Steric and electronic effects of the R in IndTiCl2(OR) catalysts on the syndiospecific polymerization of styrene

Article abstract of DOI:10.1016/S1381-1169(01)00082-6

Four alkoxyl ligand substituted indenyl titanium dichloride complexes, IndTiCl₂(OR) (R = Me (2), Et (3), ⁱPr (4), cyclohexyl (5)) were prepared, and evaluated as catalysts for the syndiospecific polymerization of styrene when activated with methylaluminoxane (MAO). Alkoxyl ligand substituted complexes showed higher catalytic activities than IndTiCl₃ (1) except for complex 5. When R = Et, the catalyst 3 showed the highest activity. A study of the steric and electronic effects of alkoxyl ligand revealed that the more electron-donating and less steric bulky R group was more suitable for the improvement of the catalytic activity. When the polymerization was carried in solution at high molar ratio of Al/Ti = 4000, the s-PS% of obtained polymer were in the range of 99.0-99.6%. The highest melting point of 276.9°C was obtained by using 2 as catalyst. The influence of polymerization temperature was also investigated. The maximum polymerization activities were found at 50°C for all of the above complexes, but the percentages of s-PS were insensitive to the polymerization temperature.

Full text of DOI:10.1016/S1381-1169(01)00082-6

Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
Steric and electronic effects of the R in IndTiCl (OR) catalysts on
2
the syndiospecific polymerization of styrene
∗
Haiyan Ma, Bin Chen, Jiling Huang, Yanlong Qian
The Laboratory of Organometallic Chemistry, East China University of
Science and Technology, Shanghai 200237, PR China
Received 18 August 2000; accepted 22 January 2001
Abstract
i
Four alkoxyl ligand substituted indenyl titanium dichloride complexes, IndTiCl2(OR) (R = Me (2), Et (3), Pr (4), cy-
clohexyl (5)) were prepared, and evaluated as catalysts for the syndiospecific polymerization of styrene when activated with
methylaluminoxane (MAO). Alkoxyl ligand substituted complexes showed higher catalytic activities than IndTiCl3 (1) except
for complex 5. When R = Et, the catalyst 3 showed the highest activity. A study of the steric and electronic effects of alkoxyl
ligand revealed that the more electron-donating and less steric bulky R group was more suitable for the improvement of the
catalytic activity. When the polymerization was carried in solution at high molar ratio of Al/Ti = 4000, the s-PS% of obtained
◦
polymer were in the range of 99.0–99.6%. The highest melting point of 276.9 C was obtained by using 2 as catalyst. The
◦
influence of polymerization temperature was also investigated. The maximum polymerization activities were found at 50 C
for all of the above complexes, but the percentages of s-PS were insensitive to the polymerization temperature. © 2001 Elsevier
Science B.V. All rights reserved.
Keywords: Syndiotactic polystyrene; Titanocene; Alkoxyl ligand; Steric and electronic effects
1
. Introduction
havior [7–12]. It was found that the electron-donating
ability of the ␲-donor ligands (such as cyclopentadi-
enyl, indenyl, etc.), steric effects and chirality of the
ligands attached to the group 4 metal centers strongly
influenced the polymerization. The effects of the sub-
stituents attached to the cyclopentadienyl or indenyl
ligand of (␩ -Cp)Ti(O Pr)3 and (␩ -Ind)TiCl3 on the
styrene polymerization have been discussed [4–16].
But the effect of the ␴-bonded ligands has not been
reported properly.
Ishihara and co-workers’ work [1,2] led to a fur-
ther search for the new types of s-PS catalysts.
In 1993, Ready et al. reported the first s-PS cata-
lyst containing indenyl ligand and found that the
5
5
i
5
(␩ -indenyl)TiCl3/MAO system catalyzed the syn-
diospecific polymerization of styrene over a wide
range of polymerization temperature more effec-
tively than CpTiCl3/MAO system [3–6]. More ef-
forts were devoted to the syntheses of new kinds of
half-sandwich titanocenes and the elucidation of the
relationship of precursor structure and its catalytic be-
Our previous work proved that one alkoxyl
group substituted complexes of general formula
CpTiCl2(OR) were more active than CpTiCl3 [17–20].
i
When R = Pr and cyclohexyl, the catalytic activities
7
∗
were as high as 6.33–6.58 × 10 gPS/(molTi molS h)
Corresponding author. Fax: +86-21-64702573.
