Extremely active polymerizations of propene by bisindenylzirconocenes and tetra(pentafluorophenyl)-borate

Abstract

The homogeneous homopolymerization of propene was conducted with the two catalyst precursors Me 2Si(Ind) 2ZrBz 2 ( 1) and Me 2Si(2-Me-4-Ph-Ind) 2ZrBz 2 ( 2) and triphenylmethyltetrakis(pentafluorophenyl)borate [C(CH 3) 3][B(C 6F 5) 4] ( 3) as cocatalyst. After synthesizing the dibenzyl compounds from their dichloride derivatives the catalyst system ( 1)/( 3) was optimized in respect to the catalyst/cocatalyst ratio and the amount of tri(isobutyl) aluminum (TIBA). The polymerization behavior of the catalyst system ( 2)/( 3) is investigated using a central composite experimental design. In this design the dependence of the polymer properties on temperature, catalyst and monomer concentration are modeled. The dibenzyl compound ( 2) shows extremely high catalytic activities of 600 000 kg PP/mol Zr h mol p. The polymers produced with this catalyst exhibit very high melting points and molecular weights.