82.6(1)
101.3(1)
N(1)–Ti–N(2)
N(2)–Ti–N(3)
93.2(1)
170.8(1)
92.5(1)
100.9(1)
86.3(1)
179.6(1)
86.8(1)
78.7(1)
N(3)–Ti–Cl(1)
N(1)–Ti–Cl(2)
N(2)–Ti–Cl(1)
N(1)–Ti–Cl(2Ј)
N(2)–Ti–Cl(2Ј)
Cl(2)–Ti–Cl(2Ј)
C(11)–C(12)–C(17)
C(13)–C(12)–C(17)
120.8(2)
120.7(2)
Ti–N(3)–C(9)
structure thus differs from the trimer indicated by osmometry
in CH2Cl2 and proposed as a cyclic bridging imide.3 Bond dis-
tances and angles for the complex are contained in Table 1.
Each titanium atom has a distorted octahedral geometry con-
sisting of the imido and amine ligands and terminal and bridg-
ing chloro ligands. The Ti–N(1) and Ti–Cl(1) bond lengths
[1.695(2) and 2.4332(6) Å respectively] are similar to those in a
variety of other titanium imides.11 In the asymmetric chlorine
bridge the Ti–Cl(2) bond length [2.4639(6) Å] is longer than the
terminal Ti–Cl(1) bond length but the Ti–Cl(2Ј) bond length
[2.8142(6) Å] where Cl(2Ј) lies trans to the imido function is
very long and must nearly represent the limit for this type of
bonding. In CDCl3 solution the NMR spectra become more
complex with time but there is evidence in the 13C-{1H} spec-
trum that the solid state structure is present initially, as the
major features are one imido ligand quaternary (δ 72.2) and two
non-equivalent amine ligand quaternaries (δ 52.6 and 52.2).
The long Ti–Cl(2Ј) bond length in the crystal structure indicates
that dissociation into two monomers would be facile and other
work has shown that dissociation of the amine ligands can
occur,3 so that these processes could give rise to the solution
dynamics observed.
Fig. 2 Molecular structure of complex 3; details as in Fig. 1.
butylؒN-trimethylsilylamine,1 indicated that the imido exchange
reaction in the absence of pyridine or tmeda was rapid. By
adding o-toluidine to the [TiCl2(NCMe3)(NH2CMe3)]x reaction
mixture, stirring the solution for one hour and then adding
pyridine, a 70% yield of [TiCl2(NC6H4Me-2)(py)3] could be
obtained. This complex was characterised by NMR spectro-
scopy as prolonged drying in vacuo or recrystallisation from
a hexane-layered CH2Cl2 solution, gave the bis-pyridine
adduct [TiCl2(NC6H4Me-2)(py)2]2 3. Its crystal structure
(Fig. 2) showed a chloro-bridged dimer which compares with
the monomeric structures proposed for other [TiCl2(NR)(py)2]
complexes13 and that found by X-ray crystallography for
[TiCl2(NCMe3)(OPPh3)2].3 The structure is most like the azide
bridged complexes [TiCl(N3)(NCMe3)(py)2]2 and [TiCl(N3)-
(NCy)(py)2]2 (Cy = cyclohexyl).4
Bond lengths and angles for complex 3 are shown in Table 2.
The Ti–Cl(1) and Ti–Cl(2) bond lengths [2.3788(6) and
2.4529(6) Å respectively] are a little shorter than in 1 [2.4332(6)
and 2.4639(6) Å respectively] where the amine ligands are cis to
each other and not trans as in complex 3, but the Ti–Cl(2Ј)
bond length [2.7123(6) Å] is considerably shorter than in 1
[2.8142(6) Å]. The phenyl ring orientates in dimer 3 with the
methyl groups of the dimer sitting directly above Cl(2) and
Cl(2Ј). The Ti–N(1)–C(11) bond angle [170.4(2)Њ] is essentially
linear and there is little difference in the N(1)–Ti–Cl(1) and
N(1)–Ti–Cl(2) bond angles [97.8(1) and 100.9(1)Њ respectively]
so that the methyl group appears to have little effect on the
coordination geometry. Simple molecular models indicate that
the methyl group could move over the pyridine ligands so that
the imido ligand C–N bond rotation would not be restricted.
For the d2 molybdenum complex [MoCl2(NC6H3Me2-2,6)-
(PMe3)3] NMR studies show hindered rotation of this kind at
low temperature.14
Alkylimido complexes are easily generated using TiCl4 and a
primary alkylamine,1–3 but arylimido complexes are not gener-
ated by this process or other usual routes.10 However they can
be generated by imido group exchange in the [TiCl2(NCMe3)-
(py)3] system.12,13 Our initial attempts at exchanging the tert-
butylimido ligand in the TiCl4/tert-butylamine reaction product
using 2-tert-butyl- or 2-phenyl-aniline did not give a single
isolatable product. 13C-{1H} NMR spectral analysis of the
product obtained by addition of an excess of aniline to complex
1 in benzene or CH2Cl2 at room temperature showed loss of the
tert-butylimido ligand quaternary (δ 72.2), resonances charac-
teristic of tert-butylamine ligands (ca. δ 52) and two phenyl-
imido ipso-carbon resonances (ca. δ 154). Refluxing in benzene
for a short period gave predominantly one phenylimido species.
Consequent thermalisation of 2,6-di-isopropylaniline and
complex 1 in toluene for an extended period gave rise to [TiCl2-
(NC6H3Pri2-2,6)(NH2CMe3)2]x 2 which was isolated in 51%
yield. A dimeric chloro-bridged structure with trans orientated
tert-butylamine ligands is proposed for the complex based on
the crystal structure of 1 and the appearance of only one set
1
of tert-butylamine resonances in the H and 13C-{1H} NMR
spectra. A similar structure has been proposed for the complex
[TiCl2(NCHEt2)(NH2CHEt2)2]x.3 NMR tube studies showed
that addition of pyridine or tmeda to complex 2 gave rise to the
adducts [TiCl2(NC6H3Pri2-2,6)(py)3]13 and [TiCl2(NC6H3Pri2-
2,6)(tmeda)].