E-mail address: qianling@online.sh.cn (Y. Qian).
and were three times as that of CpTiCl3 [19]. Were
1381-1169/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S1381-1169(01)00082-6

68
H. Ma et al. / Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
there similar influences on the catalytic activity when
a chloride atom was substituted by an alkoxyl group
in IndTiCl3?
7.55 (m, 2H), 7.19 (d, 2H, J = 12 Hz), 7.16 (t, 1H,
J = 12 Hz).
In this work, we prepared four single-alkoxyl-ligand
substituted indenyl titanium dichloride complexes of
general formula IndTiCl2(OR) (R = Me (2), Et (3),
2.3. Preparation of IndTiCl2(OMe) (2)
The complex was synthesized according to a mod-
ified literature method [21]. A solution of n-BuLi
(3.75 mmol) in 10 ml n-hexane was treated with dry
methanol (0.1200 g, 3.75 mmol) in 1.7 ml n-hexane
and 1 ml THF at room temperature. After the end
i
Pr (4), cyclohexyl (5)), and compared their catalytic
behavior with IndTiCl3 in the syndiospecific polymer-
ization of styrene.
◦
of gas evolution, the mixture was cooled to −40 C
2
. Experimental
and treated with a solution of IndTiCl3 (1.010 g,
3.75 mmol) in 25 ml CH2Cl2. The reaction mixture
2
.1. General procedures
was slowly warmed to ambient temperature, and
stirred overnight. Then it was filtered and concen-
trated. The obtained solid was recrystallized with
CH2Cl2 and n-hexane to afford red crystals in 63.6%.
H NMR (δ, ppm): 7.80 (m, 2H), 7.45 (m, 2H), 6.87
(m, 2H), 6.82 (m, 1H), 4.37 (s, 3H).
All operations were carried out under an argon
atmosphere using the standard Schlenk techniques.
Tetrahydrofuran, toluene, hexane were distilled from
sodium/benzophenone ketyl under argon prior to use.
Methylene chloride was distilled under argon from
phosphoric anhydride. Methanol and ethanol were
refluxed with sodium under argon then were distilled.
Isopropanol, cyclohexanol were refluxed with CaH2
under argon, then were distilled under reduced pres-
sure. Methylaluminoxane (MAO) was produced by
Witco GmbH. Styrene was purified by distillation
1
2.4. Preparation of IndTiCl2(OEt) (3)
A solution of n-BuLi (4.34 mmol) in 14 ml n-hexane
was treated with a solution of dry ethanol (0.200 g,
4.34 mmol) in 2.5 ml n-hexane at room temperature.
After the end of gas evolution, the mixture was cooled
◦
◦
under reduced pressure twice, and stored at −20 C in
to −50 C and treated with a solution of IndTiCl3
darkness prior to use.
(1.17 g, 4.34 mmol) in 25 ml CH2Cl2. The reaction
mixture was slowly warmed to ambient temperature,
and stirred overnight. After filtration, the solvent
was removed under reduced pressure to give a red
solid. The solid was washed with n-hexane twice
and dried under vacuum. Recrystallization of the
solid with CH2Cl2/n-hexane afforded red crystals in
1H NMR spectra were recorded on a Var-
ian GERMINI-300 spectrometer. IR spectra were
recorded on a Nicolet MAGNA-IR 500 spectrome-
ter. Mass spectra were obtained at 70 eV using a HP
5
989A mass spectrometer. Elemental analyses were
performed on an EA-1106 spectrometer. X-ray struc-
ture was determined by a Rigaku AFC7R diffractome-
ter with graphite monochromatic Mo K␣ radiation
◦
1
58%, mp 86–88 C. H NMR (δ, ppm): 7.79 (dd, 2H,
J = 6.3 Hz, J = 3.0 Hz), 7.45 (dd, 2H, J = 6.3 Hz,
J = 3.0 Hz), 6.84 (d, 2H, J = 3.4 Hz), 6.80 (t, 1H,
J = 3.4 Hz), 4.60 (q, 2H, J = 5.3 Hz), 1.31 (t, 3H,
(λ = 0.71073 Å) and a 12 W rotating anode generator.
