Theoretical Study on the Reduction Mechanism of CO2 Catalyzed by ZnCl2

초록

The reaction mechanism on the reduction of CO2 in the presence of N-methylaniline and PhSiH3 catalyzed by ZnCl2 was studied by the density functional theory at the M05-2X[(SMD,CH2Cl2) 6- 311++G(d,p)//M06-2X/6-31G(d) level. The calculations show that an initial catalytic formylation of the N-methylaniline using CO2 followed by the 6 electron reduction of the carbamic acid intermediate is adopted for the formation of methylation product, which is energetically more favorable than the pathway involving the formation of the formoxysilane and methoxysilane species via the hydrosilylation of CO2 with PhSiH3. The rate determining step for the uncatalyzed reaction was the hydrosilation of CO2 with PhSiH3 but that for catalyzed reaction was the formylation of the N-methylaniline with CO2. With respect to the uncatalyzed reaction, the energy barrier for the rate determining step is lowered from 41.7 to 34.6 kcal mol-1, indicating that the simple zinc catalyst exhibits a good catalytic performance in the titled reaction.