Synthesis and polymerization catalytic properties of aryl-substituted tetramethylcyclopentadienyl zirconocenes

Article abstract of DOI:10.1016/S1381-1169(02)00036-5

A series of aryl-substituted tetramethylcyclopentadienyl zirconocenes (C₅Me₄C₆H₄X-4)Cp′ MCl₂ [CP′ = C₅H₅, X = H (5), Me (6), Cl (7) or OMe (8); Cp′ = Ind, X = H (9), Me (10) or Cl (11); Cp′ = 2-Ph-Ind, X = H (12)] and (C₅Me₄C₆H₄X-4)₂ ZrCl₂ [X = H (13), Me (14), Cl (15)], with different substituents at the 4-position of phenyl, have been prepared by the reaction of the corresponding ligands (C₅Me₄HC₆H₄X-4) [X = H (1), Me (2), Cl (3) or OMe (4)] with n-BuLi, ZrCl₄ and Cp′Li or with n-BuLi and ZrCl₄. Ethylene polymerization with these complexes in combination with MAO has been studied. The electron donor (Me) at the 4-position of phenyl led to an increase in catalytic activity while the electron-withdrawing group (Cl) and the strong π donor (OMe) led to its decrease. Complexes 5, 6, 9 and 10 exhibited very high activities, but 13-15 showed much lower activities due to the bulky steric effect. The molecular structure of 5 has been determined by X-ray diffraction. The relationship between structures of catalysts and catalytic activities were discussed.

Full text of DOI:10.1016/S1381-1169(02)00036-5

Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
Synthesis and polymerization catalytic properties
of aryl-substituted tetramethylcyclopentadienyl zirconocenes
Xiaobin Denga,d, Baiquan Wanga,d,∗, Shansheng Xua,d, Xiuzhong Zhoua,d
,
Ling Yangb, Yufei Lib, Youliang Hub, Yang Lic, Fenglou Zouc
a
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China
b
Research Institute of Beijing Yanshan Petrochemical Co., Ltd., Beijing 102500, PR China
c
Institute of Chemistry, Chinese Academy of Science, Beijing 100080, PR China
d
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai, PR China
Received 4 October 2001; received in revised form 26 November 2001; accepted 19 January 2002
Abstract
A series of aryl-substituted tetramethylcyclopentadienyl zirconocenes (C5Me4C6H4X-4)CpꢀMCl2 [Cpꢀ = C5H5, X =
H (5), Me (6), Cl (7) or OMe (8); Cpꢀ = Ind, X = H (9), Me (10) or Cl (11); Cpꢀ = 2-Ph-Ind, X = H (12)] and
(C5Me4C6H4X-4)2ZrCl2 [X = H (13), Me (14), Cl (15)], with different substituents at the 4-position of phenyl, have been
prepared by the reaction of the corresponding ligands (C5Me4HC6H4X-4) [X = H (1), Me (2), Cl (3) or OMe (4)] with
n-BuLi, ZrCl4 and CpꢀLi or with n-BuLi and ZrCl4. Ethylene polymerization with these complexes in combination with
MAO has been studied. The electron donor (Me) at the 4-position of phenyl led to an increase in catalytic activity while
the electron-withdrawing group (Cl) and the strong ␲ donor (OMe) led to its decrease. Complexes 5, 6, 9 and 10 exhibited
very high activities, but 13–15 showed much lower activities due to the bulky steric effect. The molecular structure of 5 has
been determined by X-ray diffraction. The relationship between structures of catalysts and catalytic activities were discussed.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: Zirconocene; Metallocene; Ethylene polymerization; Polyethylene; Electronic effect
1. Introduction
catalytic activity than the bridged ones for group 4
metallocenes [8]. The steric and electronic effects of
cyclopentadienyl ring substituents greatly influence
catalytic activity [9]. Thus the variation of cyclopenta-
dienyl ligands is the first strategy for efficient catalysts.
Because of the special electronic and steric effect of
the phenyl group [10–17], in this study, a series of aryl-
substituted tetramethylcyclopentadienyl zirconocenes,
with different substituents at the 4-position of phenyl,
has been synthesized. Ethylene polymerization was
investigated with these complexes in combination
with MAO in order to examine the electronic effect
of the substituents of phenyl on catalytic activities.
Metallocene catalysts have been one of the most
widely studied topics for more than 20 years [1–7].
Various types of metallocene complexes have been
studied as olefin polymerization catalysts. It was found
that the unbridged species generally show higher
∗
Corresponding author. Present address: Department of Chem-
istry, State Key Laboratory of Elemento-Organic Chemistry,
Nankai University, Tianjin 300071, PR China.
