Synthesis, structure, and catalytic properties of ansa-zirconocenes, Me2Si(RInd)(2)ZrCl2 (R = 2-p- or 3-p-tolyl)

Abstract

ansa-Ligands, Me2Si(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 Me2SiCl2 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 H-1-NMR spectroscopy. These results imply that 1 and 2 undergo the diastereomerization process by migration of silicon moiety and hydrogen atom, respectively. ansa-Zirconocenes, Me2Si(RInd)(2)ZrCl2 [R = 2-p (3) and 3-p-tolyl (4)], have been prepared from the reactions of the corresponding dilithiated ligands with ZrCl4 in diethyl ether and hexane at - 78 degrees 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 degrees C by the enantiomorphic site control mechanism and meso-4 affords a syndiotactic dominant PP having a rr triad of 49% at - 30 degrees C by the chain end control mechanism. (C) 1998 Elsevier Science S.A. All rights reserved.