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.