Synthesis, structure, and polymerization behavior of novel azulenyl metallocenes producing propylene-ethylene pseudo-copolymer

Article abstract of DOI:10.1021/om0494418

Novel bridged bis-azulenyl metallocenes bearing substituants at the 2-, 4-, and 8-positions, dichlorodimethylsilylenebis(2-methyl-4-phenyl-8-n-butyl-8H-azulenyl)hafnium and dichlorodimethylsuylenebis(2-methyl-4,8-diphenyl-8H-azulenyl)hafnium, were synthesized. The structure of the former compound was determined by X-ray crystallographic analysis to have C₂ symmetry. When activated with methylaluminoxane (MAO), both compounds gave an active propylene polymerization catalyst. In propylene homopolymerization, propyleneethylene pseudo-copolymer was obtained unexpectedly. Although the metallocene has C₂ symmetry, the obtained polypropylene was elastomeric and showed no melting point on measurement by differential scanning calorimetry (DSC). The ¹³C NMR analysis of the polymer showed the presence of a large amount of regioinversion.

Full text of DOI:10.1021/om0494418

132
Organometallics 2005, 24, 132-135
Synthesis, Structure, and Polymerization Behavior of
Novel Azulenyl Metallocenes Producing
Propylene-Ethylene Pseudo-Copolymer
Naoshi Iwama*,† and Yasuko T. Osano‡
Polymerization Technical Center, Japan Polypropylene Corporation,
Yokkaichi, Mie, 510-0848, Japan, and Center for Analytical Chemistry and Science,
Mitsubishi Chemical Group Science and Technology Research Center Inc.,
Aoba-ku, Yokohama, 227-8502, Japan
Received July 22, 2004
Novel bridged bis-azulenyl metallocenes bearing substituents at the 2-, 4-, and 8-positions,
dichlorodimethylsilylenebis(2-methyl-4-phenyl-8-n-butyl-8H-azulenyl)hafnium and dichlo-
rodimethylsilylenebis(2-methyl-4,8-diphenyl-8H-azulenyl)hafnium, were synthesized. The
structure of the former compound was determined by X-ray crystallographic analysis to have
C2 symmetry. When activated with methylaluminoxane (MAO), both compounds gave an
active propylene polymerization catalyst. In propylene homopolymerization, propylene-
ethylene pseudo-copolymer was obtained unexpectedly. Although the metallocene has C2
symmetry, the obtained polypropylene was elastomeric and showed no melting point on
measurement by differential scanning calorimetry (DSC). The 13C NMR analysis of the
polymer showed the presence of a large amount of regioinversion.
Introduction
are important, and for this reason, extensive develop-
ment and optimization of 2,4-substitutents were exam-
ined in order to obtain higher melting point isotactic
polypropylene. As previously reported, we have synthe-
sized the bis-azulenyl zirconocenes bearing methyl
groups at the 2-position and phenyl groups at the
4-position of the azulenyl rings: Me2Si(2-Me-4-Ph-4H-
Azu)2ZrCl2.6 We made a comparison between the bis-
azulenyl zirconocene and the bis-indenyl zirconocene,
especially the difference of ring size in each system, i.e.,
six-membered and seven-membered, and the polymer-
ization behavior was compared with that of the bis-
indenyl analogue, Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (5). The
biggest difference between the two metallocenes is the
carbon atom at the 4-position. The carbon atom at the
4-position to which phenyl groups were attached does
not have the same hybridization in both systems, i.e.,
an sp3 carbon in bis-azulenyl and an sp2 carbon in the
bis-indenyl system.
