Abstract
Novel unsymmetrical ansa-metallocenes Me 2 C(3-t-Bu-C 5 H 3 )(3-R-C 9 H 5 )MCl 2 (R=t-Bu; M =Ti (1a), M=Zr (1b), M= Hf(1c)), Me 2 Si(3-t-Bu-C 5 H 3 )(3-t-Bu-C 9 H 5 )ZrCl 2 (2), and Me 2 C(3-t-Bu-C 5 H 3 )-(3-Me-C 9 H 5 )ZrCl 2 (3) were synthesized and separated into threo and erythro isomers by repeated recrystallization. The molecular structure of Me 2 C(3-t-BuC 5 H 3 )(3-t-Bu-C 9 H 5 )ZrCl 2 (threo-1b) was determined by X-ray crystallography. Polymerization of propylene with one of these metallocene complexes (threo-1b) coupled with MAO (methylaluminoxane) in toluene was found to afford a highly isotactic polymer of M w 105 000 with % mm >99.6 which shows an extremely high melting point of 161°C
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