NMR tube experiments indicated that the imido exchange
reaction of complex 1 with substituted anilines, particularly
those with a single ortho substituent, was facilitated by addition
of pyridine or tmeda. However similar NMR studies on
[TiCl2(NCMe3)(NH2CMe3)]x, prepared from TiCl4 and tert-
Addition of 2-tert-butylaniline to [TiCl2(NCMe3)(NH2-
CMe3)]x followed by pyridine gave a complex which NMR
spectroscopy showed to be [TiCl2(NC6H4CMe3-2)(py)3]. Drying
in vacuo or recrystallisation from a hexane-layered CH2Cl2
solution gave the bis-pyridine adduct [TiCl2(NC6H4CMe3-2)-
(py)2]2 4. Analytical data for a crystalline sample were obtained
J. Chem. Soc., Dalton Trans., 2001, 232–239
233

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Table 4 Selected bond lengths (Å) and bond angles (Њ) for [TiCl2-
(NC6H4Ph-2)(py)]2 5
Table 3 Selected bond lengths (Å) and bond angles (Њ) for [TiCl2-
(NC6H4CMe3-2)(py)2]2 4
Ti–N(1)
Ti–N(3)
Ti–Cl(2)
N(1)–C(1)
1.702(2)
2.189(2)
2.4373(7)
1.379(3)
Ti–N(2)
Ti–Cl(1)
Ti–Cl(2Ј)
2.200(2)
2.3503(6)
2.6825(7)
Ti–N(1)
Ti–N(3)
Ti–Cl(2)
N(1)–C(1)
1.719(2)
Ti–N(2)
Ti–Cl(1)
Ti–Cl(2Ј)
2.206(2)
2.3956(7)
2.6781(7)
2.241(2)
2.4497(7)
1.380(3)
Ti–N(1)–C(1)
N(1)–Ti–N(3)
N(1)–Ti–Cl(1)
N(2)–Ti–Cl(2)
N(3)–Ti–Cl(2)
Cl(1)–Ti–Cl(2)
N(3)–Ti–Cl(2Ј)
Cl(1)–Ti–Cl(2)
Ti–Cl(2)–TiЈ
165.9(2)
93.9(1)
95.4(1)
89.4(1)
91.8(1)
161.5(1)
84.7(1)
84.6(1)
103.0(1)
122.2(2)
121.1(2)
112.2(2)
N(1)–Ti–N(2)
N(2)–Ti–N(3)
N(3)–Ti–Cl(1)
N(1)–Ti–Cl(2)
N(2)–Ti–Cl(1)
N(1)–Ti–Cl(2Ј)
N(2)–Ti–Cl(2Ј)
Cl(2)–Ti–Cl(2Ј)
C(2)–C(7)–C(9)
C(2)–C(7)–C(10)
C(8)–C(7)–C(9)
C(8)–C(7)–C(10)
C(9)–C(7)–C(10)
94.9(1)
170.6(1)
87.7(1)
103.1(1)
88.2(1)
172.3(1)
86.2(1)
77.0(1)
109.6(2)
110.1(2)
108.4(2)
106.6(2)
109.8(2)
Ti–N(1)–C(1)
N(1)–Ti–N(3)
N(1)–Ti–Cl(1)
N(2)–Ti–Cl(2)
N(3)–Ti–Cl(2)
Cl(1)–Ti–Cl(2)
N(3)–Ti–Cl(2Ј)
Cl(1)–Ti–Cl(2Ј)
Ti–Cl(2)–TiЈ
164.1(2)
102.2(1)
98.0(1)
80.4(1)
84.3(1)
166.9(1)
92.3(1)
89.2(1)
102.3(1)
N(1)–Ti–N(2)
N(2)–Ti–N(3)
N(3)–Ti–Cl(1)
N(1)–Ti–Cl(2)
N(2)–Ti–Cl(1)
N(1)–Ti–Cl(2Ј)
N(2)–Ti–Cl(2Ј)
Cl(2)–Ti–Cl(2Ј)
C(1)–C(6)–C(7)
C(5)–C(6)–C(7)
93.7(1)
163.7(1)
86.6(1)
95.0(1)
87.7(1)
170.5(1)
89.8(1)
77.7(1)
121.7(2)
119.8(2)
C(1)–C(2)–C(7)
C(3)–C(2)–C(7)
C(2)–C(7)–C(8)
Fig. 4 Molecular structure of complex 5; details as in Fig. 1.
Fig. 3 Molecular structure of complex 4; details as in Fig. 1.
by adding 2-tert-butylaniline to [TiCl2(NCMe3)(py)3].13,15
the phenyl substituent sits over but between the pyridine and
bridging chloro ligands. Bond lengths and angles are contained
in Table 4. The Ti–N bonds in complexes 5 and 3 are similar in
length but the Ti–Cl(1) bond length is larger in 5 [2.3956(7) Å]
than in 3 [2.3788(6) Å] whereas the Ti–Cl(2) and Ti–Cl(2Ј)
bonds are more similar in the respective complexes [2.4497(7)
and 2.4529(6) Å; 2.6781(7) and 2.7123(6) Å]. The Ti–N(1)–C(1)
bond angle [164.1(2)Њ] is smaller than that observed in com-
plex 3 [170.4(2)Њ] but does not represent any meaningful change
to the imido linkage.16 The N(1)–Ti–Cl(1) bond angle [98.0(1)Њ]
is similar to that in 3 [97.8(1)Њ] but N(1)–Ti–Cl(2) [95.0(1)Њ]
is smaller than in 3 [100.9(1)Њ] where the methyl substituent
sits directly over Cl(2). The effect of the phenyl substituent
in 5 can also be seen in the Ti–N(3) bond length [2.241(2) Å]
which is longer than Ti–N(2) [2.206(2) Å]. The N(1)–Ti–
N(2) [93.7(1)Њ] is significantly smaller than N(1)–Ti–N(3)
[102.2(1)Њ] and this angle is significantly larger than the equiv-
alent bond angle in complex 3 [93.2(1)Њ]. With the N(1)–Ti–
N(3) bond angle widened in 5 the phenyl substituent does not
push away from the adjacent pyridine ligand [C(1)–C(6)–
C(7) and C(5)–C(6)–C(7) bond angles 121.7(2) and 119.8(2)Њ
respectively].
Addition of 2-tert-butylaniline to [TiCl2(NCMe3)(tmeda)]
in CH2Cl2 gave [TiCl2(NC6H4CMe3-2)(tmeda)] 6 for which a
crystal structure showed a monomer consisting of a pseudo
square-prismatic geometry about titanium with the imido
ligand occupying the apical site (Fig. 5). Bond lengths and
angles are contained in Table 5. The imido ligand phenyl ring is
rotated so that the tert-butyl group sits over a tmeda ligand
methyl group and this positioning results in the Ti–N(1)–C(1)
angle decreasing to 155.5(2)Њ but the Ti–N(1) bond length
[1.715(2) Å] is no different to the others reported here. It has
been shown that M–N–C bond angles in other imido complexes
are somewhat flexible and can reduce to about 150Њ as a result
of steric effects and crystal packing forces.16 Analysis of the
crystal packing in the unit cell of 6 indicates there is a pocket
above the tmeda ligand that accommodates the tert-butyl group
and there is no stacking of the phenyl rings.
A
crystal structure determination of 4 (Fig. 3) shows a dimeric
chloro-bridged structure similar to that found for complex 3.
However in 3 the methyl group sits over a bridging chloride
[Cl(2)], whereas in 4 the tert-butyl group sits over a terminal
chloro ligand [Cl(1)]. With this orientation in 4 the chloro
ligand bonding tightens up somewhat in comparison to 3
[Ti–Cl(1) bond lengths 2.3503(6) and 2.3733(6) Å, Ti–Cl(2)
bond lengths 2.4373(7) and 2.4529(6) Å, Ti–Cl(2Ј) bond lengths
2.6825(7) and 2.7123(6) Å respectively] but there is little change
in the pyridine or imido ligand bond lengths (Table 3).
