New o-methoxyphenylcyclopentadienylchromium (III) complexes: Synthesis, structures and catalytic properties for ethylene polymerization

Article abstract of DOI:10.1016/j.jorganchem.2006.11.047

Two new ligands 1-(2-methoxyphenyl)-3,4-diphenylcyclopentadiene (1) and 1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadiene (2), as well as their corresponding cyclopentadienylchromium complexes η⁵-1-(2-methoxyphenyl)-3,4-diphenylcyclopentadienyl chromium dichloride (3) and η⁵-1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadienyl chromium dichloride (4) were synthesized and characterized. Molecular structures of 3 and 4 were determined by single-crystal X-ray diffraction. Complexes 3 and 4 were tested as catalyst precursors for ethylene polymerization. When activated with Al(ⁱBu)₃ and Ph₃ C⁺ B (C₆ F₅)₄^-, complex 3 shows reasonable catalytic activity while 4 exhibits high catalytic activity for ethylene polymerization. The effects of temperature and Al/Cr ratio on the catalytic activity were studied. The molecular weight and melting temperature of the produced polyethylenes were determined.

Full text of DOI:10.1016/j.jorganchem.2006.11.047

Journal of Organometallic Chemistry 692 (2007) 1505–1510
www.elsevier.com/locate/jorganchem
New o-methoxyphenylcyclopentadienylchromium (III)
complexes: Synthesis, structures and catalytic properties
for ethylene polymerization
*
Jiansheng Xu, Wei Gao, Yuetao Zhang, Jincai Li, Ying Mu
Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, School of Chemistry, Jilin University, 2699 Qianjin Street,
Changchun, Jilin Province 130012, People’s Republic of China
Received 23 August 2006; received in revised form 22 November 2006; accepted 29 November 2006
Available online 8 December 2006
Abstract
Two new ligands 1-(2-methoxyphenyl)-3,4-diphenylcyclopentadiene (1) and 1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadiene
(2), as well as their corresponding cyclopentadienylchromium complexes g5-1-(2-methoxyphenyl)-3,4-diphenylcyclopentadienyl chro-
mium dichloride (3) and g5-1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadienyl chromium dichloride (4) were synthesized and
characterized. Molecular structures of 3 and 4 were determined by single-crystal X-ray diffraction. Complexes 3 and 4 were tested as
catalyst precursors for ethylene polymerization. When activated with Al(iBu)3 and Ph3CþBðC6F5Þꢀ, complex 3 shows reasonable cata-
4
lytic activity while 4 exhibits high catalytic activity for ethylene polymerization. The effects of temperature and Al/Cr ratio on the cat-
alytic activity were studied. The molecular weight and melting temperature of the produced polyethylenes were determined.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Cyclopentadienyl ligands; Chromium complexes; Metallocenes; Ethylene polymerization
1. Introduction
tral nitrogen donor, either bridged or unbridged to the
Cp unit [4]. Several efficient catalyst precursors for ethylene
polymerization are listed in Chart 1. Jolly et al. [5–7]
reported that half-sandwich type chromium complexes (a)
shows good activity for the polymerization of ethylene to
give polyethylenes with high molecular weights. Enders
et al. [8,9] described cyclopentadienylchromium(III) com-
plexes (b and c) functionalized by quinolinyl or N,N-dim-
ethylanilinyl group exhibit high catalytic activity for
ethylene polymerization. Most recently, Huang et al. [10]
reported the bridged cyclopentadienylchromium complexes
(d) as effective ethylene polymerization catalysts. So far, the
functionalized cyclopentadienylchromium catalysts are
mainly limited to the nitrogen donor substituted
compounds. Reports concerning oxygen donor substituted
cyclopentadienyl chromium catalysts are scarce.
Previously, we demonstrated that phenoxy substituted
cyclopentadienyl titanium complexes (e and f in Chart 2)
are good catalysts for ethylene polymerization [11,12]. In
this paper, we report the synthesis and characterization
Chromium-based catalysts play a significant role in the
coordination polymerization of olefins. It is well known
that the chromium-based heterogeneous catalysts such as
the Phillips catalyst [1] and the Union Carbide Unipol cat-
alyst [2] are among the most important catalysts for the
production of high-density polyethylene (HDPE) and have
been put to widespread commercial use. However, the
chromium catalyst systems were largely ignored for long
time in the development of the homogeneous olefin poly-
merization catalyst systems that have attracted so much
attention in the past decade [3]. It is mainly due to the dif-
ficulty of studying the chemistry of Cr (III) as a result of its
paramagnetic nature. Recently, some of the most signifi-
cant advances in Cp-based chromium catalyst systems have
been made with the catalysts that bear an additional neu-
*
Corresponding author. Tel.: +86 431 5168376; fax: +86 431 5193421.
