Effect of ligand in ethylene/styrene copolymerization by [Me2Si(C5Me4)(NR)]TiCl2 (R = tert-Bu, cyclohexyl) and (1,3-Me2 C5H3) TiCl2(O-2,6- iPr2C<

Article abstract of DOI:10.1016/S1381-1169(02)00223-6

Copolymerization of ethylene with styrene using linked cyclopentadienyl-amide titanium(IV) complexes, [Me₂Si(C₅Me₄) (R)]TiCl₂ [R = tert-Bu (1), cyclohexyl (2)], and non-bridged (1,3-Me₂ C₅H

Full text of DOI:10.1016/S1381-1169(02)00223-6

Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
Effect of ligand in ethylene/styrene copolymerization by
[Me2Si(C5Me4)(NR)]TiCl2 (R = tert-Bu, cyclohexyl) and
(1,3-Me2C5H3)TiCl2(O-2,6-iPr2C6H3)-MAO catalyst system
Kotohiro Nomura∗, Hiroshi Okumura, Takashi Komatsu,
Naofumi Naga, Yukio Imanishi
Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
Received 12 September 2001; accepted 20 February 2002
Abstract
Copolymerization of ethylene with styrene using linked cyclopentadienyl-amide titanium(IV) complexes, [Me2Si(C5Me4)
(R)]TiCl2 [R = tert-Bu (1), cyclohexyl (2)], and non-bridged (1,3-Me2C5H3)TiCl2(O-2,6-iPr2C6H3) (3)-MAO catalysts have
been explored. Although the catalytic activity by 2 was lower than 1, 2 showed more efficient styrene incorporation than 1
under the same conditions. Moreover, the resultant copolymer prepared by 2 possessed completely different microstructure
from those by 1, indicating that the nature of amide ligand affects both styrene incorporation and monomer sequence.
© 2002 Elsevier Science B.V. All rights reserved.
Keywords: Titanium; Ethylene/styrene copolymerization; Constrained geometry catalyst
1. Introduction
merization catalysts that would be different from both
ordinary metallocene type and so-called ‘constrained
geometry’ (hybrid ‘half-metallocene’) type catalysts
Olefin polymerization by homogeneous transition
metal catalysis attracts particular attention in the field
of organometallic chemistry, catalysis, and of poly-
mer chemistry. Many efforts have thus been reported
concerning this topic especially using early transi-
tion metal complexes [1]. We especially focused to
non-bridged half-metallocene type group 4B transi-
tion metal complexes of the type, CpꢀM(L)X2 (Cpꢀ =
cyclopentadienyl group; M = Ti, Zr; L = anionic
ligand such as OAr; X = halogen, alkyl, etc.) [2–10],
because we expected that this type of complexes
would exhibit unique characteristics as olefin poly-
t
[1d,1e,11–16] like [Me2Si(C5Me4)(N Bu)]TiCl2 (1).
Another reason why we focused to this type is that
the synthesis is not so complicated (shorter synthetic
steps with relatively high yields), and that the mod-
ification of ligand moiety, L, sterically and/or elec-
tronically should be thus easier especially than the
ordinary bridged-type complexes [2–17].
We have recently reported that non-bridged (cyclo-
pentadienyl)(aryloxy)titanium(IV) complexes-MAO
catalyst system exhibited unique characteristics not
only for ethylene homopolymerization, ethylene/␣-
olefin copolymerization [2], but also for styrene ho-
mopolymerization, ethylene/styrene copolymerization
[17]. The activity could be tuned only by replacing
substituent on Cpꢀ group (1,3-Me2C5H3)TiCl2(O-2,6-
∗
Corresponding author. Tel.: +81-743-72-6041;
fax: +81-743-72-6049.
E-mail address: nomurak@ms.aist-nara.ac.jp (K. Nomura).
1381-1169/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S1381-1169(02)00223-6

