ELECTROCHEMICAL REDUCTION OF PENTAFLUOROPHENYLXENONIUM, PENTAFLUOROPHENYL-DIAZONIUM, PENTAFLUOROPHENYL-IODONIUM, PENTAFLUOROPHENYL-BROMONIUM, AND PENTAFLUOROPHENYL-PHOSPHONIUM SALTS

Cyclic voltammetry measurements on pentafluorophenylonium compounds of [C6F5X](+) Y- type with X = Xe, N-2, C6F5Br, C6F5I, and (C6F5)(3)P we re carried out. In these series [C6F5Xe](+) shows the lowest and [(C6F 5)(4)P](+) the highest reduction potential. One electron reduction of [C6F5Xe](+) and [C6F5N2](+) followed by the loss of Xe or N-2, respect ively, leads to the generation of the [C6F5](.) radical. Favoured foll owing reactions of the [C6F5](.) radical are the abstraction of hydrog en from MeCN or dimerisation. After the first reduction step the other onium cations split off the pentafluorophenyl element molecule such a s (C6F5)(3)P, C6F5Br, or C6F5I, respectively. These molecules undergo further seductions. The low reduction potential of [C6F5Xe](+) is in c ontrast to former measurements on partially fluorinated or chlorinated phenylxenonium cations. A plausible explaination for the different be haviour of these Xe-C compounds in electrochemical reduction processes is given.