E-mail address: ymu@jlu.edu.cn (Y. Mu).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.11.047

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J. Xu et al. / Journal of Organometallic Chemistry 692 (2007) 1505–1510
R1
2. Results and discussion
R1
2.1. Synthesis of ligands
X
Cr
N
R
Cr
Ligand 1 was prepared by the reaction of 3, 4-diphenyl-
2-cyclopentenone with lithium salt of anisole in toluene at
room temperature followed by hydrolysis and dehydration
(Scheme 1). The lithium salt of anisole was obtained by the
reaction of anisole with n-BuLi without solvent at 80 ꢁC.
The lithium salt of anisole could not be obtained when
the reaction was carried out in the presence of a solvent
such as Et2O or THF. Ligand 2 was synthesized by the
same procedure with 2,3,4,5-tetramethyl-2- cyclopentenone
as starting material. Ligands 1 and 2 can also be synthe-
sized in Et2O or THF in similar yields. 1 and 2 were char-
acterized by elemental analysis and 1H and 13C NMR
spectroscopy. 1H NMR spectroscopic analysis indicates
that 2 exists as a mixture of three isomers. Similar behavior
has been observed before for the N,N-dimethylaminophe-
nyl-tetramethylcyclopentadiene ligand system [9] and the
tetramethylcyclopentadienylphenol ligand system [12].
The same phenomenon was not found for ligand 1 which
exists as one isomer.
X
N
R2
Cl
Cl
b
a
Cl
Cl
R1
Cr
R2
N
N
Cr
Cl
Cl
d
c
Chart 1.
Ph
Ph
2.2. Synthesis of complexes 3 and 4
Cl
Cl
Ti
Cl
Cl
O
R1
Ti
Complexes 3 and 4 were synthesized via a straightfor-
ward procedure (Scheme 2) from the reaction of CrCl3
with the lithium salt of corresponding ligand. Ligand 1
or 2 was treated with one equivalent of n-BuLi, and then
a solution of CrCl3 in THF was slowly added at ꢀ78 ꢁC.
After filtration and concentration of the reaction mixture,
complex 3 or 4 was obtained as a green or blue crystalline
solid in a moderate yield. The reaction was also tried in
toluene and it was found that complexes 3 and 4 could
not be obtained for the low solubility of CrCl3 in toluene.
Complexes 3 and 4 were found to be air and moisture
sensitive in solution, but they are considerably stable in
the solid state and could be exposed to air for several
days without obvious decomposition. Due to paramag-
netic nature, NMR study for complexes 3 and 4 was
not feasible. Elemental analysis of complexes 3 and 4 fits
their respective structures obtained by X-ray crystallo-
graphic study.
O
R1
R
R
R = tBu, Ph, Me
R1= tBu, H
R = Ph, tBu, Me
R1=H, tBu
e
f
Chart 2
.
of two oxygen donor substituted cyclopentadiene ligands
1-(2-methoxyphenyl)-3,4-diphenylcyclopentadiene (1) and
1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadiene (2),
and their chromium complexes g5-1-(2-methoxyphenyl)-
3,4-diphenylcyclopentadienylchromium dichloride (3) and
g5-1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadienyl-
chromium dichloride (4), as well as the catalytic perfor-
mance of complexes 3 and 4 for ethylene polymerization.
R1
R2
R1
R1
OMe
OMe
OMe
LiO
R2
R2
R2
OMe
O
Li
nBuLi
1. NH4Cl (aq)
2. HCl
R2
R1
R2
R1
R1
R1 = H, R2 = Ph (1)
R1 = R2 = Me (2)
Scheme 1. Synthetic procedure of ligands 1 and 2.

J. Xu et al. / Journal of Organometallic Chemistry 692 (2007) 1505–1510
1507
R2
Li
R1
R1
R2
R2
R1
OMe
OMe
R2
R2
R1
OMe
R2
CrCl3
-78 oC
Cl
R1
Cl
nBuLi
R1
Cl
Cr
Cr
Cl
R1
R2
R2
OMe
R1
R1 = H, R2 = Ph (3)
R1 = R2 = Me (4)
Scheme 2. Synthetic procedure of complexes 3 and 4.
