Hydroboration of CO2 to Methyl Boronate Catalyzed by a Manganese Pincer Complex: Insights into the Reaction Mechanism and Ligand Effect.

The conversion of carbon dioxide to fuels, polymers, and chemicals is an attractive strategy for the synthesis of high-value-added products and energy-storage materials. Herein, the density functional theory method was employed to investigate the reaction mechanism of CO2 hydroboration catalyzed by manganese pincer complex, [Mn(Ph2PCH2SiMe2)2NH(CO)2Br]. The carbonyl association and carbonyl dissociation mechanisms were investigated, and the calculated results showed that the carbonyl association mechanism is more favorable with an energetic span of 27.0 kcal/mol. Meanwhile, the solvent effect of the reaction was explored, indicating that the solvents could reduce the catalytic activity of the catalyst, which was consistent with the experimental results. In addition, the X ligand effect (X = CO, Br, H, PH3) on the catalytic activity of the manganese complex was explored, indicating that the anionic complexes [MnI - Br]- and [MnI - H]- have higher catalytic activity. This may not only shed light on the fixation and conversion of CO2 catalyzed by earth-abundant transition-metal complexes but also provide theoretical insights to design new transition-metal catalysts.