It is well known that ansa-metallocenes of group IV
transition metals having C2 symmetry produce isotactic
polypropylene, when activated with methylaluminoxane
(MAO) and other cocatalysts.1 Many efforts have been
focused on improving the polymerization performance
in terms of activity, melting point, and molecular weight
of the polymer. During the development of a large
number of bridged bis-indenyl and bis-cyclopentadienyl
systems, it was found that stereoselectivity (stereode-
fect) and regioselectivity (regioinversion) of the inserted
propylene monomer are influenced by the steric effect
of the substituents on the indenyl or cyclopentadienyl
moieties.2-5 In particular, it was elucidated that both
the 2- and 4-positions of the bridged bis-indenyl system
* To whom correspondence should be addressed. E-mail:
Iwama.Naoshi@mc.japanpp.co.jp.
† Japan Polypropylene Corp.
‡ Mitsubishi Chemical Group Science and Technology Research
Center, Inc.
We have now synthesized novel bis-azulenyl metal-
locenes bearing substituents at the 2-, 4-, and 8-posi-
tions: Me2Si(2-Me-4-Ph-8-n-Bu-8H-Azu)2HfCl2 (4a) and
Me2Si(2-Me-4,8-Ph2-8H-Azu)2HfCl2 (4b). As the carbon
atoms at the 4-position are sp2 hybridized in these
systems, it would be expected that a more precise
(1) (a) Ewen, J. A. J. Am. Chem. Soc. 1984, 106, 6355. (b) Brintz-
inger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M.
Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (c) Resconi, L.; Cavallo,
L.; Fait, A.; Piemontesi, F. Chem. Rev. 2000, 100, 1253.
(2) (a) Spaleck, W.; Antberg, M.; Rohrmann, J.; Winter, A.; Bach-
mann, B.; Kiprof, P.; Behm, J.; Herrmann, W. A. Angew. Chem., Int.
Ed. Engl. 1992, 31, 1347. (b) Spaleck, W.; Ku¨ber, F.; Winter, A.;
Rohrmann, J.; Bachmann, B.; Antberg, M.; Dolle, V.; Paulus, E. F.
Organometallics 1994, 13, 954. (c) Stehling, U.; Diebold, J.; Kirsten,
R.; Ro¨ll, W.; Brintzinger, H.-H.; Ju¨ngling, S.; Mu¨lhaupt, R.; Lang-
hauser, F. Organometallics 1994, 13, 964. (d) Schneider, N.; Hutten-
loch, M. E.; Stehling, U.; Kirsten, R.; Schaper, F.; Brintzinger, H.-H.
Organometallics 1997, 16, 3413. (e) Kashiwa, N.; Kojoh, S.; Imuta, J.;
Tsutsui, T. In Metalorganic Catalysts for Synthesis and Polymerization;
Kaminsky, W., Ed.; Springer-Verlag: Berlin, 1999; p 30. (f) Kato, T.;
Uchino, H.; Iwama, N.; Imaeda, K.; Kashimoto, M.; Osano, Y.; Sugano,
T. In Metalorganic Catalysts for Synthesis and Polymerization; Ka-
minsky, W., Ed.; Springer-Verlag: Berlin, 1999; p 192.
(4) (a) Ewen, J. A.; Jones, R. L.; Elder, M. J.; Rheingold, A. L.; Liable-
Sands, L. M. J. Am. Chem. Soc. 1998, 120, 10786. (b) Ewen, J. A.;
Jones, R. L.; Elder, M. J. In Metalorganic Catalysts for Synthesis and
Polymerization; Kaminsky, W., Ed.; Springer-Verlag: Berlin, 1999; p
150. (c) Ewen, J. A.; Elder, M. J.; Jones, R. L.; Rheingold, A. L.; Liable-
Sands, L. M.; Sommer, R. D. J. Am. Chem. Soc. 2001, 123, 4763. (d)
Ryabov, A. N.; Gribkov, D. V.; Izner, V. V.; Voskoboynikov, A. Z.
Organometallics 2002, 21, 2842.
(5) (a) Mise, T.; Miya, S.; Yamazaki, H. Chem. Lett. 1989, 1853. (b)
Yamazaki, H.; Kimura, K.; Nakano, M.; Ushioda, T. Chem. Lett. 1999,
1311.
