Synthesis and crystal structures of unbridged bis(4-R-1,2-diphenylcyclopentadienyl)zirconium dichlorides (R = phenyl, cyclohexyl), and catalysis for olefin polymerization

Article abstract of DOI:10.1016/S0277-5387(00)00484-8

Zirconocene complexes carrying sterically bulky tri-substituted cyclopentadienyl ligands, (η⁵-4-R-1,2-Ph₂C₅H₂)₂ZrCl₂ [R = phenyl (3), cyclohexyl (4)], were synthesized by the reaction of Zr

Full text of DOI:10.1016/S0277-5387(00)00484-8

www.elsevier.nl/locate/poly
Polyhedron 19 (2000) 1941–1947
Synthesis and crystal structures of unbridged
bis(4-R-1,2-diphenylcyclopentadienyl)zirconium dichlorides
(R=phenyl, cyclohexyl), and catalysis for olefin polymerization
Fan Zhang a, Ying Mu a,*, Jianhui Wang a, Zhan Shi a,b, Weiming Bu c, Shirong Hu a,
Yuetao Zhang a, Shouhua Feng a,b
a Department of Chemistry, Jilin Uni6ersity, Changchun 130023, PR China
b Key Laboratory of Inorganic Hydrothermal Synthesis, Department of Chemistry, Jinlin Uni6ersity, Changchun 130023, PR China
c Key Laboratory of Supramolecular Structure and Spectroscopy, Jilin Uni6ersity, Changchun 130023, PR China
Received 31 March 2000; accepted 9 June 2000
Abstract
Zirconocene complexes carrying sterically bulky tri-substituted cyclopentadienyl ligands, (h5-4-R-1,2-Ph2C5H2)2ZrCl2 [R=
phenyl (3), cyclohexyl (4)], were synthesized by the reaction of ZrCl4 with lithio salt of 1,2,4-triphenylcyclopentadiene (1) or
4-cyclohexyl-1,2-diphenylcyclopentadiene (2), respectively. The single-crystal X-ray structure analysis reveals that both complexes
crystallize in C2-symmetric conformation in solid state. When activated with methylaluminoxane (MAO), complexes 3 and 4
polymerize ethylene with moderate activities to produce ultra-high-molecular-weight polyethylenes with high melting transition
temperatures at low Al/Zr ratios. Under ambient conditions, both systems of 3–MAO and 4–MAO show relatively high activities
in propylene oligomerization. The molecular weight of the polypropylene produced from the 3–MAO system is lower than that
from the 4–MAO system. In comparison with 4, complex 3 is more active in both ethylene and propylene polymerization. © 2000
Elsevier Science Ltd. All rights reserved.
Keywords: Zirconocene; Crystal structures; Catalysis; Olefin polymerizations
1. Introduction
consideration that the conformation conversion of the
metallocene molecule could be controlled by the intro-
duction of appropriate substituents on the cyclopenta-
dienyl or indenyl ligand to block the rotation of the
ligand during polymerization, so that the stereospecific-
ity of the polymer could be controlled. It was believed
that the p-stacking between the aryl substituents plays a
crucial role in blocking the conversion between the
rac-like and meso-like conformations of the catalyst
molecule [13,17]. On the other hand, it has been
demonstrated that modification of the ligand with
phenyl substituent whether on the ligand ring [8,12–19]
or even on the bridging moiety [20] has a considerably
strong influence on the catalytic properties of metal-
locenes due to the special steric and electronic charac-
teristics of phenyl group. In these respects, we have
concentrated our efforts on designing a series of un-
bridged sterically hindered metallocenes containing
phenyl substituents and investigating their polymeriza-
Group 4 metallocenes have attracted extensive re-
search attention in recent years because of their appli-
cation as catalysts in olefin polymerization [1–4]. In the
development of new metallocene catalysts, modification
of the cyclopentadienyl ligand is an effective means of
optimizing catalyst activity as well as polymer proper-
ties such as molecular weight, stereoregularity and mi-
crostructure, etc. [5–10]. Recently, unbridged
zirconocenes bearing trisubstituted cyclopentadienyl or
mono-substituted indenyl ligands have drawn much
attention because some of this type of zirconocenes
produce semi-isotactic polypropylene elastomers [11–
16]. The design of this type of catalyst was based on the
* Corresponding author. Tel.: +86-431-892-2331 ext. 3120; fax:
+86-431-894-9334.
