Highly stable catalysts for the stereospecific polymerization of styrene

Article abstract of DOI:10.1021/om950990a

The synthesis of eight new catalyst precursors is described, and their catalysis of syndiospecific styrene polymerization when activated by methylaluminoxane (MAO) is compared with IndTiCl₃. Phenyl substitution increases polymerization activity (A) in the order 1,3-Ph₂Ind < 2-PhInd < 1-PhInd; the opposite trend was observed for the yield (SY) of syndiotactic polystyrene (s-PS). The optimum polymerization temperature (T_p) is 50°C; an increase of T_p decreases A, SY, and molecular weight (MW) of s-PS. Benz[e]IndTiCl₃ (6a) as well as the 2-methyl (6b) and 1,2,3-trimethyl (11) derivatives have been synthesized. Complexes 6a/MAO and 6b/MAO have exceedingly high values of A ≈ 1.8 × 10⁸ g of PS/ (mol of Ti·mol of styrene·h) for a turnover rate of 450 s^-1, SY over 92%, and MW ≈ 5 × 10⁵. These parameters were only slightly lowered at T_p = 100°C, indicating very thermally stable, catalytically active species. These catalyst precursors are stable in solution toward air and moisture up to 48 h and are indefinitely stable in the solid state. Though 11/MAO has a lower A, it has a higher SY which changes to lesser degrees with increase in T_p than for either 6a or 6b/MAO. Attempts to make benz[f]indenyltrichlorotitanium have so far been unsuccessful.

Full text of DOI:10.1021/om950990a

2404
Organometallics 1996, 15, 2404-2409
High ly Sta ble Ca ta lysts for th e Ster eosp ecific
P olym er iza tion of Styr en e
Patrick Foster, J ames C. W. Chien,* and Marvin D. Rausch*
Department of Chemistry, Department of Polymer Science & Engineering, University of
Massachusetts, Amherst, Massachusetts 01002
Received December 28, 1995X
The synthesis of eight new catalyst precursors is described, and their catalysis of
syndiospecific styrene polymerization when activated by methylaluminoxane (MAO) is
compared with IndTiCl3. Phenyl substitution increases polymerization activity (A) in the
order 1,3-Ph2Ind < 2-PhInd < 1-PhInd; the opposite trend was observed for the yield (SY)
of syndiotactic polystyrene (s-PS). The optimum polymerization temperature (Tp) is 50 °C;
an increase of Tp decreases A, SY, and molecular weight (MW) of s-PS. Benz[e]IndTiCl3
(6a ) as well as the 2-methyl (6b) and 1,2,3-trimethyl (11) derivatives have been synthesized.
Complexes 6a /MAO and 6b/MAO have exceedingly high values of A ≈ 1.8 × 108 g of PS/
(mol of Ti‚mol of styrene‚h) for a turnover rate of 450 s-1, SY over 92%, and MW ≈ 5 × 105.
These parameters were only slightly lowered at Tp ) 100 °C, indicating very thermally stable,
catalytically active species. These catalyst precursors are stable in solution toward air and
moisture up to 48 h and are indefinitely stable in the solid state. Though 11/MAO has a
lower A, it has a higher SY which changes to lesser degrees with increase in Tp than for
either 6a or 6b/MAO. Attempts to make benz[f]indenyltrichlorotitanium have so far been
unsuccessful.
In tr od u ction
and its catalytic behavior. The effects of methyl, phenyl,
diphenylphosphino, and trimethylsilyl substituents have
been reported by Kucht et al.8 Ready et al.9 observed
that IndTiCl3 is a significantly better precursor than
CpTiCl3.
Ishihara and co-workers1 reported in 1986 that syn-
diotactic polystyrene (s-PS) could be produced with high
stereoregularity and yield under conventional conditions
using an organic or inorganic titanium compound
activated with methylaluminoxane (MAO).1 There have
been only a few reports2-5 on the kinetic and mecha-
nistic studies of this novel catalysis. In fact, s-PS is a
new macromolecule; previously only amorphous (a-PS)
and isotactic (i-PS) structures were known. Many
patents have been issued to Idemitsu Kosan Co.6 and
to Dow Chemical Co.7 for their work in this area.
In contrast to the modest interest in s-PS catalysis,
there are currently intense research activities in the
isospecific polymerization of propylene,10 which is un-
doubtedly related to the commercial value of isotactic
polypropylene (i-PP). The stereospecificity, activity, and
molecular weight of polypropylene produced by isospe-
cific ansa-zirconocene catalysts were enhanced by aro-
matic substituents.11
(η5-Cyclopentadienyl)trichlorotitanium (CpTiCl3) was
the most active precursor found by Ishihara et al.,1
although the trivalent CpTiCl2 exhibits high activity
and stereospecificity as well.1 We have been interested
in elucidating the relationship of precursor structure
The central objective of this work is to introduce
aromatic substituents in the design of styrene catalysts
optimized for high activity, syndiospecificity, and stabil-
ity as well as low probability to chain terminate, which
would result in high molecular weight products.
X Abstract published in Advance ACS Abstracts, April 1, 1996.
(1) (a) Ishihara, T.; Seimiga, T.; Kuramoto, M.; Uoi, M. Macromol-
ecules 1986, 19, 2464. (b) Ishihara T.; Kuramoto, M.; Uoi, M. Macro-
molecules 1988, 21, 3256.
(2) (a) Zambelli, A.; Oliva, L.; Pellechia, C. Macromolecules 1989,
22, 2129. (b) Zambelli, A.; Pellechia, C.; Oliva, L.; Longo, P.; Grassi,
A. Makromol. Chem. 1991, 192, 223. (c) Grassi, A.; Pellechia, C.; Longo,
P.; Zambelli, A. Gazz. Chem. Ital. 1987, 19, 2565. (d) Pellechia, C.;
Longo, P.; Grassi, A.; Humendola, P.; Zambelli, A. Makromol. Chem.
