Mechanism of Excited-State Dissociation of Ni-C and Ni-Br Bonds in (bpy)Ni(alkyl)(Br) Complexes.

NiRX (R = aryl, alkyl; X = halogen) complexes containing bipyridine (bpy)-type ligands play a crucial role in metallaphotoredox-catalyzed cross-coupling reactions. Despite the excited-state dissociation of Ni-C and Ni-halide bonds in the (bpy)Ni(aryl)(halide) complex being well understood, the corresponding (bpy)Ni(alkyl)(halide) complex remains largely unexplored. Experimentally, it is challenging due to its instability, making isolation and characterization difficult and necessitating computational investigations. This study employs high-level computational methods to investigate the excited-state dissociation of Ni-C and Ni-Br bonds in (bpy)Ni(alkyl)(Br) complexes. Additionally, we explored the influence of bpy substituents (OMe, -Bu, Me, H, COMe, CF, Cl, Ph) at the 4,4' positions, along with other ligands, bi-imidazole (Hbim) and phenanthroline (phen), revealing key electronic factors governing bond homolysis. Our findings provide fundamental insights into excited-state properties that impact catalytic performance, guiding the rational design of visible light-induced Ni-catalyzed alkylation reactions.