LAUSR

Abstract The mechanisms of the cascade H2 activation and CO2 reduction over the β-Diketiminato (BDI)-ligated group 13 metal complexes were studied by the density functional theory (DFT) in the framework of ONIOM method. For the initial H2 activation, the intermolecular 1,4-addition pathway is demonstrated to be kinetically more favorable than the intramolecular 1,2 or 1,4-addition pathway. With the intermolecular Lewis acid-base cooperation catalysis, the heterolytic H⋯H bond cleavage adopts an electron transfer model, which involves the concerted donation from the H H σ bonding orbital to the empty 4pz orbital of the GaIII center, and the backdonation from the π-orbital of the exocyclic alkene in the BDI ligand to the H H σ anti-bonding orbital. Furthermore, it is interesting to note that the simultaneous introduction of the electron-withdrawing group ( CF3) on the GaIII center and the electron-donating group ( OMe or NMe2) on the C6 position of the BDI ligand is effective for enhancing the reactivity of the BDI-GaIII complex in H2 activation. CO2 might be reduced barrierlessly with the more reactive gallium hydride anion that is generated in H2 activation. For both H2 activation and CO2 reduction processes, the BDI-ligated gallium complexes exert the better catalytic effect than the aluminum analogues.