Electrophotocatalytic perfluoroalkylation by LMCT excitation of Ag(II) perfluoroalkyl carboxylates.

Abstract

Molecular Ag(II) complexes are superoxidizing photoredox catalysts capable of generating radicals from redox-reticent substrates. In this work, we exploited the electrophilicity of Ag(II) centers in [Ag(bpy)2(TFA)][OTf] and Ag(bpy)(TFA)2 (bpy, 2,2'-bipyridine; OTf, CF3SO3-) complexes to activate trifluoroacetate (TFA) by visible light-induced homolysis. The resulting trifluoromethyl radicals may react with a variety of arenes to forge C(sp2)-CF3 bonds. This methodology is general and extends to other perfluoroalkyl carboxylates of higher chain length (RFCO2-; RF, CF2CF3 or CF2CF2CF3). The photoredox reaction may be rendered electrophotocatalytic by regenerating the Ag(II) complexes electrochemically during irradiation. Electrophotocatalytic perfluoroalkylation of arenes at turnover numbers exceeding 20 was accomplished by photoexciting the Ag(II)-TFA ligand-to-metal charge transfer (LMCT) state, followed by electrochemical reoxidation of the Ag(I) photoproduct back to the Ag(II) photoreactant.