PHOTOINDUCED ATOM-TRANSFER REACTIONS BETWEEN TRANSITION-METAL CENTERS

In contrast to outer-sphere electron transfer, the intrinsic barriers to redox reactions accomplished by atom-transfer processes have receiv ed little attention. We have begun a study of the self-exchange atom t ransfer process for both two-equivalent and one-equivalent systems. In the former studies, NMR techniques ranging from line broadening to ma gnetization transfer were used for C5H5(CO)3M-/C5H5(CO)3M-X self-excha nge reactions (M = Mo, W; X = Cl, Br, I). For the one-equivalent proce sses, we have applied isotopically labeled materials and a photochemic al method to the direct determination of the self-exchange rates for C 5H5(CO)3M./C5H5(CO)3M-X couples. The metal radicals are produced by ph otocleavage of metal-metal bonded dimers by visible light.