(6) Iwama, N.; Uchino, H.; Osano, T. Y.; Sugano, T. Organometallics
2004, 23, 3267.
(3) (a) Resconi, L.; Piemontesi, F.; Camurati, I.; Sudmeijer, O.;
Nifant’ev, I. E.; Ivchenko, P. V.; Kuz’mina, L. G. J. Am. Chem. Soc.
1998, 120, 2308. (b) Resconi, L.; Balboni, D.; Baruzzi, G.; Fiori, C.;
Guidotti, S. Organometallics 2000, 19, 420.
10.1021/om0494418 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 12/04/2004

Novel Azulenyl Metallocenes
Scheme 1
Organometallics, Vol. 24, No. 1, 2005 133
Figure 1. ORTEP drawing of 4a. Thermal ellipsoids are
shown at the 50% probability level. The hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and angles
(deg): Hf-Cl 2.3999(14), Hf-Cp (centroid) 2.2293, C(5)-
C(6) 1.456(7), C(6)-C(11) 1.489(7), Si-C(22) 1.881(7), Si-
C(3) 1.896(5), Cl-Hf-Cl 96.16(8), C(22)-Si-C(22) 103.5(5),
C(3)-Si-C(3) 93.4(3), C(1)-C(5)-C(6) 124.0(4), C(11)-
C(6)-C(5) 117.5(4), C(7)-C(6)-C(11) 117.0(5), C(7)-C(6)-
C(5) 125.4(5), Cp-Hf-Cp 126.87.
comparison of ring size is possible, and it is very
interesting to compare the polymerization behavior in
the bis-indenyl and these systems.
Table 1. Comparison of Angles for 4a, 5, and 6
4a
5a
6b
ring system
5/7
5/6
5/5
torsion anglec
5.4
-7.2
-8.5
Results and Discussion
d
θ1e
124.0(4)
117.5(4)
131.4
122.9
139.3
126.2
θ2
Novel metallocenes were synthesized as shown in
Scheme 1. As previously reported, reaction of azulene
and alkyllithium or aryllithium gave the corresponding
lithium salt of dihydroazulene by addition at the 4-posi-
tion of the azulenyl ring.7 After quenching with water,
treatment of dihydroazulene with tetrachloro-1,4-ben-
zoquinone (chloranil) quantitatively gave the corre-
sponding 4-substituted azulene. Furthermore, addition
of alkyllithium or aryllithium to the 4-substituted azu-
lene occurred at the 8-position of the azulenyl ring to
give 4,8-substituted azulene. 2-Methyl-4-phenylazulene
(1) was quantitatively prepared by the reaction of 2-
methylazulene and phenyllithium followed by treatment
with chloranil. By reaction of 1 with butyllithium or
phenyllithium, the lithium salts of dihydroazulenes
(2a-c) were obtained. Subsequent reaction of the li-
thium salts of dihydroazulenes (2a-c) and dichloro-
dimethylsilane in the presence of a catalytic amount of
1-methylimidazole gave bis(dihydroazulenyl)silane (3a-
c). 3a and 3b were obtained in good yield and used
without further purification. However, 3c was relatively
unstable and the yield was low, probably because of
steric repulsion between the bulky 8-tert-butyl group
and the dimethylsilyl group in 3c. It is possible that
dichlorodimethylsilane could react at the 1-position or
the 3-position of 2; however, it reacts at the 1-position.
This shows that the 3-position of 2 is more sterically
hindered by the 4-phenyl groups than the 1-position of
2 is hindered by the 8-substituent groups to give 3. The
bis-azulenyl hafnocenes (4a and 4b) were obtained by
the subsequent reaction of 3a or 3b with n-butyllithium
and hafnium tetrachloride as rac/meso mixtures. The
mixture of 4a was purified by recrystallization from
toluene to give pure rac-4a. However, 4b was recrystal-
a Data from ref 2b. b Data from ref 4c. c Torsion angle between
Cp moiety and 4-Ph group bond. d Ligand mouth angles (I, Chart
1). e Angles between 4-Ph group bond and fused ring moiety (I,
Chart 1).
lized from toluene/diisopropyl ether to give the rac/meso
mixture (r/m ) 5:1) and used for further polymeriza-
tion.
