Bis(η5-cyclopentadienyl)bistriphenylsilanolatozirconium( IV): a new precursor for ethylene polymerization catalysis

Abstract

Trialkylsilanols were reported to modify and also to improve the catalytic performance in ethylene polymerization when added to zirconocene/methylaluminoxane (MAO) systems. In order to obtain more information about the chemistry involved, a new stable catalytic precursor was investigated in this work. The precursor bis(h5-cyclopentadienyl)bistriphenylsilanolatozirconium(IV) [ZrCp2(OSiPh3)2] was compared to ZrCp2(CH3)2 and ZrCp4, which can generate ZrCp2(OSiPh3)2 in situ on triphenylsilanol addition. In ethylene polymerization, ZrCp2(OSiPh3)2 exibits a comparable activity and a larger stability than dicyclopentadienylzirconium complexes. On addition of triphenylsilanol to zirconocenes, the productivity increased and the molecular weight sharply decreased, thus suggesting the occurrence of ligand substitution in solution. The reported results are discussed with reference to the proposed mechanism of ethylene polymerization with the conventional ZrCp2Cl2/MAO system.