Although the Ti–Cl(2Ј) bond length in complex 4 is still long,
suggesting easy dissociation in solution to a monomer, the
NMR spectra in CDCl3 solution indicate the presence of only
one species with no solution dynamics being evident. There is
little difference in the various N(1)–Ti–Cl bond angles between
complexes 4 and 3 and with the Ti–N(1)–C(1) bond angle in 4
at 165.9(2)Њ the tert-butyl group sits easily over Cl(1) (straddled
by the C(9) and C(10) methyls and without significant widening
of the C(9)–C(7)–C(10) bond angle) and appears to have little
influence on the molecule overall. In CDCl3 solution at room
temperature the NMR spectra show no sign of the methyl
hydrogens becoming diastereotopic indicating that the tert-
butyl group rotates. Simple molecular models suggest that
movement of the tert-butyl group over a rotating pyridine
ligand would not be easy so that this substituent is likely to be
trapped in the vicinity of Cl(1). However rotation about the
N–C bond of the imido ligand would be more likely to occur if
dissociation of the dimer produced a 5-co-ordinate complex
with widened out N(imido)–Ti–N(py) angles (see later). In
general no change in the 1-σ, 2-π nature of an M–N triple bond
is expected for Ti–N–C bond angles down to about 150Њ in
organoimido complexes.16
The complex [TiCl2(NC6H4Ph-2)(py)2]2 5 formed when the
tris-pyridine parent crystallised and a crystal structure (Fig. 4)
showed a similar overall geometry to that of complex 4. How-
ever the structure is more like that of o-toluimide 3 except that
234
J. Chem. Soc., Dalton Trans., 2001, 232–239

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Table 6 Selected bond lengths (Å) and bond angles (Њ) for [TiCl2-
(NC6H4Ph-2)(tmeda)]2 7
Table 5 Selected bond lengths (Å) and bond angles (Њ) for [TiCl2-
(NC6H4CMe3-2)(tmeda)] 6
Ti–N(1)
Ti–N(3)
Ti–Cl(2)
1.715(2)
2.300(2)
2.3200(9)
Ti–N(2)
Ti–Cl(1)
N(1)–C(1)
2.247(2)
2.3514(8)
1.404(3)
Ti–N(1)
Ti–N(3)
Ti–Cl(2)
N(1)–C(1)
1.717(2)
Ti–N(2)
Ti–Cl(1)
Ti–Cl(2Ј)
2.312(2)
2.3699(8)
2.7060(8)
2.312(2)
2.4350(8)
1.390(3)
Ti–N(1)–C(1)
155.5(1)
110.2(1)
103.3(1)
158.5(1)
86.9(1)
N(1)–Ti–N(2)
N(2)–Ti–N(3)
N(1)–Ti–Cl(2)
N(2)–Ti–Cl(2)
N(3)–Ti–Cl(2)
Ti–N(2)–C(13)
Ti–N(2)–C(11)
Ti–N(3)–C(16)
C(1)–C(2)–C(7)
C(3)–C(2)–C(7)
C(2)–C(7)–C(8)
C(8)–C(7)–C(9)
C(8)–C(7)–C(10)
95.9(1)
77.3(1)
106.0(1)
87.9(1)
142.0(1)
111.1(2)
105.4(2)
110.2(2)
121.9(2)
121.1(3)
112.7(3)
106.9(3)
107.0(3)
N(1)–Ti–N(3)
N(1)–Ti–Cl(1)
N(2)–Ti–Cl(1)
N(3)–Ti–Cl(1)
Cl(1)–Ti–Cl(2)
Ti–N(2)–C(14)
Ti–N(3)–C(15)
Ti–N(3)–C(12)
C(8)–C(7)–C(10)
C(9)–C(7)–C(10)
C(2)–C(7)–C(9)
C(2)–C(7)–C(10)
C(9)–C(7)–C(10)
Ti–N(1)–C(1)
N(1)–Ti–N(3)
N(1)–Ti–Cl(1)
N(3)–Ti–Cl(1)
N(2)–Ti–Cl(2)
Cl(1)–Ti–Cl(2)
N(2)–Ti–Cl(2Ј)
Cl(1)–Ti–Cl(2Ј)
Ti–Cl(2)–TiЈ
Ti–N(2)–C(16)
Ti–N(3)–C(17)
Ti–N(3)–C(14)
C(7)–C(2)–C(3)
165.0(2)
92.4(1)
98.7(1)
N(1)–Ti–N(2)
N(2)–Ti–N(3)
N(2)–Ti–Cl(1)
N(1)–Ti–Cl(2)
N(3)–Ti–Cl(2)
N(1)–Ti–Cl(2Ј)
N(3)–Ti–Cl(2Ј)
Cl(2)–Ti–Cl(2Ј)
Ti–N(2)–C(15)
Ti–N(2)–C(13)
Ti–N(3)–C(18)
C(1)–C(2)–C(7)
100.0(1)
76.0(1)
89.1(1)
92.6(1)
92.6(1)
168.9(1)
87.4(1)
76.4(1)
113.7(1)
110.6(1)
118.7(2)
122.7(2)
162.8(1)
163.3(1)
99.97(3)
90.7(1)
84.20(3)
103.62(3)
108.1(1)
112.5(2)
101.9(2)
118.9(2)
95.9(1)
113.9(2)
112.4(2)
109.9(2)
107.0(3)
111.1(3)
110.4(2)
108.6(2)
111.1(3)
Fig. 6 Molecular structure of complex 7; details as in Fig. 1.
H4Ph-2)(tmeda)]2 7 (see Fig. 6), with a distorted octahedral
co-ordination geometry about each titanium atom similar to
that found for complex 1. Bond lengths and angles for 7 are
contained in Table 6. The imido ligand phenyl ring orientates in
a similar manner to that in complex 6, but with the face of the
aromatic ring substituent lying above a tmeda ligand methyl
group. Even with this “closed up” 6-co-ordinate geometry the
phenyl substituent is easily accommodated above the tmeda
methyl group with the Ti–N(1)–C(1) bond angle at 165.0(1)Њ
[cf. 155.5(1)Њ in 5-co-ordinate complex 6], N(1)–Ti–N(2) at
100.0(1) [cf. 95.9(1)Њ in 6] and C(1)–C(2)–C(7) and C(3)–C(2)–
C(7) at 122.7(2) and 118.9(2)Њ [cf. 121.9 and 121.1(3)Њ in 6]. The
Ti–N(1) bond lengths in 6 and 7 are similar [1.715(2) and
1.717(2) Å] but the Ti–N(2) and Ti–N(3) bond lengths in 7
[both 2.312(2) Å] are similar to the longer Ti–N(3) [2.300(2) Å]
in complex 6. In 7 the N(1)–Ti–Cl(1) and N(1)–Ti–Cl(2) bond
angles are 98.7(1) and 92.6(1)Њ which compare with 98.8(1) and
98.7(1)Њ in dimer 1 and 103.3(1) and 106.0(1)Њ in monomer 6.
The Ti–Cl(2Ј) bond distance in 7 [2.7060(8) Å] is shorter than in
dimer 1 [2.8142(6) Å] but similar to those found in the other
dimeric complexes reported.
Fig. 5 Molecular structure of complex 6; details as in Fig. 1.
The Ti–Cl(1) and Ti–Cl(2) bond lengths in complex 6
[2.3514(8) and 2.3200(9) Å] are not much different but Ti–N(3)
[2.300(2) Å], which involves the nitrogen atom of the tmeda
ligand that is adjacent to the imido ligand tert-butyl group,
is a little longer than Ti–N(2) [2.247(2) Å]. However these
Ti–Cl and Ti–N bonds are no different to those found in
[TiCl2(NCMe3)(tmeda)].3 The N(1)–Ti–Cl(1), N(1)–Ti–Cl(2)
and N(1)–Ti–N(2) bond angles in 6 are also not much different
to those in [TiCl2(NCMe3)(tmeda)]. The N(1)–Ti–N(3) bond
angle in 6 [110.2(1)Њ] is much larger than N(1)–Ti–N(2)
[95.9(1)Њ] and the comparable N–Ti–N bond angles in [TiCl2-
(NCMe3)(tmeda)] are 100.7(2) and 101.9(2)Њ.3 Thus in 6 the
tert-butyl substituent is mainly accommodated by distortions in
the Ti–N(1)–C(1) and N(1)–Ti–N(3) bond angles.
The Ti–N–C bond angles involving the tmeda ligand are all
very similar and the imido ligand tert-butyl group is not pushed
upwards to any extent [C(1)–C(2)–C(7) and C(3)–C(2)–C(7)
bond angles 121.9(2) and121.1(3)Њ respectively]. However the
two methyl groups of this substituent that straddle the tmeda
ligand methyl do open out a little but the effect is small [C(8)–
C(7)–C(10) and C(8)–C(7)–C(9) bond angles 107.0(3) and
106.9(3)Њ respectively; C(9)–C(7)–C(10) 111.1(3)Њ]. The 1H
NMR spectrum of the complex in CDCl3 solution shows a
sharp resonance for these methyls indicating rotation is not
restricted. The spectum also shows that full rotation of the
imido ligand C–N bond might occur as there is a sharp singlet
for the tmeda ligand methylene protons and not the expected
AB quartet if the solid state asymmetric structure is locked.
However if the tert-butyl group sits above and between Cl(1)
and Cl(2) [or over C(11) and C(12) of the tmeda ligand] in
solution a symmetrical structure results in which the tmeda
methylenes are equivalent.
In CDCl3 solution the 1H NMR spectrum of complex 7 sug-
gests one species is present but over the time taken to accumu-
late the 13C-{1H} NMR spectrum a second species is evident,
there being double the expected number of carbon resonances.
This was not observed in the spectrum of 2-tert-butylimido
complex 6 and probably results from the dimeric form observed
in the solid state converting into a monomer when the 2-phenyl-
imido ligand is present.