Rapid Commun. 1987, 8, 277. (e) Pellechia, C.; Pappalardo, D.; Oliva,
L.; Zambelli, A. J . Am. Chem. Soc. 1995, 117, 6593.
(6) (a) Ishihara, N. Eur. Pat. Appl., 1986, Patent 210615, to Idemitzu
Kosan Co. (b) Ishihara, N.; Kuramoto, M.; Uoi, M. Eur. Pat. Appl.,
1986, Patent 224096, to Idemitzu Kosan Co.
(7) (a) Campbell, R. E., J r.; Hefner, J . G. Int. Pat. Appl. 1988, WO.88/
10275, to Dow Chemical Co. (b) Campbell, R. E., J r. U.S. Pat., 1991,
Patent 5066741, to Dow Chemical Co. (c) Newman, T. H. U.S. Pat.,
1993, Patent 5237069, to Dow Chemical Co. (d) Campbell, R. E., J r.
U.S. Pat., 1993, Patent 5206197, to Dow Chemical Co. (e) Campbell,
R. E., J r. Int. Pat. Appl., 1993, WO.93/03067, to Dow Chemical Co.
(8) (a) Kucht, A.; Kucht, H.; Barry, S.; Chien, J . C. W.; Rausch, M.
D. Organometallics 1993, 12, 3075. (b) Kucht, H.; Kucht, A.; Chien, J .
C. W.; Rausch, M. D. Appl. Organomet. Chem. 1994, 8, 393.
(9) (a) Ready, T. E.; Day, R. O.; Chien, J . C. W.; Rausch, M. D.
Macromolecules 1993, 26, 5822. (b) Ready, T. E.; Chien, J . C. W.;
Rausch, M. D. J . Organomet. Chem., in press.
(3) (a) Chien, J . C. W.; Salajka, Z. J . Polym. Sci., Part A 1991, 29,
1243. (b) Chien, J . C. W.; Salajka, Z. J . Polym. Sci., Part A 1991, 29,
1253. (c) Salajka, Z.; Dong, S. H.; Chien, J . C. W. Macromolecules 1992,
25, 3199.
(4) Soga, K.; Yu, C. H.; Shiono, T. Makromol. Chem. Rapid Commun.
1988, 9, 351.
(5) (a) Wang, Q.; Quyoum, R.; Gillis, D. J .; Tudoret, M.-J .; J eremic,
D.; Hunter, B. K.; Baird, M. C. Organometallics 1996, 15, 693. (b)
Quyoum, R.; Wang, Q.; Tudoret, M.-J .; Baird, M. C.; Gillis, D. J . J .
Am. Chem. Soc. 1994, 116, 6435. (c) Gillis, D. J .; Tudoret, M.-J .; Baird,
M. C. J . Am. Chem. Soc. 1993, 115, 2543.
(10) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
(11) (a) Spaleck, W.; Kuber, F.; Wimter, A.; Rohrmann, J .; Bach-
mann, B.; Antberg, M.; Dolle, V.; Paulus, E. F. Organometallics 1994,
13, 954. (b) Stehling, U.; Diebold, J .; Kirsten, R.; Roll, W.; Brintzinger,
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1994, 13, 964.
S0276-7333(95)00990-3 CCC: $12.00 © 1996 American Chemical Society

Catalysts for the Polymerization of Styrene
Organometallics, Vol. 15, No. 9, 1996 2405
Sch em e 1
Sch em e 2
Sch em e 3
Resu lts
Syn th esis of Ca ta lyst P r ecu r sor s. 2-Phenylindene
(1b),12 1,3-diphenylindene (1c),13 benz[e]indene (4a ),11a
and 2-methylbenz[e]indene (4b)11b were synthesized by
literature procedures. 3-Phenylindene (1a ),12 3-benzyl-
indene (1d ),14 and 3-(2-phenylethyl)indene (1e)15 were
prepared by modifications of the literature methods, as
described in the Experimental Section. 1,2,3-Trimeth-
ylbenz[e]indene (9) was synthesized as shown in Scheme
1. The substituted indenes were converted into the
trimethylsilyl derivatives by reaction of the indene with
butyllithium followed by chlorotrimethylsilane (Schemes
1-3). The corresponding titanium complexes were
obtained by reaction of the substituted (trimethylsilyl)-
indene derivatives with TiCl4 in a dichloromethane
solution (Schemes 1-3).16
Sch em e 4
Benz[f]indene (12) was prepared by modification17 of
a literature procedure,18 which significantly improved
the yield and decreased the reaction time (see Experi-
mental Section). Benz[f]indene was readily converted
into the trimethylsilyl derivative (13) (Scheme 4). Two
attempts were made to prepare the corresponding
titanium complex (14) (Scheme 4). The reaction be-
tween (trimethylsilyl)benz[f]indene and TiCl4 was car-
ried out at -78 °C in both CH2Cl2 and toluene. Both
1
attempts gave a green solid, which gave no H NMR
spectrum and could not be recrystallized.
P olym er iza tion of Styr en e. The newly synthesized
catalyst precursors were examined using MAO as co-
catalyst at various polymerization temperatures. The
results of the phenyl-substituted precursors are sum-
marized in Table 1, while those of the annelated
precursors are found in Table 2. In general, the highest
activity was obtained at 50 °C and Al:Ti ) 4000:1,
except for compound 3e which was slightly more active
at Al:Ti ) 2000:1. At most polymerization temperatures
(Tp), compounds 3a -c all exhibited high activities and
syndiotacticity. Molecular weights and melting points
were consistent with those previously reported3b for
s-PS. The reproducibility of the amount of total polymer
obtained, activity, and MW is estimated at (5%.