E-mail address: ymu@mail.jlu.edu.cn (Y. Mu).
0277-5387/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(00)00484-8

1942
F. Zhang et al. / Polyhedron 19 (2000) 1941–1947
tion behavior. The present paper describes the synthesis
and structure characterization of two new C2-symmetric
unbridged zirconocenes (h5-4-R-1,2-Ph2C5H2)2ZrCl2
[R=phenyl (3), cyclohexyl (4)], as well as their catalytic
properties for ethylene and propylene polymerizations.
The ligand precursor 1 is well soluble in toluene,
while only slightly soluble in other common organic
solvents. Therefore, 1 was deprotonated with butyl-
lithium in toluene. The produced lithium salt was easily
isolated from solvent as white precipitate in ca. 90%
yield. Interestingly, the ligand precursor 2 has a pretty
good solubility in hexane. The lithium salt of 2 was
therefore prepared in hexane in high yields (ꢀ95%)
with convenient isolation and purification. THF was
found to be an unsuitable solvent for the lithiation
reaction due to low yield and difficulty in isolation. The
zirconocene dichlorides 3 and 4 were prepared from the
reaction of two equivalents of lithium salt of corre-
sponding ligand with ZrCl4 in toluene. The reaction
mixture was heated at 60–70°C for hours until a bright
yellow solution was formed, which indicates the com-
pletion of the reaction. Pure complexes 3 and 4 were
obtained by recrystallization of the crude products
from hexane–toluene in high yields (80% for 3 and 74%
for 4). Both 3 and 4 were found to be stable to air and
moisture for several days.
2. Results and discussion
2.1. Synthesis
1,2,4-Triphenyl-1,3-cyclopentadiene (1) was synthe-
sized by a modified literature procedure [21]. Treatment
of 3,4-diphenyl-2-cyclopenten-1-one with phenyl
lithium in THF formed the intermediate 1-hydroxy-
1,3,4-triphenyl-2-cyclopentene, which was then con-
verted into 1 by dehydration with p-toluenesulfonic
acid monohydrate (Scheme 1). Pure 1 was obtained as
pale yellow needles by recrystallization from 1:3
CH2Cl2–hexane in a good yield (70%). THF was used
as solvent because of the good solubility of 3,4-
diphenyl-2-cyclopenten-1-one and the increased reactiv-
ity of the addition of phenyllithium to the keto group
of a–b unsaturated ketone. 4-cyclohexyl-1,2-diphenyl-
1,3-cyclopentadiene (2) was prepared in a similar man-
ner to 1 by the reaction of 3,4-diphenyl-2-cyclo-
penten-1-one with cyclohexyl magnesium chloride.
Compound 2 was obtained in low yields (less than 30%)
presumably due to that the bulky cyclohexyl Grignard
reagent disfavors 1,2-addition to the keto group of the
a–b unsaturated ketone. Pure 2 was obtained by
column chromatography as a yellow oil which solidified
slowly at room temperature. Attempts to prepare 2
with cyclohexyl lithium instead of cyclohexyl magne-
sium chloride were unsuccessful. 1H NMR spectro-
scopic analysis indicates that both 1 and 2 were
obtained in single isomer form (as depicted in Scheme
1). The chemical shifts of the cyclopentadiene ring
protons of 2 (l 3.47 and 6.31 ppm) are shifted up-field
0.5–0.8 ppm compared with those (l 3.95 and 7.06
ppm) of 1 due to the electronic donating effect of the
cyclohexyl substituent.
1H and 13C NMR spectra reveal that 3 and 4 both
exhibit C26 symmetry in solution due to the rapid
rotation of the cyclopentadienyl ligands around the
CpꢀZr axis and all phenyl groups in both complexes are
in free rotating fashion at room temperature. In com-
plex 3, the down-field shift of the Cp ring proton
resonance (l 6.75 ppm) compared to that (l 6.64 ppm)
in 4 is in agreement with the result mentioned above for
their ligand precursors 1 and 2. In 13C NMR spectra,
down-field shifts of the resonances (l 125.1 and 125.4
ppm in 3, 128.0 ppm in 4) assigned to the Cp ring
carbons linked to phenyl groups compared to reso-
nances of other Cp ring carbons were also observed due
to the electron-withdrawing effect of the phenyl
substituents.
