Photoinduced Perfluoroalkylation Mediated by Cobalt Complexes Supported by Naphthyridine Ligands

Cobalt(III) and cobalt(II) perfluoroethyl complexes supported by 1,8-naphthyridine or its mono-or dimethylsubstituted analogues were synthesized, and their reactivity has been investigated in light-induced radical perfluoroethylation of arenes and heteroarenes. Similar to previously reported NiIII complexes, CoIII naphthyridine-based complexes show light induced CoIII-C2F5 bond homolysis to generate the C2F5 radical, while the CoII complex was significantly less reactive. In the presence of a stoichiometric amount of electron-rich arene or heteroarene, the products of monoperfluoroethylation by the cationic [(naphthyridine)2CoIII(C2F5)2]+ complexes were obtained selectively and with good yields. This reactivity was further enhanced in the presence of one-electron oxidants or benzoquinone. Moderate catalytic turnover was obtained when pentafluoroethyl-1,2-benziodoxol-3(1H)-one (Acid C2F5-Togni reagent) was used, although the substrate scope and the reactivity remain limited to electron-rich substrates.