47598-50-5Relevant academic research and scientific papers
Electron paramagnetic resonance and electrochemical study of the oxidation chemistry of mononuclear and binuclear chromium carbonyl thiolates
Springs, Jerry,Janzen, Christopher P.,Darensbourg, Marcetta Y.,Calabrese, Joseph C.,Krusic, Paul J.,Verpeaux, Jean-No?l,Amatore, Christian
, p. 5789 - 5797 (1990)
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 Hu?ckel MO calculations. The unpaired electron resides to a large extent in a p-type orbital on the trigonal sulfur, which is μ-conjugated to d orbitals of the neighboring Cr atoms. This orbital is part of a three-center pseudoallylic μ system occupied by five electrons, totally analogous to that with four-electron occupancy put forward previously for binuclear phosphinidine 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.