Catalysis
Some preliminary results of olefin polymerisations are reported
which demonstrate the ability of the imido-cis-dichloro system
to act in catalysis. The solid state structures of [TiCl2(NCMe3)-
(tmeda)] and [TiCl2(NC6H4CMe3-2)(tmeda)] 6 show that the
Cl–Ti–Cl bond angles [93.9(1)3 and 95.9(1)Њ respectively]
are similar to that found in [TiCl2Cp2] [94.4(1)Њ17] which is
catalytically active towards olefin polymerisation.7 Initially we
attempted to prepare [Ti(CH3)2(NCMe3)(tmeda)] for olefin
A
crystal structure determination showed that after
crystallisation the reaction of 2-phenylaniline and [TiCl2-
(NCMe3)(tmeda)] gave a chloro-bridged dimer, [TiCl2(NC6-
J. Chem. Soc., Dalton Trans., 2001, 232–239
235

View Article Online
Table 7 Polymerisations with MAO co-catalysta
Complex
Amount/µmol
Monomer
Al:Ti
Time/min
Yield/g
Activityb
[TiCl2(NCMe3)(tmeda)]
117
99
46
64.5
47
Ethene
Ethene
Ethene
Ethene
Propene
1-Hexene
Ethene
Ethene
Ethene
Ethene
137
116
142
102
140
68
1024
130
130
100
20
20
10
20
30
30
20
30
30
30
0.18
0.47
0.17
0.46
0.00
0.14
0.09
0.01
0.01
0.00
3.2
7.1
13.0
11.2
0.0
4.1
12.7
0.1
1
6
6
6
6
67.9
12.5
7
c
c
c
trimedaPS–[TiCl2(NCMe3]x
trimedaPS–[TiCl4]x
amPS–[TiCl2(NCMe3)(tmeda)]x
0.1
0.0
a Conditions: toluene–CH2CH2, 20–23 ЊC, ethene 1.7 bar, propene 1 bar. b g mmolϪ1 hϪ1 barϪ1 c Estimated to be less than 100 µmol.
.
polymerisation studies with B(C6F5)3 co-catalyst7 but reactions
of [TiCl2(NCMe3)(tmeda)] with MeLi or MeMgI gave tars
when diethyl ether solutions were warmed above Ϫ40Њ C.
[TiCl2(NCMe3)(py)3]12 gave a similar result. Addition of
methylaluminoxane [(MeAlO)n, MAO] to [TiCl2(NCMe3)-
(tmeda)] using a Ti:Al ratio of 1:100–150 gave much less
decomposition and the mixture was found to polymerise ethyl-
ene but with very low activity18 (3.2 g mmolϪ1 hϪ1 barϪ1) (see
Table 7) compared to [ZrCl2Cp2] or other complexes containing
cyclopentadienyl ligands where activities of up to 2000 g
mmolϪ1 hϪ1 atmϪ1 have been found (1 bar = 0.987 atm) when
much larger Ti:Al ratios (e.g. 1:1000) are used.7 With
[TiCl2(NCMe3)(NH2CMe3)2]2 1 the activity doubled and with
[TiCl2(NC6H4CMe3-2)(tmeda)] 6 a 4-fold increase in activity
was found, the overall activity being comparable to the moder-
Scheme 2 (i) HNO3, AcOH; (ii) SnCl2ؒ2H2O, EtOH; (iii) [TiCl2-
(NCMe3)(tmeda)], toluene.
ate activity18 systems [VCl2(NC6H3Pri2-2,6)(Tp)]–MAO (14 g
mmolϪ1 hϪ1 atmϪ1
)
and [TaCl2(NSiBut3)(Cp*)]–MAO (13.8 g
19
mmolϪ1 hϪ1 atmϪ1),20 but much less than for [VCl2(NCMe3)-
(Cp)]–MAO (27 g mmolϪ1 hϪ1 atmϪ1).21 Propene was not poly-
merised by complex 5–MAO under the conditions used but a
small activity was found for 1-hexene. [TiCl2(NC6H4Ph-2)-
(tmeda)]2 7 and MAO polymerised ethylene slightly more than
did complex 6.
when [VCl2(imido)(Cp)] is supported in a similar manner on
uncrosslinked polystyrene.21,22 Other studies have shown that
polystyrene supported catalysts may lose activity in comparison
to their unsupported counterparts due to the active center
becoming unavailable in the matrix.23
Heterogenisations were carried out via the tmeda addition
and imido exchange processes already studied, using modified
polystyrene resins. For the tmeda ligand a model system
was produced by adding N-benzyl-N,NЈ,NЈ-trimethylethylene-
diamine (tbeda) to complex 1 giving [TiCl2(NCMe3)(tbeda)]
which showed a single set of resonances for the tbeda and imido
ligands in the 1H and 13C-{1H} NMR spectra. N,N,NЈ,NЈ-
(trimethylmethylene)ethylenediamine functionalised cross-
linked polystyrene was prepared and treated with complex 1
(Scheme 1). TiCl4 was also supported in this way. For the imido
Conclusion
The results of this work show that when the solid state product
of a reaction between TiCl4 and tert-butylamine is a chloro-
bridged dimer with terminal imido ligands solution dynamics
occur to give other species. Tris-pyridine phenylimido com-
plexes formed by imido exchange lose a pyridine ligand on
crystallisation giving 6-co-ordinate chloro-bridged dimers in
which imido ligand C–N bond rotation may be impeded when
the substituent is 2-tert-butyl or 2-phenyl but not 2-methyl.
With the tmeda ligand present a monomeric 5-co-ordinate
complex forms when the substituent is 2-tert-butyl and imido
ligand C–N bond rotation appears not to be impeded. When
the substituent is 2-phenyl a six-co-ordinate dimer forms which
shows solution dynamics. The cis-dichloro ligands in the
monomer or dimer lead to systems that are catalytically active,
polymerising ethylene in the presence of MAO with an activity
to the low end of that recognised as moderate but similar to
that found for some other imido complexes. Heterogenisation
on crosslinked polystyrene achieved by functionalising with the
tmeda equivalent or by imido exchange gives rise to loss of
ethylene polymerisation activity in the presence of MAO, com-
pared to an increase observed when vanadium imido complexes
are immobilised on uncrosslinked linear NH2-functionalised
polystyrene.
Scheme 1 (i) LiNMeCH2CH2NMe2, thf; (ii) [TiCl(µ-Cl)(NCMe3)-
(NH2CMe3)2]2, benzene.
attachment NH2-functionalised crosslinked polystyrene was
prepared and an imido exchange reaction carried out with
[TiCl2(NCMe3)(tmeda)] (Scheme 2). Preliminary studies of
the ethylene polymerisation capability of these solids in the
presence of MAO, using similar conditions to those of the
homogeneous equivalents, show there is little or no activity.
This result compares with the increase in activity observed
Experimental
Syntheses
All preparations and manipulations were carried out under dry
236
J. Chem. Soc., Dalton Trans., 2001, 232–239

View Article Online
oxygen-free nitrogen using standard bench-top techniques for
air-sensitive substances. Light petroleum (bp 40–60 ЊC), hex-
ane, benzene, toluene and diethyl ether were distilled from
sodium wire–benzophenone and dichloromethane and pyridine
from freshly ground CaH2. Solid amines were used as received
and liquid amines dried over and distilled from freshly ground
CaH2. MAO was prepared in toluene with a modification of a
literature procedure24 using a 1:1.6 ratio of AlMe3 to water.
Polymer grade ethylene, propylene and 1-hexene were used as
received. Literature procedures were used to prepare [TiCl2-
(NCMe3)(NH2CMe3)]x,1 [TiCl2(NCMe3)(tmeda)],1,3 [TiCl2-
(NCMe3)(py)3]12 and nitro-functionalised polystyrene.25 1H and
13C-{1H} NMR spectra were recorded at 400 and 100 MHz
respectively on a Bruker AM400 spectrometer (b = broad,
bs = broad singlet, bt = broadened triplet, d = doublet, dd =
doublet of doublets, m = multiplet, obsc = obscured, s = singlet,
sept = septet, t = triplet, td = triplet of doublets). CDCl3 was
dried over, and distilled from, freshly ground CaH2. C, H and
N analyses were determined by Dr A. Cunninghame and
associates, University of Otago, New Zealand.