The structure of 4a was determined by X-ray crystal-
lographic analysis. A suitable crystal of 4a was obtained
by recrystallization from toluene/hexane solution. An
ORTEP drawing of 4a and selected bond lengths and
angles are shown in Figure 1. It was found that 4a is a
rac isomer and has C2 symmetry. The two 8-n-butyl
groups are located outside the metal center, and the
4-phenyl groups are located in front of the metal center.
The carbon atoms at the 8-positions are chiral centers
and they have the same configuration, i.e., 8,8′-(R,R)
or -(S,S).
The structure of 4a was compared with the metal-
locenes containing a smaller ring system, the 5/6 rings
in Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (5)2b and the 5/5 rings
in Me2Si(2,5-Me2-3-Ph-6-Cp[b]Tp)2ZrCl2 (6),4c as shown
in Table 1. The structural difference between the 5/6
and 5/5 ring systems has been reported previously.4c In
these metallocenes (4a, 5, and 6), the carbon atoms at
the 4-position to which the 4-phenyl groups are attached
(R position of the cyclopentadienyl moiety) have the
same hybridization, i.e., an sp2 carbon. The torsion
angles between the cyclopentadienyl moieties and the
4-phenyl group bonds (i.e., C(1)-C(5) and C(6)-C(11)
in 4a) are almost the same. The two angles depicted in
I (Chart 1) (θ1 and θ2) decrease due to the ring structure
from the 5/5 to the 5/7 ring system. In the larger ring
system, these angles become smaller and the directions
of the 4-phenyl group are changed as a consequence.
The direction of the 4-phenyl groups in 4a is arranged
(7) (a) Hafner, K.; Weldes, H. Angew. Chem. 1955, 67, 302. (b)
Hafner, K.; Weldes, H. Ann. 1957, 606, 90.

134 Organometallics, Vol. 24, No. 1, 2005
Iwama and Osano
indenyl system.11 In the propylene polymerization with
7 activated using MAO, a large amount of 3,1-units (18.9
mol %) was observed, as shown in Table 2. The reason
for the occurrence of a large amount of 3,1-units in 7
was explained by calculation and steric repulsion of the
4-methyl group in 7 and the methyl group of propylene
monomer, as discussed previously.12 Investigation of the
relationship between the structure of the metallocene
(both steric and electronic effects) and polymerization
behavior is currently under way.
Chart 1
most proximally to the metal center in a comparison of
these three metallocenes. A comparison of the different
ring structures superimposed on each other is shown
in II (Chart 1).