2.2. X-ray crystal structures analyses
The molecular structures of 3 and 4 determined by
X-ray diffraction are shown in Figs. 1 and 2, respec-
tively. Selected bond distances and angles are given in
Table 1. The geometry about zirconium in 3 or 4 can be
described as pseudo-tetrahedral and the whole molecule
adopts a C2-symmetric conformation. The two adjacent
phenyl substituents at each Cp ring lie in the front open
side of the zirconocene molecule, one of which is stag-
gered nearly over one of the two Cl atoms and the
other is oriented away from the corresponding phenyl
group at another Cp ring. The third phenyl substituent
at each Cp ring in 3 and the cyclohexyl group in 4 are
arranged backwards from the front side of the
metallocene.
In complex 3, the ClꢀZrꢀClc angle of 94.08(9)° is a
typical value for unbridged zirconocenes [22,23]. The
CentꢀZrꢀCent angle (Cent is the centroid of Cp ring)
Scheme 1.

F. Zhang et al. / Polyhedron 19 (2000) 1941–1947
1943
[25]. The angles between the Cp and the phenyl planes
are separately 56.9, 33.3 and 24.1°. Compared with the
value (less than 10°) of the angle between the phenyl
and indenyl planes in bis(2-phenylindenyl)zirconium
dichloride [13], the angle (24.1°) between the Cp plane
and the phenyl ring at the 4-position in 3 is quite large.
This angle is also larger than those for complexes
(1,2-Me2-4-Ph-C5H2)ZrCl2 (18.8, 13.6°) [15], while close
to that (22.5°) in (1,2-Me2-4-p-tolyC5H2)2ZrCl2 [13].
,
The ZrꢀCl bond distance of 2.441(3) A is in a normal
range for zirconocene dichloride [25]. The distance from
Zr atom to the centriod of cyclopentadienyl ring (2.245
,
,
A) is longer than those (2.215–2.223 A) found in
analogous bulky zirconocene compounds [19,26]. The
C(1)ꢀC(2) bond has the longest bond length [1.458(9)
,
A] among five wedges of the Cp ring. It seems likely
that the two adjacent phenyl substituents sterically
force the CꢀC bond longer. The bond lengths for
2
2
2
,
C(1)(sp )ꢀC(6)(sp ) [1.495(9) A] and C(2)(sp )ꢀC(12)-
(sp2) [1.510(9) A] are longer than that of
Fig. 1. ORTEP plot of complex 3 at 50% probability ellipsoids. The
solvent molecules and hydrogen atoms were omitted for clarity
reasons.
,
2
2
,
C(4)(sp )ꢀC(18)(sp ) [1.490(9) A], which might be at-
tributed to that the bonds C(1)ꢀC(6) and C(2)ꢀC(12)
are in more sterically congest environments.
The structure of 4 is similar to that of 3 with the
substituted cyclohexyl group at each Cp ring adopting a
Table 1
,
Selected bond lengths (A) and angles (°) for complexes 3 and 4
3
4
ZrꢀCl(1)
ZrꢀC(1)
ZrꢀC(2)
ZrꢀC(3)
ZrꢀC(4)
2.439(2)
2.617(6)
2.612(7)
2.497(7)
2.472(6)
2.539(5)
1.406(8)
1.423(9)
1.427(9)
1.371(9)
1.458(9)
1.495(9)
1.510(9)
1.490(8)
2.245
2.4303(7)
2.605(2)
2.583(2)
2.502(3)
2.516(2)
2.551(3)
1.413(4)
1.411(4)
1.417(4)
1.411(4)
1.433(4)
1.479(4)
1.488(4)
1.507(4)
2.251
ZrꢀC(5)
C(5)ꢀC(1)
C(5)ꢀC(4)
C(4)ꢀC(3)
C(3)ꢀC(2)
C(2)ꢀC(1)
C(1)ꢀC(6)
C(2)ꢀC(12)
C(4)ꢀC(18)
CentꢀZr
Cl(1)ꢀZrꢀCl(1)c
C(1)ꢀC(5)ꢀC(4)
C(5)ꢀC(4)ꢀC(3)
C(2)ꢀC(3)ꢀC(4)
C(3)ꢀC(2)ꢀC(1)
C(5)ꢀC(1)ꢀC(2)
C(5)ꢀC(4)ꢀC(18)
C(3)ꢀC(4)ꢀC(18)
C(3)ꢀC(2)ꢀC(12)
C(1)ꢀC(2)ꢀC(12)
C(2)ꢀC(1)ꢀC(6)
C(5)ꢀC(1)ꢀC(6)
Cent(1)ꢀZrꢀCent(1)c
€
94.08(9)
109.3(6)
106.2(5)
110.1(6)
107.8(6)
106.6(5)
126.9(6)
126.6(6)
126.4(6)
125.6(5)
129.5(6)
122.4(6)
129.3
93.71(4)
110.3(2)
105.6(2)
110.3(2)
106.7(2)
107.0(2)
126.6(2)
126.4(2)
123.8(2)
129.1(2)
130.1(2)
122.4(2)
131.6
Fig. 2. ORTEP plot of complex 4 at 50% probability ellipsoids. The
solvent molecules and hydrogen atoms were omitted for clarity
reasons.
