Noncovalent Ni–Phenyl Interactions Promoted α-Diimine Nickel-Catalyzed Copolymerization of Ethylene and Methyl Acrylate

As a widely used functional polyolefin, the industrial ethylene (E)-methyl acrylate (MA) copolymer (EMA), prepared by free radical polymerization under harsh conditions, is a lightly branched copolymer with in-chain and terminal MA incorporation. Metal-catalyzed E/MA copolymerization as an alternative polymerization technique is highly attractive and challenging. Herein, we first report efficient direct E/MA copolymerization using "sandwich" dibenzobarrelene-derived α-diimine nickel catalysts. The produced lightly branched EMA copolymers with in-chain, pendant, and terminal MA units have a chain structure very similar to industrial EMA, which is not prepared using the previously reported nickel and palladium catalysts. Experimental results support that noncovalent Ni–phenyl interactions in α-diimine nickel catalysts promote E/MA copolymerization. Density functional theory studies clearly illuminate the crucial role of Ni–phenyl interactions in E/MA copolymerization and well explain the formation of in-chain, pendant, and terminal MA units in the EMA copolymer chain.