Table 1
Selected bond lengths and angles
Complex 3
Cr(1)–C(1)
Cr(1)–C(2)
Cr(1)–C(3)
Cr(1)–C(4)
Cr(1)–C(5)
Cr(1)–Cl(1)
Cr(1)–Cl(2)
Cr(1)–Cl(1A)
Cr(1)–Cp(cent)
C(1)–C(6)
2.259(3)
2.238(3)
2.304(4)
2.230(3)
2.202(3)
2.3680(12)
2.2795(13)
2.3582(10)
1.893
Cl(2)–Cr(1)–Cl(1)
95.17(5)
120.9
124.2
90.3
90.1
92.7
88.9
87.9
88.99(4)
91.01(4)
Cp(cent)–Cr(1)–Cl(1)
Cp(cent)–Cr(1)–Cl(2)
Cr(1)–Cp(cent)–C(1)
Cr(1)–Cp(cent)–C(2)
Cr(1)–Cp(cent)–C(3)
Cr(1)–Cp(cent)–C(4)
Cr(1)–Cp(cent)–C(5)
Cr(1)–Cl(1)–Cr(1A)
Cl(1)–Cr(1)–Cl(1A)
1.467(5)
Complex 4
Cr(1)–C(1)
Cr(1)–C(2)
Cr(1)–C(3)
Cr(1)–C(4)
Cr(1)–C(5)
Cr(1)–Cl(1)
Cr(1)–Cl(2)
Cr(1)–Cl(1A)
Cr–Cp(cent)
C(1)–C(10)
2.228(3)
2.243(3)
2.237(3)
2.205(4)
2.245(3)
2.3716(11)
2.2808(12)
2.3736(10)
1.875
Cl(1)–Cr(1)–Cl(2)
96.25(5)
123.4
122.4
89.7
90.7
90.5
88.7
90.4
90.74(3)
89.26(3)
Cp(cent)–Cr(1)–Cl(1)
Cp(cent)–Cr(1)–Cl(2)
Cr(1)–Cp(cent)–C(1)
Cr(1)–Cp(cent)–C(2)
Cr(1)–Cp(cent)–C(3)
Cr(1)–Cp(cent)–C(4)
Cr(1)–Cp(cent)–C(5)
Cr(1)–Cl(1)–Cr(1A)
Cl(1)–Cr(1)–Cl(1A)
Fig. 1. Structure of complex 3 (thermal ellipsoids are drawn at the 30%
probability level).
1.490(4)
disordered. Both complexes 3 and 4 (Figs. 1 and 2) exist
in dimeric form connected through two chloride bridges
in the solid state, and the two molecular units comprising
the dimer are each constrained by a crystallographic center
of inversion. Each chromium atom is bonded to one Cp
ligand, one terminal chloride atom and two bridging chlo-
ride atoms, completing the familiar pseudo-octahedral
coordination environment of a three-legged piano stool.
Bond distances from each chromium atom to the non-
Fig. 2. Structure of complex 4 (thermal ellipsoids are drawn at the 30%
probability level).
˚
˚
equivalent bridging chlorides for 3 (2.3680 A, 2.3582 A)
˚
˚
and 4 (2.3716 A, 2.3736 A) are elongated from the Cr–Cl
˚
˚
2.3. Crystal structures of 3 and 4
(terminal) distances of 3 (2.2795 A) and 4 (2.2808 A),
respectively. The Cr–Cl(bridging)–Cr and Cl(bridging)–
Cr–Cl(bridging) angles for 3 and 4 are 88.99ꢁ, 91.01ꢁ and
90.74ꢁ, 89.26ꢁ, respectively. The two chromium atoms
and two bridging chlorides are coplanar and the mean
deviations from the planes are 0 A for both complexes.