129.3° is almost identical to that (129.7°) observed in
[h5-C5H3-1,3-(CMe3)2]2ZrCl2 [24], smaller than the one
of 131.3° for bis(2-phenylindenyl)zirconium dichoride
[12], but much larger than that of 119.4° found in
[bis(h5-7,9-diphenylcyclopenta[a]acenaphthadienyl)] zir-
conium dichloride [19]. The angle (€) between two Cp
ring planes (56.6°) is larger than the one (51.4°) ob-
served for (Me3CCp)2ZrCl2 and analogous metallocenes
56.6
53.1

1944
F. Zhang et al. / Polyhedron 19 (2000) 1941–1947
Table 2
activation of MAO does not change very much with the
change in Al/Zr ratios. In addition, the samples of
polyethylene produced by 3 and 4 show high molecular
weights and melting transition temperatures. These re-
sults could be explained on the basis of steric effects of
the complexes. X-ray structures of 3 and 4 exhibit that
the bulky substituents at the Cp ring construct a steri-
cally crowded environment around the metal center,
which could weaken the interaction between cationic
zirconium center and anionic cocatalyst and therefore
could efficiently prevent the active catalyst from bi-
molecular deactivation. Therefore, a smaller amount of
MAO is needed to keep the catalyst in the active state.
On the other hand, the large steric hindrance of the
complexes could effectively block the chain termination
by b-H transfer, thus long polymer chains could be
formed.
Polymerization of ethylene with 3–MAO, 4–MAO and Cp2ZrCl2–
MAO under similar conditions a
Catalyst
Al–Zr Activity×10−3 b Mh×10−6 c Tm (°C) d
3
300 1.28
1000 1.87
1500 1.92
300 1.01
1000 1.12
1500 1.26
300 1.09
1000 2.26
1500 3.69
1.41
1.18
0.91
1.35
1.05
0.87
0.47
0.43
0.42
140.9
140.0
138.4
140.6
140.2
138.1
132.9
131.9
131.5
4
Cp2ZrCl2
a Polymerization conditions: catalyst 1.7 mmol, volume of toluene
50 ml, time 1 h, temp. 18°C, ethylene pressure 6 bar.
b kg PE (mol Zr)−1 h−1
.
c Measured in decahydronaphthalene at 135°C.
d Determined with DSC at a heating rate of 10°C min−1
.
The results in Table 2 also reveal that replacement of
the phenyl group (in 3) at the 4-position of Cp ring by
a cyclohexyl group (in 4) leads to a decrease in catalytic
activities. As can be seen from their structures, complex
3 has a smaller angle of CentꢀZrꢀCent and a larger
angle of CpꢀCp than 4. This means that the steric
hindrance of 4 in the front side of Zr atom is larger and
the coordination gap aperture for the monomer is
smaller, and hence the catalytic activity of 4 is lower
than that of 3. Obviously, the steric effect of the ligands
in 3 and 4 seems to play a predominant role in ethylene
polymerization. Otherwise, the electron donating effect
of the cyclohexyl group should increase the catalytic
activity of 4.
twist-chair conformation. The ClꢀZrꢀCl angle of
93.71(4)° is smaller than that for 3. The CentꢀZrꢀCent
(131.6°) is nearly equal to the value of 131.5° for
(1,2-Me2-4-Ph-C5H2)2ZrCl2 [15] and close to those
(130.3 and 131.0°) in bis(2-phenyl-4,5,6,7-tetrahydroin-
denyl)(2-cyclohexylindenyl)zirconium dibromide [13].
