Ethylene (Co)polymerization by Binuclear Nickel Phenoxyiminato Catalysts with Cofacial Orientation

Abstract

A series of neutral binuclear nickel phenoxyiminato catalysts connected by rigid skeletons of different lengths have been efficiently synthesized. The rigid skeleton and bulky tert-butyl groups together force two nickel coordination planes to get close and stack in an anti cofacial fashion. With reduced nickel–nickel distances, these binuclear nickel complexes displayed higher catalytic activity, produced polymers with higher molecular weight, and showed less inhibition by the presence of additional polar monomers in ethylene polymerization and copolymerization. We attributed these effects to a favorable consequence of the enhanced bimetallic effect and steric hindrance due to the cofacial orientation.