Tel.: +86-22-23504781; fax: +86-22-23502458.
E-mail address: bqwang@public.tpt.tj.cn (B. Wang).
1381-1169/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S1381-1169(02)00036-5

58
X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
2. Experimental
2.1. General procedures
2,3,4,5-tetramethylcyclopent-2-enone using a method
similar to that as described for 1. 2: b.p.
=
100–104 ◦C/0.4 mmHg, yellow liquid (71%). 1H-NMR
(CDCl3): δ 7.32–7.06 (m, 4H, Ph-H), 3.24–3.11 (m,
1H, C5Me4H), 2.34 (s, 3H, Ph-Me), 2.00 (s, 3H, Me),
1.91 (s, 3H, Me), 1.85 (s, 3H, Me), 0.95, 0.91 ppm
(s, s, 3H, Me). 3: b.p. = 111–113 ◦C/0.6 mmHg,
All operations were carried out under an argon
atmosphere using the standard Schlenk techniques.
Diethyl ether, toluene and DME were distilled from
sodium/benzophenone ketyl under argon prior to
use. 1H-NMR spectra were recorded on a Bruker
AC-200, and MS spectra on a VG-7070E HF spec-
trometer. Elemental analyses were made on a CHN
Corder MF-3 spectrometer. The molecular struc-
ture of 5 was determined by X-ray diffraction on
an Enraf-Nonius CAD4 diffractometer with graphite
monochromated Mo K␣ radiation (λ = 0.71073 Å).
Polymerization grade ethylene (Yanshan Petrochem,
China) was used without further purification. MAO
was purchased from Aldrich. The molecular weight
of the polyethylene was measured in decalin solu-
tion using an AVS 300 viscometer at 135 0.1 ◦C.
1
yellow waxy solid (82%). H-NMR (CDCl3): δ 7.29
(d, J = 8.4 Hz, 2H, Ph-H), 7.13 (d, J = 8.4 Hz,
2H, Ph-H), 3.24–3.04 (m, 1H, C5Me4H), 1.98 (s,
3H, Me), 1.90 (s, 3H, Me), 1.84 (s, 3H, Me), 0.93,
0.90 ppm (s, s, 3H, Me). Anal. found: C, 77.17%; H,
7.13%. C15H17Cl (calc.): C, 77.41%; H, 7.36%.
2.4. Preparation of C5Me4HC6H4OMe-4 (4)
To 1.2 g (0.05 mol) of magnesium turnings
and 20 ml of diethyl ether, 9.35 g (0.05 mol) of
4-bromoanisole in 40 ml of diethyl ether was added
with vigorous stirring. After stirring at RT for 1 h, the
mixture was cooled down to 0 ◦C and 6.9 g (0.05 mol)
of 2,3,4,5-tetramethylcyclopent-2-enone was added.
After stirring overnight at RT, the mixture was hy-
drolyzed. The organic phase was washed with 20 ml
of hydrochloric acid and dried with Na2CO3. After
removal of the solvents, the residue was distilled at
126–130 ◦C/0.7 mmHg to give 7.0 g (61%) of 4 as
2,3,4,5-Tetramethylcyclopent-2-enone
2-phenylindene [11] were prepared according to
literature.
[18]
and
2.2. Preparation of C5Me4HPh (1)
To 45.7 ml (2.19 M, 0.10 mol) of n-BuLi/hexane
solution and 100 ml of diethyl ether, 15.7 g (0.10 mol)
of bromobenzene in 100 ml of diethyl ether was
added dropwise at 0 ◦C. After heating under reflux for
1 h, the mixture was cooled down to 0 ◦C and 13.8 g
(0.10 mol) of 2,3,4,5-tetramethylcyclopent-2-enone
was added. After stirring overnight at room tempera-
ture (RT), the mixture was hydrolyzed. The organic
phase was washed with 20 ml of hydrochloric acid
and dried with Na2CO3. After removal of the sol-
vents, the residue was distilled at 88–92 ◦C/0.3 mmHg
1
light yellow liquid. H-NMR (CDCl3): δ 7.21–7.00
(m, 2H, Ph-H), 7.00–6.76 (m, 2H, Ph-H), 3.80 (s, 3H,
OMe), 3.21–3.04 (m, 1H, C5Me4H), 1.98 (s, 3H, Me),
1.90 (s, 3H, Me), 1.84 (s, 3H, Me), 0.94, 0.90 ppm (s,
s, 3H, Me).
