Transition metals oxidation with dimethyl sulfoxide

Diphenyl sulfoxide and dimethyl sulfoxide are oxidized electrochemically to the coiresponding sulfones in acetonitrile and 1 M H2SO4, respectively. The product yields are enhanced the presence of transition metal salts or oxides of W, V, Mo or Se. In some cases sulfonic acid salts are formed with C—S cleavage. Sulfoxides react with oxygen under photochemical conditions to give sulfones in good yields. ... 

The oxidation of OH by [Fe(CN)6] in solution has been examined. Application of an electrical potential drives the reaction electrochemically, rather than merely generating a local concentration of OH at the anode, as has been suggested previously, to produce both O and [Fe(CN)6] in the vicinity of the same electrode. With high [OH ] or [Fe(CN)6] /[Fe(CN)6] ratio, the reaction proceeds spontaneously with a second-order rate constant of 2.2 x 10 M s at 25 °C. Under anaerobic conditions, iron(III) porphyrin complexes in dimethyl sulfoxide solution are reduced to the iron(II) state by addition of hydroxide ion or alkoxide ions. Excess hydroxide ion serves to generate the hydroxoiron(II) complex. The oxidation of hydroxide and phenoxide ions in acetonitrile has been characterized electrochemically " in the presence of transition metal complexes [Mn(II)L] [M = Fe,Mn,Co,Ni L = (OPPh2)4,(bipy)3] and metalloporphyrins, M(por) [M = Mn(III), Fe(III), Co(II) por = 5,10,15,20-tetraphenylpor-phinato(2-), 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphinato(2-)]. Shifts to less positive potentials for OH and PhO are suggested to be due to the stabilization of the oxy radical products (OH and PhO ) via a covalent bond. Oxidation is facilitated by an ECE mechanism when OH is in excess. 

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