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

Abstract ansa -Ligands, Me 2 Si(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 2 SiCl 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 1 H-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 2 Si(RInd) 2 ZrCl 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.