2.5. Preparation of (C5Me4Ph)CpZrCl2 (5)
To a solution of 1.98 g (10 mmol) of 1 in 40 ml of
toluene, 4.57 ml (2.19 M, 10 mmol) of n-BuLi/hexane
solution was added dropwise. After stirring at RT
overnight, 2.33 g (10 mmol) of ZrCl4 was added to
the resulting suspension. After heating under reflux
for 24 h, 10 mmol of CpLi (prepared from cyclopen-
tadiene and n-BuLi) was added to the resulting red
suspension. The mixture was refluxed for 24 h. After
removal of solvents, 40 ml of CH2Cl2 and 10 ml of
HCl (6 N) was added to the residue. After separa-
tion, the organic phase was washed with water and
dried with Na2SO4. Upon concentration and addition
of hexane, 2.3 g (52%) of 5 was obtained as yellow
1
to give 15.5 g (78%) of 1 as yellow liquid. H-NMR
(CDCl3): δ 7.32–7.06 (m, 5H, Ph-H), 3.24–3.11 (m,
1H, C5Me4H), 2.00 (s, 3H, Me), 1.91 (s, 3H, Me),
1.85 (s, 3H, Me), 0.95, 0.91 ppm (s, s, 3H, Me).
2.3. Preparation of C5Me4HC6H4Me-4 (2)
and C5Me4HC6H4Cl-4 (3)
Complexes 2 and 3 were prepared from 4-bromo-
toluene or 4-bromochlorobenzene with n-BuLi and

X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
59
crystals; m.p.: 225–227 ◦C. Anal. found: C, 56.33%;
2.7. Preparation of (C5Me4C6H4X-4)(Ind)ZrCl2
[X = H (9), Me (10), Cl (11)]
H, 5.37%. C20H22Cl2Zr (calc.): C, 56.59%; H, 5.22%.
1H-NMR (CDCl3): δ 7.49–7.11 (m, 5H, Ph-H), 6.14
(s, 5H, C5H5), 2.22 (s, 6H, Me), 2.05 ppm (s, 6H, Me).
MS (EI): m/z 422 (22, M+), 386 (14, M+ −HCl), 357
(100, M+ − C5H5), 321 (21, M+ − HCl–C5H5), 225
(24, M+−C5Me4Ph), 197 (11, [C5Me4Ph]+), 165 (49,
[C5MeZr]+), 91 (16, [C7H7]+), 77 (12, [C6H5]+), 65
(8, [C5H5]+).
Complexes 9–11 were synthesized from the corre-
sponding ligands 1–3, n-BuLi, ZrCl4 and IndLi using
a method similar to that as described for 5.
9: Yellow crystals (84%); m.p.: 280–281 ◦C. Anal.
found: C, 60.44%; H, 5.04%. C24H24Cl2Zr (calc.): C,
1
60.74%; H, 5.10%. H-NMR (CDCl3): δ 7.64–7.16
(m, 9H, Ar-H), 6.09 (d, 2H, Ind-H), 5.87 (t, 1H,
Ind-H), 2.26 (s, 6H, Me), 2.00 ppm (s, 6H, Me). MS
(EI): m/z 472 (4, M+), 357 (99, M+ − Ind), 359
(100, M+ + 2-Ind), 321 (27, M+ − HCl–Ind), 275
(19, [IndZrCl2]+), 197 (6, [C5Me4Ph]+), 165 (31,
[C5MeZr]+), 115 (67, [Ind]+), 77 (8, [C6H5]+).
10: Yellow crystals (79%); m.p.: 209–210 ◦C. Anal.
found: C, 61.60%; H, 5.23%. C25H26Cl2Zr (calc.): C,
2.6. Preparation of (C5Me4C6H4X-4)CpZrCl2
[X = Me (6), Cl (7), OMe (8)]
Complexes 6–8 were synthesized from the corre-
sponding ligands 2–4, n-BuLi, ZrCl4 and CpLi using
a method similar to that as described for 5.
6: Light yellow solid (77%); m.p.: 162–164 ◦C.
Anal. found: C, 57.24%; H, 5.21%. C21H24Cl2Zr
1
61.45%; H, 5.36%. H-NMR (CDCl3): δ 7.64–7.51
1
(calc.): C, 57.51%; H, 5.52%. H-NMR (CDCl3): δ
(m, 2H, Ar-H), 7.37–7.22 (m, 4H, Ar-H), 7.10 (d, 2H,
Ar-H), 6.09 (d, 2H, Ind-H), 5.87 (t, 1H, Ind-H), 2.41 (s,
3H, Ph-Me), 2.26 (s, 6H, Me), 2.00 ppm (s, 6H, Me).
