P. J. Shapiro et al.
FULL PAPER
1
uum (yield: 3.05 g, 75%). H NMR (300 K, CDCl3): δ ϭ 7.57 (m,
3 H, C6H5), 7.38 (m, 14 H, C6H5), 6.97 (m, 3 H, C6H5), 6.60 (m,
better than that of a silicon-bridged species used as a
benchmark in industry, the poor thermal stability of the
boron-bridged system and our inability to isolate the rac
isomer 4 from the mixture diminishes its utility.
The fairly high percentage of isotactic triads (63.6%) and
pentads (52.4%) in the polypropylene formed with 4Ϫ6 is
interesting because it indicates that rac isomer 4 is the most
active species among the three diastereomers, since it con-
stitutes only about 25% of the mixture. A more dramatic
effect of the higher activity of a rac isomer on the isotactic-
ity of polypropylene produced by a mixture of rac and meso
ansa-zirconocene species has been reported by Collins et
al.[22]
2
4 H, C5H4), 5.51 (m, 4 H, C5H4), 2.67 (d, JPH ϭ 16.5 Hz, 2 H,
PCH2) ppm. 13C{1H} NMR (300 K, CDCl3): δ ϭ 135, 133.3
(BC6H5), 133.4, 133.3, 129.2, 129.1 (PC6H5), 127.112, 125.0, 124.8
(C5H4), 122.9 (d, JP,C ϭ 84 Hz, PCH2) ppm. 31P{1H} NMR
1
(300 K, CDCl3): δ ϭ 37.1 ppm. 11B NMR (300 K, CDCl3): δ ϭ
Ϫ9.1 ppm. C35H30BCl2PZr (654.5): calcd. C 64.22, H 4.62; found
C 64.03, H 4.71.
(Ph)(2-CH3-4-Ph-ind)2B: PhBCl2 (1.3 mL, 1.58 g, 10 mmol) was
added to a solution of (2-Me,4-Ph-ind)Li (4.2 g, 20 mmol) in Et2O
(70 mL) at Ϫ78 °C. The reaction mixture turned from red to yellow
as it warmed to room temperature. After stirring for 15 h, the reac-
tion was filtered, and the filtrate was dried under vacuum, to give
a yellow solid that consisted of (Ph)(2-CH3-4-Ph-ind)2B as a mix-
ture of double bond isomers complexed by 0.5 equiv. Et2O (yield:
4.8 g, 91%). 1H NMR (300 K, C6D6): δ ϭ 7.60Ϫ7.50 (m, 6 H,
Alternative synthetic methods designed to increase selec-
tivity for rac isomer 4 were explored, such as the reaction
between (Ph)B(2-CH3-4-Ph-ind)2and Zr(NMe2)4
[27,28]
and
the reaction of (Ph)B(2-CH3-4-Ph-ind)2Li2 with either C6H5), 7.30Ϫ7.01 (m, 30 H, C6H5 ϩ PhC6H3), 6.50 (d, PhC6H3),
Cl2(PEt3)2Zr(η2Ϫ1,4-Ph2ϪC4H4)[24,25] or Cl2(THF)Zr[PhN-
4.18, 4.11(s, 2 H, MeC5H2), 3.01 (m, 2 H, Et2O), 1.84, 1.81, 1.73
(s, 6 H, CH3), 0.90 (3 H, Et2O) ppm.
(CH2)3NPh);[29] these methods have been used successfully
for the rac-selective synthesis of other bridged bis(indenyl)-
zirconium complexes. Unfortunately, these approaches did
not afford isolable ansa-zirconocene products.
(Ph)B(2-CH3-4-Ph-Ind)2Li2:
Lithium
bis(trimethylsilyl)amide
(2.88 g, 17.20 mmol) was added to a solution of (Ph)B(2-CH3-4-
Ph-ind)2 (4.20 g, 7.93 mmol) in toluene (150 mL) cooled to Ϫ78
°C. The reaction mixture was allowed to warm to room tempera-
The preparation of other ylide-like adducts of these bo-
ron-bridged ansa-zirconocene complexes is currently being ture and then heated at 75 °C with stirring for 48 h to give a suspen-
sion. The precipitate was isolated by filtration and washed with
explored in order to generate more stable species from
which the pure rac isomer can be isolated.
toluene (30 mL ϫ 2) and petroleum ether (50 mL), and dried under
1
vacuum, to give a grey-orange solid (yield: 2.30 g, 54%). H NMR
(300 K, [D6]DMSO): δ ϭ 7.73 (d, 3JH,H ϭ 7.4 Hz, 6 H, C6H5), 7.34
3
3
(t, JH,H ϭ 7.5 Hz, 9 H, C6H5), 7.13 (t, JH,H ϭ 7.0 Hz, 2 H, inde-
nyl), 6.78 (d, 3JH,H ϭ 7.8 Hz, 2 H, 6.29 (m, 2 H, indenyl), 6.06 (m,
2 H, indenyl), 1.89 (s, 6 H, CH3) ppm.
Experimental Section
Me2S(Ph)B(2-CH3-4-Ph-ind)2ZrCl2 (3): Zr(SMe2)2Cl4 solid (0.98 g,
2.74 mmol) was added to a suspension of (Ph)B(2-CH3,4-Ph-
ind)2Li2 (1.40 g, 2.74 mmol) in toluene (120 mL) cooled to Ϫ78 °C.
