Olefin Polymerization with Non-metallocene Catalysts (Late Transition Metals)

Abstract

Diimine Pd and Ni complexes catalyze the polymerization of ethylene, propylene, and α-olefins. The reaction involves isomerization of the growing terminal (chain walking) and, as its result, produces highly branched polyethylene and poy(α-olefin)s having a smaller number of the alkyl substituents than expected from the monomer structure. Ni complexes with salicylaldimine or iminocarboxamide ligands and Pd complexes with phosphinesulfonate ligands are used as single component catalysts for ethylene polymerization. Especially, the latter catalysts show tolerance towards polar functional groups and promote copolymerization of ethylene with wide varieties of polar monomers. The Pd and Ni complexes are able to catalyze ethylene polymerization in aqueous media to yield polyethylene particles. Fe and Co complexes with bis(imino)pyridine ligands show high catalytic activity for ethylene polymerization to yield linear polyethylene. Complexes of the metals such as Rh, Ir, Ru, and Ag were revealed to become catalytically active by proper design of the ligand. Not only monometallic complexes but also bimetallic or multimetallic complexes are used for ethylene polymerization. Late transition metal complexes catalyze selective cyclopolymerization of non-conjugated dienes and trienes to afford the polymers with cycloalkane groups with controlled stereochemistry.