226
K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
iPr2C6H3) (3) was thus found to be effective for
styrene polymerization, whereas Cp∗TiCl2(O-2,6-iPr2
C6H3) was quite effective for both ethylene/␣-olefin
copolymerization and ethylene homopolymerization.
It was also revealed that 3 would be a useful cat-
alyst for preparing ethylene/styrene copolymer with
high styrene contents with uniform comonomer dis-
tribution (we confirmed the comonomer distribution
(even with narrow molecular weight distribution by
GPC) by cross-fractionation chromatography, and
GPC-IR, e.g. see [18]), and that the microstruc-
ture for the resultant copolymer was different from
that prepared by 1 [17]. We believe that this is one
of the unique characteristics for this kind of cata-
lysts. However, we do not have clear reason why
polystyrene structure possessed in the copolymer was
atactic, although styrene homopolymerization by 3
afforded highly syndiotactic polystyrene exclusively.
This should also be an important question to consider
the catalytically-active species for both styrene poly-
merization and ethylene/styrene copolymerization
especially using half-titanocene catalysts (e.g. syn-
diospecific styrene polymerization by half-titanocene
complex catalysts, see [19]; for review, see [20]; ethy-
lene/styrene copolymerization by CpꢀTiX3 (X = Cl,
benzyl, OPh, etc., see [21]; and ethylene/styrene
copolymerization by bridged Cp-amide titanium cat-
alysts, see [22]). In addition, precise control of both
monomer sequence and stereospecificity by ligand
modification in ethylene/styrene copolymerization
has been a challenging subject, because electronic
and/or steric nature of ligand should directly affect
not only the insertion mode (2,1- or 1,2-insertion),
but also the comonomer incorporation. One example
for preparing alternating poly(ethylene-co-styrene)
with well defined isotactic polystyrene structure by
Scheme 1.
ported that the indenyl and the benzylamine analogues
that would have more open structures promoted the
highest styrene incorporation. Small percentage of
head-to-tail styrene coupling (T␤␤ and S␣␣, Scheme 1)
in addition to the tail-to-tail coupling of styrene unit
or head-to-head bridged by an intervening ethylene
unit (S␣␤) was also observed by the benzyl analogue
[22d]. We also showed our preliminary results con-
cerning the effect in cyclopentadienyl fragment in the
previous communication [17].
Under these circumstances mentioned above, we
had decided to explore the effect of ligand for ethy-
lene/styrene copolymerization as well as for ethy-
lene and/or styrene homopolymerization with various
half-metallocene type titanium complexes containing
Cpꢀ-aryloxy and/or Cpꢀ-amide ligand. In this paper,
we thus wish to show one interesting example con-
cerning the effect of amide ligand in ethylene/styrene
copolymerization.
t
using [Me2Si(Flu)(N Bu)]TiMe+[B(C6F5)4]− un-
der the specified conditions (e.g. molar ratio of
styrene/ethylene: ca. 40 at 50 ◦C) has been known, but
this complex showed less styrene incorporation than 1,
and the percentage of copolymer based on total poly-
mer formed strongly depended upon polymerization
temperature [22g]. Okuda and coworkers also showed
the ligand effect in ethylene/styrene copolymerization
with several linked Cpꢀ-amide titanium and zirco-
nium complexes (1, [Me2Si(C5Me4)(NCH2Ph)]TiCl2,
2. Results and discussion
We chose cyclohexyl analogue, [Me2Si(C5Me4)
(NCy)]TiCl2 (2), not only because this complex pos-
sesses both bulky and electron-donating substituents
like tert-butyl group in amide fragment which
would stabilize the catalytically-active species under
t
t
[Me2Si(Ind)(N Bu)]TiCl2, [Me2Si(Flu)(N Bu)]ZrCl2,
t
[Me2Si(3-Me3Si-Ind)(N Bu)]TiCl2, [22d]), and re-

