Titanium(IV) complexes with monocyclopentadienyl and phenoxy-alkoxo ligands: Synthesis, structures and catalytic properties for ethylene polymerization

Article abstract of DOI:10.1016/j.poly.2007.03.012

Three monochlorotitanium complexes Cp′Ti(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)Cl [Cp′ = η⁵-C₅H₅ (2), η⁵-C₅(CH₃)₅ (3), η⁵-C

Full text of DOI:10.1016/j.poly.2007.03.012

Polyhedron 26 (2007) 3357–3362
www.elsevier.com/locate/poly
Titanium(IV) complexes with monocyclopentadienyl and
phenoxy-alkoxo ligands: Synthesis, structures and catalytic
properties for ethylene polymerization
*
Tie-Qi Xu, Wei Gao, Ying Mu , Ling Ye
Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, School of Chemistry, Jilin University, 2699 Qianjin Street,
Changchun 130012, People’s Republic of China
Received 11 December 2006; accepted 8 March 2007
Available online 15 March 2007
Abstract
Three monochlorotitanium complexes Cp0Ti(2,4-tBu2-6-(CPh2O)C6H2O)Cl [Cp0 = g5-C5H5 (2), g5-C5(CH3)5 (3), g5-C5H2Ph2CH3
(4)] have been synthesized in high yields (>90%) by the reaction of corresponding Cp0TiCl3 with the dilithium salt of ligand 2,4-tBu2-
6-(CPh2OH)C6H2OH (1). When activated by [Ph3C]+[B(C6F5)4]ꢀ and AliBu3, complexes 2–4 exhibit reasonable catalytic activity for eth-
ylene polymerization, producing polyethylenes with moderate molecular weights and melting points. Addition of excess water to complex
2 gave the oxo-bridged complex [Ti(g5-C5H5)(2,4-tBu2-6-(CPh2O)C6H2O)]2O (5). Complexes 4 and 5 were characterized by single crystal
X-ray diffraction.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Titanium complexes; Ethylene polymerization; Homogeneous catalysis; Metallocene catalysts
1. Introduction
scarce [4], although they are active for olefin polymeriza-
tion and are also of potential interest in the context of sin-
gle-site olefin polymerization catalysis. Therefore, our
current focus is the development of this class of monochlo-
rotitanium complexes, and investigation of the influence of
different substituents at cyclopentadienyl (Cp) on their cat-
alytic activity.
Polyolefins are the largest volume synthetic materials
used in the world, and have been almost applied in every
aspect of our daily lives and productions. One of the most
active areas of polyolefins research over the past decades
has been the discovery and development of Ziegler–Natta
catalysis for polymerization of ethylene and a-olefins. Since
Kaminsky et. al. discovered the highly active zirconocene
dichloride/methylaluminoxane (MAO) catalytic system
for olefin polymerization [1], intensive research work has
been focused on developing new Group 4 metallocene cat-
alysts for improving catalytic activities and polymer prop-
erties [2,3]. Most of Group 4 metallocene and related
complexes for olefin polymerization typically have two or
more alkyl (or halide) groups attached to the metal. Exam-
ples of precatalysts containing only one such group are
In this work, a new bidentate chelating ligand 2,4-tBu2-
6-(CPh2OH)C6H2OH (1) was firstly synthesized and intro-
duced into the monochlorotitanium system, based on the
following considerations: (i) the phenoxy-alkoxo bidentate
ligand comprising the alkoxo group linked with the phenol
group has two different active oxygen functionalities in the
metalation reaction, therefore increasing the selectivity of
forming the desired complexes in the synthetic reaction;
(ii) recently, Doherty et al. have reported that introducing
phenyl groups on the alkoxo ligand are able to increase cat-
alytic activity of the precatalysts [CpTi{NC5H4(CR2O)-
2}Cl2] [5], so here we choose the alkoxo ligand containing
phenyl groups. With the new ligand, we successfully
*
Corresponding author. Tel.: +86 431 85168472; fax: +86 431
85193421.
