DFT study on Ni–C bond dissociation enthalpies of nickel-carbon complexes in photoredox/nickel dual catalysis C(sp2)-C(sp3) coupling reactions

Abstract

Traditional transition metal catalysis efficiently forms C(sp²)-C(sp²) bonds, but C(sp²)-C(sp³) couplings remain challenging due to sluggish C(sp³) oxidative addition and metalation, and the propensity for β-hydride elimination. A notable advancement is the development of dual catalytic platforms that synergistically integrate transition metal catalysts with photoredox catalysts, offering a powerful strategy for constructing challenging C(sp²)-C(sp³) linkages. Nickel complexes, recognized for their cost-effectiveness, earth-abundant nature, and catalytic efficiency, have emerged as pivotal players in this field. Their compatibility with photoredox catalysis enables a unique mechanistic pathway where nickel intermediates coordinate with (hetero)aryl halides or alkyl radicals, forming critical Ni–C bonds during the reaction cycle. Accurately quantifying the strength of these Ni–C bonds through homolytic bond dissociation enthalpy (BDE) measurements hold critical importance for understanding catalytic behavior. In this study, we systematically evaluated 14 nickel-carbon complexes using ten density functional theory (DFT) methodologies, benchmarking calculated BDE values against experimental data. The M06 functional outperformed others, exhibiting the lowest root-mean-square error (RMSE) of 2.7 kcal/mol. Leveraging this finding, the M06 functional was applied to evaluate Ni–C BDEs in model complexes I and II under Ni/photoredox dual catalytic conditions, while probing substituent effects. Supplementary investigations, natural bond orbital (NBO) analyses and frontier molecular orbital energy assessments, were conducted to further understand the variation patterns of Ni–C BDE. Transition state characterization further uncovered a direct correlation between Ni–C bond strength and activation free energies, establishing a structure-activity framework that links thermodynamic stability with mechanistic feasibility.