Experimental Section
General Procedures. All manipulations were performed
under a nitrogen atmosphere. THF was distilled from sodium/
benzophenone. Dehydrated hexane, toluene, diisopropyl ether,
and dichloromethane were purchased from Kanto Chemical
Co. and used without further purification. Dichlorodimethyl-
The liquid propylene polymerization of the bis-azu-
lenyl metallocenes (4a, 4b) has been examined using
MAO as cocatalyst.8 The polymerization data are shown
in Table 2 with the reference data obtained for the other
ring system. In propylene homopolymerization of 4a and
4b, propylene-ethylene pseudo-copolymer was unexpect-
edly obtained instead of isotactic polypropylene. Al-
though 4a has C2 symmetry, the obtained polypropylene
was elastomeric and showed no melting point on DSC
measurement. The 13C NMR analysis showed the pres-
ence of a large amount of 3,1-units (12.5 mol %). The
reason for the occurrence of a large amount of 3,1-units
in 4a can be explained by the proximity of the 4-phenyl
group to the monomer coordination site compared with
those in the smaller ring system in 5 and 6. In the 5/7
ring system (4a), greater steric repulsion between the
4-phenyl group and the methyl group of propylene
monomer results in favor of 2,1-insertion. Sequentially,
3,1-units arise from the isomerization of the 2,1-units.9
The increase in the amount of regioinversion (2,1-units
and 3,1-units) is consistent with the decrease in the
angles (θ1 and θ2). In the polymer obtained by 4a, no
2,1-units were observed and the amount of mrrm is
larger than that in 4b. However, a small amount of 2,1-
units was observed and the amount of mrrm was
decreased in 4b. The difference of the microstructure
in the polymers obtained by 4a and 4b is possibly
attributed to the difference in the electronic effect of the
8-substituents (n-butyl groups in 4a and phenyl groups
in 4b). In a comparison of the chemical shifts of the
protons on the Cp moieties (on the 3-position of the
azulenyl rings), a difference in the chemical shift (6.32
ppm for 4a and 6.47 ppm for 4b) is observed, possibly
due to the difference in the electronic effect of the metal
center. As the 8-n-butyl groups are located outside the
metal center, as shown in Figure 1, the steric effect on
the insertion of propylene monomer is negligible.
1
silane was freshly distilled before use. H NMR spectra were
recorded on a Varian Gemini-300 and a Bruker AVANCE 400
spectrometer at 300 and 400 MHz, respectively. 13C NMR spec-
tra were recorded on a JEOL GSX-400 spectrometer at 100
MHz. Electron impact (EI) mass spectra were measured on a
JEOL DX-300. Mass spectra of metallocenes were measured
on a JEOL JMS-700/MStation using the negative desorption
chemical ionization (DCI) mode (isobutane) and an Applied
Biosystems Voyager Elite-DE using the matrix-assisted laser
desorption ionization time-of-flight (MALDI-TOF) mode.
Synthesis of 2-Methyl-4-phenylazulene (1). A solution
of 2-methylazulene (1.46 g, 10.3 mmol) in hexane (20 mL) was
treated with a solution of phenyllithium in cyclohexane/diethyl
ether (12.0 mL, 12.3 mmol, 1.03 M) at 0 °C. After stirring for
40 min at room temperature, the violet color of the solution
disappeared and the lithium salt of 2-methyl-4-phenyldihy-
droazulene was precipitated. After quenching with water, the
organic phase was separated and dried over MgSO4, and the
solvent was removed to give the crude product 2-methyl-4-
phenyldihydroazulene. To a solution of the crude product in
toluene (30 mL) was added tetrachloro-1,4-benzoquinone (2.77
g, 11.28 mmol) at room temperature. The mixture was stirred
for 2 h at room temperature. After the solvent was evaporated,
the resulting mixture was purified by column chromatography
with silica gel (using hexane as eluent) to give 2-methyl-4-
phenylazulene, 1 (2.29 g, quantitative), as a violet viscous oil.
1: 1H NMR (400 MHz, CDCl3) δ 2.59 (s, 3 H, 2-Me), 6.91 (s, 1
H), 7.14 (d, 2 H), 7.43-7.60 (m, 7 H), 8.23 (d, 1 H); 13C NMR
(100 MHz, CDCl3) δ 16.65 (Me), 119.16, 119.28, 122.02, 126.12,
127.64, 128.05, 129.16, 134.54, 134.80, 138.03, 141.58, 143.95,
147.79, 149.67; EI-MS m/z (relative intensity) 218 (M+, 100),
202 (52), 101 (13).