K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
227
polymerization conditions, but also because the
2.1. Copolymerization of ethylene with styrene by
1–3-MAO catalyst systems
styrene incorporation may be improved by reducing
the steric bulk around the metal center by the replace-
ment, as presented by [Me2Si(C5Me4)(NCH2Ph)]TiCl2
[22d]. In addition, we have recently found that the
replacement of methyl group into cyclohexyl group in
Cp∗TiCl2(NMeR) (R = Me, Cy) drastically improved
the catalytic activity for ethylene polymerization in
the presence of methylaluminoxane (MAO) [23].
(1,3-Me2C5H3)TiCl2(O-2,6-iPr2C6H3) (3) was also
chosen as the reference (see Chart 1).
Copolymerizations of ethylene with styrene by
1–3 were performed in toluene at 25 ◦C by using
100 ml scale autoclave in the presence of MAO.
MAO white solid prepared by removing toluene and
AlMe3 from commercially available MAO (PMAO-S,
Tosoh Finechem Co.) was used as the cocatalyst,
because the use of this MAO was effective to obtain
poly(ethylene-co-1-butene) both with high molecu-
lar weight and narrow molecular weight distribution
when 1 was used as the catalyst precursor [2b]. The
polymerizations were terminated at the initial stage
in order to control the monomer conversion less than
10% (to minimize the effect of monomer concen-
tration during the copolymerization). The resultant
polymer was separated by boiling acetone, and then
by boiling tetrahydrofuran (THF). The results are
summarized in Table 1.
It was revealed that both 1 and 3 exhibited the
remarkable catalytic activities, and the resultant
Table 1
Ethylene/styrene copolymerization catalyzed by [Me2Si(C5Me4)(NR)]TiCl2-MAO systema
Run no. Catalyst Ethylene Styrene
Acetone soluble Activityc THF soluble fraction
Contentd of THF
Insoluble fraction
(atm)
(ml)
contentb
e
e
Contentd Mw
(wt.%)
Mw/Mn
Styrene
(×10−4
)
(mol%)f (wt.%)
1
2
3
4
5
6
7
8
9
10
11
12
13
1
1
2
2
2
2
2
2
2
2
3i
3i
3i
4
4
4
4
4
4
6
6
8
8
4
4
4
5
10
3
5
5
10
3
5
3
5
0.3
0.3
tr.
0.3
2.4
tr.
tr.
tr.
tr.
tr.
5110
5630
1370
1640
280h
1980
1140
1430
1030
1340
3670
4280
4140
1.5
99.6
99.8
99.6
97.6
99.8
99.4
99.7
99.7
99.5
97.1
98.2
98.2
–
18
–
–
98.1g
tr.
tr.
tr.
tr.
1.8
1.7
1.9
1.7
1.8
1.5
2.3
1.5
1.7
1.8
2.1
1.6
32.7
40.9
44.6
48.4
45.7
37.0
42.0
36.0
41.2
32.3
38.5
49.0
4.8
5.0
2.3
4.5
4.2
3.0
7.5
7.3
6.4
6.0
3.7
tr.
0.5
0.2
0.2
0.4
2.9
0.7
0.7
3
5
10
tr.
1.5
1.1
a Reaction conditions: catalyst 1.0 ␮mol (2 ␮mol/ml toluene), total volume of toluene and styrene = 30 ml, MAO white solid (Al/Ti =
2000, molar ratio), 25 ◦C, 10 min, 100 ml scale autoclave.
b Percentage of content in acetone soluble fraction based on polymer formed.
c Polymerization activity (kg polymer/mol Ti h), polymer yield in acetone insoluble fraction.
d Percentage of content based on whole polymer produced (in acetone insoluble fraction).
e GPC data in o-dichlorobenzene versus polystyrene standard.
f Styrene content (mol%) in copolymer by 1H NMR (C2D2Cl4).
g Poly(ethylene-co-styrene) was obtained as THE insoluble fraction (Mw = 2.52 × 105, Mw/Mn = 2.0, styrene 12.2 mol%), catalyst
17.0 ␮mol.
h Polymerization at 0 ◦C, catalyst 67 ␮mol.
i (1,3-Me2C5H3)TiCl2(O-2,6-iPr2C6H3) (3) was used in place of 2.