MS (EI): m/z 486 (3, M+), 371 (96, M+ − Ind), 373
(100, M+ +2-Ind), 335 (26, M+ −HCl–Ind), 275 (22,
[IndZrCl2]+), 165 (30, [C5MeZr]+), 115 (54, [Ind]+).
11: Yellow solid (37%); m.p.: 209–210 ◦C. Anal.
found: C, 56.13%; H, 4.90%. C24H23Cl3Zr (calc.): C,
56.63%; H, 4.55%. 1H-NMR (CDCl3): δ 7.58 (m, 2H,
Ar-H), 7.41 (d, J = 8.32 Hz, 2H, Ar-H), 7.28 (m,
2H, Ar-H), 7.15 (d, J = 8.32 Hz, 2H, Ar-H), 6.10
(d, 2H, Ind-H), 5.93 (t, 1H, Ind-H), 2.23 (s, 6H, Me),
2.01 ppm (s, 6H, Me). MS (EI): m/z 506 (4, M+),
391 (75, M+ − Ind), 393 (100, M+ + 2-Ind), 355
(16, M+ − HCl–Ind), 275 (22, [IndZrCl2]+), 165 (54,
[C5MeZr]+), 115 (69, [Ind]+).
7.21 (d, J = 8.0 Hz, 2H, Ph-H), 7.02 (d, J = 8.0 Hz,
2H, Ph-H), 6.13 (s, 5H, C5H5), 2.38 (s, 3H, Ph-Me),
2.22 (s, 6H, Me), 2.04 ppm (s, 6H, Me). MS (EI):
m/z 436 (20, M+), 400 (8, M+ − HCl), 371 (100,
M+ − C5H5), 335 (21, M+ − HCl–C5H5), 225
(10, M+ −C5Me4C6H4Me), 211 (16, M+ −CpZrCl2),
196 (15, [C5Me4C6H4]+), 179 (29, [C5MeCH2Zr]+),
165 (57, [C5MeZr]+), 91 (12, [C7H7]+), 65 (10,
[C5H5]+).
7: White crystals (71%); m.p.: 135–137 ◦C. Anal.
found: C, 52.14%; H, 4.48%. C20H21Cl3Zr (calc.): C,
52.34%; H, 4.61%. 1H-NMR (CDCl3): δ 7.37 (d, J =
8.4 Hz, 2H, Ph-H), 7.08 (d, J = 8.4 Hz, 2H, Ph-H),
6.15 (s, 5H, C5H5), 2.19 (s, 6H, Me), 2.04 ppm (s, 6H,
Me). MS (EI): m/z 456 (7, M+), 420 (4, M+ − HCl),
391 (20, M+ −C5H5), 355 (4, M+ −HCl–C5H5), 225
(81, M+ − C5Me4C6H4Cl), 165 (100, [C5MeZr]+),
65 (19, [C5H5]+).
2.8. Preparation of (C5Me4C6H5)(2-Ph-Ind)ZrCl2
(12)
8: Yellow crystals (46%); m.p.: 162–164 ◦C. Anal.
found: C, 55.33%; H, 4.72%. C21H24Cl2OZr (calc.):
Complex 12 was synthesized from the ligand
1, n-BuLi, ZrCl4 and 2-Ph-IndLi (prepared from
2-Ph-indene and n-BuLi) using a method similar to
that as described for 5 as yellow crystals (36%); m.p.:
125–127 ◦C. Anal. found: C, 64.97%; H, 5.37%.
C30H28Cl2Zr (calc.): C, 65.43%; H, 5.12%. 1H-NMR
(CDCl3): δ 7.64 (m, 2H, Ar-H), 7.46–7.12 (m, 10H,
Ar-H), 6.94 (m, 2H, Ar-H), 6.71 (s, 2H, Ind-H), 2.01
(s, 6H, Me), 1.79 ppm (s, 6H, Me). MS (EI): m/z
548 (1, M+), 357 (70, M+ − (2-Ph-Ind)), 351 (5,
1
C, 55.49%; H, 5.32%. H-NMR (CDCl3): δ 7.07 (d,
J = 8.7 Hz, 2H, Ph-H), 6.93 (d, J = 8.7 Hz, 2H,
Ph-H), 6.13 (s, 5H, C5H5), 3.83 (s, 3H, OMe), 2.21
(s, 6H, Me), 2.03 ppm (s, 6H, Me). MS (EI): m/z
452 (25, M+), 416 (6, M+ − HCl), 387 (96, M+
−
C5H5), 389 (100, M+ + 2-C5H5), 351 (18, M+
−
HCl–C5H5), 225 (39, M+−C5H5Me4C6H4OMe), 179
(23, [C5MeCH2Zr]+), 165 (62, [C5MeZr]+), 91 (15,
[C7H7]+), 65 (11, [C5H5]+).

