Photoinduced atom-transfer reactions between transition-metal centres

In contrast to outer-sphere electron transfer, the intrinsic barriers to redox reactions accomplished by atom-transfer processes have received little attention. We have begun a study of the self-exchange atom transfer process for both two-equivalent and one-equivalent systems. In the former studies, NMR techniques ranging from line broadening to magnetization transfer were used for C₅H₅(CO)₃M^-/C₅H₅(CO)₃M-X self-exchange reactions (M = Mo, W; X = Cl, Br, I). For the one-equivalent processes, we have applied isotopically labeled materials and a photochemical method to the direct determination of the self-exchange rates for C₅H₅(CO)₃M./C₅H₅(CO)₃M-X couples. The metal radicals are produced by photocleavage of metal-metal bonded dimers by visible light.