Olefin polymerization using palladium complexes with phosphine-sulfonate ligands

Anionic methylpalladium(II) complex 2 with a bidentate phosphine-sulfonate ligand was prepared by reaction of diarylphosphinobenzene-2-sulfonic acid 1 with ⁱPr₂EtN, followed by addition of [PdMeCl(cod)]. Reaction of 2 with 2,6-lutidine in the presence of K₂CO₃ provided neutral methylpalladium(II) complex 3 also in good yield. Copolymerization of ethylene and methyl acrylate with 2 or 3 afforded highly linear copolymers in which acrylate units are incorporated into the polyethylene backbone, and notably, use of NaB[3,5-(CF₃)₂C₆H ₃]₄ as an additive for the copolymerization with 2 led to an increase in activity. When reaction of 2 or 3 with methyl acrylate was performed, complex 4, formed by 2,1-insertion of methyl acrylate into the Pd-Me bond, was observed by NMR spectroscopy.