The Cr–Cp(cent) distances are 1.893 A for 3 and 1.875 A
for 4. The Cr–C(ring) distances are in the range 2.202–
The molecular structures of complexes 3 and 4 were
determined by X-ray crystal structure analysis. The
ORTEP drawings of the molecular structures are shown
in Figs. 1 and 2, respectively. The selected bond lengths
and angles are summarized in Table 1. There is a CH2Cl2
molecule in the unit cells of both complexes 3 and 4. One
more thing that should be mentioned is that the Cl atoms
of the CH2Cl2 molecule in the unit cell of complex 4 are
˚
˚
˚
˚
˚
2.304 A for 3 and 2.205–2.245 A for 4. The angle (57.3ꢁ)
between the Cp ring plane and the phenyl ring plane in

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J. Xu et al. / Journal of Organometallic Chemistry 692 (2007) 1505–1510
Table 2
Summary of ethylene polymerization catalyzed by complex 3 and 4 (activated by Al(iBu)3 and Ph3Cþ½BðC6F5Þ ꢁꢀ)a
4
b
No.
Cata.
Al:Cr
T (ꢁC)
Yield (g)
Activity
Mgc · 10ꢀ4
Tm (ꢁC)d
1
2
3
4
5
6
7
8
9
3
3
3
3
3
4
4
4
4
4
300
300
300
200
400
300
300
300
200
400
100
80
60
80
80
100
80
60
80
80
0.22
0.63
0.34
0.28
0.37
6.04
6.86
2.58
4.28
2.45
0.04
0.13
0.07
0.06
0.07
1.21
1.37
0.52
0.86
0.49
8.09
11.64
10.83
9.52
10.17
6.13
6.03
7.01
8.41
7.46
127.9
126.3
126.7
125.9
127.4
125.2
126.0
125.4
124.7
125.3
10
a
Polymerization conditions: solvent 50 mL of toluene, catalyst 1 lmol (2 lmol Cr), B/Cr ratio 1.5, time 30 min, ethylene pressure 5 bar.
b
c
103 kg PE/ mol Cr h bar.
Measured in decahydro-naphthalene at 135 ꢁC.
d
Determined by DSC at a heating rate of 10 ꢁC minꢀ1
.
complex 4 is larger than that (26.6ꢁ) in 3, which should be
attributed to the repulsion of the Me groups on the Cp ring
in complex 4.
also lower the rate of the chain termination by b-H elim-
ination, and hence increase the molecular weight of the
produced polyethylene. If it was not the case, the elec-
tron-withdrawing methoxyphenyl group on the cyclopen-
tadienyl ring would lower the catalytic activity of the
catalysts, and the catalytic activity of 4 should be lower
than that of simple pentametnylcyclopentadienylchro-
mium-based catalysts. It is expected that complex 4 shows
higher catalytic activity than 3 since the four electron-
donating Me groups on the Cp ring of 4 would increase
its catalytic activity [12]. The catalytic activity of com-
plexes 3 and 4 is low at room temperature and increases
at elevated temperatures. For both complexes, the cata-
lytic activity increases with the increase in Al/Cr ratio
and reaches the highest catalytic activity with the Al/Cr
ratio of 300. Further increase in the Al/Cr ratio results
in a decrease in the catalytic activity. It is possible that
2.4. Ethylene polymerization studies
Complexes 3 and 4 were studied as ethylene polymeri-
zation catalysts and the results are summarized in Table 2.
Upon activation with Al(iBu)3 and Ph3CþBðC6F5Þꢀ, com-
4
plex 3 shows reasonable catalytic activity while 4 exhibits
high catalytic activity for ethylene polymerization, pro-
ducing polyethylene with moderate molecular weight
and melting temperature. No oligomer was obtained from
the polymerization solution for both catalysts. The cata-
lytic activity of 3 and 4 and the molecular weight of the
obtained polyethylene are much higher than those reported
for simple cyclopentadienylchromium-based catalyst sys-
tems [13,14] and more similar to the results obtained from
constrained geometry cyclopentadienylchromium catalyst
systems [8,9]. These results imply that the catalytic active
species formed from complexes 3 and 4 during the poly-
merization reaction might have similar structures to that
formed from complex c in Chart 1, and the oxygen atom
in the catalytic active species might coordinate to the
chromium atom. A similar mononuclear cyclopentadie-
nylchromium complex with a coordinated ether side-chain
has been reported before [6]. However, our attempts to
obtain the crystal structure of the catalytic active species
or to get IR spectroscopic evidence to verify the structure
of the catalytic active species were unsuccessful. On the
basis of common knowledge about the olefin polymeriza-
tion mechanism and the relationship between catalyst
structure and property, it could be known that the coor-
dination of the oxygen atom to the chromium atom
would increase the stability of the chromium cation and
weaken the interaction between the cationic chromium
center and the anionic cocatalyst, therefore increase the
catalytic activity of the catalyst. In addition, the coordina-
tion of the oxygen atom to the chromium atom would
excessive
Al(iBu)3
would
consume
some
of
Ph3CþBðC6F5Þꢀ, which results in that the catalyst could
4
not be efficiently activated [15]. It is also worth noting
that the less active catalyst 3 gives higher molecular
weight polyethylene, which could be explained by that
the slow chain propagation in 3 will ensure to have suffi-
cient monomer to coordinate to the catalyst metal center
and thus suppress the chain termination through b-H
elimination [11].