(12) Greifenstein, L. G.; Lambert, J . B.; Nienhuis, R. J .; Fried, H.
E.; Pagani, G. A. J . Org. Chem. 1981, 46, 5125.
(13) Miller, W. G.; Pittman, C. U., J r. J . Org. Chem. 1974, 39, 1955.
(14) Hubert, A. J .; Reimlinger, H. J . Chem Soc. C 1969, 944.
(15) Malkhasyan, A. T.; Dzhandzhulyan, Z. L.; Mirakyan, S. M.;
Martirosyan, G. T. Arm. Khim. Zh. 1980, 33, 728.
(16) (a) Cardoso, A. M.; Clark, R. J . H.; Moorhouse, S. J . Chem. Soc.,
Dalton Trans. 1980, 1156. (b) Llinas, G. H.; Mena, M.; Palacios, F.;
Royo, P.; Serrano, R. J . Organomet. Chem. 1988, 340, 37.
(17) Imamoto, T.; Takeyama, T.; Kusumoto, T. Chem. Lett. 1985,
1491.
(18) Carpino, L. A.; Lin, Y. J . Org. Chem. 1990, 55, 247.

2406 Organometallics, Vol. 15, No. 9, 1996
Foster et al.
Ta ble 1. P olym er iza tion of Styr en e w ith Su bstitu ted In d TiCl3 Com p ou n d s Activa ted w ith MAOa
IndTiCl3 compds
no.
R1
R2
H
R3
H
Tp (°C)
10-7Ab
s-PSc (%)
Tmd (°C)
Mwe 10-5
3f
H
50
75
100
50
75
100
50
75
100
50
75
100
50
3.7
1.8
1.1
7.7
3.0
2.4
5.2
2.6
2.1
3.6
4.1
2.2
0.2
0.1
0.07
1.1
1.2
0.6
98.2
96.3
89.6
90.0
91.1
88.9
91.3
90.5
87.6
94.8
93.5
91.5
87.2
78.6
66.7
88.2
8.0
270.8
7.20
3a
3b
3c
3d
3e
Ph
H
H
H
H
H
H
H
260.7
260.9
268.5
262.5
260.7
259.2
262.0
268.0
260.3
268.3
262.3
261.7
267.8
260.8
260.9
4.24
1.88
1.06
3.23
1.81
1.62
4.96
3.42
2.01
3.23
1.81
1.02
4.01
2.42
0.95
H
Ph
Ph
H
CH2Ph
75
100
50
75
100
H(CH2)2Ph
H
42.7
a
Polymerization conditions: [Ti] ) 50 µM; Al/Ti ) 4000:1; [styrene] ) 0.88 M; time of polymerization is from 10 to 30 min depending
on A. A (activity) ) g of PS/(mol of Ti‚mol of styrene‚h). c s-PS % ) (g of polymer insoluble in 2-butanone)/(g of total polymer) × 100%.
b
Tm ) melting point of s-PS. e Molecular weights determined by intrinsic viscosity. f Data were obtained from ref 9b.
d
Ta ble 2. P olym er iza tion of Styr en e w ith Un su bstitu ted a n d Su bstitu ted BEIn d TiCl3 Com p ou n d s Activa ted
w ith MAOa
BEIndCl3 compds
e
no.
6a
R1
R2
R3
Tp (°C)
10-7Ab
s-PSc (%)
Tmd (°C)
10-5Mw
H
H
H
50
75
100
50
75
100
50
17
14
10
18
92.5
91.3
89.0
92.8
91.4
90.1
96.0
97.6
95.0
270.4
263.3
256.8
275.2
261.0
258.4
276.0
275.2
271.9
5.45
3.22
1.28
4.24
1.88
1.06
3.23
1.81
1.02
6b
11
H
Me
Me
H
15
7.0
2.0
2.0
2.0
Me
Me
75
100
a
Polymerization conditions: [Ti] ) 50 µM; Al/Ti ) 4000:1; [styrene] ) 0.88 M; time of polymerization is from 10 to 30 min depending
on A. A (activity) ) g of PS/(mol of Ti‚mol of styrene‚h). c s-PS % ) (g of polymer insoluble in 2-butanone)/(g of total polymer) × 100%.
b
Tm ) melting point of s-PS. e Molecular weights determined by intrinsic viscosity.
d
Discu ssion
catalyst due to the increased possible resonance stabi-
lization. It has been shown that phenyl substituents
in the 1 and/or 3 positions of indene decrease the pKa,
stabilizing the anion formed. However, phenyl substi-
tution in the 2 position is much less effective in
stabilizing the anion due to the fact that the negative
charge cannot be effectively delocalized into the phenyl
ring.19 Taking these factors into account, the increasing
order of A of IndTiCl3 < 2-PhIndTiCl3 < 1-PhIndTiCl3
can be rationalized. The 1,3-Ph2IndTiCl3 (3c)/MAO
catalyst has an A value at 50 °C that is comparable to
the unsubstituted system 3/MAO and significantly less
than catalysts derived from the monophenyl-substituted
precursors 3a ,b. However, at Tp ) 75 °C, 3c/MAO is
more active and produces s-PS having higher MW than
catalysts derived from 3, 3a , or 3b. These results
indicate that steric problems can arise with phenyl
substitution at both C-1 and C-3 but that an increase
of temperature may reduce the steric effects. Also, 3c
is air stable in the solid state for prolonged periods and
there was no decrease in A after 3c was exposed to air
for 4 weeks. This phenomenon is probably due to the
steric effects which protect the metal center from
decomposition (vida infra).
