Pentafluorophenyl radicals from the photolysis of pentafluoroiodobenzene react with benzene and toluene to give high yields of pentafluorobiphenyls. Much slower reactions occur with nitrobenzene, hexafluorobenzene, and pentafluorobenzene. Photolysis with carbon tetrachloride yields chloropentafluorobenzene, formed in much higher yield from the same reactants in the dark at 290째. The thermal decomposition of pentafluoroiodobenzene is not a satisfactory route to the pentafluorophenyl radical, but reactions of the iodo-compound with copperbronze and with mercury at 300째 give high yields of decafluorobiphenyl and bispentafluorophenylmercury, respectively.