Electron paramagnetic resonance and electrochemical study of the oxidation chemistry of mononuclear and binuclear chromium carbonyl thiolates Academic Article uri icon

abstract

  • The oxidation chemistry of RSCr (CO)5- thiolate anions, 1(R)-, and of their binuclear analogues RS[Cr(CO)5]2-, 2(R)-, has been studied by cyclic voltammetry, EPR, and low-temperature IR. Rapid potential scan cyclic voltammetry shows that the radicals 1(R)⋅ have lifetimes of less than 50 μs and decay by first-order kinetics. Chemical studies are consistent with fragmentation of 1(R)⋅ into an alkylthiyl radical RS⋅ and a Cr(CO)5 fragment. The slower reactions following the initial irreversible oxidation have been elucidated by cyclic voltammetry. The major product of chemical and electrochemical oxidation of 1(R)- is the monodentate disulfide complex (RS-SR)Cr(CO)5 formed by complexation of Cr(CO)5 fragments to the organic disulfide resulting from dimerization of RS⋅ radicals. The electrochemical oxidation of 2(R)- proceeds in two chemically reversible steps to the corresponding 2(R)⋅ radicals and 2(R)+ sulfonium cations. The intensely colored 2(R)⋅ radicals have limited thermal stability and were characterized by EPR, low-temperature IR, and extended Hückel MO calculations. The unpaired electron resides to a large extent in a p-type orbital on the trigonal sulfur, which is π-conjugated to d orbitals of the neighboring Cr atoms. This orbital is part of a three-center pseudoallylic π system occupied by five electrons, totally analogous to that with four-electron occupancy put forward previously for binuclear phosphinidene complexes RP[MLn]2, e.g., RP[Cr(CO)5]2, which is isoelectronic with 2(R)+. The X-ray structures of t-BuSCr(CO)5- and t-BuS[Cr(CO)5]2- are also presented. © 1990, American Chemical Society. All rights reserved.

published proceedings

  • Journal of the American Chemical Society

author list (cited authors)

  • Springs, J., Janzen, C. P., Darensbourg, M. Y., Calabrese, J. C., Krusic, P. J., Verpeaux, J. N., & Amatore, C

citation count

  • 31

complete list of authors

  • Springs, Jerry||Janzen, Christopher P||Darensbourg, Marcetta Y||Calabrese, Joseph C||Krusic, Paul J||Verpeaux, Jean Noel||Amatore, Christian

publication date

  • July 1990