E-mail address: ymu@mail.jlu.edu.cn (Y. Mu).
obtained a series of monochlorotitanium complexes
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.03.012

3358
T.-Q. Xu et al. / Polyhedron 26 (2007) 3357–3362
Cp0Ti(2,4-tBu2-6-(CPh2O)C6H2O)Cl (Cp0 = g5-C5H5 (2),
g5-C5(CH3)5 (3), g5-C5H2Ph2CH3 (4)) which have different
substituents in cyclopentadienyl in high yield (>90%), and
studied their application in ethylene polymerization and
their hydrolysis reactions.
in toluene in high yields (Scheme 2). These complexes were
found to be easily hydrolyzed. Addition of excess water to
toluene solution of complex 2 gave the oxo-bridged com-
plex
[Ti(g5-C5H5)(2,4-tBu2-6-(CPh2O)C6H2O)]2O
(5)
(Scheme 3). However, the same reaction with complexes
3 and 4 caused complete decomposition of both complexes
to a mixture of unknown composition in which no organo-
metallic complexes were isolated. All complexes were char-
acterized by elemental analysis and NMR spectroscopy.
Complexes 4 and 5 were characterized by single crystal
X-ray diffraction.
2. Results and discussion
2.1. Synthesis and characterization
The new bidentate ligand 1 was synthesized with 2,4-di-
tert-butylphenol as the starting material. 2-Bromo-4,6-di-
tert-butylphenol was easily prepared from the reaction of
Br2 with 2,4-di-tert-butylphenol in CHCl3/CCl4 at 0 ꢁC.
The reaction of dilithium phenoxide, obtained by treating
2-bromo-4,6-di-tert-butylphenol with 2 equiv. of nBuLi,
with benzophenone in Et2O at ꢀ15 ꢁC, followed by hydro-
lysis with saturated NH4Cl produced the ligand 1 in a mod-
erate yield (Scheme 1). The monochlorotitanium complexes
2–4 were prepared by reaction of Cp0TiCl3 (Cp0 = g5-
C5H5, g5-C5(CH3)5, g5-C5H2Ph2CH3) with equimolar
amount of dilithium salt of 2,4-tBu2-6-(CPh2OH)C6H2OH
2.2. Crystal Structures of 4 and 5
Crystals of complexes 4 and 5 suitable for single-crystal
X-ray diffraction study were grown by cooling the satu-
rated solutions of 4 and 5 in mixed CH2Cl2/hexane. The
ORTEP drawings of the molecule structures are shown in
Figs. 1 and 2. The selected bond lengths and angles are
summarized in Table 1. The geometry around titanium in
4 can be described as a pseudo-tetrahedral coordination
environment, which is defined by a substituted Cp ring
Scheme 1. Synthetic procedure of ligand 1.
Scheme 2. Synthetic procedure of complexes 2–4.
Scheme 3. Synthetic procedure of complex 5.

T.-Q. Xu et al. / Polyhedron 26 (2007) 3357–3362
3359
Table 1
Selected bond lengths and angles
Complex 4
Ti–O(1)
Ti–Cl
Ti–C(2)
Ti–C(4)
O(1)–C(33)
C(1)–C(2)
C(3)–C(4)
C(1)–C(5)
Cp(cent)–Ti–O(1)
O(1)–Ti–O(2)
O(2)–Ti–Cl
1.778(3)
2.268(7)
2.336(6)
2.445(6)
1.428(6)
1.420(8)
1.447(7)
1.408(7)
Ti–O(2)
Ti–C(1)
Ti–C(3)
Ti–C(5)
O(2)–C(19)
C(2)–C(3)
C(4)–C(5)
Cp(cent)–Ti
Cp(cent)–Ti–O(2)
O(1)–Ti–Cl
Cp(cent)–Ti–Cl
1.831(4)
2.409(6)
2.374(6)
2.423(6)
1.380(6)
1.421(8)
1.408(8)
2.071
121.5
90.7(2)
105.0(1)
113.7
104.0(1)
117.7
Complex 5
Ti–O(1)
1.803(2)
Ti–O
1.812(1)
Ti–O(2)
Ti–C(2)
Ti–C(4)
O(2)–C(6)
C(1)–C(2)
C(3)–C(4)
C(1)–C(5)
Cp(cent)–Ti–O(1)
Cp(cent)–Ti–O
O(1)–Ti–O
1.848(2)
2.366(3)
2.373(3)
1.377(3)
1.348(7)
1.408(7)
1.345(6)
119.5
120.7
103.9(8)
Ti–C(1)
Ti–C(3)
Ti–C(5)
O(1)–C(20)
C(2)–C(3)
C(4)–C(5)
Cp(cent)–Ti
Cp(cent)–Ti–O(2)
O(1)–Ti–O(2)
O(2)–Ti–O
2.402(4)
2.341(4)
2.403(4)
1.435(3)
1.413(7)
1.367(7)
2.069
111.3
93.1(9)
104.0(7)
Fig. 1. Molecular structure of complex 4.
