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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 CO 2 hydroboration catalyzed by manganese pincer complex, [Mn(Ph 2 PCH 2 SiMe 2 ) 2 NH(CO) 2 Br]. 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, PH 3 ) on the catalytic activity of the manganese complex was explored, indicating that the anionic complexes [Mn I - Br] - and [Mn I - H] - have higher catalytic activity. This may not only shed light on the fixation and conversion of CO 2 catalyzed by earth-abundant transition-metal complexes but also provide theoretical insights to design new transition-metal catalysts.

A density functional theory method was employed to investigate the mechanism of C-O bond activation of butanoic acid substrates bearing the 8-aminoquinoline (AQ) group catalyzed by Pd(OAc) 2 . The whole reaction consists of five fundamental steps: the chelation of substrate A1 , the C-H activation step, the C-N coupling step, the protodepalladation step, and the release of the final product. The calculated results indicated that the protodepalladation step is the rate-determining step with a free energy barrier of 24.3 kcal/mol. This theoretical study pointed out that the energy barriers of C-H activation in the presence and absence of AQ are 11.3 and 26.6 kcal/mol, respectively. This is to say that the installation of the AQ directing group is critical to the regioselectivity of C-H activation and the β-O elimination steps, and this reason enables selective activation of the γ C-O bond. Furthermore, this chelating functionality facilitated the protodepalladation step because the energy barrier of the protodepalladation step was decreased with the coordination of the AQ directing group with a Pd center, and that was 39.3 kcal/mol in the absence of AQ. This also explains why no product formation was observed in the experiment upon changing the directing AQ group to a phenylamino group. Finally, other substrates bearing the phenol leaving group at the β- and δ-positions of carbonyl were investigated in order to expand the applicability of the AQ directing strategy. This work could provide new theoretical insights into the activation of strong alkyl C(sp 3 ) covalent bonds via the AQ directing strategy.