Synthesis of Me2Si(2-Me-4-Ph-8-n-Bu-8H-Azu)2HfCl2
(4a). A solution of 2-methyl-4-phenylazulene (2.02 g, 9.26
mmol) in a mixture of hexane (50 mL) and diisopropyl ether
(5 mL) was treated with a solution of n-butyllithium in hexane
(5.9 mL, 9.26 mmol, 1.56 M) at 0 °C. After stirring for 30 min
at room temperature, THF (1 mL) was added and stirred for
another 1 h at the same temperature. The reaction mixture
was cooled to 0 °C, and THF (19 mL), 1-methylimidazole (20
µmol), and 0.5 equiv of dichlorodimethylsilane (0.56 mL, 4.63
mmol) were added sequentially. The mixture was warmed to
room temperature and stirred at this temperature for 2 h.
After quenching with water, the organic phase was separated
and dried over MgSO4, and the solvent was removed to give
the crude product bis(2-methyl-4-phenyl-8-n-butyldihydro-
azulenyl)dimethylsilane, 3a (2.8 g), as a diastereomeric mix-
ture.
Similar propylene-ethylene pseudo-copolymers were
reported by using the bridged bis-indenyl system Et-
(4,7-Me2-H4-Ind)2ZrCl2 (7)1c,10 and an unbridged bis-
(8) The homologous zirconocene of 4a was also prepared. Although
polymerization was investigated under the same conditions as that of
the polymerization using 4a and 4b, unexpectedly no activity was
observed.
(9) (a) Grassi, A.; Zambelli, A.; Resconi, L.; Albizzati, E.; Mazzocchi,
R. Macromolecules 1988, 21, 617. (b) Busico, V.; Cipullo, R.; Chadwick,
J. C.; Modder, J. F.; Sudmeijer, O. Macromolecules 1994, 27, 7538. (c)
Resconi, L.; Fait, A.; Piemontesi, F.; Colonnesi, M.; Rychlicki, H.;
Zeigler, R. Macromolecules 1995, 28, 6667.
(10) (a) Spaleck, W.; Antberg, M.; Aulbach, M.; Bachmann, B.; Dolle,
V.; Haftka, S.; Ku¨ber, F.; Rohrmann, J.; Winter, A. In Ziegler Catalysts;
Fink, G., Mu¨lhaupt, R., Brintzinger, H.-H., Eds.; Springer-Verlag:
Berlin, 1995; p 83. (b) Resconi, L.; Camurati, I.; Sudmeijer, O. Top.
Catal. 1999, 7, 145.
(11) Dias, M. L.; Lopes, D. E. B.; Grafov, A. V. J. Mol. Catal. A:
Chem. 2002, 185, 57.
(12) Toto, M.; Cavallo, L.; Corradini, P.; Moscardi, G.; Resconi, L.;
Guerra, G. Macromolecules 1998, 31, 3431.

Novel Azulenyl Metallocenes
Organometallics, Vol. 24, No. 1, 2005 135
Table 2. Propylene Polymerization Resultsj
metallocene
Tp (°C)
Al/M
5000
5000
25 000
215 000
2000
activitya
Tm (°C)
Mw
mrrm (%)
2,1-unitsb (mol %)
3,1-units (mol %)
4a
4bc
5d
70
70
70
70
50
55
35
518
1953
5
n.d.f
n.d.
156
156
90 000g
120 000h
1 184 000
445 000
3.3
1.8
0.1
0.4
0.0
0.2
0.4
0.3
0.0
12.5
8.9
0.0
6d
0.0
7e
370 000i
18.9
a kg-polymer/mmol metal‚h. b Erythro 2,1-regioerrors determined by 13C NMR. c Rac/meso mixture (r/m ) 5:1). d Data from ref 4c.
e Data from refs 1c and 10b. f Not detected. g Mw/Mn ) 3.1. h Mw/Mn ) 2.2. i Pn from intrinsic viscosity. j Conditions: liquid propylene,
1 h, MMAO.
