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

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 (V-Pd), which showed significant variation with respect to the nature of the L ligand. Further, a strong linear correlation between Delta V-Pd and the activation barrier (E-act) of the reaction is established. The correlation plots between Delta V-Pd 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. V-Pd measures the electron-rich/-deficient nature of the metal center and provides a quantitative measure of the reactivity of the catalyst. By tuning the V-Pd value, efficient catalysts can be designed.