60
X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
[2-Ph-IndZrCl2]+), 321 (20, M+ − HCl–(2-Ph-Ind)),
197 (5, [C5Me4Ph]+), 191 (100, [2-Ph-Ind]+), 165
(57, [C5MeZr]+), 91 (11, [C7H7]+), 77 (7, [C6H5]+),
65 (3, [C5H5]+).
m/z 622 (1, M+), 391 (22, M+ − C5Me4C6H4Cl),
355 (15, M+ − HCl–C5Me4C6H4Cl), 319 (10, M+ −
2HCl–C5Me4C6H4Cl), 231 (18, [C5Me4C6H4Cl]+),
196 (34, [C5Me4C6H4]+), 181 (43, [C5Me3C6H4]+),
165 (100, [C5MeZr]+).
2.9. Preparation of (C5Me4C6H5)2ZrCl2 (13)
2.11. Ethylene polymerization
To a solution of 3.97 g (15 mmol) of 1 in 40 ml of
DME, 6.85 ml (2.19 N, 15 mmol) of n-BuLi/hexane
solution was added dropwise. After stirring at RT
overnight, the mixture was cooled down to −78 ◦C and
1.74 g (7.5 mmol) of ZrCl4 was added. After heating
under reflux for 6 h, the solvents were removed and
40 ml of CH2Cl2 and 10 ml of HCl (6 N) was added
to the residue. After separation, the organic phase
was washed with water and dried with Na2SO4. Upon
concentration and addition of hexane, 2.1 g (54%) of
13 was obtained as yellow crystals; m.p.: 242–243 ◦C.
Anal. found: C, 64.47%; H, 5.89%. C30H34Cl2Zr
Polymerization was carried out in a 250 ml glass re-
actor with a magnetic stirring bar at about 780 mmHg.
Toluene (100 ml) was introduced into the reactor, the
temperature was increased to polymerization temper-
ature, and then toluene was saturated with ethylene. A
prescribed amount of MAO and a given metallocene
dissolved in toluene were injected into the reactor to
initiate the polymerization. The polymerization was
terminated by addition of acidified EtOH. The poly-
mer product obtained was washed with ethanol and
dried in vacuo at 60 ◦C.
1
(calc.): C, 64.72%; H, 6.16%. H-NMR (CDCl3): δ
7.40–7.24 (m, 6H, Ph-H), 7.05 (d, 4H, Ph-H), 1.99
(s, 12H, Me), 1.79 ppm (s, 12H, Me). MS (EI): m/z
554 (4, M+), 357 (99, M+ − C5Me4Ph), 359 (100,
3. Results and discussion
M
+ + 2-C5Me4Ph), 321 (26, M+ − HCl–C5Me4Ph),
The ligands 1–3 were synthesized by the reaction of
4-substituted bromobenzene with n-BuLi and 2,3,4,5-
tetramethylcyclopent-2-enone. 4-Bromoanisole reac-
ted with magnesium turnings to form the Grignard
reagent, which further reacted with 2,3,4,5-tetramethyl-
cyclopent-2-enone to give the ligand 4 (Scheme 1).
The ligands 1–4 reacted with n-BuLi and 1 equiv.
of ZrCl4 to form the corresponding aryl-substituted
tetramethylcyclopentadienyl zirconium trichlorides,
which further reacted in situ with CpLi, IndLi or
2-Ph-IndLi to give the mixed-ring zirconocene com-
plexes 5–12 in high yield, respectively (Scheme 2).
197 (21, [C5Me4Ph]+), 165 (44, [C5MeZr]+), 91 (14,
[C7H7]+), 77 (6, [C6H5]+).
2.10. Preparation of (C5Me4C6H4X-4)2ZrCl2
[X = Me (14), Cl (15)]
Complexes 14 and 15 were synthesized from the
corresponding ligands 2 and 3, n-BuLi and ZrCl4 using
a method similar to that as described for 13.
14: Yellow crystals (71%); m.p.: 261–263 ◦C.