TiCl4 (2.83 g, 14.9 mmol) in hexane (35 cm3) at 0 ЊC and the
mixture stirred for 14 h and refluxed for 2 h. o-Toluidine (1.5 g,
14.0 mmol) was added, the mixture stirred for 1 h, pyridine (5.5
cm3, 68.3 mmol) added and the mixture stirred for 48 h. The
solution was filtered through Celite and concentrated where-
upon crystals of the tris-pyridine complex were deposited
which were washed with CH2Cl2 (7 cm3) and hexane (15 cm3)
and dried in vacuo to give a green-brown powder. Yield 4.8 g
(70%). This complex was characterised by NMR spectroscopy.
1H NMR: δ 2.36 (s, 3 H, Me), 6.65 [td, 3J(HH) 7.4, 4J(HH) 1.1,
3
1 H, p-H(imido)], 6.87 [m, 2 H, m-H(imido)], 7.18 [d, J(HH)
7.4, 1 H, o-H(imido)], 7.18 [obsc, 2 H, m-H(py)], 7.29 [t, 3J(HH)
6.9, 4 H, m-H(py)], 7.64 [bt, 1 H, p-H(py)], 7.77 [t, 3J(HH) 7.6,
3
2 H, p-H(py)], 8.76 (b, 2 H, o-H(py)] and 9.08 [d, J(HH) 7.6
Hz, 4 H, o-H(py)]. 13C-{1H} NMR: δ 18.2 (Me), 121.6 [p-CH-
(imido)], 123.4 [o-CH(imido)], 123.9 [m-CH(trans-py)], 125.3
[m-CH(imido)], 126.1 [m-CH(cis-py)], 129.1 [m-CH(imido)],
132.7 [o-C(imido)], 137.0 [p-CH(cis-py)], 138.5 [p-CH(trans-
py)], 150.8 [o-CH(cis-py)], 151.5 [o-CH(trans-py)] and 158.5
(ipso-C). {Assignments made by COESY and comparison with
the spectrum of [TiCl2(NCMe3)(py)3].} The complex was dis-
solved in CH2Cl2 and layered with hexane to give crystals of the
bis-pyridine complex [Found: C, 46.3; H, 4.1; N, 9.1.
C34H34Cl4N6Ti2ؒ2CH2Cl2 requires C, 46.3; H, 4.1; N, 9.0%].
Two molecules of CH2Cl2 per dimeric unit were found in the
unit cell of the crystal structure. The complex was insufficently
soluble to obtain NMR spectra.
Preparations
[TiCl2(NCMe3)(NH2CMe3)2]2 1. A rapidly stirred solution of
TiCl4 (5.2 g, 27.4 mmol) in hexane (100 cm3) was cooled to 0 ЊC
and tert-butylamine (20 cm3, 190 mmol) added dropwise.
The mixture was stirred for 4 h, filtered through Celite which
was washed with hexane (20 cm3) and the volume reduced.
On standing at Ϫ20 ЊC for several h large orange crystals were
formed which were dried in vacuo. Yield 6.7 g (70%). Analytical
data show that the material corresponds closely to the bis-
amine complex [Found: C, 41.8; H, 9.4; N, 12.5. C12H31Cl2N3Ti
[TiCl2(NC6H4CMe3-2)(py)2]2 4. tert-Butyl-N-trimethylsilyl-
amine (0.63 g, 4.34 mmol) was added dropwise to TiCl4 (2.83 g,
14.9 mmol) in CH2Cl2 (20 cm3) at 0 ЊC and the mixture stirred
for 14 h. 2-tert-Butylaniline (0.33 g, 2.21 mmol) was added and
the mixture refluxed for 1 h and stirred for 14 h. The solution
was filtered, the precipitate washed with CH2Cl2 (3 times 10
cm3) and pyridine (ca. 5 cm3) added to the combined filtrates.
The solution was stirred for 14 h and an excess of hexane added
giving the tris-pyridine complex as a yellow-brown powder after
drying for a short period in vacuo. Yield 0.5 g (46%). This
1
requires C, 42.9; H, 9.3; N. 12.5%]. H NMR: δ 1.00 (s, Me),
1.15 (s, Me), 1.37 (bs, Me), 1.50 (s, Me), 1.58 (s, Me), 2.69 (s,
NH), 3.40 (s, NH), 4.25 (s, NH), 4.56 (s, NH) and 8.20 (bs,
NH). 13C-{1H} NMR: δ 28.2 (CMe3), 30.4 (CMe3), 30.7
(CMe3), 31.0 (CMe3), 31.2 (CMe3), 31.4 (CMe3), 31.5 (CMe3),
51.8 (C), 52.2 (C), 52.6 (C), 72.2 (C) and 73.9 (C).
1
complex was characterised by NMR spectroscopy. H NMR:
[TiCl2(NC6H3Pri2-2,6)(NH2CMe3)2]x 2. 2,6-Diisopropyl-
aniline (2.8 g, 15.8 mmol) was added to a solution of complex 1
(5.4 g. 8.03 mmol) in toluene (30 cm3) and the mixture stood
for 3 h and then refluxed for 14 h. The solution was cooled to
Ϫ20 ЊC and the solid filtered off, washed with hexane (5 cm3)
and dried in vacuo giving the complex as a yellow powder. Yield
1.8 g (51%).The analytical sample was obtained by recrystallis-
ation from hexane [Found: C, 54.8; H, 9.3; N, 9.6. C20H39-
Cl2N3Ti requires C, 54.6; H, 8.9; N, 9.5%]. 1H NMR: δ 1.24 [d,
3J(HH) 6.9, 12 H, CHMe2], 1.41 (s, 18 H, CMe3), 3.65 (bs, 4 H,
NH2), 4.44 [sept, 3J(HH) 6.9, 2 H, CH], 6.81 [t, 3J(HH) 7.0, 1 H,
3
4
δ 1.38 (s, 9 H, CMe3), 6.73 [td, J(HH) 7.4, J(HH) 1.4, 1 H,
p-H(imido)], 7.02 [m, 2 H, ], 7.20 [bs, 2 H, ], 7.31 [t, 3J(HH) 6.9,
4 H, m-H(py)], 7.65 [bt, 3J(HH) 6.9, 1 H, 7.77 [t, 3J(HH) 7.6, 2
H,], 7.88 [d, 3J(HH) 7.6, 1 H], 8.72 [b, 2 H, o-H(py)] and 9.10 [d,
3J(HH) 7.6 Hz, 4 H, o-H(py)]. 13C-{1H} NMR: δ 30.2 (CMe3),
35.1 (C), 122.1 [p-CH(imido)], 123.6 [o-CH(imido)], 124.0
[m-CH(trans-py)], 124.6 [m-CH(imido)], 125.9 [m-CH(cis-py)],
132.8 [m-CH(imido)], 136.7 [p-CH(cis-py)], 138.6 [p-CH(trans-
py)], 140.8 [o-C(imido)], 150.7 [o-CH(cis-py)], 151.4 [o-CH-
(trans-py)] and 158.7 (ipso-C). (Assignments made by
comparison with spectrum of complex 3.) A solution of this
complex in CH2Cl2 was concentrated and layered with hexane
to give yellow-brown crystals of the bis-pyridine complex
[Found: C, 53.0; H, 5.3; N, 9.2. C40H46Cl4N6Ti2ؒCH2Cl2 requires
C, 52.8; H, 5.2; N, 9.0%]. One molecule of CH2Cl2 per dimeric
unit was found in the unit cell of the crystal structure. 1H
NMR: δ 1.39 (s, 9 H, CMe3), 6.79 [td, 3J(HH) 7.6, 4J(HH) 1.4, 1
H, p-H(imido)], 7.08 [m, 2 H, m-H(imido)], 7.24 [t, 3J(HH) 6.4,
4 H, m-H(py)], 7.73 [td, 3J(HH) 6.4, 4J(HH) 1.5, 2 H, p-H(py)],
3
p-H] and 6.90 [d, J(HH) 7.0 Hz, 2 H, m-H]. 13C-{1H} NMR:
δ 24.1 (CHMe2), 27.1 (CH), 31.3 (CMe3), 53.0 (C), 122.9 (CH),
123.5 (CH), 144.8 (o-C) and 157.5 (ipso-C).