In comparison with complex 3, the CentꢀZrꢀCent angle
in 4 is increased by 2.3° and the angle between the Cp
ring planes (53.1°) is reduced by 3.5°. The angles be-
tween the substituted phenyl and Cp planes (42.6 and
30.8°) are quite different from those (56.9 and 33.3°) for
complex 3. Obviously, the bulky cyclohexyl groups
demand more space at the back part of the zirconocene
molecule and result in these differences.
Complexes 3 and 4 were also tested for propylene
polymerization under ambient conditions. From two
typical experiments, 2.5 g of colorless oily propylene
oligomer (catalytic activity: 1470 kg PP (mol Zr)−1 h−1
was obtained from 3, and 1.2 g of similar product
(catalytic activity: 706 kg PP (mol Zr)−1 h−1 was
,
The ZrꢀCl bond length [2.4303(7) A] is also a typical
,
value. The distance (2.251 A) of ZrꢀCent is somewhat
larger than that in 3. The bond lengths for
2
2
2
1
,
C(1)(sp )ꢀC(6)(sp ) [1.479(4) A] and C(2)(sp )ꢀC(12)-
obtained from 4. From the H NMR spectra of the
2
2
,
(sp ) [1.488(4) A] are smaller than those for C(1)(sp )ꢀ
oligomer samples, resonances (l 4.65, s; 4.72, s) for
vinylidene end group were observed as the only signals
in the unsaturated end group region, which indicates
that b-H elimination is the single detectable chain ter-
mination pathway. The number average molecular
weights (Mn) of propylene oligomers produced by 3 and
4 were calculated by end group analysis. It was found
that the molecular weight of the propylene oligomer
(Mn: 1.89×103 g mol−1) produced by 3 is lower than
2
2
2
,
C(6)(sp ) [1.495(9) A] and C(2)(sp )ꢀC(12)(sp ) [1.510(9)
,
A] in 3, probably due to stronger p-binding resulted
from the smaller angle between the substituted phenyl
and Cp planes in 4.
2.3. Polymerization
that (Mn: 2.52×103 g mol−1) of the sample from 4. 13
C
Complexes 3 and 4 were studied as ethylene polymer-
ization catalysts. For comparison purposes, some poly-
merization experiments were also carried out with
Cp2ZrCl2 as catalyst under the same conditions (Table
2). Upon activation with MAO, both 3 and 4 polymer-
ize ethylene with moderate activities at lower Al/Zr
ratios. Unlike Cp2ZrCl2, the catalytic activities of 3 and
4 do not decrease very much when the Al/Zr ratio
changes from 1500 to 300, which suggests that the
concentration of cationic active species formed by the
NMR spectra revealed that the polypropylene samples
produced by 3 and 4 are highly regioregular and no
2,1-insertion takes place during the polymerization re-
action. The reason for the lower catalytic activity of 4
would be the same as above mentioned for ethylene
polymerization. Compared with 3, the increased steric
hindrance of 4 would result in a decline in the rates of
chain propagation and chain termination, while the
decrease in the chain termination rate seems to be more

F. Zhang et al. / Polyhedron 19 (2000) 1941–1947
1945
remarkable, and thus longer polymer chains are
3.2. 1,2,4-Triphenyl-1,3-cyclopentadiene (1)
produced.
It was demonstrated that the stereospecificity of
polypropylene could be improved by introducing a bulky
substituent at the appropriate position of the Cp ring to
restrict the rotation of the ligand ring, e.g. polyprop-
ylene with high isotacticity (49.8%) was produced by
rac-(1-Me-3-tBuC5H3)2ZrCl2–MAO [15]. At ambient
conditions, the lack of stereospecificity for 3 and 4
suggests that the bulky substituents at their Cp rings
could not efficiently block the rapid rotation of the Cp
rings to make the catalyst molecule maintain an isospe-
cific coordination site-switching model with a long
enough life-time during the polymerization [27,28]. On
the other hand, it has been reported that high stereoreg-
ularity could be obtained with analogous complex bis(2-
aryindenyl)zirconium dichloride [12–14]. In this case, the
phenyl group and the rigid indenyl moiety have been
believed to be two crucial factors for generating appro-
priate p-stacking and establishing a balance between two
conformational isomers (from rac to meso) of the catalyst
[12–14,17]. In the present case, there seems to be no
effective p-stacking interaction in both 3 and 4 during
polymerization. Investigations on the propylene poly-
merization under different conditions are currently un-
derway in our laboratory.