3. Experimental
3.1. General comments
Reactions with organometallic reagents were carried out
under argon atmosphere (ultra-high purity) using standard
schlenk techniques [16]. Solvents were dried and distilled
prior to use [17]. Polymerization grade ethylene was further
purified by passage through columns of 10 A molecular
sieves and MnO. Al(iBu)3, n-BuLi and CrCl3 were
purchased from Aldrich. 2,3,4,5-tetramethyl-2-cyclopente-
none [18], 3,4-diphenyl-2-cyclopentenone [19], and

J. Xu et al. / Journal of Organometallic Chemistry 692 (2007) 1505–1510
1509
Ph3CþB- ðC6F5Þ [20] were prepared according to literature
(0.24 g, 50.5%). Anal. Calcd for (C24H19Cl2CrO)2
(892.44): C, 64.59, H, 4.29. Found: C, 64.48, H, 4.22%.
4
procedures. NMR spectra were measured using a Varian
Mercury-300 NMR spectrometer.
3.5. Synthesis of g5-1-(2-methoxyphenyl)-2,3,4,5-
tetramethylcyclopentadienyl chromium dichloride dimer (4)
3.2. Synthesis of 1-(2-methoxyphenyl)-3,4-
diphenylcyclopentadiene (1)
Reaction of the lithium salt of 2 (0.35 g, 1.53 mmol) with
CrCl3 (0.24 g, 1.53 mmol) in THF (40 mL) was carried out
in the same way as described above for the synthesis of 3.
Pure 4 (0.18 g, 35.1%) was obtained as blue crystals. Anal.
Calcd for (C16H19Cl2CrO)2 (700.45): C, 54.87, H, 5.47.
Found: C, 54.78, H, 5.29%.
8.3 mL of anisole (76 mmol) was slowly added to
76 mmol of pure n-BuLi and the mixture was heated to
80 ꢁC for 48 h to form the lithium salt of anisole. The lithium
salt was washed with n-hexane and dissolved in toluene
(100 mL). To the solution 3,4-diphenyl-2-cyclopentenone
(17.8 g, 76 mmol) was added at ꢀ15 ꢁC and the mixture
was stirred at room temperature overnight. The reaction
mixture was hydrolyzed with 100 mL of H2O and then acid-
ified with 20 mL of concentrated HCl. The organic layer was
separated, dried over MgSO4, filtered and concentrated by
distillation under reduced pressure. Pure product (13.8 g,
53.4%) was obtained by column chromatography over silica
(hexanes/CH2Cl2, 3:2) as yellowish crystalline solid. Anal.
Calcd for C24H20O (324.415): C, 88.77, H, 6.16. Found: C,
3.6. X-ray structure determinations of 3 and 4
Single crystals of 3 and 4 suitable for X-ray structural
analysis were obtained from solutions in mixed CH2Cl2/
hexane (V/V = 1/2). Data were collected at 293(K) on the
Bruker SMART-CCD diffractometer (graphite-monochro-
˚
mated MoKa-radiation: k = 0.71073 A). Details of the
crystal data, data collections, and structure refinements
are summarized in Table 3. Both structures were solved
by direct methods [21] and refined by full-matrix least-
squares on F2. All non-hydrogen atoms were refined
anisotropically and the hydrogen atoms were included in
idealized position. All calculations were performed using
the SHELXTL [22] crystallographic software packages.
1
88.72, H, 6.22%. H NMR (CDCl3, 300 MHz; 298 K): d
6.95–7.56 (m, 15H, Cp, Ph), 3.93 (s, 3H, OMe), 4.06 (s,
2H, Cp), 13C NMR (CDCl3, 75.4 MHz; 298 K): d 157.26,
142.57, 141.97, 139.17, 137.78, 137.26, 136.07, 128.75,
128.67, 128.46, 128.13, 128.06, 128.02, 127.24, 126.59,
125.10, 120.95, 111.42, 55.51, 47.26.
