DFT Mechanism Study of Ligand-Controlled Ru-Catalyzed Selective Aerobic Oxidative Generation of Homocoupled Imines and Nitriles

This study employs density functional theory to investigate the mechanisms underlying Ru-H-catalyzed aerobic amine oxidation, which results in the formation of homocoupled imines and nitriles, focusing on the effects of the ligands on the catalytic efficiency and selectivity. The energy span and catalytic turnover frequency across the catalytic cycle are analyzed, revealing that nitrile formation is energetically favored. For homocoupled imine formation, the two mechanistic pathways, i.e., Paths A and B, involve C═N bond activation, with Path B the preferred route. Differences between the ligands OMe-BIAN (OMe = methoxy, BIAN = bis(imino)acenaphthene) and 1,10-phenanthroline significantly affect the reaction pathway and product selectivity. The steric bulk and enhanced noncovalent interactions of OMe-BIAN promote nitrile production, and the ClO4- counterion is critical in facilitating product formation.