228
K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
polymers were poly(ethylene-co-styrene)s almost ex-
clusively (runs 1–2, 11–13). It is clear that 3 showed
more efficient styrene incorporation than 1 (run 1 ver-
sus run 12, and run 2 versus run 13). The Mw value
by 3 decreased with the increase in the styrene con-
tent (runs 11–13). Although 2 exhibited the lower ac-
tivity under the same conditions (runs 2, 6, and 13),
the activity seemed to be not so low as reported by
[Me2Si(C5Me5)(NCH2Ph)]TiCl2 (38 kg polymer/mol
Ti h), in which 100 times decrease in the activity com-
pared to 1 was observed under the same conditions
[22d]. The Mw/Mn values were narrow in all cases,
and Mw value by 1 was higher than those by 2 or 3.
It turned out that 2 exhibited more efficient styrene
incorporation than 1 or 3 under the same conditions,
and the efficiency by 2 should be the highest among a
series of linked Cpꢀ-amide titanium complexes (Fig. 1)
[22]. It seemed impossible to prepare the copolymer
with styrene contents higher than ca. 50 mol%, but
this is the same trend observed for this copolymeriza-
tion by 1. On the other hand, the styrene content in
poly(ethylene-co-styrene) increased upon the increase
in [styrene]/[ethylene] molar ratios, if 3 was used as
the catalyst (runs 11–13). These results thus indicate
that the nature of ligand directly affects the styrene
incorporation.
The activity by 2 was not strongly affected by the
ethylene pressure although the styrene content de-
creased at higher ethylene pressure (runs 3, 7, 9 or
runs 4, 8, 10, Table 1), and relatively higher activity
was observed under higher styrene concentrations
(runs 3–4, 6 or runs 7–8, runs 9–10). The styrene con-
tent of 36.0 mol% could be obtained by 2 at 8 atm of
ethylene with relatively low styrene molar ratio (run
9, [styrene]/[ethylene] = 0.87/0.97 mmol/ml) (e.g.
ethylene concentrations under the reaction conditions
were estimated by the equation quoted by Kissin
[24a]), whereas styrene content of 32.7 mol% by 1
was attained at ethylene 4 atm with relatively higher
styrene molar ratio (run 2, [styrene]/[ethylene] =
2.91/0.48 mmol/ml) (e.g. the ethylene solubilities in
the reaction mixture (1 atm) were used as those in
toluene reported in [24b]). Both electronic and steric
bulk of cyclohexyl substituent can be thus considered
for the notable increase in the styrene incorporation.
In addition, this complex was also found to be effi-
cient catalyst for preparing the copolymer exclusively
even at 0 ◦C (run 5), and this is also an interesting
contrast with the fact that the attempted copolymer-
t
ization using [Me2Si(Flu)(N Bu)]TiX2 gave only
polyethylene at 0 ◦C even under the molar ratio of
[styrene]/[ethylene] = 40 [22g].
2.2. Microstructure of poly(ethylene-co-styrene)s
prepared by 1–3
Fig. 2 shows 13C NMR spectrum (methylene and
methine region) of the copolymer (THF soluble frac-
tion) prepared by 1. Fig. 3 also shows the 13C NMR
spectrum of the copolymer prepared by 3. As reported
previously [17], the copolymer prepared by 3 (Fig. 3)
showed the resonances at δ = 40.7 (T␤␤, three styrene
unit connected to head-to-tail coupling, Scheme 1),
43.1–43.5 and 43.8–44.5 ppm (S␣␣ and T␤δ, two
styrene unit connected to head-to-tail coupling) in
addition to the resonances at δ = 34.3 and 35.1 ppm,
which are attributed to S␣␤ (tail-to-tail coupling of
styrene unit or head-to-head bridged by an interven-
ing ethylene unit, Scheme 1).1 This is an especially
1
Fig. 1. Plots of styrene content (mol%) in poly(ethylene-co-
styrene)s vs. [styrene]/[ethylene] (molar ratio) in feed for ethy-
lene/styrene copolymerization by 1–3-MAO catalyst systems
(Table 1). Catalyst: 1 (᭜), 2 (᭹), and 3 (ᮀ).
It seemed very difficult to calculate r-parameters from the triad
sequence distribution only from these NMR spectra, since the
signals for S , and S at δ = 36.8 and 37.0 ppm as well as those
␣␥
␣␦
for S , S and S at δ = 29.7 ppm are difficult to separate.
␥␥
␥␦
␦␦

K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
229
Fig. 2. 13C NMR spectrum (in CDCl3 at 60 ◦C) of poly(ethylene-co-styrene) (methylene and methine region, THF soluble fraction) prepared
by 1 (run 2, Table 1, styrene 32.7 mol%).
Fig. 3. 13C NMR spectrum (in CDCl3 at 60 ◦C) of poly(ethylene-co-styrene)s (methylene and methine region, THF soluble fraction)
prepared by 3 (run 13, Table 1, styrene 49.0 mol%).

230
K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
Fig. 4. 13C NMR spectra (in CDCl3 at 60 ◦C) of poly(ethylene-co-styrene)s (methylene and methine region, THF soluble fraction) prepared
by 2-MAO catalyst system: (a) run 7, styrene 37.0 mol%, (b) run 4, styrene 44.6 mol%.
interesting contrast with that prepared by 1 (Fig. 2),
and the preparation of poly(ethylene-co-styrene)s
with higher styrene contents than 50% can be thus
possible with the efficient manner by 3.
37.0 mol%). Three resonances attributed to Tδδ,
S␣␥ and S␤␤ carbons were observed in addition to
resonances attributed to S␣δ, S␤δ and S␥␥ carbons
(Scheme 2), but no resonances attributed to S␣␤
carbon were observed. Moreover, no resonances at-
tributed to S␣␣ and T␤δ carbon (two styrene unit
connected to head-to-tail coupling, Scheme 1), which
Fig. 4a shows 13C NMR spectrum (methylene
and methine region) of the copolymer (THF solu-
ble fraction) prepared by 2 (run 7, styrene content