CpTiCl3 may be considered as the reference catalyst
precursor for s-PS catalysis. It exhibits maximum
activity A ) 1.4 × 107 g of PS/(mol of Ti‚mol of styrene‚h)
at 50 °C.9a The syndiospecificity is only modest as
measured by yield in weight percent of product insoluble
in refluxing 2-butanone, SY ) 67%.9a Both A and SY
decline at higher or lower polymerization temperature
(Tp). The polymerization results could be influenced
significantly by one of several experimental variables,
i.e. concentration of monomer, catalyst precursor, or
MAO, and also by the type of solvent used.
We have studied more thoroughly a closely related
system CpTi(OBu)3/ MAO.3b,c The optimum Tp was 45
°C at which A ) 3.1 × 107 g of PS/(mol of Ti‚mol of
styrene‚h), SY ) 93%, MW of s-PS ) 4 × 104, and Mw/
Mn ) 2.8. A and SY decreased at both higher and lower
Tp, while MW increased with the lowering of Tp.
All the catalyst precursors in the series 3a -e have
high Amax at Tp ) 50 °C (Table 1). Compared to IndTiCl3
(3), the 1,3-Ph2-substituted complex 3c has comparable
A and MW but slightly lower SY. There is a significant
increase in Amax with the 2-Ph-substituted complex 3b
and an even larger increase in the case of the 1-Ph
derivative 3a , both giving s-PS of very high MW ((4-5)
× 105). The trend of A is consistent with the aromatic
substituent having an effect on the behavior of the
(19) (a) Bordwell, F. G.; Drucker, G. E. J . Org. Chem. 1980, 45, 3325.
(b) Bordwell, F. G.; Satish, A. V. J . Am. Chem. Soc. 1992, 114, 10173.

Catalysts for the Polymerization of Styrene
Organometallics, Vol. 15, No. 9, 1996 2407
The steric effect of phenyl substitution could also
cause a reduction of stereochemical control as is evi-
denced by the lower SY for compounds 3a -c relative
to 3. In a current mechanism for syndiospecific styrene
polymerization2,3 both the last benzyl group in the
propagating chain and the styrene monomer are pos-
tulated to complex with the titanium center via multi-
hapto interaction. Coordination of this type is thought
to regulate the regio- and stereochemistry of styrene
complexation and insertion. Any phenyl substituents
may cause lowering of the ligand-metal interaction and
consequently diminish SY.
Compounds 3d ,e were synthesized to investigate
several effects: (1) breaking of conjugation between the
indenyl ring and the phenyl substituent; (2) coordination
of the phenyl substituent to titanium; (3) mobility of the
substituent. The results in Table 1 show that, compared
with IndTiCl3, 1-(PhCH2CH2)IndTiCl3 (3e) has a third
of the activity and there is another drop of a factor of 5
for 1-(PhCH2)IndTiCl3 (3d ). The former behaves as
expected for breaking of conjugation, and the activity
of 3e is comparable to that of 1-MeIndTiCl3.9b Steric
effects as proposed above for the phenyl substituents
would interfere with hapto interactions at the metal
center. This effect is most pronounced for the PhCH2
substituent and not as strong in the case of the PhCH2-
CH2 substituent, because of the more flexible spacer
unit -CH2CH2-.
A dynamic interaction between the phenyl group with
titanium in 3d ,e cannot be entirely discounted, however.
It has been shown that if a coordinating substituent is
present (e.g., -CH2CH2NMe2), polymerization of both
ethylene and styrene is possible.20 In this regard,
styrene polymerization activity is much lower for 3d
than for 3e, while ethylene polymerization activity
shows the opposite trend. The catalyst 3d /MAO exhib-
its a reasonably high ethylene polymerization activity
of 3.4 × 105 g of PE/(mol of Ti‚h), while 3e/MAO is
inactive.
F igu r e 1. Log of activity versus time plot for the loss of
activity of 6b and CpTiCl3 when exposed to air in a toluene
solution. A (activity) ) g of PS/(mol of Ti‚mol of styrene‚h);
[Ti] ) 50 µM; Tp ) 50 °C; Al/Ti ) 4000:1;[styrene] ) 0.88
M; time ) time catalyst precursor solution was exposed to
air.
on the C5 ring. Further evidence of enhanced stability
of the catalyst system 2-MeBEIndTiCl3/MAO is shown
in Figure 1, which is a plot of activity versus time, where
time is the length of time the catalyst solution was
exposed to air. The long stability and activity of the
catalyst solution is suprising, since solutions of cyclo-
pentadienyl- and indenyltrichlorotitanium complexes
normally decompose readily in air (Figure 1).
The most interesting catalyst precursor is 11 because
of the temperature invariance of its polymerization
activity as well as its very high stereospecificity in the
Tp range investigated. The three methyl groups in 11
provide both more electron donation and steric hin-
drance to help stabilize it against reduction,21 dimer-
ization,22 or reaction with oxygen and moisture as well
as â-hydride elimination. The syndiospecificity of 11
is higher than that of 6a ,b, which is analogous to the
behavior of (pentamethylcyclopentadienyl)trichloro-
titanium versus the unsubstituted cyclopentadienyl
catalyst CpTiCl3.8b
All the systems in Table 1 have optimal Tp in the
vicinity of 50 °C. Benz[e]indenylTiCl3 (BEIndTiCl3, 6a )
and the 2-methyl (6b) and 1,2,3-trimethyl (11) deriva-
tives were synthesized with the idea that annelation of
the aromatic ring might improve both catalytic activity
and stability. Previously, ansa-zirconocene studies
involving benz[e]indene showed appreciable increases
in activity and steroeselectivity over indene for prop-
ylene polymerization.11
Attempts to synthesize (benz[f]indenyl)trichlorotita-
nium (14) were unsuccessful. Reaction of (benz[f]-
indenyl)lithium, derived from 12, with chlorotrimeth-
ylsilane went as expected, forming 1-(trimethylsilyl)-
benz[f]indene (13). However, when attempts were made
to convert 13 into 14, the desired product (14) could not
be isolated.
