C–H Activation of Methane by Nickel–Methoxide Complexes: A Density Functional Theory Study

Abstract

Density functional theory is used to analyze methane C–H activation by neutral and cationic nickel–methoxide complexes. This research seeks to identify strategies to reduce high barriers through evaluation of supporting ligand modifications, solvent polarity, overall charge of complex, metal identity, and counterion effects. A Ni–OMe pincer complex was substituted at the para positions of the phenyl and pyridine rings with different electron-donating and -withdrawing groups, and the results showed that resonance effects did not significantly change the ΔG⧧act and ΔGrxn compared to the reference complex, which was confirmed by frontier orbitals plots and Hammett graphs. The effect of solvent polarity is greater upon the thermodynamics more than transition state energies. Among modeled supporting ligands, bipyridine was the most promising. Overall, neutral complexes are calculated to have lower activation barriers than the cationic complexes. For both neutral and cationic complexes, the methane C–H activati...