K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
231
titanium catalysts [2e,2f] is that the difference
observed here concerning the microstructure between
1 and 2 may be due to the flexibility of the cat-
alytically active species. The steric bulk should be
reduced by replacing tert-butyl group (1) into cy-
clohexyl group (2) in [Me2Si(C5Me4)(NR)]TiCl2,
and this would be one probable reason for improved
styrene incorporation. Although this might be a prob-
able reason for explaining the improved styrene in-
corporation for 2 from 1, however, we do not have
a clear explanation why 2 incorporates styrene in an
alternating manner.
Scheme 2.
were observed for the copolymer prepared by indenyl
analogue, [Me2Si(Ind)(N Bu)]TiCl2 [22d], were
3. Summary
t
seen, although styrene incorporation was remarkably
improved by 2. The result presented here is an in-
teresting contrast especially with that prepared by 1,
because no resonances ascribed to styrene repeated
units including the typical resonance attributed to S␣␤
carbon (styrene repeat unit by tail-to-tail coupling,
Scheme 1) for the copolymer by 1 were observed.
It should be noted that the intensity of resonances
attributed to S␤δ and S␥␥ carbons decreased, if the
styrene content in the copolymer was increased up to
44.6 mol% (Fig. 4b). Only trace (negligible) amount
of the styrene repeated units (S␣␤) were observed for
the poly(ethylene-co-styrene) prepared by 22 in spite
of that the copolymer contain 44.6 mol% of styrene
We have shown that 2 exhibits more efficient styrene
incorporation than 1 in the copolymerization, afford-
ing the copolymer with almost alternating manner. The
styrene incorporation and microstructure for the re-
sultant poly(ethylene-co-styrene)s strongly depended
upon the ligand in half-metallocene type titanium com-
plexes (1–3). We do not have an exact reason why 2
incorporate styrene in an alternating manner with re-
gioregular insertion, but this should be an important
finding for designing efficient catalyst precursor for
controlled copolymerization. We are doing more re-
search concerning this chemistry, and further results
will be introduced in the near future.
1
(which was independently determined by H NMR).
It is clear that this is a crucial reason for the difficulty
to prepare the copolymer with styrene content higher
than ca. 50 mol%, because styrene should be incorpo-
rated into the copolymer after inserted ethylene even
at almost equal molar ratio if 2 was employed as the
catalyst. Although the polystyrene structure was atac-
tic, this should be an interesting example to prepare
the copolymer with a controlled insertion manner only
by simple replacement of amide fragment from 1. One
probable assumption based on our previous results for
ethylene/␣-olefin copolymerization with Cpꢀ-aryloxy
4. Experimental
All synthetic experiments were carried out under a
nitrogen atmosphere in a vacuum atmospheres drybox
or using standard Schlenk techniques unless otherwise
specified. All chemicals used were of reagent grade
and were purified by the standard purification proce-
dures. Toluene for the polymerization was distilled
over sodium and benzophenone under nitrogen atmo-
sphere, and was stored in a sealed bottle in the drybox
in the presence of molecular sieves (mixture of 3A
and 4A 1/16, and 13X). Reagent grade of styrene was
distilled under nitrogen in the presence of CaH2 after
the standard purification procedure, and was stored in
a Schlenk tube under N2 in the freezer. Ethylene for
polymerization was of polymerization grade (purity
>99.9%, Sumitomo Seika Co. Ltd.) and was used
2
The broad resonance observed at 41 ppm in Fig. 4b should be
due to the T
of styrene repeated units. However, we suspect
␤␤
that this would be due to the atactic polystyrene contaminated
in the copolymer. The peak at 30.5 ppm is due to the impurity
(2,6-di-tert-butyl-p-creasol as the added stabilizing agent) in the
copolymer.

