A DFT Study of the Copolymerization of Methyl Vinyl Sulfone and Ethylene Catalyzed by Phosphine–Sulfonate and α-Diimine Palladium Complexes

Abstract

Density functional theory (DFT) calculations were comparatively carried out to reveal the origins of different catalytic performances from phosphine–benzene sulfonate (A, [{P^O}PdMe(L)] (P^O = Κ2-P,O-Ar2PC6H4SO3 with Ar = 2-MeOC6H4)) and α-diimine (B, [{N^N}PdMe(Cl)] (N^N = (ArN=C(Me)-C(Me)=NAr) with Ar = 2,6-iPr2C6H3)) palladium complexes toward the copolymerization of ethylene and methyl vinyl sulfone (MVS). Having achieved agreement between theory and experiment, it was found that the favorable 2,1-selective insertion of MVS into phosphine–sulfonate palladium complex A was due to there being less structural deformations in the catalyst and monomer. Both the MVS and ethylene insertions were calculated, and the former was found to be more favorable for chain initiation and chain propagation. In the case of α-diimine palladium system B, the resulting product of the first MVS insertion was quite stable, and the stronger O-backbiting interaction hampered the insertion of the incoming ethylene molecule. These computational results are expected to provide some hints for the design of transition metal copolymerization catalysts.