Computational Insights into the Effect of Ligand Redox Properties on Reductive Elimination from Au(III), Pd(II), and Pt(II) Complexes

We computationally investigated the Ar-Ar reductive elimination process in a series of biaryl Au(III), Pd(II), and Pt(II) complexes to explore the factors that govern the activation free energy associated with C-C coupling (Delta G double dagger). Contrary to conventional beliefs that emphasize metal-Ar bond strength as the primary determinant for the ease of reductive elimination, our density functional theory (DFT) calculations reveal that the key factor is the oxidation susceptibility of the Ar ligands in their anionic forms: the easier the oxidation of Ar-, the lower the activation free energy (Delta G double dagger). Indeed, we found that Delta G double dagger strongly correlates with the reduction potential for the reaction Ar center dot + e- -> Ar- (E degrees(Ar)). We further demonstrate that variations in complex net charge and metal center significantly influence the electron-accepting ability of the metal center in the transition state, thereby affecting the ease of reductive elimination. Notably, the effects of these factors (net charge and metal center) on the activation barrier were found to be largely independent of the nature of the Ar ligands.