232
K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
as received. (1,3-Me2C5H3)TiCl2(O-2,6-iPr2C6H3)
0.84–1.00 (m). 13C NMR (CDCl3): δ 140.7, 136.0,
(3) was prepared according to the previous report
[2b]. [Me2Si(C5Me4)(N Bu)]TiCl2 (1) was purchased
102.0, 64.0, 34.9, 26.2, 25.8, 16.0, 13.0, 4.9.
t
4.2. Typical reaction procedure for copolymerization
of ethylene with styrene by 1–3-MAO catalyst
from Kanto Chemical Co. Ltd. Toluene and AlMe3
in the commercially available methylaluminoxane
[PMAO-S, 9.5 wt.% (Al) toluene solution, Tosoh
Finechem Co.] were removed in vacuo in the drybox,
and used as a white solid.
Typical example (run 3) is as follows: toluene
(24.5 ml), MAO were added into the autoclave
(100 ml, stainless steel) in the drybox, and the reaction
apparatus was then replaced with ethylene. The reac-
tion mixture was then pressurized to the prescribed
ethylene pressure soon after the addition of styrene
and a toluene solution (0.5 ml) containing 2. The mix-
ture was stirred for 10 min, and the polymerization
was terminated with the addition of EtOH (15 ml).
The solution was then poured into EtOH (100 ml),
and the resultant polymer was adequately washed
with EtOH and then dried in vacuo for several hours.
According to the previous report, the resultant
polymer mixture was separated into three fractions,
and atactic polystyrene prepared only by MAO was
extracted with acetone. Poly(ethylene-co-styrene) was
extracted with THF, and polyethylene and polystyrene
(or the copolymer with low styrene content) which
were the by-product in this reaction was separated
as THF insoluble fraction. The basic experimental
procedure is as follows: the polymer sample obtained
in the copolymerization experiment was added into
a round bottom flask containing acetone (100 ml)
equipped with a reflux condenser, and the mixture
was refluxed for 6 h to separate acetone soluble and
insoluble fractions. Then the acetone insoluble frac-
tion was dried and added into a round bottom flask
containing THF (100 ml) equipped with a reflux
condenser, and the mixture was refluxed for 6 h to
separate THF soluble and insoluble fractions. These
1
All H and 13C NMR spectra were recorded on a
JEOL JNM-LA400 spectrometer (399.65 MHz, 1H;
100.40 MHz, 13C). All chemical shifts are given in
ppm and are referenced to tetramethylsilane. Ob-
vious multiplicities and routine coupling constants
are usually not listed, and all spectra were obtained
in the solvent indicated at 25 ◦C unless otherwise
noted. All deuterated NMR solvents were stored
over molecular sieves. 13C NMR spectra for the
poly(ethylene-co-styrene)s were performed by using
JEOL LA400 spectrometer (CDCl3) with proton de-
coupling at 60 ◦C. The pulse interval was 5.2 s, the
acquisition time was 0.8 s, the pulse angle was 90◦,
and the number of transients accumulated was ca.
10,000. 1H NMR spectra for the copolymer (cal-
culation of styrene content in the copolymer) were
measured in the same manner (tetrachloroethane-d4)
at 100 ◦C. The polymer solutions were prepared by
dissolving polymers in solvent up to 10 wt.%.
Molecular weight and molecular weight distribution
of the resultant copolymers were measured by gel per-
meation chromatography (Tosoh HLC-8121GPC/HT)
with polystyrene gel column (TSK gel GMHHR-H
HT × 2) at 140 ◦C using o-dichlorobenzene contain-
ing 0.05% (w/v) 2,6-di-tert-butyl-p-cresol as solvent.
The molecular weight was calculated by a standard
procedure based on the calibration with standard
polystyrene samples.
1
fractions were analyzed by H, 13C NMR and GPC.
4.1. Synthesis of [Me2Si(C5Me4)(NCy)]TiCl2 (2)
Acknowledgements
Compound 2 was prepared similarly according
to the reported procedure [25], by the reaction of
n
[Me2Si(C5Me4H)(NHCy)], BuLi, TiCl4 in the pres-
The present project is partly supported by the
Grant-in-Aid from the Ministry of Education, Science,
Sports and Culture of Japan (no. 13555253). K.N.
would like to express his heartfelt thanks to Tosoh
Finechem Corporation for donating MAO (PMAO-S).
K.N. also thanks to Dr. N. Tomotsu (Idemitsu Petro-
chemical Co. Ltd.) for helpful discussions.
ence of NEt3 in toluene. The mixed solution of
toluene/n-hexane in the freezer prepared after the
filtration and concentration procedure gave yellow
microcrystals. Yield 50%. H NMR (CDCl3): δ 4.76
(m, 1H, N–CH–), 2.21 and 2.08 (s, 12H, C5Me4), 1.84
1
(dd or m), 1.63 (d or m), 1.24–1.51 (m), 1.01–1.11,

K. Nomura et al. / Journal of Molecular Catalysis A: Chemical 190 (2002) 225–234
Patent 416815 (1991), Jpn. Patent 2623070 (1997);
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