Neutral Phosphine-Sulfonate Pd Complex-Catalyzed Copolymerization of 2-Methoxystyrene and Ethylene Polar Monomers: A DFT Mechanistic Study

Abstract

The density functional theory (DFT) method was employed to investigate the nature of the copolymerization reaction of ethylene monomers and 2-methoxystyrene catalyzed by a palladium phosphine-sulfonate complex. The calculated results indicate that (1) the ethylene molecules prefer to coordinate with neutral phosphine-sulfonate Pd catalyst along the Pd–P side to generate an intermediate owning a cis-configuration, which indicate that the chain transfer proceeds from cis-3 but not trans-5. (2) Subsequently, the insertion of polar monomers in the chain propagation is easier than that of the ethylene monomer and adopts the 2,1 insertion pathway; meanwhile, the R-configuration pathway is more favorable than the S-configuration pathway in stage II. (3) After the polar monomer insertion, the β-H elimination pathway is easier than the ethylene insertion, which makes polar monomer insertion into the in-chain easier. This work revealed the mechanism of the copolymerization reaction of ethylene and 2-methoxystyrene catalyzed by a palladium phosphine-sulfonate complex, which could provide theoretical insights into the development of new transition-metal complexes for the copolymerization reaction.