BEIndTiCl3/MAO has an extremely high value of Amax
for syndiospecific styrene polymerization of 1.7 × 108 g
of PS/(mol of Ti‚mol of styrene‚h) (Table 2). The
turnover rate is 450 s-1, which is truly remarkable for
such a bulky monomer. Also very high are the SY (93%)
and MW (5.5 × 105). These properties decline only
slightly at 100 °C. The 2-MeBEIndTiCl3/MAO catalyst
system exhibits virtually the same Amax and SY as the
unsubstituted system 6a, but unexpectedly gives slightly
lower MW for s-PS. Increasing Tp to 100 °C caused only
small reductions in activity and stereospecificity. How-
ever, the lowering of MW is about the same as that
observed for the indenyl systems of Table 1. The results
suggest that benz[e]indene significantly stabilizes the
active catalytic species compared to phenyl substitution
Exp er im en ta l Section
Reactions were carried out under an argon atmosphere
using standard Schlenk techniques. Methylaluminoxane (MAO)
was purchased from Akzo. All other reagents were purchased
from Aldrich and were used without further purification.
Toluene, diethyl ether, tetrahydrofuran (THF), hexane, and
pentane were distilled with Na/K alloy under argon. Meth-
ylene chloride and styrene were distilled from CaH2. 1H NMR
spectra were recorded on a Varian XL-200 or a Bruker NR-80
spectrometer. Elemental analyses were performed by the
Microanalytical Laboratory, University of Massachusetts, Am-
herst, MA.
3-P h en ylin d en e (1a ). A modification of the procedure of
Greifenstein et al.12 was used. To a suspension of Mg turnings
(21) Chien, J . C. W. J . Am. Chem. Soc. 1959, 81, 86.
(22) Bueschges, V.; Chien, J . C. W. J . Polym. Sci., Part A 1989, 27,
1525.
(20) Flores, J . C.; Chien, J . C. W.; Rausch, M. D. Organometallics
1994, 13, 4140.

2408 Organometallics, Vol. 15, No. 9, 1996
Foster et al.
(1.85 g, 76 mmol) in 50 mL of diethyl ether was slowly added
a solution of bromobenzene (11.93 g, 76 mmol) in 50 mL of
the same solvent. After 30 min of reflux, 1-indanone (10 g,
76 mmol) in 20 mL of ether was added and the solution was
stirred overnight. The mixture was hydrolyzed with an
aqueous solution of NH4Cl (8 g in 40 mL of H2O). The organic
phase was separated, extracted with water, and dried (Na2SO4),
and the solvent was removed. The oily residue was dissolved
in 150 mL of benzene, p-toluenesulfonic acid (200 mg, 1 mmol)
was added, and the solution was refluxed using a Dean-Stark
apparatus until separation of water subsided. The organic
mixture was extracted with saturated NaHCO3 and water, and
dried (MgSO4), and the solvent was removed. Fractional
distillation (110-112 °C/ 0.1 mmHg) of the residue gave
3-phenylindene as a yellow liquid (9.7 g, 66%). 1H NMR
(CDCl3): δ 7.27-7.61 (m, 9H, arom H), 6.57 (t, 1H, H-C5(2)),
3.50 (d, 2H, CH2).
as a yellow oil. 1H NMR (CDCl3): δ 7.21-7.65 (m, 14H, arom.
H), 6.93 (s, 1H, H-C5), -0.11 (s, 9H, Si-CH3).
(1,3-Dip h en ylin d en yl)tr ich lor otita n iu m (3c). Follow-
ing the procedure described for 3a , 2c (2.1 g, 6.2 mmol) and
TiCl4 (1.2 g, 6.2 mmol) gave 3c (0.82 g, 32%) as green crystals.
1H NMR (CDCl3): δ 7.50-8.31 (m, 14H, arom H), 7.48 (s, 1H,
H-C5). Anal. Calcd for C21H15Cl3Ti: C, 59.82; H, 3.59.
Found: C, 59.78; H, 3.63.
3-Ben zylin d en e (1d ). A solution of indene (4.7 g, 41 mmol)
in 60 mL of THF was cooled to 0 °C, 1.6 M butyllithium (25.6
mL, 41 mmol) was added, and the solution was stirred for 3
h. Benzyl chloride (5.2 g, 41 mmol) was added, and the
mixture was warmed to room temperature and stirred over-
night. The solvent was removed, and the residue was ex-
tracted with 50 mL of hexane. Removal of the solvent followed
by distillation (102 °C /0.1 mmHg) of the residue gave 1d (3.55
g, 42%) as a yellow liquid. 1H NMR (CDCl3): δ 7.17-7.48 (m,
9H, arom H), 6.11 (t, 1H, H-C5(2)), 3.88 (m, 2H, CH2), 3.34 (d,
2H, H-C5(1)).
3-Ben zyl-1-(tr im eth ylsilyl)in d en e (2d ). Following the
procedure described for 2b, 1d (3.55 g, 17 mmol), 1.6 M
butyllithium (10.7 mL, 17 mmol), and chlorotrimethylsilane
(2.1 g, 19 mmol) gave 2d (4.0 g, 84%) as a yellow oil. 1H NMR
(CDCl3): δ 7.17-7.53 (m, 9H, arom H), 6.25 (d, 1H, H-C5(2)),
3.97 (s, 2H, CH2), 3.42 (m, 1H, H-C5(1)), -0.05 (s, 9H, Si-
CH3).