−
1
2
.2. Preparation of IndTiCl3 (1)
J = 5.3 Hz). IR (KBr, cm ): 3300s 1620m, 1460w,
1
390w, 1050w, 880s, 825s. MS (m/e): 277 (5.14,
M−H), 243 (4.51, M–Cl), 198 (5.19, M–OEt–Cl),
15 (100, indenyl). Anal. Calcd. for C11H12Cl2OTi:
IndTiCl3 was synthesized according to the litera-
1
ture method [3]. Indene was treated with n-BuLi to
give indene lithium. The indene lithium reacted with
Me3SiCl to obtain 1-SiMe3Ind in 73%. 1-SiMe3Ind
was added dropwise to the solution of TiCl4 in
CH2Cl2, then the solvent was removed to give a dark
red solid. After recrystallization, dark red crystals
C, 47.36%; H, 4.34%. Found: C, 47.21%; H, 4.29%.
i
2.5. Preparation of IndTiCl2(O Pr) (4)
The same procedure as that described for IndTiCl2
(OEt) was used. Red needle crystals were obtained
1
were separated. H NMR (δ, ppm): 7.81 (m, 2H),

H. Ma et al. / Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
69
◦
1
in 76%, mp 78–80 C. H NMR (δ, ppm): 7.80 (dd,
2
6
thermograms were recorded with a DSC 2910 Modu-
lated DSC Universal V1.10B TA Instruments.
H, J = 6.3 Hz, J = 3.1 Hz), 7.45 (dd, 2H, J =
.3 Hz, J = 3.1 Hz), 6.82 (d, 2H, J = 3.4 Hz), 6.78
(
t, 1H, J = 3.4 Hz), 4.92 (m, 1H, J = 6.1 Hz),
−
1
1
1
1
2
.38 (d, 6H, J = 6.1 Hz). IR (KBr, cm ): 3330s,
3. Results and discussions
613m, 1458w, 1392w, 1360w, 1315w, 1200w, 1168w,
+
114w, 1050w, 884s, 768s. MS (m/e): 292 (1.98, M ),
57 (3.00, M–Cl), 250 (5.38, M–CH2=CH–CH3), 233
6.51, M–O Pr), 198 (2.88, M–O Pr–Cl), 115 (100, in-
denyl). Anal. Calcd. for C12H14Cl2OTi: C, 49.19%;
H, 4.82%. Found: C, 48.81%; H, 4.76%.
When the indenyl trichloro complex IndTiCl3 was
treated with the lithium salt of the corresponding al-
cohol, catalysts 2–5 were obtained in moderate yield
as dark red to orange crystals.
i
i
(
Crystallization of catalyst 5 from CH2Cl2/n-hexane
◦
at −20 C afforded crystals suitable for X-ray analysis.
ꢀ
ꢁ
2
.6. Preparation of IndTiCl2
(5)
The molecular structure, selected bond distances and
angles for 5 were given in Fig. 1. It was composed by
two separated molecules with different intramolecular
dimension slightly.
Complex 5 was prepared according the method
described for IndTiCl2(OEt). Orange needle crystals
were obtained in 61.3%, mp 88–90 C. H NMR
◦
1
The crystal structure showed clearly a piano-stool
configuration with the indenyl penta-hapto bonded to
the tetravalent titanium center with a ring centriod
bond distance of 2.059–2.065 Å, which was little
longer than the one in IndTiCl3 [3]. The alkoxyl
group was coordinated as a pronounced ␲-donor,
as evidenced by the short titanium oxygen length
of 1.715(2)–1.718(2) Å and the obtuse angle at the
oxygen of 159.0(3). The same interaction of oxygen
to tianium was also found in the similar complex
(
7
δ, ppm): 7.78 (dd, 2H, J = 6.4 Hz, J = 3.0 Hz),
.41 (dd, 2H, J = 6.4 Hz, J = 3.0 Hz), 6.82 (d,
H, J = 3.4 Hz), 6.79 (t, 1H, J = 3.4 Hz), 4.70
2
(
−
1
m, 1H), 2.3–1.0 (m, 10H). IR (KBr, cm ): 3300s,
2
1
930m, 2865m, 1615m, 1460w, 1398w, 1370w,
055m, 1020w, 885s, 770s. MS (m/e): 332 (0.60,
M ), 233 1.92, M–
ꢀ
ꢁ
+
, 216 (1.72, M–indenyl),
ꢀ
ꢁ
1
98 2.74, M–
–Cl , 115 (100, indenyl), 99
ꢀ
ꢁ
1
.07,
. Anal. Calcd. for C H18Cl2OTi: C,
4.09%; H, 5.45%. Found: C, 53.93%; H, 5.35%.