nol-alkoxo ligand 2,4-tBu2-6-(CPh2O)C6H2O in 5 is similar
to complex 4, showing a boat structure. The Ti–O (alkoxo)
˚
˚
bond lengths of 1.778 A in 4 and 1.803 A in 5 are shorter
˚
than Ti–O (phenoxy) bond lengths of 1.831 A in 4 and
1.848 A in 5, respectively, which may reflect O(pp)–Ti(dp)
˚
donation of alkoxo groups to the metal [5].
2.3. Ethylene polymerization studies
Fig. 2. Molecular structure of complex 5.
The experimental results of ethylene polymerization
with complexes 2–4 as precatalysts were summarized in
Table 2. Upon activation with AliBu3 and [Ph3C]+-
[B(C6F5)4]ꢀ, complexes 2–4 show good catalytic activity
for ethylene polymerization, producing polyethylenes with
moderate molecular weights and melting points. For com-
plexes 2–4 the catalytic activity increases with the increase
of Al/Ti ratio, and reaches the highest catalytic activity
with the ratio Al/Ti of 150, while further increasing the
Al/Ti ratio results in a decrease in catalytic activity. It is
possible that excessive AliBu3 would consume so much
[Ph3C]+[B(C6F5)4]ꢀ that catalysts could not be efficiently
activated [6]. The catalytic activity of all complexes
increases with the increase of polymerization temperature,
and reaches the highest value at 80 ꢁC. Further increase in
the polymerization temperature results in a decrease in the
catalytic activity. The order of catalytic activity for ethyl-
ene polymerization under similar conditions (see run 2, 7
and 12 in Table 2) is 3 > 4 > 2, which implies that both
the electronic and steric factors of substituents on the
cyclopentadienyl group play roles in determining catalytic
activity of these complexes.
(assuming Cp to occupy one coordination site), a chlorine
atom, and two oxygen atoms from the phenol-alkoxo
ligand. The phenol-alkoxo ligand adopts a puckered che-
late disposition with the typical boat conformation. The
˚
Ti–C bond lengths range from 2.336 to 2.445 A, and Ti–
˚
C4 (2.445 A) are longer than those of known Ti–C (Cp ring
carbon) bond lengths in similar monochlorotitanium com-
plexes [4]. The C–C bond lengths in the substituted Cp ring
˚
˚
range from 1.408 to 1.447 A, and the C3–C4 (1.447 A)
bond length is the longest among these values, which could
be explained by the steric and conjugate effects of the two
phenyl groups on the Cp-ring.
The molecular structure of complex 5 consists of two
[Ti(g5-C5H5)(2,4-tBu2-6-(CPh2O)C6H2O)] units linked by
Ti–O–Ti bridge. Each titanium is coordinated in a
pseudo-tetrahedral geometry by a Cp ring, and three oxy-
gen atoms (one from the oxo-bridge, and the other two
from the phenoxy-alkoxo ligand). The C–C bond lengths
in the Cp ring are close to the ones observed in know Ti–
Cp ring carbon distances. The conformation of the phe-

3360
T.-Q. Xu et al. / Polyhedron 26 (2007) 3357–3362
Table 2
organic layer was separated, dried over MgSO4, filtered,
and concentrated by distillation under reduced pressure.
Pure product (4.90 g, 64%) was obtained by column chro-
matography over silica (hexanes) as white needles. Anal.