Anal. found: C, 65.50%; H, 6.45%. C32H38Cl2Zr
(calc.): 65.73%; H, 6.55%. 1H-NMR (CDCl3): δ
7.14 (d, J = 7.95 Hz, 4H, Ph-H), 6.93 (d, J =
7.95 Hz, 4H, Ph-H), 2.36 (s, 6H, Ph-Me), 1.98 (s,
12H, Me), 1.79 ppm (s, 12H, Me). MS (EI): m/z
582 (2, M+), 371 (100, M+ − C5Me4C6H4Me),
335 (23, M+ − HCl–C5Me4C6H4Me), 211 (28,
[C5Me4C6H4Me]+), 181 (27, [C5Me3C6H4]+), 165
(36, [C5MeZr]+).
15: Yellow crystals (82%); m.p.: 267–268 ◦C. Anal.
found: C, 57.56%; H, 5.25%. C30H32Cl4Zr (calc.):
57.60%; H, 5.16%. 1H-NMR (CDCl3): δ 7.33 (d, J =
8.40 Hz, 4H, Ar-H), 7.00 (d, J = 8.40 Hz, 4H, Ar-H),
1.97 (s, 12H, Me), 1.82 ppm (s, 12H, Me). MS (EI):
Scheme 1.

X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
61
Scheme 2.
The zirconocene complexes 13–15 were synthe-
sized by the reaction of the corresponding ligands
1–3 with n-BuLi and 0.5 equiv. of ZrCl4 in DME
(Scheme 3).
Table 1
Results
of
ethylene
polymerization
catalyzed
with
zirconocenes/MAOa
The mass spectrum of a compound reflects the rel-
ative stability of the fragment ions. The fragment ion
[M − C5H5]+ is the base peak in the mass spectra
of 5, 6 and 8, indicating the ligands C5Me4C6H4X-4
(X = H, Me and MeO) complex with zirconium atom
more strongly than the cyclopentadienyl ligand. In
the mass spectrum of 7, the abundance of the frag-
ment ion [M − C5H5]+ (20%) is much smaller than
that of [M − C5Me4C6H4Cl-4]+ (81%). This indi-
cates that the introduction of an electron-withdrawing
substituent (Cl) at the 4-position of phenyl decreases
the electronic density of the cyclopentadienyl ring and
weakens the complexing ability of the ligand. Simi-
larly, the abundance of the fragment ion [M − Ind]+
(99, 96 and 75%) are much larger than that of [M −
C5Me4C6H4X-4]+ (19, 22 and 22%) in the mass spec-
tra of 9–11, indicating the stronger complexing abil-
ity of C5Me4C6H4X-4 than the indenyl ligand. Based
on the mass spectra data, the complexing ability or-
der of these ligands can be concluded as follows:
C5Me4C6H4X-4 (X = H, Me and MeO) > Cp >
C5Me4C6H4Cl-4 > Ind.
Catalyst
Tp
Ab
M␩
(◦C)
(×10−6
)
(×10−5 g/mol)
c
(C5Me4H)CpZrCl2
40
30
60
50
40
30
20
30
30
30
6.47
2.48
16.1
23.9
21.1
15.6
14.1
15.9
3.74
0.997
3.67
5
1.12
1.89
2.41
5.44
5.92
3.35
1.63
3.32
6
7
8
c
(C5Me4H)IndZrCl2
40
30
60
50
40
30
20
60
50
40
30
20
30
50
40
30
20
10
30
30
30
4.20
3.67
9.88
12.4
16.6
19.8
15.3
10.6
14.4
19.2
26.1
23.8
5.15
1.43
2.52
3.96
5.23
4.80
1.03
1.63
0.422
2.90
3.43
0.84
0.73
1.61
2.11
2.38
0.74
0.58
1.76
2.55
3.13
2.51
1.02
1.23
1.53
1.46
2.68
0.198
0.224
0.280
9
10
Complexes 5–15 in combination with MAO were
studied as catalysts for ethylene polymerization
(Table 1). From the polymerization results it is
11
12
13
14
15
a Polymerization conditions: [Zr]
=
1.0 × 10−6 mol;
Al/Zr=2000; t = 15 min; 1 atm ethylene pressure; in 100 ml
toluene.
b Activity (g PE/mol Zr h).
Scheme 3.
c Ref. [19], [Zr] = 3.0×10−6 mol; Al/Zr = 2500; t = 30 min.