15
2
[21]. Thus, we thought this kind of interaction in
5
alkoxyl substituted complexes might have significant
influence on the catalytic behavior.
2
.7. Polymerization and polymer characterization
Table 1 summarized the influence of alkoxyl lig-
ands on the polymerization of styrene in solution. Gen-
erally, the catalytic activity and the s-PS% increased
with the increasing of Al/Ti from 2000 to 4000, which
was in agreement with those reported by Ishihara [2].
The s-PS% at high molar ratio of Al/Ti = 4000 were
very high as more than 99%.
As shown in Table 1, the substitution of alkoxyl
ligands did have some influence on the catalytic ac-
tivities of the complexes. Alkoxyl ligand substituted
complexes showed higher catalytic activities than
IndTiCl3 except for complex 5. Complex 3 showed the
highest activity among the five complexes. We thought
the substitution of alkoxyl ligands introduced some
electronic effects compared to IndTiCl3. The strong
␲-donation of oxygen to titanium center decreased
both the bonding of titanium indenyl and titanium
chlorine, which could be deduced from the longer
lengths in complex 5 than in IndTiCl3 [3]. The weak-
A small ampoule bottle that was baked under
vacuum and filled with argon for several times was
used for polymerization, 2 ml (runs in solution) or
1
toluene or without toluene, MAO (10 wt.% in toluene)
and various proportions of 0.05 mol/l Ti compound
in toluene were injected into the bottle in this order
under an argon atmosphere. The total volume was
1 ml (runs in bulk) of styrene, various proportions of
1
2 ml. The bottle was put into an oil bath for a certain
time. The polymerization mixture was quenched with
1
0% HCl in ethanol, filtered, washed and dried in
◦
vacuum oven at 80 C for 24 h to a constant weight.
The polymer was then extracted with 2-butanone
for 2 h to remove any atactic polymer. The s-PS%
was determined as the amount of polymer insoluble
in 2-butanone. Melting points of the obtained syn-
diotactic polystyrene were determined by DSC. The

70
H. Ma et al. / Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
◦
Fig. 1. X-ray structure and selected bond distances (Å) and bond angles ( ) for 5: Ti(1)–O(1) 1.718(2), Ti(1)–Cl(1) 2.2526(10), Ti(1)–Cl(2)
2
2
.2719(10), Ti(1)–C(1) 2.469(3), Ti(1)–C(2) 2.333(3), Ti(1)–C(3) 2.306(3), Ti(1)–C(4) 2.320(4), Ti(1)–C(5) 2.469(3), Ti(1)–C1–C5
.059, Ti(2)–O(2) 1.715(2), Ti(2)–Cl(3) 2.2657(12), Ti(2)–Cl(4) 2.2575(11), Ti(2)–C(16)–C(20) 2.065; Cl(1)–Ti(1)–Cl(2) 103.97(4),
O(1)–Ti(1)–Cl(1) 103.30(9), O(1)–Ti(1)–C(2) 107.10(12), O(1)–Ti(1)–C(3) 88.35(12), O(1)–Ti(1)–C(4) 104.45(12), O(1)–C(10)–C(11)
12.9(3), C(15)–C(10)–O(1) 115.2(3), C(10)–O(1)–Ti(1) 159.0(3), Cl(3)–Ti(2)–Cl(4) 102.85(4).