Calc. for C27H32O2 (388.54): C, 83.46; H, 8.30. Found:
Results of ethylene polymerization using procatalysts 2–4a
Number Catalyst Al:Ti
T
Activityb · 10ꢀ5 Mgc · 10ꢀ5 Tdm
(ꢁC)
(ꢁC)
1
2
3
4
5
6
7
8
9
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
100
150
200
150
150
100
150
200
150
150
100
150
200
150
150
80 0.64
2.12
2.32
1.98
1.86
1.71
2.89
3.11
3.37
2.74
2.88
3.67
3.01
2.76
2.52
2.34
134.7
135.2
134.2
134.0
134.5
134.6
136.3
135.8
134.9
135.1
133.7
134.2
134.1
133.6
133.3
1
80 1.32
80 1.16
60 0.44
100 0.92
80 2.88
80 7.22
80 5.16
60 4.04
100 5.12
80 1.82
80 2.52
80 1.76
60 1.52
100 1.74
C, 83.38; H, 8.24%. H NMR (CDCl3, 300 MHz; 298 K):
d 8.27 (s, 1H, Ph–OH), 7.17–7.35 (m, 11H, Ph), 6.33 (d,
1H, Ph), 3.47 (s, 1H, OH), 1.39 (s, 9H, Ph–tBu), 1.11 (s,
9H, Ph–tBu). C13 NMR (CDCl3, 75.4 MHz) d, ppm:
153.4, 145.6, 140.2, 136.9, 129.4, 128.1, 127.8, 127.7,
125.4, 124.0, 85.5, 35.5, 34.5, 31.9, 30.3.
10
11
12
13
14
15
a
3.3. Synthesis of [Ti(g5-C5H5)(2,4-tBu2-6-
(CPh2O)C6H2O)Cl] (2)
n
A solution of BuLi in n-hexane (1.6 M, 1.6 ml) was
added to a solution of 2,4-tBu2-6-(CPh2OH)C6H2OH
(1.00 g, 2.57 mmol) in toluene (10 ml) at ꢀ78 ꢁC. The reac-
tion mixture was warmed to room temperature and stirred
for 1 h to give a solution of 2,4-tBu2-6-(CPh2OLi)C6H2OLi.
This reaction mixture was added to a solution of CpTiCl3
(0.56 g, 2.57 mmol) in toluene (5 ml) at ꢀ78 ꢁC, and the
reaction mixture was warmed slowly to room temperature
and then heated for another 6 h at 80 ꢁC. After allowing
the mixture to cool to room temperature, the mixture was
filtered, the solution was evaporated in vacuo, and the resul-
tant solid was extracted with n-hexane. The extract was con-
centrated and placed in the freezer. The pale yellow
microcrystals were collected. Yield 91% (1.25 g,
2.34 mmol). Anal. Calc. for C32H35ClO2Ti (534.94): C,
71.85; H, 6.59. Found: C, 71.91; H, 6.49%. 1H NMR
(CDCl3, 300 MHz; 298 K): d 7.11–7.39 (m, 11H, Ph), 6.52
(d, 1H, Ph), 6.35 (s, 5H, Cp), 1.36 (s, 9H, Ph–tBu), 1.18
(s, 9H, Ph–tBu). C13 NMR (CDCl3, 75.4 MHz) d, ppm:
158.1, 147.6, 146.2, 142.9, 128.6, 128.1, 127.2, 126.5 125.4,
123.3, 118.3, 99.9, 35.3, 34.6, 31.1, 30.7.
Polymerization conditions: solvent, 60 ml of toluene; catalyst, 2 lmol;
B/Ti ratio, 1.3; time, 5 min.
b
g PE (mol Ti)ꢀ1 hꢀ1 barꢀ1
.
c
Measured in decahydronaphthalene at 135 ꢁC.
d
Determined by DSC at a heating rate of 10 ꢁC minꢀ1
.
3. Experimental
3.1. General comments
Reactions with organometallic reagents were carried out
under an argon atmosphere (ultra-high purity) using stan-
dard Schlenk techniques [7]. Solvents were dried and dis-
tilled prior to use [8]. Polymerization grade ethylene was
˚
further purified by passage through columns of 10 A
molecular sieves and MnO. AliBu3, BuLi and TiCl4 were
n
purchased from Aldrich. [g5-C5H5]TiCl3 [9], [g5-
C5(CH3)5]TiCl3 [10], [g5-C5H2Ph2CH3]TiCl3 [11], and
[Ph3C]+[B(C6F5)4]ꢀ [12] were prepared according to the lit-
erature procedures. NMR spectra were measured using a
Varian Mercury-300 NMR spectrometer.