The mixture was allowed to warm to room temperature and stirred
for 18 h. After filtration to remove LiCl, the volatiles were removed
from the filtrate under vacuum. The filtrate residue was washed
with petroleum ether (30 mL ϫ 2) and dried under vacuum (yield:
1.70 g, 86%). Recrystallization of 3 from benzene/pentane gave a
red-brown, crystalline product with the formula 3·4C6H6. 1H NMR
General Remarks: All manipulations were carried out under argon
atmosphere using Schlenk and glovebox techniques. Argon and ni-
trogen were purified by passage over an oxy tower BASF catalyst
1
(Aldrich) and molecular sieves (4 A). H, 13C, 11B, and 31P NMR
˚
spectra were recorded on Varian Unit Plus 400 MHz NMR
(100 MHz 13C) IBM NR-300 (300 MHz 1H; 75 MHz 13C) and
1
Bruker AVANCE 500 spectrometers (500 MHz H; 125 MHz 13C).
1H and 13C spectra were referenced to residual protons in the sol-
vent. 11B and 31P were referenced to external standards (BF3·OEt2
and 80% H3PO4). Deuterated solvents were dried over molecular
3
(300 K, C6D6): minor isomer (rac): δ ϭ 7.91 (d, JH,H ϭ 7.2 Hz, 6
˚
H, C6H5) 6.46, 6.77 (m, 6 H, C6H5), 2.11 (s, 6 H, CH3) ppm; major
sieves (4 A). PhBCl2 (Aldrich) was used as received. Toluene, ben-
3
isomer (meso): δ ϭ 7.90 (d, JH,H ϭ 7.2 Hz, 6 H, C6H5), 6.61 (m,
zene, pentane, petroleum ether, and dichloromethane solvents were
dried over alumina and stored in line pots over Na/benzophenone
or CaH2 in the case of dichloromethane. Me2S(Ph)B(η5-
C5H4)2ZrCl2[11] and Ph3PCH2[30] were prepared according to litera-
ture procedures. 2-Methyl-4-phenylindene was prepared as de-
scribed in the literature[21] and was also purchased from Boulder
Scientific and used as received. Elemental analyses were performed
by Desert Analytics (Tuscon, Az).
6 H, C6H5), 2.09 (s, 6 H, CH3) ppm; both isomers: δ ϭ 7.55Ϫ7.0
(m, 22 H, indenyl and C6H5), 2.24 (s, 12 H, SCH3) ppm. 13C{1H}
NMR (300 K, C6D6): δ 140.23, 139.97, 138.82, 137.54, 137.51,
134.30, 133.64, 131.19, 129.81, 128.84, 128.81, 128.76, 128.65,
128.62, 128.58, 128.55, 128.23, 125.49, 125.17, 123.41, 119.06,
117.86, 108.11, 106.89, 104.88, 19.30, 12.29, 19.14, 17.33, 16.45,
16.36. No 11B signal was detected, possibly due to extreme broad-
ening caused by rapid exchange of the Me2S adduct. C46H41ZrCl2B
(766.8): calcd. C 74.69, H 5.39; found C 74.67, H 5.13.
Ph3PCH2(Ph)B(η5-C5H4)2ZrCl2 (2): Toluene (80 mL) was trans-
ferred to a mixture of Ph3PCH2 (1.71 g, 6.2 mmol) and 1 (3.30 g,
6.2 mmol) in a flask cooled to Ϫ78 °C. The reaction solution was Ph3PCH2(Ph)B(2-CH3-4-Ph-Ind)2ZrCl2 (4؊6): Ph3PCH2 (511 mg,
warmed to room temperature and stirred for 18 h to give a grey
suspension. The precipitate was isolated by filtration and washed
with toluene (30 mL ϫ 2), and dried under vacuum. The resulting
yellow-grey solid was redissolved in dichloromethane (20 mL) and
layered with pentane. Slow diffusion of the pentane into the di-
chloromethane caused the precipitation of crystalline product,
which was washed with pentane (30 mL ϫ 2) and dried under vac-
1.85 mmol) was added to a solution of 3 (1.21 g, 1.85 mmol) in
toluene (120 mL) at Ϫ78 °C, and the reaction was warmed to room
temperature with stirring. The reaction solution was dark red in
color after it was stirred at room temperature for 18 h. After fil-
tration, the volatiles were removed from the filtrate under reduced
pressure, and the residue was washed with pentane (50 mL ϫ 2)
and dried under vacuum to give a red solid. Recrystallization of the
3376
2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2004, 3370Ϫ3378
Shapiro, Pamela J.
