Elke Barsties

ansa-Metallocene derivatives: XVII. Racemic and meso diastereomers of group IV metallocene derivatives with symmetrically substituted, dimethylsilanediyl-bridged ligand frameworks. Crystal structure of R,S-Me2Si(3-t-Bu-5-MeC5H2)2ZrCl2☆

Abstract The formation of racemic and meso diastereomers of the disubstituted ansa-zirconocenes (CH3)2Si(1-C5H3-3-R)2ZrCl2 (R  t-butyl, trimethylsilyl, α,α-dimethylbenzyl and 1-phenylcyclohexyl) from dimethylsilanediyl-bridged, symmetrically substituted bis-cyclopentadienyl dianion derivatives and ZrCl4·2THF has been studied under a variety of conditions. Rac/meso ratios close to 1 were obtained in all cases. Similar product ratios were observed for analogous titanium and hafnium complexes with R  trimethylsilyl. A significant increase in the rac/meso product ratio was observed when an additional substituent was present next to the dimethylsilyl bridge as in (CH3)2Si(1-C5H2-3-R-5-CH3)2ZrCl2 (R  CH(CH3)2, C(CH3)3). It is suggested that intermediates with one η1-bound ring ligand control the stereochemical course of the ansa-metallocene formation. The crystal structure of R,S-(CH3)2Si(1-C5H2-3-C(CH3)3-5-CH3)2ZrCl2 is reported.

Supported metallocene complexes having heterofunctional groups in the cyclopentadienyl system as catalyst systems

A supported catalyst system that is obtained by a) reacting a finely divided carrier with an a-trisalkoxy-silyl-ω-haloalkyl compound, b) adding a metallocene complex of the indicated formula I to the reaction product of a); c) reacting the product of b) with a quaternizing agent; and d) optionally adding an open-chain or cyclic alumoxane compound. The catalyst system can be used to prepare polymers of C2 -C10 -alk-1-enes.