To a solution of 3a (2.8 g) in diisopropyl ether (15 mL) was
added a solution of n-butyllithium in hexane (6.0 mL, 9.26
mmol, 1.56 M) at 0 °C. The mixture was stirred at room
temperature overnight. To the resulting mixture was added
toluene (75 mL), the mixture was cooled at -10 °C, and
hafnium tetrachloride (1.48 g, 4.63 mmol) was added at -10
°C. After warming gradually to room temperature, the mixture
was stirred for 4 h and for 1 h at 40 °C. The resulting mixture
was concentrated under reduced pressure, washed with hexane
(20 mL × 3), and extracted with dichloromethane (20 mL) to
give a rac/meso mixture of 4a (1.2 g, 30%). Recrystallization
of the rac/meso mixture of 4a (212 mg) from toluene allowed
isolation of the pure rac-4a (23 mg).
0.15 × 0.07 mm, obtained by recrystallization from toluene/
hexane solution at room temperature. The X-ray diffraction
data were collected on a κ-axis diffractometer with a Bruker
SMART 1000 CCD detector with the ω scan mode (0.3°) using
Mo KR radiation (50 kV, 40 mA). The structure was solved by
direct methods (SHELXS97)13a and refined by full matrix least-
squares technique (SHELXL97).13b A total of 12 478 reflections
were measured, of which 4756 unique reflections were used
in the structure refinement. The final R factor was 0.0315 for
4756 reflections.
Crystal data: fw ) C44H50Cl2HfSi, orthorombic, space group
Fdd2, a ) 15.2911(14) Å, b ) 51.965(5) Å, c ) 9.8662(9) Å, â
) 90°, V ) 7839.7(13) Å3, Z ) 8, Dcalc ) 1.451 g/cm3, R ) 0.0315
for 4756 reflections (Fo > 2σ(Fo)).
Propene Polymerization. A dry 2 L steel reactor was
charged with nitrogen and liquid propene (1500 mL) at room
temperature. Then a solution of methylaluminoxane in toluene
(2.0 mL, 4.0 mmol, Al/Hf ) 5000, MMAO purchased from
Tosoh Finechem Corp.) and a solution of metallocene in toluene
(0.8 mL, 0.8 µmol) were added to the reactor at room temper-
ature. The reactor was heated to 70 °C within 10 min and kept
at this temperature for 1 h. The reaction was stopped by
venting the unreacted monomer and cooling. The yield of
polymer was determined by weighing.
Polymer Analysis Procedures. Molecular masses were
determined on a Waters 150C at 135 °C in 1,2-dichlorobenzene.
The melting point of the polymer (Tm) was determined on a
Dupont TA2000 at a heating rate of 10 °C/min. The result of
the second scan is reported. The 13C NMR analysis of the
polymer was performed on a JEOL EX-270 (67.8 MHz) at 130
°C. The sample was obtained with the polymer (200 mg)
dissolved in 1,2-dichlorobenzene (2.0 mL) and C6D6 (0.5 mL).
The 2,1-units and 3,1-units were evaluated as described
previously.14 The amount of mrrm was evaluated from the
peak of mrrm (20.0 ppm) and the peaks corresponding to the
methyl carbons (19.8-22.0 ppm). The methyl peak of the 3,1-
units (20.9 ppm) was corrected; it was overlapped by the peaks
of the methyl carbons.
1
4a: H NMR (400 MHz, CDCl3) δ 0.87 (t, 6 H, Bu), 1.03 (s,
6 H, Me2Si), 1.1-1.8 (m, 12 H, Bu), 2.22 (s, 6 H, 2-Me), 3.69
(dd, 2 H, 8-H), 5.42 (dd, 2 H), 5.90 (dd, 2 H), 6.15 (d, 2 H),
6.32 (s, 2 H, 3-H), 7.30 (br d, 10 H, arom); 13C NMR (100 MHz,
CDCl3) δ 3.73 (SiMe2), 14.09, 18.11 (2-Me), 22.74, 29.49, 36.36,
39.77, 101.99, 124.03, 126.97, 128.03, 128.09, 128.58, 129.30,
129.33, 129.80, 134.23, 134.32, 137.94, 143.71; negative MALDI-
TOF-MS, parent ion at m/z 856 (180Hf 35Cl, M-) with appropri-
ate isotope ratios. Anal. Found: C, 61.84; H, 6.82. Calcd
(C44H50Cl2SiHf): C, 61.71; H, 5.89.