[TiCl2(NC6H3Pri2-2,6)(py)3]. Complex 2 (ca. 0.03 g, 0.07
mmol) and pyridine (ca. 0.05 g, 0.6 mmol) were dissolved in
CDCl3 (ca. 0.5 cm3) and the mixture transferred to an NMR
tube. The NMR spectra were identical to those reported.13
3
4
7.90 [dd, J(HH) 7.6, J(HH) 0.9, 1 H, o-H(imido)] and 9.08
[dd, 3J(HH) 6.4, 4J(HH) 1.5 Hz, 4 H, o-H(py)]. 13C-{1H} NMR:
δ 30.1 (CMe3), 35.1 (C), 122.7 [p-CH(imido)],124.1 [m-CH(py)],
125.0 [m-CH(imido)], 126.1 [m-CH(imido)], 132.5 [o-CH-
(imido)], 138.6 [p-CH(py)], 131.3 [o-C(imido)], 150.9 [o-CH-
(py)] and 159.1 (ipso-C). (Assignments made by COESY
spectrum.)
[TiCl2(NC6H3Pri2-2,6)(tmeda)]. Complex 2 (ca. 0.03 g, 0.07
mmol) and tmeda (ca. 0.05 g, 0.4 mmol) were dissolved in
CDCl3 (ca. 0.5 cm3) and the mixture transferred to an NMR
1
3
tube. H NMR: δ 1.14 [d, J(HH) 6.7, 12 H, CHMe2], 2.21 (s,
3
12 H, Me), 2.36 (s, 4 H, CH2), 5.13 [sept, J(HH) 6.7 Hz, CH]
and 6.82 (m, 3 H, m and p-H). 13C-{1H} NMR: δ 24.5 (CH-
Me2), 25.9 (CH), 45.6 (CH3), 57.3 (CH2), 122.3 (p-C), 126.1
(m-C), 147.4 (ortho-C) and 157.5 (ipso-C).
[TiCl2(NC6H4Ph-2)(py)]2 5. The complex [TiCl2(NCMe3)-
(py)3] (1.07 g, 2.5 mmol) and 2-phenylaniline (0.39 g, 2.3 mmol)
were dissolved in CH2Cl2 (45 cm3) and the mixture was stirred
for 14 h. The solution volume was reduced and hexane (30 cm3)
[TiCl2(NC6H4Me-2)(py)2]2 3. tert-Butyl-N-trimethylsilyl-
amine (4.33 g, 29.8 mmol) in CH2Cl2 (15 cm3) was added to
J. Chem. Soc., Dalton Trans., 2001, 232–239
237

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added giving the tris-pyridine complex as a yellow-brown
powder after drying in vacuo. Yield 1.1 g (91%). This complex
was characterised by NMR spectroscopy. 1H NMR: δ 6.60–7.30
55.0 (CH2), 57.3 (CH2), 62.7 (CH2), 126.7 (p-C), 127.9 (m-C),
128.9 (o-C) and 138.8 (ipso-C).
3
4
[TiCl2(NCMe3)(tbeda)]. tbeda (0.27 g, 1.4 mmol) in CH2Cl2
(20 cm3) was added to complex 1 (0.47 g, 0.7 mmol) in CH2Cl2
(20 cm3) and the mixture stirred for 14 h. The solution was
filtered, the solvent removed and the yellow complex dried
in vacuo. Yield 0.5 g (94%) [Found: C, 49.6; H, 7.7; N, 10.4.
(m, 15 H), 7.47 [td, J(HH) 7.6, J(HH) 1.5, 1 H], 7.78 [d,
3J(HH) 7.6, 2 H], 8.48 [d, 3J(HH) 5.0, 2 H, o-H(py)] and 8.72 [d,
3J(HH) 5.0 Hz, 4 H, o-H(py)]. 13C-{1H} NMR: δ 115.1 (CH),
117.9 (CH), 121.1 (CH), 123.2 [m-CH(trans-py)], 126.0 [m-CH-
(cis-py)], 128.0 (CH), 128.3 (CH), 128.6 (CH), 129.9 (CH),
135.5 [p-CH(cis-py)], 137.7 [p-CH(trans-py)], 139.2 (C), 143.4
(C), 149.4 [o-CH(cis-py)], 151.3 [o-CH(trans-py)] and 156.3
(ipso-C). A solution of this complex in CH2Cl2 was concen-
trated and layered with hexane to give yellow-brown crystals
of the bis-pyridine complex [Found: C, 58.3; H, 4.5; N, 9.1.
C22H19Cl2N3Ti, requires C, 59.4; H, 4.3; N, 9.5%]. The complex
was insufficiently soluble to obtain NMR spectra.
1
C16H29Cl2N3Ti requires C, 50.3; H, 7.7; N, 11.0%]. H NMR:
δ 1.16 (s, 9 H, CMe3), 2.22 (s, 6 H, NMe2), 2.25 (s, 3 H, NMe),
2.47 (m, 4 H, CH2CH2), 3.53 (s, 2 H, CH2) and 7.30 (m, 5 H,
Ph). 13C-{1H} NMR: δ 30.4 (CMe3), 42.1 (NMe), 45.5 (NMe2),
54.8 (CH2), 57.1 (CH2), 62.5 (CH2), 72.6 (C), 126.5 (p-C), 127.8
(m-C), 128.7 (o-C) and 138.6 (ipso-C).
trimeda functionalised polystyrene (trimedaPS). N,N,NЈ-
Trimethylethylenediamine (0.52 g, 5.1 mmol) in THF (25 cm3)
was cooled to Ϫ40 ЊC and n-butyllithium (2.4 cm3, 2.15 M solu-
tion, 5.2 mmol) added dropwise. The mixture was stirred for 1 h
at room temperature, then added to chloromethylated poly-
styrene (2% crosslinked, 2 mequivalents Cl gϪ1, 1.06 g, 2.12
mmol Cl) and the suspension heated at reflux for 44 h. Further
trimeda (0.60 g, 5.9 mmol) was lithiated as above but in diethyl
ether (20 cm3) and hexane (20 cm3) and the solution added to
the polystyrene from the previous functionalisation and
refluxed for 12 h. The solid was filtered off, washed with water,
ethanol and CH2Cl2 and dried in vacuo to give pale orange
beads. Yield 1.15 g [Found: C, 83.7; H, 8.6; N, 4.4%. This
corresponds to more than 90% substitution of Cl by trimeda
(concentration ca. 1.32 mmol gϪ1)].
[TiCl2(NC6H4CMe3-2)(tmeda)] 6. Procedure A. tert-Butyl-
amine (4.5 cm3, 42.8 mmol) was added dropwise to TiCl4 (1.0 g,
5.1 mmol) in benzene (40 cm3) and the mixture stirred for 8 h
after which 2-tert-butylaniline (0.77 g, 5.16 mmol) was added
and the mixture refluxed for 1.5 h. After cooling to room tem-
perature tmeda (0.59 g, 5.08 mmol) was added and the mixture
stirred for 14 h. The solution was filtered, the volume reduced,
hexane (50 cm3) added and the solution cooled to Ϫ20 ЊC over-
night giving brown crystals which were washed with cold
hexane and dried in vacuo. Yield 1.3 g (67%) [Found: C, 48.8; H,
8.2; N, 10.7. C16H29Cl2N3Ti requires C, 50.2; H, 7.7; N, 11.0%].
