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 catalyticcopolymerization of styrene with carbon monoxide. One of our interests is focus onthe copolymerization reaction that catalyzed by Pd（II） coordinated with2,2’-bipyridine, which are conventional nitrogen-containing bidentate ligands withachiral C2Vsymmetry. The chain propagation mechanism for the alternatingcopolymerization as well as the side reactions, including multiple insertions of COand homopolymerization of styrene, has been investigated. This study focusedexclusively on regioisomerism and stereoisomerism. The other interest is that thealternating copolymerization reaction catalyzed by Pd（II） coordinated withelectronically modified11-R-dipyridophenazine, the thermodynamic properties havebeen investigated according to the electron-donating character of the remote Rsubstituent in the order R=NO₂, COOH, Cl, H, CH₃, NH₂.First: we have demonstrated that the strictly alternating copolymerization iskinetically and thermodynamically favored over the side reactions （i.e., multipleinsertions of CO and homopolymerization of styrene）. The regiochemistry studyindicates the2,1type. Furthermore, the stereochemistry study shows that thesyndiotactic conformation is preferred over the isotactic or atactic conformations.Second: increased catalytic activity is observed on increasing the theelectron-accepting character, the reaction barriers of the monomer inserting into theactive center and growing chain are decreased when the capability of theelectron-accepting character raising.