Divalent ansa-Zirconocenes: Stereoselective Synthesis and High Activity for Propylene Polymerization
dataset
posted on 2004-01-14, 00:00 authored by Eugene Y.-X. Chen, Richard E. Campbell,, David D. Devore, D. Patrick Green, Bernie Link, Jorge Soto, David R. Wilson, Khalil A. AbboudThe reduction of ZrCl4(PR3)2 with Li powder, in the presence of a stoichiometric amount of trans-1,4-diphenyl-1,3-butadiene, affords the Zr(II) diene complexes (1) in 90−93% yields. This reaction consists of a rate-limiting step for the formation of the chloride-bridged Zr(III) dimer (2) and a fast diene-driven disproportionation of 2 to 1 and ZrCl4(PR3)2 that re-enters the reduction cycle. The reaction of 1 with Li2{Me2Si(2-Me-4-Ph-Ind)2} in toluene produces quantitatively the desired racemic, divalent ansa-zirconocene (3) that is a highly active isospecific propylene polymerization catalyst upon activation with common activators.