1
ening of Ti–Cl bonding might make easier the methy-
lation and ligands abstraction that were thought to lead
to the formation of the active species [22]. From this
point of view, the introducing of the alkoxyl ligand
might increase the formation rate of the active species
and also the concentration of it, thus, might lead to
the increase of the catalytic activity. Since the com-
plex 5 still showed lower activity than IndTiCl3, we
thought the substitution of alkoxyl ligand also intro-
duced some steric effects. The alkoxyl ligand that was
Table 1
Syndiospecific polymerization of styrene in solution catalyzed by 1–5 and MAOa
Ab (106)
s-PSc (%)
Tm ( C)
◦
Run no.
Catalyst
[Ti]
mM)
Al/Ti
(10 )
Time
(h)
Yields
PS (g)
Conver-
sion (%)
3
(
1
2
3
4
5
6
7
8
IndTiCl3 (1)
0.42
0.21
0.42
0.21
0.42
0.21
0.42
0.21
2.0
4.0
2.0
4.0
2.0
4.0
2.0
4.0
1
1
1
1
1
1
1
1
0.1450
0.1500
0.1955
0.1616
0.2970
0.2109
0.1823
0.1736
8.0
8.3
10.8
8.9
16.4
11.6
10.1
9.6
1.67
3.45
2.25
3.72
3.41
4.85
2.10
3.99
95.9
98.9
95.8
99.3
97.7
99.6
98.2
99.1
–
275.0
–
276.9
–
274.7
–
273.3
IndTiCl2(OMe) (2)
IndTiCl2(OEt) (3)
i
IndTiCl2(O Pr) (4)
ꢀ
ꢁ
9
IndTiCl2
(5)
0.42
0.21
2.0
4.0
1
1
0.1221
0.1250
6.7
6.9
1.40
2.87
97.2
99.0
–
1
0
273.9
a
b
c
◦
Polymerization conditions: 2 ml styrene; [Al] = 0.83 M; [S] = 1.45 M; Tp = 50 C.
gPS/(molTi molS h).
g of 2-butanone insoluble polymer/g of bulk polymer.

H. Ma et al. / Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
71
Table 2
Syndiospecific polymerization of styrene in bulk catalyzed by 1–5 and MAOa
Run no. Catalyst
[Ti] (mM) Al/Ti Temperature ( C) Time (h) Yields PS (g) Conversion (%) Ab (106) s-PSc (%)
◦
1
1
1
1
1
1
1
1
1
2
3
4
5
6
7
8
IndTiCl3 (1)
0.42
0.21
0.42
0.21
0.42
0.21
0.42
0.21
300 50
300 50
300 50
300 50
300 50
300 50
300 50
300 50
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
1.0117
1.0996
1.3244
1.5709
1.5117
1.6676
0.9711
0.6765
10.2
11.0
13.3
15.8
15.2
16.7
9.8
4.23
9.19
5.54
13.1
6.32
13.9
83.7
86.4
87.8
90.1
88.4
90.1
85.2
81.3
IndTiCl2(OMe) (2)
IndTiCl2(OEt) (3)
i
IndTiCl2(O Pr) (4)
4.06
5.66
6.8
ꢀ
ꢁ
19
0
IndTiCl2
(5) 0.42
300 50
300 50
0.5
0.5
0.7794
0.2772
7.8
2.3
3.26
2.32
79.2
61.5
2
0.21
a
b
c
Polymerization conditions: 11 ml styrene; [S] = 7.98 M.
gPS/(molTi molS h).
g of 2-butanone insoluble polymer/g of bulk polymer.
considered to have been stripped during the formation
of the active species might still surround the active
species. When R was cyclohexyl, a bulky group, the
coordination and insertion of styrene to the titanium
center might be hindered due to the surrounding of
the bulk alkoxyl group, reflected in the decrease of the
activity.