3.3. Synthesis of 1-(2-methoxyphenyl)-2,3,4,5-
tetramethylcyclopentadiene (2)
Table 3
Crystal data and structural refinements details for 3 and 4
Ligand 2 was prepared in the same manner as 1 with
76 mmol of 2,3,4,5-tetramethyl-2-cyclopentenone as start-
ing material. Pure product (7.9 g, 45.6%) was obtained as
yellow oil. Anal. Calcd for C16H20O (228.329): C, 84.16,
3
4
Molecular formula
Molecular weight
Crystal system
Space group
C
531.22
Triclinic
25H21Cl4CrO
C17H21Cl4CrO
435.14
Triclinic
1
H, 8.83. Found: C, 84.07, H, 8.91%. H NMR (CDCl3,
ꢀ
ꢀ
P1
P1
300 MHz; 298 K): d 7.25 (m, 4H, Ph), 3.79 (s, 3H,
OCH3), 3.40 (q, 1H, CpH), 1.91 (s, 3H, C5Me4), 1.86 (s,
6H, C5Me4), 0.88 (d, 3H, C5Me4), 13C NMR (CDCl3,
75.4 MHz; 298 K): d 157.26, 140.86, 140.31, 138.06,
134.54, 131.35, 127.35, 126.60, 120.17, 110.72, 55.39,
50.09, 14.29, 12.84, 12.01, 11.27.
˚
a (A)
10.677(2)
10.795(2)
11.182(2)
79.04(3)
78.94(3)
72.25(3)
1192.7(4)
2
8.3829(17)
8.6849(18)
14.439(3)
75.313(3)
82.170(3)
83.892(4)
1004.5(4)
2
1.439
446
1.102
x ꢀ 2h
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
Z
3.4. Synthesis of g5-1-(2-methoxyphenyl)-3,4-
diphenylcyclopentadienyl chromium dichloride dimer (3)
Dc (g cmꢀ3
F(000)
)
1.479
542
0.943
Abs coefficient (mmꢀ1
Scan type
)
x ꢀ 2h
To a solution of 0.37 g (1.1 mmol) of 1 in 15 mL of THF
was added dropwise a solution of n-BuLi (1.1 mL, 1.0 M)
in n-hexane at ꢀ78 ꢁC. After the addition the reaction mix-
ture was stirred for 12 h at room temperature. Then the
resulting solution was added to a suspension of CrCl3
(0.17 g, 1.1 mmol) in 45 mL of THF at room temperature
and the mixture was stirred for 12 h. The color of the reac-
tion mixture turned from purple to blue during the reac-
tion. The precipitate was filtered off and the solvent was
removed to leave a blue solid. Recrystallization from
CH2Cl2/Hexane (1:2) gave pure 3 as green crystals
Collect range (deg)
Number of reflections
Number of independent
reflections
Rint
3.22 6 2h 6 27.49 2.43 6 2h 628.26
7940
4722
6339
4481
0.0318
0.0348
Number of data/restraints/
parameters
4772/12/304
4481/0/213
R(I > 2sigma(I))
Rw(I > 2sigma(I))
Goodness of fit
0.0486
0.1495
1.068
0.0579
0.1642
1.012
Largest difference in peak and
0.459 and
ꢀ0.659
0.897 and
ꢀ0.523
ꢀ3
˚
hole (e A
)

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J. Xu et al. / Journal of Organometallic Chemistry 692 (2007) 1505–1510
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A dry 250 mL steel autoclave was charged with 50 mL of
toluene, thermostated at desired temperature and saturated
with ethylene (1.0 bar). The polymerization reaction was
started by injection of a mixture of catalyst and Al(iBu)3
in toluene (5 mL) and a solution of Ph3CþBðC6F5Þꢀ in tol-
4
uene (5 mL) at the same time. The vessel was repressurized
to needed pressure with ethylene immediately and the
pressure was kept by continuously feeding monomer. After
30 min, the polymerization was quenched by injecting acid-
ified methanol [HCl (3 M):methanol = 1:1]. The polymer
was collected by filtration, washed with water, methanol,
and dried in vacuo at 60 ꢁC to a constant weight.
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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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Appendix A. Supplementary material
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CCDC 292293 and 292292 contains the supplementary
crystallographic data for 3 and 4. 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. Supplementary data associated with this
article can be found, in the online version, at
doi:10.1016/j.jorganchem.2006.04.044.
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