Hydrodefluorination of perfluoroalkyl groups using silylium-carborane catalysts

Carbon-fluorine bonds are among the most unreactive functionalities in chemistry. Interest in their activation arises in part from the high global warming potentials of anthropogenic polyfluoroorganic compounds. Conversion to carbon- hydrogen bonds (hydrodefluorination) is the simplest modification of carbon- fluorine bonds, but efficient catalytic hydrodefluorination of perfluoroalkyl groups has been an unmet challenge. We report a class of carborane- supported, highly electrophilic silylium compounds that act as long- lived catalysts for hydrodefluorination of trifluoromethyl and nonafluorobutyl groups by widely accessible silanes under mild conditions. The reactions are completely selective for aliphatic carbon- fluorine bonds in preference to aromatic carbon- fluorine bonds.