62
X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
found that the introduction of a substituent at the
4-position of phenyl greatly influences the activ-
ities of catalysts for ethylene polymerization. At
30 ◦C, the activities decrease in the following or-
der: for (C5Me4C6H4X-4)CpZrCl2, 6 (X = Me) >
5 (X = H) > 7 (X = Cl) > (C5Me4)CpZrCl2
ꢁ
8 (X = OMe); for (C5Me4C6H4X-4)(Ind)ZrCl2, 10
(X = Me) > 9 (X = H) > 11 (X = Cl) > 12 >
(C5Me4)(Ind)ZrCl2; for (C5Me4C6H4X-4)2ZrCl2, 14
(X = Me) > 13 (X = H) > 15 (X = Cl). For these
complexes, the substituents are at the 4-position of
phenyl, which is far from the metal center, so the
steric effects are similar and the catalytic activity
differences depend mainly on the electronic effect of
the substituents. The electron donor (Me) increases
the electron density of the metal center, which leads
to an increase in catalytic activity. In contrast, the
electron-withdrawing group (Cl) decreases the elec-
tron density of the metal center and leads to a de-
crease in catalytic activity. However, complex 8 with
a strong ␲ donor (OMe) shows much lower activity.
This can be attributed to the coordination of the donor
to MAO leading to inductive electron withdrawal
[21,22]. The introduction of a phenyl at 2-position
of indenyl in 12 increases the steric hindrance and
leads to a decrease in catalytic activity. The much
lower catalytic activities of 13–15 than that of the
mixed-ring zirconocenes can be attributed to the
large steric effect of the aryl-substituted tetramethyl-
cyclopentadienyl ligand than the cyclopentadienyl
ligand.
The relationship between the molecular weight of
polyethylene with the electronic effects of substituents
in phenyl is not clear. It seems that the molecular
weight of polyethylene is more sensitive to the steric
effect of catalysts. For (C5Me4C6H4X-4)CpZrCl2,
the introduction of substituents at the 4-position
of phenyl, both electron-withdrawing and donat-
ing, leads to a decrease in the molecular weight
of polyethylene; especially for complex 8 with
a strong ␲ donor (OMe), much lower molec-
ular weight of polyethylene was produced. For
(C5Me4C6H4X-4)IndZrCl2, polyethylenes with simi-
lar molecular weight were obtained. The introduction
of the bulky phenyl at 2-position of indenyl de-
creases the molecular weight of polyethylene. For
(C5Me4C6H4X-4)2ZrCl2, polyethylenes with very
low molecular weight were obtained. This indicates
Fig. 1. The molecular structure of 5.
that although bulky substituents in the ligand, such
as (C5Me5)2ZrCl2, may partially block the free co-
ordination site, suppress ␤-hydrogen elimination
reactions and increase the molecular weight of the
produced polymer [8]. However, the too bulky sub-
stituents led to a decrease in the molecular weight of
polyethylene.
From Table 1 it is also found that the introduction
of phenyl makes complexes 5, 6, 9 and 10 show much
higher activities than (C5Me4)CpZrCl2. In the molec-
ular structure of 5 (Fig. 1), the dihedral angle be-
tween phenyl and tetramethylcyclopentadienyl planes
is 47.2◦, showing that there is no conjugation effect
between phenyl ring and tetramethylcyclopentadienyl
ring. This indicates that the electronic effect is not re-
sponsible mainly for the high activity. In comparison
with (C5Me5)CpZrCl2, the introduction of a phenyl
increases the distance between zirconium atom and
the center of cyclopentadienyl ring (Zr–Cen: 2.219 Å
vs. 2.209 Å) (Table 2). This enlarges the reaction
space of the metal center and increases the catalytic
activity of 5.

X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
63
Table 2
cenes 5, 6, 9 and 10 displayed very high ethylene
polymerization activities. The X-ray crystallographic
structure of 5 revealed that the introduction of phenyl
increased the distance between zirconium atom and
the center of cyclopentadienyl ring and enlarged
the reaction space of the metal center. The elec-
tronic effects of the substituents at the 4-position
of phenyl were examined and it was found that the
electron donor (Me) led to an increase while the
electron-withdrawing group (Cl) and the strong ␲
donor (OMe) led to a decrease in catalytic activity.
Selected bond lengths (Å) and bond angles (◦) for
5 and
a
(C5Me5)CpZrCl2
5
(C5Me5)CpZrCl2
Zr–C(Cp)
Zr–C(Cpꢀꢀ)
Zr–Cen(Cp)
Zr–Cen(Cpꢀꢀ)
Zr–Cl
2.516
2.524
2.219
2.219
2.507(31)
2.524(14)
2.209(2)
2.219(2)
2.442(1)
2.437(2) 2.429(2)
∠Cen–Zr–Cen
∠Cp–Cpꢀꢀ
131.1
52.4
96.8(1)
This work
130.01(7)
53.4(2)
97.78(3)
[20]
∠Cl–Zr–Cl
Reference
a Cen: the center of C5 ring.
