Stereochemistry of First Monomer Insertion into a Metal−Methyl Bond: Enantioselectivity and Diastereoselectivity in 3-Methyl-1-pentene Polymerization with Metallocene Catalysts

Abstract

The stereochemistry of first monomer insertion in the polymerization of racemic 3-methyl-1-pentene ((RS)-3MP1) with three different metallocene complexes, Me2Si(Ind)2ZrCl2 (I), Me2Si(BenzInd)2ZrCl2 (II), and Me2Si(MeBenzInd)2ZrCl2 (III), in the presence of MAO/Al(13CH3)3 cocatalyst has been studied and the results have been compared to those previously obtained using the traditional isospecific TiCl3/Al(13CH3)3 heterogeneous catalyst. The highest enantioselectivity and diastereoselectivity are observed with the least hindered metallocene (catalyst I). While enantioselectivity decreases due to benzannelation of the ligand with catalyst II, the methyl substitution in the 2-position of the cyclopentadienyl rings with catalyst III causes an almost complete lack of diastereoselectivity.