1H NMR: δ 1.59 (s, 9 H, CMe3), 2.89 (s, 12 H, Me), 3.15 (s, 4 H,
3
4
CH2), 6.76 [td, J(HH) 8.0, J(HH) 1.0, 1 H, p-H], 6.95 [td,
3J(HH) 7.7, 4J(HH) 1.0, 1 H, m-H], 7.11 [dd, 3J(HH) 7.7,
3
4J(HH) 1.0, 1 H, m-H] and 7.30 [d, J(HH) 7.7 Hz, 1 H, o-H].
13C-{1H} NMR: δ 30.9 (CMe3), 35.5 (C), 51.2 (Me), 58.8 (CH2),
124.2 (m-CH), 125.6 (m-CH), 125.7 (m-CH), 129.9 (o-CH),
141.3 (o-C) and 160.8 (ipso-C).
trimedaPS-[TiCl2(NCMe3)]x. trimedaPS [0.17 g (ca. 0.22
mmol trimeda)] and complex 1 (0.21 g, 0.297 mmol) were
refluxed in benzene (30 cm3) for 2 d. A further portion of com-
plex 1 (0.4 g, 0.60 mmol) was added and the mixture refluxed
for 1 d. The cooled solution was filtered and the orange-brown
beads washed with CH2Cl2 and dried in vacuo.
Procedure B. 2-tert-Butylaniline (1.16 g, 7.8 mmol) was
added to [TiCl2(NCMe3)(tmeda)] (2.46 g, 8.0 mmol) and the
mixture stirred for 14 h and worked up as under procedure
A. Crystals suitable for X-ray analysis were obtained by layer-
ing a CH2Cl2 solution with hexane and leaving to stand
overnight.
trimedaPS-[TiCl4]x. trimedaPS [0.21 g (ca. 0.28 mmol tri-
meda)] was suspended in CH2Cl2 (20 cm3) and TiCl4 (1 cm3, 9.1
mmol) added via a syringe. After refluxing the solution for 14 h
the brown beads were washed with CH2Cl2 and dried in vacuo.
Yield 0.27 g.
[TiCl2(NC6H4Ph-2)(tmeda)]2 7. A mixture of [TiCl2(NC-
Me3)(tmeda)] (1.17 g, 3.8 mmol) and 2-phenylaniline (0.63 g,
3.7 mmol) was dissolved in CH2Cl2 (30 cm3) and stirred for 14
h. Hexane (40 cm3) was layered on top and the solution allowed
to stand for 2 d. The crystals were filtered off, one was removed
for X-ray crystallography, and the remainder were washed with
hexane and dried in vacuo. Yield 0.6 g (39%) [Found: C, 53.4; H,
6.5; N, 10.4. C18H25Cl2N3Ti requires C, 53.8; H, 6.3; N, 10.5%].
1H NMR: δ 2.62 (s, 12 H, Me), 2.78 (s, 4 H, CH2), 6.80 (m, 1 H),
6.98 [d, 3J(HH) 7.3, 1 H], 7.15 (m, 2 H), 7.29 (m, 1 H), 7.42 (m,
2 H) and 7.60 [d, 3J(HH) 7.4 Hz, 2 H]. 13C-{1H} NMR: δ 44.7
(Me), 51.2 (Me), 54.2 (CH2), 58.4 (CH2), 115.7 (CH), 118.7
(CH), 122.1 (CH), 126.7 (CH), 127.1 (CH), 127.6 (CH), 128.0
(CH), 128.4 (CH), 128.8 (CH), 129.1 (CH), 129.2 (CH), 130.3
(CH), 130.4 (CH),139.5 (C), 141.0 (b, C), 143.5 (CH) and 156.0
(ipso-C) [2C and an ipso-C not observed in the accumulation].
Amino
functionalised
polystyrene
(amPS).
Nitro-
functionalised polystyrene (2.25 g, ca. 21.6 mmol, 28% NO2)
and tin() chloride dihydrate (25.4 g, 113 mmol) in ethanol (40
cm3) were refluxed for 66 h and the yellow-orange polymer
beads filtered off and washed with ethanol. The beads were
suspended in hydrochloric acid (8 M) for 1 h and then filtered
off, washed successively with water, ethanol–water (1:1), etha-
nol, soaked in aqueous KOH (2 M) for 40 minutes and washed
with aqueous KOH (1 M). The washing and soaking process
was repeated and the beads were then washed with water,
ethanol–water (1:1), ethanol and finally with CH2Cl2. They
were dried at 130 ЊC and again in vacuo. Yield 1.95 g [Found: C,
83.0; H,6.9; N, 2.5%. This corresponds to ca. 71% reduction of
the nitro functionality]. IR (cmϪ1): 3450 (NH2) and 1600 (NH2).
Me2NCH2CH2NMe(CH2Ph) (tbeda). N,N,NЈ-Trimethyl-
ethylenediamine (trimeda) (1.45 g, 14.2 mmol) in diethyl ether
(25 cm3) was cooled to 0 ЊC and n-butyllithium (7.0 cm3, 2.15 M
solution, 15.1 mmol) added dropwise. The solution was stirred
overnight at room temperature, recooled to 0 ЊC and benzyl
chloride (1.9 g, 15.0 mmol) added. After stirring for 2 d the
solution was filtered through Celite and the volatiles removed to
give a yellow oil which NMR spectroscopy showed to be essen-
tially pure. Yield 1.9 g (70%). Distillation gave a colourless
liquid. Yield 1.2 g (44%) 1H NMR: δ 2.11 (s, 6 H, NMe2), 2.14
(s, 3 H, NMe), 2.36 (m, 4 H, CH2CH2), 3.42 (s, 2 H, CH2) and
7.16 (m, 5 H, Ph). 13C-{1H} NMR: δ 42.3 (NMe), 45.7 (NMe2),
amPS–[TiCl2(NCMe3)(tmeda)]x. A solution of complex 1
(0.80 g, 1.19 mmol) and tmeda (1.08 g, 9.29 mmol) in toluene
(10 cm3) was added to amPS (0.8 g) and the heterogeneous
mixture refluxed for 7 d. The dark brown polymer beads
were washed with toluene followed by CH2Cl2, dried in vacuo
and used in the polymerisation reaction without further
characterisation.
Polymerisations
Polymerisations were performed in a 400 cm3 flame-dried pres-
sure bottle equipped with a head containing inlet and outlet
238
J. Chem. Soc., Dalton Trans., 2001, 232–239

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Table 8 Crystallographic data for complexes 1, 3, 4, 5, 6 and 7
1
3
4
5
6
7
Formula
M
C24H62Cl4N6Ti2
672.4
C34H62Cl4N6Ti2
932.1
C40H46Cl4N6Ti2
1188.14
C44H38Cl4N6Ti2
888.4
C16H29Cl2N3Ti
382.22
C36H50Cl4N6Ti2
804.42
Crystal symmetry
Space group
Monoclinic
P21/n
Monoclinic
P21/c
Triclinic
P1
Monoclinic
P21/n
Monoclinic
P21/c
Triclinic
P1
¯
¯
a/Å
b/Å
c/Å
a/Њ
13.6191(2)
10.4143(2)
14.51000(10)
9.90300(9)
15.9595(2)
13.57730(10)
8.042(2)
10.73410(10)
16.4281(2)
77.0130(10)
77.14(10)
84.5900(10)
1345.67(2)
2
10.1087(4)
17.1958(6)
12.4949(5)
15.1800(4)
7.5428(2)
17.0488(5)
7.7374(5)
10.4470(7)
12.5090(9)
75.8640(10)
80.6930(10)
77.2650(10)
950.15(11)
2
b/Њ
117.7330(10)
101.1590(10)
111.42
90.7510(10)
c/Њ
U/Å3
1821.59(5)
2
0.754
2105.32(3)
4
0.921
2021.97(13)
4
0.700
1951.93(9)
4
0.713
Z
µ/mmϪ1
0.930
0.736
T/K
R1
203(2)
0.0355
0.0821
4027, 172
203(2)
0.0366
0.0948
4717, 236
203(2)
0.0638
0.0616
6103, 292
203(2)
0.0612
0.0992
4557, 253
203(2)
0.0974
0.0967
4337, 207
203(2)
0.0436
0.1124
3830, 217
wR2 (F 2, all data)
Data parameters
4 C. J. Carmalt, S. R. Whaley, P. S. Lall, A. H. Cowley, R. A. Jones,
B. G. McBurnett and J. G. Ekerdt, J. Chem. Soc., Dalton Trans.,
1998, 553.
