Synthesis of linear polyolefins with palladium complexes

Reaction conditions for copolymerization of ethylene and methyl acrylate with 2 or 3 to afford highly linear copolymers were screened. Lowering the temperature of the copolymerization reaction led to an increase in molecular weight. Terminating end group analysis showed that copolymers prepared with 3 predominantly possess 2-methoxycarbonylethenyl group, instead of vinyl group. By decreasing the amount of methyl acrylate used and increasing the ethylene pressure, M_n up to 28200 was achieved. Ethylene homopolymerization with 3 also provided highly linear polyethylene with a molecular weight of 70000. Reaction of 3 with ethylene provided palladium complexes with long n-alkyl ligands, which suggests coordination polymerization to produce linear polyolefins takes place on the palladium metal.