(3-Ben zylin d en yl)tr ich lor otita n iu m (3d ). Following the
procedure described for 3a , 2d (4.0 g, 14 mmol) and TiCl4 (2.6
g, 14 mmol) gave 3d (1.8 g, 36%) as purple crystals. 1H NMR
(CDCl3): δ 7.25-7.83 (m, 9H, arom H), 7.14 (dd, 1H, H-C5-
(2)), 6.93 (d, 1H, H-C5(3)), 4.52 (s, 2H, CH2). Anal. Calcd for
3-P h en yl-1-(tr im eth ylsilyl)in d en e (2a ). To a stirred
solution of 1a (2.35 g, 12 mmol) in 50 mL of hexane was added
a 1.6 M solution of butyllithium in hexane (7.6 mL, 12 mmol)
at 0 °C. The mixture was stirred at 0 °C for 1 h and at room
temperature for 7 h. The solvent was removed by filtration,
and the solid residue was washed with pentane. Fresh hexane
(50 mL) was added, and the solution was cooled to 0 °C.
Chlorotrimethylsilane (1.43 g, 13.2 mmol) was added, and the
mixture was stirred overnight. The mixture was filtered to
remove the lithium chloride, and the solvent was removed to
give 2a (2.0 g, 63%) as a pale yellow oil. 1H NMR (CDCl3): δ
7.26-7.68 (m, 9H, arom H), 6.75 (d, 1H, H-C5(2)), 3.68 (d, 1H,
H-C5(1)), 0.07 (s, 9H, Si-CH3).
(1-P h en ylin d en yl)tr ich lor otita n iu m (3a ). To a solution
of 2a (2.0 g, 7.6 mmol) in 50 mL of CH2Cl2 was added TiCl4
(1.6 g, 8.3 mmol) at 0 °C. The mixture was warmed to room
temperature and stirred overnight and the solvent removed.
The solid residue was washed with pentane, 50 mL of fresh
CH2Cl2 was added, and the solution was filtered. The filtrate
was cooled to -20 °C to give 3a (1.2 g, 46%) as purple crystals.
1H NMR (CDCl3): δ 7.47-8.20 (m, 9H, arom H), 7.38 (d, 1H,
H-C5(2)), 7.31 (dd, 1H, H-C5(3)). Anal. Calcd for C15H11Cl3Ti:
C, 52.14; H, 3.21. Found: C, 51.93; H, 3.14.
C
16H13Cl3Ti: C, 53.45; H, 3.64. Found: C, 52.94; H, 3.80.
3-(2-P h en yleth yl)in d en e (1e). To a suspension of Mg
turnings (1.9 g, 80 mmol) in 60 mL of diethyl ether was slowly
added (2-bromoethyl)benzene (14.8 g, 80 mmol). The mixture
was refluxed for 1 h, 1-indanone (10 g, 80 mmol) in 20 mL of
ether was added, and the solution was stirred overnight at
room temperature. The mixture was hydrolyzed with aqueous
NH4Cl (8 g in 40 mL of H2O), and the organic layer was
separated. The latter was dried (Na2SO4) and filtered, and
the solvent was removed. The residue was dissolved in 100
mL of toluene, oxalic acid (5 g) was added, and the solution
refluxed for 2 h using a Dean-Stark trap to separate the H2O
formed. The mixture was washed with 10% aqueous NaHCO3,
dried (MgSO4), and evaporated to give crude 1e. Distillation
(150 °C /0.1 mmHg) of the residue gave 1e (11.1 g, 63%) as a
yellow liquid. 1H NMR (CDCl3): δ 7.15-7.43 (m, 9H, arom
H), 6.22 (m, 1H, H-C5(2)), 3.31 (d, 2H, H-C5(1)), 2.95-3.00 (m,
4H, CH2CH2).
2-P h en yl-1-(tr im eth ylsilyl)in d en e (2b). 2-Phenylindene
(1b) (1.57 g, 8.0 mmol), prepared by the procedure of Greif-
enstein et al.12 [mp 162-164 °C, 67%], was dissolved in 50
mL of THF. The mixture was cooled to 0 °C, and 1.6 M
butyllithium (5.1 mL, 8.0 mmol) was added. The solution was
warmed to room temperature and allowed to stir for 8 h. The
THF was removed, and the solid was washed with two 20-mL
portions of pentane. The solid was dissolved in 50 mL of THF,
chlorotrimethylsilane (0.98 g, 9.0 mmol) was added at room
temperature, and the mixture was stirred overnight. The THF
was removed, the residue was extracted with 50 mL of
pentane, and the mixture was filtered. The pentane was
removed to give 2b (1.6 g, 74%) as a yellow oil. 1H NMR
(CDCl3): δ 7.16-7.52 (m, 9H, arom H), 7.07 (s, 1H, H-C5(3)),
4.11 (s, 1H, H-C5(1)), -0.25 (s, 9H, Si-CH3).
3-(2-P h en yleth yl)-1-(tr im eth ylsilyl)in d en e (2e). Fol-
lowing the procedure described for 2b, 1e (3.5 g, 16 mmol),
1.6 M butyllithium (10 mL, 16 mmol), and chlorotrimethylsi-
1
lane (2.0 g, 18 mmol) gave 2e (3.86 g, 82%) as a yellow oil. H
NMR (CDCl3): δ 7.14-7.40 (m, 9H, arom H), 6.31 (m, 1H,
H-C5(2)), 3.38 (m, 1H, H-C5(1)), 2.98 (br s, 4H, CH2CH2), -0.09
(s, 9H, Si-CH3).
(2-P h en ylin d en yl)tr ich lor otita n iu m (3b). To a solution
of 2b in 50 mL of CH2Cl2 was added TiCl4 (1.1 g, 6.0 mmol) at
0 °C. The mixture was warmed to room temperature and
stirred overnight. The solvent was removed and the residue
extracted with 50 mL of toluene. The extracts were filtered,
and the toluene was removed. The solid residue was dissolved
in 20 mL of CH2Cl2 and cooled to -20 °C to give 3b (0.80 g,
39%) as a red solid. The product was dried at 70 °C in vacuo.