To a solution of phenyl lithium (25 ml, 1.8 M in
cyclohexane–ether, 0.045 mol) was added dropwise a
solution of 3,4-diphenyl-2-cyclopenten-1-one (10 g, 0.043
mol) in THF (70 ml) at −10°C. The deep reddish
solution was allowed to warm to r.t. and stirred for 6 h.
After quenching with 40 ml of ice–water, the organic
layer was separated and the aqueous phase was extracted
with diethyl ether (2×30 ml). The combined organic
phases were stirred with p-toluenesulfonic acid monohy-
drate (1 g) for 2 h. The mixture was neutralized by
addition of 30 ml acqueous NH4Cl and then the organic
solution was dried over MgSO4. After removal of the
solvent, pure 1 was obtained as a pale yellow needle solid
by recrystallization from hexane–CH2Cl2 (3:1). Yield
1
7.73 g (61.1%). H NMR (CDCl3, 400 MHz): l 3.95 (s,
2H, C5H3), 7.06 (s, 1H, C5H3), 7.1–7.6 (m, 15H, Ph) ppm.
3.3. 4-Cyclohexyl-1,2-diphenyl-1,3-cyclopentadiene (2)
THF (40 ml) was added to a dry 200 ml Schlenk flask
under argon. Cyclohexylmagnesium chloride (21.5 ml,
2.0 M in diethyl ether, 0.043 mol) was added, followed
by dropwise addition of a solution of 3,4-diphenyl-2-cy-
clopenten-1-one (10 g, 0.043 mol) in THF (50 ml) at
−10°C. The mixture was allowed to warm to r.t. and
stirred for 5 h. After the solution was quenched with 40
ml of ice water, the organic layer was extracted with
diethyl ether (2×30 ml). The combined organic phases
were treated with concentrated HCl (3×20 ml). The
mixture was washed with saturated NH4Cl (aq). After
drying with MgSO4 and filtering, the solvent was evap-
orated under reduced pressure. Pure 2 was obtained as
yellow–brown oil by chromatography over silica gel
(eluent: hexane–CH2Cl2 (15:1), which was gradually
made more polar to a ratio of 6:1). Yield: 3.26 g, 25.3%.
1H NMR (CDCl3, 400 MHz): l 0.95–1.98 (br m, 10H,
Cy), 2.40 (br m, 1H, Cy), 3.47 (s, 2H, C5H3), 6.31 (s, 1H,
C5H3), 7.02–7.40 (m, 10H, Ph).
3. Experimental
3.1. General procedures and material
All reactions with moisture- and air-sensitive com-
pounds were carried out under argon with use of Schlenk
techniques. Toluene and THF were refluxed over sodium
benzophenone ketyl and distilled prior to use. Hexane
and CH2Cl2 were refluxed and distilled from CaH2 under
nitrogen. Polymerization grade ethylene and propylene
were further purified by passage through columns of 10
,
A molecular sieves and MnO. 3,4-Diphenyl-2-cyclopen-
ten-1-one was prepared by a known procedure [29].
Methylaluminoxane (MAO, 10 wt.% solution in toluene,
M=800 g mol−1, Al=5.3 wt.%) was purchased from
Witco. Cyclohexylmagnesium chloride (2.0 M in diethyl
ether), phenyllithium (1.8 M in cyclohexane–ether) and
nBuLi (1.6 M in hexanes), ZrCl4, and Cp2ZrCl2 were
purchased from Aldrich. NMR spectra were recorded on
3.4. Bis(1,2,4-triphenylcyclopentadienyl)zirconium
dichloride (3)
1,2,4-Triphenyl-1,3-cyclopentadiene (0.88 g, 2.99
n
mmol) was dissolved in toluene (40 ml). BuLi (2.0 ml,
1
Varian Unity-400 (FT 400 MHz, H; 100 MHz, 13C)
1.6 M, 3.20 mmol) was added dropwise at −78°C to give
a creamy suspension. The mixture was stirred for 18 h
at r.t. After the solvent had been removed by filtration,
the solid residue was washed with hexane (20 ml) and
then suspended in toluene (40 ml). ZrCl4 powder (0.34
g, 1.46 mmol) was added slowly at −15°C and the
suspension was allowed to warm to r.t. The mixture was
stirred over night and heated to 70°C for further 18 h.
