A DFT investigation of the mechanism for alternating copolymerization of styrene with carbon monoxide catalyzed by Pd(II) complexes

Density functional theory has been employed to study the homogeneous catalytic copolymerization of styrene with carbon monoxide. The copolymerization reaction is catalyzed by Pd(II) coordinated with 2,2′-bipyridine, a conventional nitrogen-containing bidentate ligand with achiral C2v symmetry. The chain propagation mechanism for the alternating copolymerization as well as the side reactions, including multiple insertions of CO and homopolymerization of styrene, has been investigated. This study focused exclusively on regioisomerism and stereoisomerism. We have demonstrated that the strictly alternating copolymerization is kinetically and thermodynamically favored over the side reactions (i.e., multiple insertions of CO and homopolymerization of styrene). The regiochemistry study indicates the 2,1 type. Furthermore, the stereochemistry study shows that the syndiotactic conformation is preferred over the isotactic or atactic conformations.