title: Divalent ansa-zirconocenes: stereoselective synthesis and high activity for propylene polymerization.
abstract: The 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.
authors.affiliation: The Dow Chemical Company, Midland, Michigan 48674, USA. eychen@lamar.colostate.edu
authors.forename: Eugene Y-X
authors.initials: EY
authors.lastname: Chen
authors.forename: Richard E
authors.initials: RE
authors.lastname: Campbell
authors.forename: David D
authors.initials: DD
authors.lastname: Devore
authors.forename: D Patrick
authors.initials: DP
authors.lastname: Green
authors.forename: Bernie
authors.initials: B
authors.lastname: Link
authors.forename: Jorge
authors.initials: J
authors.lastname: Soto
authors.forename: David R
authors.initials: DR
authors.lastname: Wilson
authors.forename: Khalil A
authors.initials: KA
authors.lastname: Abboud