The precipitate was filtered off and the solution was
spectrometer. Elemental analyses were carried out on
Perkin–Elmer 240 C elemental analyzer. Viscosity-aver-
age molecular weights of the polyethylenes were deter-
mined in decahydronaphthalene at 135°C using Schott
Gerate Mod. AVS/T2 Ubbelohde viscosimeter. Melting
transition temperatures (Tm) of the polyethylenes were
determined by DSC (Du Pont 910 differential scanning
calorimeter) at a heating rate of 10°C min−1
.

1946
F. Zhang et al. / Polyhedron 19 (2000) 1941–1947
concentrated in vacuo. Recrystallization from toluene–
added BuLi (1.8 ml, 1.6 M in hexane, 2.88 mmol) at
−78°C. The mixture was allowed to warm to r.t. and
stirred overnight. The solvent was removed by filtration
and the solid was suspended in toluene (50 ml) and
cooled to −15°C. ZrCl4 (0.30 g, 1.3 mmol) was added
to the suspension. The mixture was stirred overnight at
r.t. and for 18 h at 70°C. The resulting suspension was
filtered to remove precipitate. The solution was concen-
trated in vacuo and pure 4 was given as green–yellow
micro-crystals by recrystallization from toluene–hexane
(1:3). Yield: 0.73 g (73.8%). 1H NMR (CDCl3, 400
MHz): l 0.71–0.82, 1.02–1.10, 1.37–1.61 (br m Cy,
20H), 1.78 (br m, Cy, 2H), 6.64 (s, 4H, Cp), 7.26–7.44
(m, 20 H, Ph). 13C NMR (CDCl3, 100 MHz): l 25.6
(double intensity), 33.2, 36.2 (Cy), 117.4, 127.3, 128.0
(Cp), 128.7, 129.8, 133.3, 133.6 (Ph). C46H46Cl2Zr
(760.95): Anal. Calc. C, 72.61, H, 6.09. Found: C,
72.99, H, 6.18%.
hexane (1:3) afforded 3 as a yellow crystalline powder.
1
Yield: 0.89 g (80.3%). H NMR (CDCl3, 400 MHz): l
6.75 (s, 4H, Cp), 7.00–7.20 (m, 30H, Ph). 13C NMR
(CDCl3, 100 MHz): l 116.1, 125.1, 125.4 (Cp), 127.4,
127.6, 127.8, 129.0, 129.5, 130.8, 131.9, 133.0 (Ph).
C46H34Cl2Zr (748.85): Anal. Calc. C, 73.78; H, 4.58.
Found: C, 73.98; H, 4.65%.
3.5. Bis(4-cyclohexyl-1,2-diphenylcyclo
pentadienyl)zirconium dichloride (4)
To a solution of 4-cyclohexyl-1,2-diphenyl-1,3-cyclo-
pentadiene (0.78 g, 2.65 mmol) in hexane (30 ml) was
Table 3
Crystallographic data and parameters of the crystal structure determi-
nations
3·2CH2Cl2
4·CH2Cl2
3.6. X-ray structural determination of complex 3
Formula
Fw
C48H38Cl6Zr
918.70
C47H48Cl4Zr
845.87
Crystals of 3 with two CH2Cl2 solvent molecules
were obtained by recrystallization from a solution of
hexane–CH2Cl2 (4:1). A yellow crystal suitable for
X-ray diffraction sealed in a glass capillary was used.
Data were collected on a Siemens P4 four-circle diffrac-
tometer with a graphite monochromator using Mo Ka
radiation. The structure was solved by direct methods
and refined by full-matrix least-squares methods on F2.
The hydrogen atoms were located by combination of
difference Fourier map and HYDROHEN program. All
calculations were performed using SHELX-93 [30]. Crys-
tallographic data and parameters are summarized in
Table 3.
