Table 1 Polymerization of propene with rac-1c in toluene as solvent and
direct methods (SHELXS-97) and refined by full-matrix least-squares
(SHELXL-97) on F2 for all data with Chebyshev weights to R = 0.038
(obs.), wR = 0.105 (all data), 595 parameters, S = 1.02, H atoms riding,
max. shift/error 0.001, residual rmax = 0.775 e Å23. CCDC 000/000.
rac-1c: C27H26BCl2PZr·2.5CH2Cl2, Mr = 766.69, orange prism, crystal
size 0.18 3 0.32 3 0.32 mm, a = 33.5561(8), b = 10.9508(2), c =
20.6866(6) Å, b = 121.201(2)°, U = 6502.1(3) Å3, T = 100 K, monoclinic,
MAO as activatora
Tacticity
Productivity/kg
(% mmmm-
T/°C
Al:Zr
PP mol[Zr]21 h21 1023 Mw/g mol21 pentades)
20
40
40
40
60
1000
220
1000
5000
1000
326
783
1052
1232
174
315
161
129
97
96
93
90
93
85
space group C2/c (no. 15), Z = 8, Dc = 1.57 g cm23, m = 0.98 mm21
.
Siemens SMART diffractometer, Mo-Ka X-radiation, l = 0.71073 Å.
34678 measured reflections, no absorption correction, 11860 unique, 8996
observed [I > 2.0s(Fo2)]. The structure was solved by direct methods
(SHELXS-97) and refined by full-matrix least-squares (SHELXL-97) on F2
for all data with Chebyshev weights to R = 0.062 (obs.), wR = 0.137 (all
data), 357 parameters, S = 1.13, H atoms riding, max. shift/error 0.001,
residual rmax = 2.678 e Å23 (0.789 Å from Cl6 in solute).
62
a Polymerization conditions: 2 bar propene, 1 h, ca. 30 mmol l21 [Zr].
crystallographic files in .cif format.
for ethene polymerization producing high molecular weight
polymer (Mw ≈ 700000 g mol21 as determined by GPC), this
complex turned out to be a rather poor catalyst for the
polymerization of propene. For example, using a Al/Zr ratio of
1000, activities of only 10–75 kg PP mol[Zr]21 h21 were
observed at room temperature with the production of atactic oily
PP (Mw ≈ 20000 g mol21). In contrast, the phosphine adduct
rac-1c displayed remarkably high activity and stereoselectivity
(Table 1). 13C NMR spectra of typical PP samples obtained at
various polymerization temperatures demonstrate high degrees
of isotacticity, e.g. 96% isotacticity at room temperature.
Thus, complex rac-1c is the first boron-bridged zirconocene
which catalyzes the polymerization of propene. It competes
well with other ansa-type zirconocenes, especially with respect
to isotacticity and molecular weight.5,6 Since the ether analog
rac-1a is a poor catalyst, it is obvious that the nature of the
donor ligand at boron is crucial. A possible explanation is that
for rac-1a excess MAO induces decomplexation of the donor
ligand, thereby initiating the decomposition of the ansa-
metallocene, whereas for rac-1c the donor ligand PMe3 remains
bonded to boron throughout the polymerization. Whatever the
exact explanation may be, it is clear that the use of PMe3
provides a handle to control activity and tacticity. It remains to
be seen whether other phosphines or different donor ligands
induce similar effects.
1 Reviews: Ziegler Catalysts: Recent Scientific Innovations and Techno-
logical Improvements, ed. G. Fink, R. Mülhaupt and H. H. Brintzinger,
Springer, Berlin, 1995; M. Bochmann, J. Chem. Soc., Dalton Trans.,
1996, 255; H.-H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger and R.
Waymouth, Angew. Chem., 1995, 107, 1255; Angew. Chem., Int. Ed.
Engl., 1995, 34, 1143; see also: L. Resconi, F. Piemontesi, I. Camurati, O.
Sudmeijer, I. E. Nifant’ev, P. V. Ivchenko and L. G. Kuz’mina, J. Am.
Chem. Soc., 1998, 120, 2308; I.-M. Lee, W. J. Gauthier, J. M. Ball, B.
Iyengar and S. Collins, Organometallics, 1992, 11, 2115.
2 (a) M. T. Reetz, H. Brümmer, M. Kessler and J. Kuhnigk, Chimia, 1995,
49, 501; (b) M. Bochmann, S. J. Lancaster and O. B. Robinson, J. Chem.
Soc., Chem. Commun., 1995, 2081; (c) D. S. Stelck, P. J. Shapiro, N.
Basickes and A. L. Rheingold, Organometallics, 1997, 16, 4546: (d) R.
Duchateau, S. J. Lancaster, M. Thornton-Pett and M. Bochmann,
Organometallics, 1997, 16, 4995; (e) S. J. Lancaster, M. Thornton-Pett,
D. M. Dawson and M. Bochmann, Organometallics, 1998, 17, 3829; (f)
J. Ruwwe, G. Erker and R. Fröhlich, Angew. Chem., 1996, 108, 108;
Angew. Chem., Int. Ed. Engl., 1996, 35, 80.
3 K. A. Rufanov, V. V. Kotov, N. B. Kazennova, D. A. Lemenovskii, E. V.
Avtomonov and J. Lorberth, J. Organomet. Chem., 1996, 525, 287; K.
Rufanov, E. Avtomonov, N. Kazennova, V. Kotov, A. Khvorost, D.
Lemenovskii and J. Lorberth, J. Organomet. Chem., 1997, 536–537, 361;
personal communication from K. A. Rufanov to M. Willuhn, 1997.
4 For the use of weakly nucleophilic bases for the deprotonation of
cyclopentadienyl- and indenyl-boranes see also: G. E. Herberich and A.
Fischer, Organometallics, 1996, 15, 58; G. E. Herberich, E. Barday and
A. Fischer, J. Organomet. Chem., 1998, 567, 127; E. Barday, B. Frange,
B. Hanquet and G. E. Herberich, J. Organomet. Chem., 1999, 572,
225.
Notes and references
† Crystal data: rac-1b: C28H25BCl2OZr, Mr = 550.41, orange prism,
crystal size 0.28 3 0.32 3 0.49 mm, a = 10.746(1), b = 15.510(3), c =
16.308(3) Å, a = 62.15(1), b = 82.92(1), g = 83.25(1)°, U = 2379.2(7)
5 A. Z. Voskoboynikov, A. Y. Agarkov, E. A. Chernyshev, I. P.
Beletskaya, A. V. Churakov and L. G. Kuz’mina, J. Organomet. Chem.,
1997, 530, 75.
6 W. A. Herrmann, J. Rohrmann, E. Herdtweck, W. Spaleck and A. Winter,
Angew. Chem., 1989, 101, 1536; Angew. Chem., Int. Ed. Engl., 1989, 28,
1511.
¯
Å3, T = 293 K, triclinic, space group P1 (no. 2), Z = 4, Dc = 1.54 g cm23
,
m = 0.71 mm21. Enraf-Nonius CAD4 diffractometer, Mo-Ka X-radiation,
l = 0.71069 Å. 11215 measured reflections, no absorption correction,
10815 unique, 8006 observed [I > 2.0s(Fo2)]. The structure was solved by
Communication 9/02543J
1106
Chem. Commun., 1999, 1105–1106