Certainly, the substitutions of the other three alkoxyl
ligands also introduced some steric effects. Compared
to the electron-donating ability, the steric effects were
Table 3
The effect of polymerization temperaturea
Catalyst
[Ti] (mM) Al/Ti Temperature ( C) Time (h) Yields PS (g) Conversion (%) Ab (106) s-PSc (%)
◦
IndTiCl3 (1)
0.42
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
300
25
50
70
90
25
50
70
90
25
50
70
90
25
50
70
90
0.5
0.5
1
0.5242
1.0117
1.4586
1.5403
0.9766
1.3244
1.6544
1.8724
0.9050
1.5117
1.7451
2.2418
0.6550
0.9711
0.9550
1.5126
5.3
10.2
14.6
15.5
9.8
13.3
16.6
18.8
9.1
15.2
17.5
22.5
6.6
2.19
4.23
3.05
1.61
4.08
5.54
3.46
1.95
3.78
6.32
3.65
2.34
2.74
4.06
2.00
1.58
65.1
83.7
86.6
80.0
85.2
87.8
90.3
87.7
83.3
88.4
91.2
90.7
77.7
85.2
80.3
81.9
0
0
0
.42
.42
.42
2
IndTiCl2(OMe) (2)
IndTiCl2(OEt) (3)
0.42
0.5
0.5
1
0
0
0
.42
.42
.42
2
0.42
0.5
0.5
1
0
0
0
.42
.42
.42
2
i
IndTiCl2(O Pr) (4)
0.42
0.5
0.5
1
0
0
0
.42
.42
.42
9.8
9.6
15.2
2
ꢀ
ꢁ
IndTiCl2
(5) 0.42
300
25
0.5
0.5462
5.5
2.28
70.5
0
0
0
.42
.42
.42
300
300
300
50
70
90
0.5
1
2
0.7794
0.9459
1.3250
7.8
9.5
13.3
3.26
1.98
1.38
79.2
79.2
77.1
a
Polymerization conditions: 11 ml styrene; [Al]=0.125M; [S]= 7.98 M.
gPS/(molTi.molS.h).
g of 2-butanone insoluble polymer/g of bulk polymer.
b
c

72
H. Ma et al. / Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
rather weak, thus, complexs 2 and 3 showed higher cat-
alytic activities than IndTiCl3, and complex 3 showed
highest activity. When R was isopropyl, there existed
the steric and electronic effects either of them would
be the dominant factor due to the different polymeriza-
tion conditions. Under the given conditions in Table 1,
the electronic effect became the dominant factor, thus,
the activity increased.
more electron-donating and less steric bulky R group
was more suitable for the improvement of the cat-
alytic activity. When the polymerization was carried
in solution at high molar ratio of Al/Ti = 2000–4000,
the s-PS% of obtained polymer were in the range of
◦
95.8–99.6%. The highest melting point of 276.9 C
was obtained by using 2 as catalyst. The maximum
◦
polymerization activities were found at 50 C for all of
When we carried the polymerization in bulk with a
low molar ratio of Al/Ti = 300 (Table 2), the steric
hindrance became a further dominant factor due to the
high monomer concentration, as a result, complexes 4
and 5 showed lower catalytic activities than IndTiCl3.
Complex 3 still showed the highest activity (run 15,
the complexes. The percentages of s-PS obtained by
the alkoxyl ligand substituted complexes were insen-
sitive to the polymerization temperature.
Acknowledgements
1
6).
The percentages of syndiotactic polystyrene were
We gratefully acknowledge the financial support
from the Special Funds for Major State Basic Research
Projects (G1999064801), National Natural Science
Foundation of China (NNSFC) and Sino Petroleum
Company (29734145), and NNSFC (29871010).
not as high as those in Table 1. High styrene concen-
tration increased both the syndiospecific polymeriza-
tion rate and the aspecific polymerization rate [23,24].
The catalytic activities were higher than those in
Table 1 (Al/Ti = 2000–4000). As shown in Table 2,
the activities of complexes 1, 2 and 3 increased twice
with the decrease of [Ti] from 0.42 to 0.21 mmol/l at
a constant Al/Ti (run 11 with 12 and so on). It was
suggested that the polymerization rates were almost
same for [Ti] = 0.21–0.42 mmol/l due to the very
high styrene concentration. As to complexes 4 and 5,
because of the steric hindrance, the activities did not
increase so much as those of complexes 1, 2 and 3
References
[1] N. Ishihara, T. Seimiya, M. Kuramoto, M. Uoi,
Macromolecules 19 (1986) 2464–2465.
