CO2 hydroboration is an important method of CO2 conversion. Developing low-cost and environmentally friendly metal catalysts that can facilitate valuable chemical transformations is of great significance. In the present study, the detailed reaction mechanisms of CO2 hydroboration catalyzed by low-valent Mg(I) dimers (Mg(I)2) and monomagnesium hydride Mg-H were investigated by DFT calculations. The work determined the detailed catalytic cycle of the bimetallic Mg(I)2-catalyzed CO2 hydroboration, confirming that Mg(I)2 is merely the precatalyst, and that complex A2, in which one HBpin is inserted into the carbonate Mg(I)2 complex, is the true catalyst. Although Mg-H can catalyze the CO2 hydroboration, it is not the true catalyst in the title reaction because the formation of Mg-H is strongly endothermic. CH3OBpin is the thermodynamic-controlled product and O(Bpin)2 is the kinetic-controlled product. Our results identify the true catalyst, offering a rational explanation for the experimental results of Mg(I)2-catalyzed CO2 hydroboration, which shed light on the small-molecule activation and expand the usage of the environment friendly main-group metal compounds.
Yang et al. (Thu,) studied this question.