1H NMR (CDCl3): δ 7.45-7.96 (m, 9H, arom H), 7.27 (s, 2H,
(1-(2-P h en yleth yl)in d en yl)tr ich lor otita n iu m (3e). To
a solution of 2e (3.9 g, 13 mmol) in 50 mL of toluene was added
TiCl4 (2.5 g, 13 mmol) at 0 °C. The mixture was warmed to
room temperature, and the solution was stirred overnight. The
mixture was filtered and concentrated to half its original
volume. Pentane (8 mL) was added, and the mixture was
cooled to -20 °C giving 3e (1.9 g, 39%) as a burgundy solid.
1H NMR (CDCl3): δ 7.19-7.75 (m, 9H, arom H), 7.11 (d, 1H,
H-C5), 6.82 (d, 1H, H-C5), 3.48 (t, 2H, CH2), 3.05 (t, 2H, CH2).
Anal. Calcd for C17H15Cl3Ti: C, 54.66; H, 4.05. Found: C,
54.72; H, 4.07.
H-C5), 5.32 (s, 0.7H, CH2Cl2). Anal. Calcd for C15H11
-
Cl3Ti‚1/3CH2Cl2: C, 49.27; H, 3.14. Found: C, 49.02; H, 3.18.
1,3-Dip h en yl-1-(tr im eth ylsilyl)in d en e (2c). Following
the procedure described for 2b, 1,3-diphenylindene (1c) (2.14
g, 8.0 mmol), prepared by the procedure of Miller et al.13 [mp
82-84 °C, 75%], 1.6 M butyllithium (5.0 mL, 8.0 mmol), and
chlorotrimethylsilane (0.98 g, 9.0 mmol) gave 2c (2.1 g, 77%)
1-(Tr im et h ylsilyl)b en z[e]in d en e (5a ). Following the
procedure described for 2b, benz[e]indene (4a ) (2.0 g, 12 mmol)
prepared by the procedure of Spaleck et al.,11a 1.6 M butyl-
lithium (8.0 mL, 12 mmol), and chlorotrimethylsilane (1.4 g,
13 mmol) gave 5a (2.3 g, 80%) as a yellow oil. 1H NMR

Catalysts for the Polymerization of Styrene
Organometallics, Vol. 15, No. 9, 1996 2409
(CDCl3): δ 7.44-8.25 (m, 7H, arom H and H-C5(3)), 6.88 (dd,
1H, H-C5(2)), 3.78 (m, 1H, H-C5(1)), 0.02 (s, 9H, Si-CH3).
(Ben z[e]in d en yl)tr ich lor otita n iu m (6a ). Following the
procedure described for 3a , 5a (2.3 g, 9.6 mmol) and TiCl4 (1.8
g, 9.6 mmol) gave 6a (2.2 g, 71%) as red-orange crystals. 1H
NMR (CDCl3): δ 8.25-8.29 (m, 1H, arom H), 7.59-7.91 (m,
6H, arom H and H-C5(3)), 7.26 (m, 1H, H-C5(2)), 7.21 (m, 1H,
H-C5(1)). Anal. Calcd for C13H9Cl3Ti: C, 48.87; H, 2.84; Cl,
33.29. Found: C, 48.29; H, 2.80; Cl, 32.99.
1,2,3-Tr im eth yl-1-(tr im eth ylsilyl)ben z[e]in d en e (10).
Following the procedure described for 2b, 9 (2.9 g, 14 mmol),
1.6 M butyllithium (9.0 mL, 14 mmol), and chlorotrimethyl-
silane (1.5 g, 14 mmol) gave 10 (2.28 g, 58%) as an orange oil.
1H NMR (CDCl3): δ 7.34-8.56 (m, 6H, arom H), 2.57 (s, 3H,
CH3), 2.07 (s, 3H, CH3), 1.52 (s, 3H, CH3), -0.16 (s, 9H, Si-
CH3).
(1,2,3-Tr im eth ylben z[e]in d en yl)tr ich lor otita n iu m (11).
Following the procedure described for 3a , 10 (2.28 g, 8.0 mmol)
and TiCl4 (1.5 g, 8.0 mmol) gave 11 (1.2 g, 41%) as purple
crystals. 1H NMR (CDCl3): δ 8.82-8.86 (m, 1H, arom H),
7.91-8.21 (m, 5H, arom H), 3.39 (s, 3H, CH3), 3.08 (s, 3H,
CH3), 2.92 (s, 3H, CH3). Anal. Calcd for C16H15Cl3Ti: C, 53.15;
H, 4.18. Found: C, 52.60; H, 4.32.
2-Meth yl-1-(tr im eth ylsilyl)ben z[e]in d en e (5b). Follow-
ing the procedure described for 2b, 2-methylbenz[e]indene (4b)
(6.2 g, 35 mmol) prepared by the procedure of Stehling et al.,11b
1.6 M butyllithium (22 mL, 35 mmol), and chlorotrimethylsi-
1
lane (4.4 g, 40 mmol) gave 5b (7.6 g, 86%) as a yellow oil. H
NMR (CDCl3): δ 7.37-8.20 (m, 6H, arom H), 7.18 (m, 1H,
H-C5(3)), 3.58 (s, 1H, H-C5(1)), 2.34 (d, 3H, CH3), -0.02 (s, 9H,
Si-CH3).
