Dinuclear α‐Diimine Ni^II and Pd^II Complexes that Catalyze Ethylene Polymerization and Copolymerization

Abstract

Abstract A series of dinucleating α‐diimine ligands and the corresponding nickel and palladium complexes were synthesized and characterized. The dinucleating α‐diimine ligands are designed to incorporate naphthalene‐, biphenylene‐, and xanthene‐bridged structures, which may lead to different metal–metal distances. The properties of these dinuclear complexes in ethylene polymerization and copolymerization with methyl acrylate are investigated. Higher catalytic activity, higher polyethylene molecular weight, and much lower polyethylene branching density were observed for the dinuclear Ni complexes compared with the mononuclear analogue in ethylene polymerization. For the dinuclear palladium complexes, much more dramatic differences in activity and polyethylene molecular weight were observed. Most interestingly, similar catalytic activities were observed for the dinuclear and mononuclear palladium complexes in ethylene–methyl acrylate copolymerization, whereas only the mononuclear complex was able to incorporate an appreciable amount of the methyl acrylate monomer.