Acknowledgements
We greatly appreciate the financial support from
the National Natural Science Foundation of China
(29734142), China Petrochemical Corporation
(SINOPEC) and the Scientific Research Foundation
for the Returned Overseas Chinese Scholars, State
Education Ministry.
Table 3
The effects of Al/Zr ratio on polymerization activities for 5 and 9a
Catalyst
Al/Zr
A (×10−6
)
M␩ (×10−5 g/mol)
5
3200
2500
2000
1200
640
31.4
26.5
21.1
17.2
1.66
3.08
2.46
2.46
2.47
1.22
References
9
3200
2500
2000
1200
640
18.8
32.4
29.1
18.6
3.74
1.83
2.14
2.50
2.71
1.82
[1] H. Sinn, W. Kaminsky, Adv. Organomet. Chem. 18 (1980)
99.
[2] H.H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger,
R.M. Waymouth, Angew. Chem. Int. Ed. Engl. 34 (1995)
1143.
a Polymerization conditions: [Zr] = 5.0 × 10−7 mol; T p
=
50 ◦C for 5, 30 ◦C for 9; t = 15 min; 1 atm ethylene pressure; in
[3] G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem. Int.
Ed. Engl. 38 (1999) 428.
100 ml toluene.
[4] H.G. Alt, A. Koppl, Chem. Rev. 100 (2000) 1205.
[5] U. Siemeling, Chem. Rev. 100 (2000) 1495.
[6] H. Butenschon, Chem. Rev. 100 (2000) 1527.
[7] G.W. Coates, Chem. Rev. 100 (2000) 1223.
[8] W. Kaminsky, M. Arndt, Advances in Polymer Science,
Springer, Berlin, 1997, p. 143.
[9] P.C. Möhring, N.J. Coville, J. Organomet. Chem. 479 (1994)
1.
[10] W. Spaleck, F. Kuber, A. Winter, J. Rohrmann, B. Bachmann,
M. Antberg, V. Dolle, E.F. Paulus, Organometallics 13 (1994)
954.
Complex 5 shows the highest activity at 50 ◦C,
while complexes 9–12 reach the maximum activ-
ities at low temperature, due to the poor thermal
stabilities of indenyl zirconocene complexes. For
complexes 5 and 9, the effects of Al/Zr ratio on cat-
alytic activities were also examined (Table 3). The
activity increases with increasing Al/Zr ratio for 5,
but the highest activity is obtained at Al/Zr = 2500
for 9.
[11] G.W. Coates, R.M. Waymouth, Science 267 (1995) 217.
[12] E. Hauptman, R.M. Waymouth, J.W. Ziller, J. Am. Chem.
Soc. 117 (1995) 11586.
[13] M.D. Bruce, G.W. Coates, E. Hauptman, R.M. Waymouth,
J.W. Ziller, J. Am. Chem. Soc. 119 (1997) 11174.
[14] R. Kravchenko, A. Masood, R.M. Waymouth, C.L. Myers, J.
Am. Chem. Soc. 120 (1998) 2039.
[15] K. Kimura, K. Takaishi, T. Matsukawa, T. Yoshimura, H.
Yamazaki, Chem. Lett. (1998) 571.
4. Conclusions
In this study, we demonstrated that mixed-ring
aryl-substituted tetramethylcyclopentadienyl zircono-

64
X. Deng et al. / Journal of Molecular Catalysis A: Chemical 184 (2002) 57–64
[16] F. Zhang, Y. Mu, L. Zhao, Y. Zhang, W. Bu, C. Chen, H.
Zhai, H. Hong, J. Organomet. Chem. 613 (2000) 68.
[17] F. Zhang, Y. Mu, J. Wang, Z. Shi, W. Bu, S. Hu, Y. Zhang,
S. Feng, Polyhedron 19 (2000) 1941.
[18] F.X. Kohl, P. Jutzi, J. Organomet. Chem. 243 (1983) 119.
[19] G. Tian, B. Wang, S. Xu, X. Zhou, Transition Met. Chem.
25 (2000) 568.
[20] R.D. Rogers, M.M. Benning, L.K. Kurihara, K.J.
Moriarty, M.D. Rausch, J. Organomet. Chem. 293 (1985)
(51).
[21] N. Piccolrovazzi, P. Pino, G. Consiglio, A. Sironi, M. Moret,
Organometallics 9 (1990) 3098.
[22] I.-M. Lee, W.J. Gauthier, J.M. Ball, B. Iyengar, S. Collins,
Organometallics 11 (1992) 2115.