Theoretical Study of Early Transition-Metal-Catalyzed Oxidative Coupling Reaction of Acethylene with Carbon dioxide

摘要

Cp_2Ti- and (MeO)_2Ti-catalyzed oxidative coupling reactions of acetylene with carbon dioxide were theoretically investigated with DFT,MP2-MP4(SDQ),and CCSD(T) methods.Cp_2Ti-catalyzed coupling reaction easily takes place with moderate activation barrier of 7.4 kcal/mol and significantly large exothermicity of 31.7 kcal/mol.(MeO)_2Ti-catalyzed coupling reaction occurs with nearly no barrier,while the exothermicity (34.6 kcal/mol) is similar to that of the Cp_2Ti-catalyzed reaction.The charge-transfer from the d_(pi)-pi~* back-donating orbital of the Ti(C_2H_2) moiety to the pi~* orbital of CO_2 is important in the reaction.The regio-selectivity of the coupling reaction is discussed in terms of the bond energies and the charge-transfer interaction.