Determination of the Mechanism and True Catalyst in CO 2 Hydroboration Catalyzed by the Low-Valent Magnesium(I) Dimer: A Computational Study

CO 2 hydroboration is an important method of CO 2 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 CO 2 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 CO 2 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 CO 2 hydroboration, it is not the true catalyst in the title reaction because the formation of [Mg]-H is strongly endothermic. CH 3 OBpin 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 CO 2 hydroboration, which shed light on the small-molecule activation and expand the usage of the environment friendly main-group metal compounds.