3.4. Synthesis of [Ti(g5-C5(CH3)5)(2,4-tBu2-6-
(CPh2O)C6H2O)Cl] (3)
3.2. Synthesis of 2,4-tBu2-6-(CPh2OH)C6H2OH (1)
Complex 3 was synthesized in the same way as described
above for the synthesis of 2 with [g5-C5(CH3)5]TiCl3
(0.74 g, 2.57 mmol) as the starting material. Pure complex
3 was obtained as yellow crystals. Yield 90% (1.40 g,
2.31 mmol). Anal. Calc. for C37H45ClO2Ti (605.07): C,
73.45; H, 7.50. Found: C, 73.37; H, 7.42%. 1H NMR
(CDCl3, 300 MHz; 298 K): d 7.08–7.45 (m, 11H, Ph), 6.48
(d, 1H, Ph), 1.99 (s, 15H, Cp–Me), 1.39 (s, 9H, Ph–tBu),
1.03 (s, 9H, Ph–tBu). C13 NMR (CDCl3, 75.4 MHz) d,
ppm: 156.1, 146.3, 145.2, 141.6, 128.8, 128.5, 127.4, 126.3,
125.4, 123.6, 118.8, 98.6, 35.3, 34.9, 31.8, 30.1, 12.6.
A solution of Br2 (5.2 ml, 95 mmol) in CHCl3 (20 ml)
was added dropwise to a solution of 2,4-Di-tert-butylphe-
nol (19.6 g, 95 mmol) in CHCl3 (20 ml) and CCl4 (20 ml)
over 2 h at 0 ꢁC. The mixture was stirred for 1 h at this tem-
perature. The organic phase was separated, and washed six
times with water (50 ml), dried with MgSO4. Pure product
(24.4 g, 90%) was obtained by column chromatography
over silica (hexanes) as white crystals. A solution of 2-
bromo-4,6-di-tert-butylphenol (5.71 g, 20 mmol) in Et2O
(40 ml) was added dropwise to a solution of nBuLi
(40 mmol) in Et2O (40 ml) at ꢀ15 ꢁC. The mixture was
slowly warmed to room temperature and stirred overnight.
The solution was cooled to ꢀ15 ꢁC, and a solution of ben-
zophenone (7.32 g, 40 mmol) in Et2O (20 ml) was added
dropwise. The reaction mixture was stirred overnight and
then quenched with 60 ml of saturated NH4Cl (aq). The
3.5. Synthesis of [Ti(g5-C5H2Ph2CH3)(2,4-tBu2-6-
(CPh2O)C6H2O)Cl] (4)
Complex 4 was synthesized in the same way as described
above for the synthesis of 2 with [g5-C5H2Ph2CH3] TiCl3

T.-Q. Xu et al. / Polyhedron 26 (2007) 3357–3362
3361
Table 3
(0.99 g, 2.57 mmol) as the starting material. Pure complex 4
Crystal data and structural refinements details for 4 and 5
was obtained as yellow crystals. Yield 95% (1.71 g,
2.44 mmol). Anal. Calc. for C45H45ClO2Ti (701.16): C,
77.08; H, 6.47. Found: C, 77.14; H, 7.54%. 1H NMR
(CDCl3, 300 MHz; 298 K): d 7.06–7.46 (m, 21H, Ph),
6.51 (d, 1H, Ph), 6.32 (d, 1H, Cp), 6.19 (d, 1H, Cp), 1.98
(s, Cp–Me), 1.28 (s, 9H, Ph–tBu), 1.06 (s, 9H, Ph–tBu).
C13 NMR (CDCl3, 75.4 MHz) d, ppm: 158.4, 148.2,
146.6, 143.2, 135.0, 134.2, 133.6, 132.8, 131.3, 129.7,
129.5, 129.4, 129.1, 128.8, 128.6, 128.4, 128.3, 128.2,
128.1, 128.0, 127.9, 127.7, 127.6, 127.4, 123.3, 118.9,
118.2, 99.5, 35.6, 34.5, 31.5, 30.5, 15.5.
4
5
Molecular formula
Molecular weight
Crystal system
Space group
C45H45ClO2Ti C64H70O5Ti2
701.16
triclinic
1015.00
triclinic
ꢀ
ꢀ
P1
P1
˚
a (A)
9.174(4)
10.511(0)
22.379(3)
77.27(7)
82.02(0)
68.98(0)
1960.8(3)
2
10.721(8)
11.192(8)
13.145(7)
103.86(7)
102.81(5)
104.76(5)
1412.1(8)
1
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
3.6. Synthesis of [Ti(g5-C5H5)(2,4-tBu2-6-
(CPh2O)C6H2O)]2O (5)
Dcalc (g cmꢀ3
F(000)
)
1.188
1.194
740
538
Absorption coefficient (mmꢀ1
)
0.321
0.330
Collect range (ꢁ)
Number of independent reflections
Rint
0.93 6 h 6 25
6058
0.0238
1.67 6 h 6 27.48
6274
0.0599
To a solution of complex 2 (0.60 g, 1.12 mmol) in tolu-
ene (20 ml) was added H2O (0.04 g, 2 mmol) at room tem-
perature. The reaction mixture was stirred for 12 h at room
temperature, and the solvent was removed under vacuum.
