Nitrogen Donor Ligand (α‐Diamine vs. α‐Diimine) Makes Big Differences in Palladium‐Catalyzed Ethylene (Co)Polymerization

Abstract The nitrogen donor atom is widely used in the design and synthesis of olefin polymerization catalysts, while the amine donor featured sp 3 hybridized N is less applied in the ligand design than the imine donor featured sp 2 hybridized N. We have herein reported the synthesis and characterization of α ‐diamine palladium complexes with two sp 3 hybridized N donors and their catalytic properties toward homopolymerization of ethylene and copolymerization of ethylene with methyl acrylate (MA). The X‐ray crystallographic analyses identify that the α ‐diamine palladium complexes have a significantly distorted chelate ring (N─C─C─N─Pd), which is distinct from conventional α ‐diimine palladium complexes with a planar chelate ring. Ethylene polymerization results elucidate that bulky steric hindrance of the α ‐diamine palladium catalyst is required to achieve high activity and high molecular weight polymer. Comparisons of ethylene (co)polymerization results between the α ‐diamine palladium catalyst and the classic α ‐diimine palladium analogue disclose that the variation from imine donor to amine donor makes a decreasing change in catalytic activity and polymer molecular weight but an increase in the degree of linearity of polymeric product and MA incorporation in EMA copolymer.