Electrochemical Ortho Functionalization of 2‑Phenylpyridine with Perfluorocarboxylic Acids Catalyzed by Palladium in Higher Oxidation States

The electochemical oxidation of palladium acetate or palladium perfluoroacetate in the presence of 2-phenylpyridine promotes catalytic ortho C–H substitution reactions. As possible intermediates, Pd­(II) metallacycles with Pd-bound acetate, perfluoroacetate, and perfluoroheptanoate substituents have been isolated and characterized: binuclear [(PhPy)­Pd­(μ-OAc)]2 and [(PhPy)­Pd­(μ-TFA)]2 and mononuclear [(PhPy)­Pd­(TFA)]­(CH3CN), [(PhPy)­Pd­(TFA)]­(PhPy), and [(PhPy)­Pd­(PFH)]­(PhPy). The fluorinated derivatives were found to exist in solvent-dependent equilibria between mononuclear and binuclear forms. Cyclic voltammetry was used to elucidate redox properties of the palladacycles and the oxidation route to the final products.