Interpreting Oxidative Addition of Ph-X (X = CH3, F, Cl, and Br) to Monoligated Pd(0) Catalysts Using Molecular Electrostatic Potential.

Abstract

A B3LYP density functional theory study on the oxidative addition of halogenobenzenes and toluene to monoligated zerovalent palladium catalysts (Pd–L) has been carried out using the “L” ligands such as phosphines, N-heterocyclic carbenes, alkynes, and alkenes. The electron deficiency of the undercoordinated Pd in Pd–L is quantified in terms of the molecular electrostatic potential at the metal center (VPd), which showed significant variation with respect to the nature of the L ligand. Further, a strong linear correlation between ΔVPd and the activation barrier (Eact) of the reaction is established. The correlation plots between ΔVPd and Eact suggest that a priori prediction on the ability of the palladium complex to undergo oxidative addition is possible from VPd analysis. In general, as the electron-donating nature of ligand increases, the suitability of Pd(0) catalyst to undergo oxidative addition increases. VPd measures the electron-rich/-deficient nature of the metal center and provides a quantitative measure of the reactivity of the catalyst. By tuning the VPd value, efficient catalysts can be designed.