Synthesis, structure, and catalytic properties of ansa-zirconocenes, Me 2Si(RInd) 2ZrCl 2 (R=2- p- or 3- p-tolyl)

Abstract

ansa-Ligands, Me 2Si(RInd) 2 [R=2- p ( 1) and 3- p-tolyl ( 2)], have been prepared as a mixture of rac- and meso-isomers in a ratio of 1:1 from the reactions of Me 2SiCl 2 with cyanocuprates of 1- p-tolylindene and 2- p-tolylindene in diethyl ether, respectively. Pure rac-isomers, 1r and 2r, have been isolated by fractional recrystallization of 1 and 2. Thermal diastereomerization of 1 and 2 between rac- and meso-isomers has been studied by 1H-NMR spectroscopy. These results imply that 1 and 2 undergo the diastereomerization process by migration of silicon moiety and hydrogen atom, respectively. ansa-Zirconocenes, Me 2Si(RInd) 2ZrCl 2 [R=2- p ( 3) and 3- p-tolyl ( 4)], have been prepared from the reactions of the corresponding dilithiated ligands with ZrCl 4 in diethyl ether and hexane at −78°C. The molecular structure of rac- 3 has been determined by a single crystal X-ray diffraction study. Propylene polymerization has been studied using rac- 3 and meso- 4 in the presence of methylaluminoxane (MAO). Catalyst rac- 3 produces a highly isotactic polypropylene (PP) at 0°C by the enantiomorphic site control mechanism and meso- 4 affords a syndiotactic dominant PP having a rr triad of 49% at −30°C by the chain end control mechanism.