Synthesis of Me2Si(2-Me-4,8-Ph2-8H-Azu)2HfCl2 (4b). A
solution of 2-methyl-4-phenylazulene (2.0 g, 9.3 mmol) in a
mixture of hexane (50 mL) and diisopropyl ether (1 mL) was
treated with a solution of phenyllithium in cyclohexane/diethyl
ether (9.4 mL, 9.3 mmol, 0.99 M) at 0 °C. After stirring for 2
h at room temperature, the lithium salt of 2-methyl-4,8-
diphenyldihydroazulene was precipitated and the supernatant
liquid was removed by decantation. To the reaction mixture
were added THF (25 mL), hexane (20 mL), 1-methylimidazole
(20 µmol), and 0.5 equiv of dichlorodimethylsilane (0.53 mL,
4.4 mmol) sequentially. The mixture was warmed to room
temperature and stirred at this temperature for 30 min. After
quenching with water, the organic phase was separated and
dried over MgSO4, and the solvent was removed to give the
crude product bis(2-methyl-4,8-diphenyldihydroazulenyl)di-
methylsilane, 3b (3.1 g), as a diastereomeric mixture.
To a solution of 3b (3.1 g) in diisopropyl ether (20 mL) was
added a solution of n-butyllithium in hexane (5.6 mL, 8.7
mmol, 1.59 M) at 0 °C. The mixture was stirred at room
temperature overnight. To the resulting mixture was added
toluene (70 mL), the mixture was cooled to -10 °C, and
hafnium tetrachloride (1.4 g, 4.4 mmol) was added at -10 °C.
After warming gradually to room temperature, the mixture
was stirred for 1 h and for 2 h at 40 °C. The resulting mixture
was concentrated under reduced pressure, washed with hexane
(25 mL), and extracted with toluene (15 mL) and diisopropyl
ether (40 mL) to give a rac/meso mixture of 4b (1.2 g, 31%).
Recrystallization of the rac/meso mixture of 4b (1.05 g) from
a mixture of toluene (10 mL) and diisopropyl ether (10 mL)
gave the rac/meso mixture of 4b (80 mg, r/m ) 5:1).
Acknowledgment. We thank the Center for Ana-
lytical Chemistry and Science, Mitsubishi Chemical
Group Science and Technology Research Center Inc., for
help in the measurement of mass spectra and elemental
analysis.
Supporting Information Available: Crystallographic
details, including lists of positional parameters, thermal
displacement parameters, bond lengths, and bond angles for
4a. This material is available free of charge via the Internet
at http://pubs.acs.org.
1
4b: H NMR (400 MHz, CDCl3) δ 1.01 (s, 6 H, Me2Si), 2.38
(s, 6 H, 2-Me), 5.18 (d, 2 H), 5.7-6.1 (m, 6 H), 6.47 (s, 2 H,
3-H), 7.2-7.4 (m, 20 H, arom); negative DCI-MS, parent ion
at m/z 896 (180Hf 35Cl, M-) with appropriate isotope ratios.
Anal. Found: C, 63.46; H, 5.57. Calcd (C48H42Cl2SiHf): C,
64.32; H, 4.72.
Crystallographic Studies. The X-ray crystallographic
analysis was performed using the crystal with the size 0.2 ×
OM0494418
(13) (a) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(b) Sheldrick, G. M. SHELXL97, Program for Crystal Structure
Refinement; University of Go¨ttingen: Germany, 1997.
(14) Tsutsui, T.; Ishimaru, N.; Mizuno, A.; Toyota, A.; Kashiwa, N.
Polymer 1989, 30, 1350.