Temperature (K)
Crystal system
Space group
293 (2)
trigonal
P3(1)21
12.2157 (13)
12.2157 (13)
24.245 (6)
90
90
120
3133.2 (9)
3
0.454
293 (2)
monoclinic
P2/c
8.8746 (7)
11.1902 (9)
21.0399 (18)
90
91.7260 (10)
90
2088.5 (3)
2
,
a (A)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Absorption coefficient
0.551
(mm−1
)
F(000)
Dcalc (Mg m−3
Crystal size (mm)
936
1.461
0.36×0.38×0.4
0.71073
−1BhB14;
−14BkB1;
−1BlB28
1.92BqB25.00
ꢀ–2q
876
1.345
0.40×0.12×0.12
0.71073
−9BhB9;
−12BkB11;
−22BlB23
3.48BqB23.26
ꢀ–2q
)
,
Wavelength (A)
3.7. X-ray structural determination of complex 4
Collection region
A yellow crystal of 4 with one CH2Cl2 solvent
molecule crystallized from hexane–CH2Cl2 (5:1) was
mounted in a thin-walled glass capillary under nitrogen.
Data collection was performed using a standard
Siemens SMART CCD diffractometer with graphite-
monochromated Mo Ka radiation. Hydrogen atoms
were located by combination of difference Fourier map
and HYDROGEN program. Except for CH2Cl2 molecu-
lar, all non-hydrogen atoms were refined with an-
isotropic thermal parameters, while hydrogen atoms
were refined isotropically. The disorder CH2Cl2
molecule founded in the lattice as a solvent of recrystal-
lization exhibited high thermal parameters. The disor-
der CH2Cl2 was refined as 50/50 disordered. All
calculations were performed using SHELX crystallo-
graphic package [31]. Crystallographic data and
parameters are summarized in Table 3.
q Range (°)
Scan type
Absorption correction
Max and min
transmission
Number of reflections
collected
semi-empirical
0.923 and 0.599
empirical
0.882 and 0.658
4860
9092
Number of uniqe
reflections
3674
(Rint=0.0388)
2401
2999 (Rint=0.0425)
Reflections with
2498
(F2o\3|(F2o))
Number of variables
Goodness-of-fit on F2
R1 (wR2) a
311
1.160
0.0431 (0.0879)
341
1.002
0.0320 (0.0773)
Largest difference peak 0.963 and −0.671 0.382 and −0.256
−3
,
and hole (e A
)
a R1=SꢀFo−Fcꢀ/SꢀFoꢀ, wR2={[Sw(Fo2−Fc2)2]/SwFo4}0.5
, w=1/
[|2(Fo2)+(mP)2+0.0000P], P=(Fo2+2Fc2)/3, (3, m=0.0508; 4, m=
0.0536).

F. Zhang et al. / Polyhedron 19 (2000) 1941–1947
Waymouth, Angew. Chem., Int. Ed. Engl. 34 (1995) 1143.
1947
3.8. Polymerizations
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stirrer was evacuated and pressurized with ethylene to 1.0
bar. Toluene and appropriate amount of MAO were
added to the reactor through a septum port via syringe.
After the solution was saturated with ethylene for 30 min,
a solution of catalyst (1.7 mmol) in toluene was injected
(total volume of the polymerization solution is 50 ml after
the addition of catalyst). The vessel was repressurized to
the required pressure with ethylene as soon as the catalyst
was injected and the pressure was maintained by contin-
uously feeding monomer. After the mixture was stirred
for the desired reaction time, the reactor was vented and
the polymerization was terminated by injecting acidified
methanol [HCl (3 M)–methanol=1:1]. The polymer was
stirred in acidified methanol overnight, washed with
water and methanol, dried in vacuo at 60°C. Polymeriza-
tion of propylene was performed under ambient condi-
tions (1 bar, temperature 20°C, time 1 h, Al/Zr=1000/1,
catalyst=1.7 mmol). The procedure was similar to that
for ethylene polymerization. After the reaction mixture
was treated with acidified methanol and stirred
overnight, the organic layer was separated and the
aqueous phase was extracted with toluene. The organic
layers were combined and dried over MgSO4. After the
solvent was removed, the propylene oligomer was ob-
tained as a colorless oil.
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4. Supplementary data
Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre,
CCDC Nos. 140596 and 140597. Copies of the data can
be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge, CB2 1EZ, UK (fax: +44-
1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
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Acknowledgements
This work was supported by the National Natural
Science Foundation of China (No. 29734143 and No.
29672013) and the Sinopec.
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