The residue was extracted with n-hexane. The extract was
concentrated and placed in the freezer. The yellow micro-
crystals were collected. [Ti(g5-C5H5)(2,4-tBu2-6-(CPh2O)-
C6H2O)]2O (5): Yield 80% (0.91 g, 0.90 mmol). Anal.
Calc. for C64H70O5Ti2 (1014.97): C, 75.73 H, 6.95. Found:
C, 75.66; H, 7.01%. 1H NMR (CDCl3, 300 MHz; 298 K): d
7.06–7.46 (m, 22 H, Ph), 6.51 (d, 2H, Ph), 5.91 (s, 10H, Cp),
1.36 (s, 18H, Ph–tBu), 1.07 (s, 18H, Ph–tBu). C13 NMR
(CDCl3, 75.4 MHz) d, ppm: 158.8, 148.1, 146.7, 142.1,
129.1, 128.5, 127.7, 126.1, 125.0, 123.1, 118.9, 107.6, 35.1,
34.2, 31.9, 30.2.
Number of data/restraints/
parameters
R1(I > 2r)
wR2(I > 2r)
Goodness-of-fit
6058/0/449
6274/0/328
0.0617
0.1538
0.997
0.384 and
ꢀ0.380
0.0720
0.1800
0.958
0.786 and
ꢀ0.558
Largest difference in peak and hole
ꢀ3
˚
(e A
)
continuously feeding of ethylene. After 5 min, the
polymerization was quenched by injecting acidified
methanol [HCl (3M)/methanol = 1:1], and the polymer
was collected by filtration, washed with water,
methanol, and dried at 60 ꢁC in vacuo to a constant
weight.
3.7. X-ray structure determinations of 4 and 5
4. Conclusions
Single crystals of complexes 4 and 5 suitable for X-ray
structural analysis were obtained from the mixture of
CH2Cl2/hexane. The data were collected at 293 K on Rig-
aku R-AXIS RAPID IP diffractometer for complexes 4
We have synthesized and characterized three new mono-
chlorotitanium complexes based on mono-Cp and phen-
oxy-alkoxo mixed ligands. These complexes were found
to be stable in air, but can be easily hydrolyzed. The reac-
tion of complex 2 with excess water gave the oxo-bridged
complex 5. When activated with [Ph3C]+[B(C6F5)4]ꢀ and
AliBu3, these monochlorotitanium complexes exhibit good
catalytic activity for ethylene polymerization and produce
moderate molecular weight polyethylene. These new cata-
lysts represent a valuable addition to the limited list of
monochlorotitanium ethylene polymerization catalysts.
˚
and 5 with Mo Ka (k = 0.71073 A). Details of the crystal
data, data collections, and structure refinements are sum-
marized in Table 3. Both structures were solved by direct
methods [13] and refined by full-matrix least-squares on
F2. All non-hydrogen atoms were refined anisotropically
and the hydrogen atoms were included in idealized posi-
tion. All calculations were performed using the SHELXTL
[14] crystallographic software packages.
3.8. Ethylene polymerization
5. Supplementary material
A
dry 250 ml steel autoclave was charged with
CCDC 623912 and 623913 contain the supplementary
crystallographic data for 4 and 5. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/
conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
50 ml of toluene, thermostated at desired temperature
and saturated with ethylene (1.0 bar). The polymeriza-
tion reaction was started by injection of a mixture of
catalyst and AliBu3 in toluene (5 ml) and a solution of
[Ph3C]+[B(C6F5)4]ꢀ in toluene (5 ml) at the same time.
The vessel was repressurized to needed pressure with
ethylene immediately and the pressure was kept by

3362
T.-Q. Xu et al. / Polyhedron 26 (2007) 3357–3362
(d) V. Tabernero, T. Cuenca, Eur. J. Inorg. Chem. (2005)
Acknowledgement
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This work was supported by the National Natural Sci-
ence Foundation of China (Nos. 20674024 and 20374023).
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