5 P. Mountford, Chem. Commun., 1997, 2127.
6 R. Duchateau, A. J. Williams, S. Gambarotta and M. Y. Chiang,
Inorg. Chem., 1991, 30, 4863.
7 W. Kaminsky, J. Chem. Soc., Dalton Trans., 1998, 1413; M.
Bochmann, J. Chem. Soc., Dalton Trans., 1996, 255; H. H.
Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger and R. Waymouth,
Angew. Chem., Int. Ed. Engl., 1995, 34, 1143.
8 B. P. Santora, P. S. White and M. R. Gagne, Organometallics, 1999,
18, 2557; B. P. Santora, A. O. Larsen and M. R. Gagne,
Organometallics, 1998, 17, 3138; E. S. Johnson, G. J. Balaich,
P. E. Fanwick and I. P. Rothwell, J. Am. Chem. Soc., 1997,
119, 11086; M. G. Thorn, J. E. Hill, S. A. Waratuke, E. S. Johnson,
P. E. Fanwick and I. P. Rothwell, J. Am. Chem. Soc., 1997, 119, 8630;
E. S. Johnson, G. J. Balaich and I. P. Rothwell, J. Am. Chem. Soc.,
1997, 119, 7685; G. J. Balaich, J. E. Hill, S. A. Waratuke, P. E.
Fanwick and I. P. Rothwell, Organometallics, 1995, 14, 656.
9 A. J. Nielson, M. W. Glenny, C. E. F. Rickard and J. M. Waters,
J. Chem. Soc., Dalton Trans., 2000, 4569.
taps and a pressure guage. Homogeneous reactions were carried
out by dissolving a weighed amount of catalyst in CH2Cl2 (10
cm3) and transferring the solution to the pressure bottle. A
toluene solution of MAO was added via a syringe, the mixture
stirred for 10 minutes, the vessel flushed 3 times with ethylene or
propene and the pressure then maintained at 1.7 atm. 1-Hexene
was dissolved in CH2Cl2 (10 cm3) and added after the 10 minute
induction period. The polymerisation was quenched with acid-
ified ethanol and the polymer washed with CH2Cl2 and dried in
vacuo to constant weight. Heterogeneous reactions were carried
out by suspending the polystyrene supported catalyst (0.1 g) in
toluene (10 cm3), adding a toluene solution of MAO and allow-
ing an initiation time of 10 minutes before introducing the
olefin monomer and working up as for the homogeneous reac-
tions. The mass of polymer was obtained by subtracting the
initial weight of polystyrene supported catalyst from the dry
weight of the insoluble product.
10 A. J. Nielson, unpublished work.
Crystallography
11 D. E. Wigley, Prog. Inorg. Chem., 1994, 42, 239.
12 P. E. Collier, S. C. Dunn, P. Mountford, O. V. Shishkin and
D. Swallow, J. Chem. Soc., Dalton Trans., 1995, 3743.
13 A. J. Blake, P. E. Collier, S. C. Dunn, W.-S. Li, P. Mountford and
O. V. Shishkin, J. Chem. Soc., Dalton Trans., 1997, 1549.
14 F. Montilla, A. Galindo, E. Carmona, E. Gutierrez-Puebla and
A. Monge, J. Chem. Soc., Dalton Trans., 1998, 1299.
15 S. C. Dunn, A.S. Batsanov and P. Mountford, J. Chem. Soc., Chem.
Commun., 1994, 2007.
16 P. Barrie, T. A. Goffey, G. D. Forster and G. Hogarth, J. Chem. Soc.,
Dalton Trans., 1999, 4519; A. Bell, W. Clegg. P. W. Dyer, M. R. J.
Elsegood, V. C. Gibson and E. L Marshall, J. Chem. Soc., Dalton
Trans., 1994, 2247.
17 A. Clearfield, D. K. Warner, C. H. Saldarriaga-Molina, R. Ropal
and I. Bernal, Can. J. Chem., 1975, 53, 1622.
18 G. J. P. Britovsek. V. C. Gibson and D. F. Wass, Angew. Chem., Int.
Ed., 1999, 38, 429.
19 S. Scheuer, J. Fischer and J. Kress, Organometallics, 1995, 14,
2627.
20 D. M. Antonelli, A. Leins and J. M. Stryker, Organometallics, 1997,
16, 2500.
21 M. P. Coles and V. C. Gibson, Polym. Bull., 1994, 33, 529.
22 M. C. W. Chan, K. C. Chew, C. I. Dalby, V. C. Gibson,
A. Kohlmann, I. R. Little and W. Reed, J. Chem. Soc., Dalton
Trans., 1998, 1673.
23 Q. H. Fan, C. Y. Ren, C. H. Yeung, W. H. Hu and A. S. C. Chan,
J. Am. Chem. Soc., 1999, 121, 7407; D. C. Sherrington. Chem.
Commun., 1998, 2275; A. Akela and D. C. Sherrington, Chem. Rev.,
1981, 81, 557.
24 E. G. M. Tornqvist and H. C. Welborn, Jr., Eur. Pat., 208 561, 1987.
25 R. B. King and E. M. Sweet, J. Org. Chem., 1979, 44, 389.
26 R. H. Blessing, Acta Crystallogr., Sect. A, 1995, 51, 33.
27 G. M. Sheldrick, SHELXS, Institut für Anorganische Chemie,
Universität Göttingen, 1990.
28 G. M. Sheldrick, SHELXL 93, Institut für Anorganische Chemie,
Universität Göttingen, 1993.
Data were collected on a Siemens SMART diffractometer using
Mo-Kα radiation (λ = 0.71073 Å). The data collection covered a
nominal sphere of reciprocal space, by a combination of 4 sets
of exposures. Each set had a different ꢀ angle for the crystal and
each exposure covered 0.3Њ in α. Coverage of the unique data
sets was at least 98% complete to 56Њ in 2θ. Crystal decay was
monitored by repeating the initial frames at the end of the data
collection and analysing the duplicate reflections. Unit cell
parameters were obtained by least-squares fit of all the data
with I > 10σ(I). Lorentz and polarisation reflections were
applied and absorption corrections made by the method of
Blessing.26 The structures were solved by Patterson and Fourier
techniques and refined by full-matrix least squares. All non-
hydrogen atoms were allowed to assume anisotropic thermal
motion. Hydrogen atoms were placed geometrically and refined
with a riding model with Uiso constrained to 1.2 times Ueq of the
carrier atom. Crystallographic data for the complexes are con-
tained in Table 8. Programs used were SHELXS27 for structure
solution and SHELXL 9328 for refinement.
CCDC reference number 186/2279.
See http://www.rsc.org/suppdata/dt/b0/b008232p/ for crystal-
lographic files in .cif format.
References
1 A. J. Nielson, Inorg. Chim. Acta, 1988, 154, 177.
2 R. T. Cowdell and G. W. A. Fowles, J. Chem. Soc., 1960, 2522.
3 T. S. Lewkebandara, P. H. Sheridan, M. J. Heeg, A. P. Rheingold
and C. H. Winter, Inorg. Chem., 1994, 33, 5879; C. H. Winter,
P. H. Sheridan, T. S. Lewkebandara, M. J. Heeg and J. W. Proscia,
J. Am. Chem. Soc., 1992, 114, 1095.
J. Chem. Soc., Dalton Trans., 2001, 232–239
239