(2-Meth ylben z[e]in d en yl)tr ich lor otita n iu m (6b). Fol-
lowing the procedure described for 3a , 5b (4.3 g, 17 mmol) and
TiCl4 (3.2 g, 17 mmol) gave 6b (3.7 g, 65%) as red crystals. 1H
NMR (CDCl3): δ 8.19-8.23 (m, 1H, arom H), 7.58-7.86 (m,
5H, arom H), 7.45 (d, 1H, H-C5), 7.09 (d, 1H, H-C5), 2.70 (s,
3H, CH3). Anal. Calcd for C14H11Cl3Ti: C, 50.42; H, 3.32.
Found: C, 50.67; H, 3.39.
Ben z[f]in d en e (12). Benz[f]indene was synthesized by
modification of the procedure of Carpino and Lin.18 A solution
of CeCl3 (14.0 g, 57 mmol) in 100 mL of dry THF was stirred
for 1 h. 4-Bromobenz[f]indan-1-one (10 g, 38 mmol), synthe-
sized by the literature procedure, was added in 50 mL of dry
THF followed by slow addition of LiAlH4 (9.4 g, 0.25 mol) in
50 mL of dry THF. The mixture was refluxed for 18 h. The
reaction mixture was cooled in an ice bath and quenched by
slow addition of 10 mL of H2O, 10 mL of 15% aqueous NaOH,
and finally 30 mL of H2O. The resulting suspension was
filtered, and the solution was dried (MgSO4). After filtration,
the solvent was evaporated to give benz[f]indan-1-ol (5.6 g,
80%) as a light yellow solid having the same 1H NMR spectrum
as previously reported. The benz[f]indan-1-ol was then con-
verted to 12 by the literature method.
2,3-Dim eth ylben z[e]in d en e (8). To a suspension of Mg
(6.2 g, 0.26 mol) in 60 mL of diethyl ether was slowly added
CH3I (36.3 g, 0.26 mol), and the mixture was stirred for 1 h.
2-Methylbenz[e]indanone (7) (50 g, 0.26 mol), prepared by the
procedure of Stehling et al.,11b in 20 mL of ether was added,
and the solution was stirred for 8 h. The mixture was
hydrolyzed with aqueous NH4Cl (25 g in 130 mL of H2O), and
the organic layer was separated. The latter was dried
(Na2SO4) and filtered, and the solvent was removed. The
residue was dissolved in 300 mL of toluene, and 50 g of oxalic
acid was added. The mixture was refluxed, using a Dean-
Stark trap, until the formation of water subsided. The mixture
was washed with 300 mL of 10% NaHCO3 and dried (MgSO4).
After filtration, the solution was mixed with 40 g of silica gel
and evaporated to dryness. The residue was chromatographed
over 150 g of silica gel with a hexane/ethyl acetate (49:1) eluent
mixture to give 8 (29.8 g, 60%) as a yellow liquid. 1H NMR
(CDCl3): δ 8.48-8.51 (m, 1H, arom H), 7.35-7.90 (m, 5H, arom
H), 3.43 (s, 2H, CH2), 2.53 (d, 3H, CH3), 2.15 (s, 3H, CH3).
1,2,3-Tr im eth ylben z[e]in d en e (9). To a solution of 8
(16.73 g, 86 mmol) in 100 mL of THF was slowly added 1.6 M
butyllithium (54 mL, 86 mmol) at 0 °C. The mixture was
warmed to room temperature and stirred for 8 h. The solvent
was removed, and the solid was washed with two 50 mL
portions of pentane. THF (100 mL) was added followed by
CH3I (12.2 g, 86 mmol) and the mixture stirred for 4 h. The
solvent was removed, and the solid was extracted with 50 mL
of pentane. The extracts were filtered, and the solvent was
removed. The residue was chromatographed over a short silica
gel column using a hexane/ethyl acetate (49:1) eluent mixture
to give 9 (7.6 g, 42%) as an orange oil. 1H NMR (CDCl3): δ
7.30-8.56 (m, 6H, arom H), 3.52 (m, 1H, CH), 2.08 (br s, 6H,
2 × CH3), 1.42 (m, 3H, CH3). MS (EI): m/ z 208 (M+, 97%),
1-(Tr im eth ylsilyl)ben z[f]in d en e (13). Following the pro-
cedure described for 2b, 12 (2.32 g, 14 mmol), 1.6 M butyl-
lithium (8.8 mL, 14 mmol), and chlorotrimethylsilane (1.6 g,
15 mmol) gave 13 as a white solid (2.0 g, 61%, mp 90-92 °C).
1H NMR (CDCl3): δ 7.33-7.85 (m, 6H, arom H), 6.76-6.99
(m, 2H, H-C2,3), 3.57 (m, 1H, CH2), 0.00 (s, 9H, Si-CH3).
P olym er iza tion P r oced u r e. A 250 mL glass pressure
bottle was sealed under a nitrogen atmosphere. Freshly
distilled toluene (50 mL) was added via a syringe followed by
styrene (5.0 mL, 44 mmol) and the appropriate amount of
methylaluminoxane (MAO). The bottle was placed in a bath
at the desired polymerization temperature and stirred for 10
min. The titanium catalyst (25 µmol, 1 mL of a 2.5 mM
solution) in toluene was then added, and the mixture was
stirred until the desired reaction time was reached. The
reaction mixture was subsequently quenched with 10% HCl
in methanol, filtered, and dried in a vacuum oven at 70 °C.
The polymer was then extracted with 2-butanone for 24 h in
a Soxhlet extractor to remove any atactic polymer. The
remaining polymer was again dried in a vacuum oven at 70
°C.
P olym er An a lyses. Molecular weights were determined
by intrinsic viscosity in 1,3,5-trichlorobenzene at 135 °C.
Melting points were determined with a Perkin-Elmer DSC-4
system at a heating rate of 20 °C/min. The % s-PS was
determined as the amount of polymer insoluble in 2-butanone.
193 (M+ - CH3, 100%), 178 (M+ - 2CH3, 20%), 163 (M+
3CH3, 5%).
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OM950990A