[
[
[
[
[
[
2] N. Ishihara, M. Kuramoto, M. Uoi, Macromolecules 21 (1988)
356–3360.
3] T.E. Ready, R.O. Day, J.C.W. Chien, M.D. Rausch,
Macromolecules 26 (1993) 5822–5823.
4] P. Foster, T.E. Ready, J.C.W. Chien, M.D. Rausch, Polym.
Prep. 37 (1) (1996) 258–259.
5] P. Foster, J.C.W. Chien, M.D. Rausch, Organometallics 15
3
(run 17, 18 and so on).
We also investigated the influence of temperature on
the syndiospecific polymerization of styrene in bulk.
From the results in Table 3, we found the maxi-
(
1996) 2404–2409.
6] T.E. Ready, J.C.W. Chien, M.D. Rausch, J. Organomet. Chem.
19 (1996) 21–28.
◦
mum polymerization activities were obtained at 50 C.
5
◦
Higher temperature (90 C) led to the decrease of the
7] G. Xu, E. Ruckenstein, J. Polym. Sci. A: Polym. Chem. 37
(1999) 2481–2488.
activities. The percentages of s-PS obtained by alkoxyl
ligand substituted complexes were affected slightly by
the polymerization temperature. Furthermore, unlike
the cyclopentadienyl analogues [19,20], the indenyl
complexes 2–5 exhibited high syndiospecificities even
[8] N. Schneider, M.-H. Prosenc, H.-H. Brintzinger, J.
Organomet. Chem. 545/546 (1997) 291–295.
[9] M.S. Blais, J.C.W. Chien, M.D. Rausch, Organometallics 17
(
1998) 3775–3783.
[
[
[
[
[
10] G. Tian, S. Xu, Y. Zhang, B. Wang, X. Zhou, J. Organomet.
◦
at low polymerization temperature of 25 C.
Chem. 558 (1998) 231–233.
11] R. Duchateau, H.C.L. Abbenhuis, R.A. Santen, S.K.-H.
Thiele, M.F.H. Tol, Organometallics 17 (1998) 5222–5224.
12] J.C. Flores, T.E. Ready, J.C.W. Chien, M.D. Rausch, J.
Organomet. Chem. 562 (1998) 11–15.
13] W. Kaminsky, S. Lenk, V. Schoz, H.W. Roesky, A. Herzog,
Macromolecules 30 (1997) 7647–7650.
4
. Conclusions
The results of this study indicated that alkoxyl lig-
and substituted complexes showed higher catalytic ac-
tivities than IndTiCl3 (1) except for complex 5, and the
14] W. Kaminsky, Macromol. Chem. Phys. 197 (1996) 3907–
3945.

H. Ma et al. / Journal of Molecular Catalysis A: Chemical 170 (2001) 67–73
73
[
15] Q. Wu, Z. Ye, S. Lin, Macromol. Chem. Phys. 198 (1997)
823–1828.
16] Y. Kim, B.H. Koo, Y. Do, J. Organomet. Chem. 527 (1997)
55–161.
[20] H. Ma, Y. Zhang, B. Chen, J. Huang, Y. Qian, J. Polym. Sci.
A: Polym. Chem., 2000, unpublished results.
[21] J. Okuda, P. König, I.L. Rushkin, H.-C. Kang, W. Massa, J.
Organomet. Chem. 501 (1995) 37–39.
1
[
1
[
[
17] J. Liu, J. Huang, Y. Qian, Polym. Bull. 37 (1996) 719–721.
18] J. Liu, J. Huang, Y. Qian, F. Wang, A.S.C. Chan, Polym. J.
[22] R. Pó, N. Cardi, Prog. Polym. Sci. 21 (1996) 47–88.
[23] J.C.W. Chien, Z. Salajka, J. Polym. Sci. Polym. Chem. 29
(1991) 1243–1251.
[24] J.C.W. Chien, Z. Salajka, J. Polym. Sci. Polym. Chem. 29
(1991) 1253–1263.
2
9 (2) (1997) 182–183.
19] J. Liu, H. Ma, J. Huang, Y. Qian, Eur. Polym. J. 36 (2000)
055–5058.
[
5