Unexpected fragmentation of phenyldithiobenzoate, formation and X-ray structure of [μ,η2(S,S)-1,2-(dithio)-1,2-(diphenylethylene)] diiron hexacarbonyl complex

The reaction of Fe2(CO)9 with phenyldithiobenzoate PhCS2Ph 1 afforded four colored compounds: [(μ-η3(C,S,S)PhCS2Ph)]Fe2(CO)62, (μ-S)2Fe3(CO)93, (μ-SPh)2Fe2(CO)64 and [μ-η2(S,S)][PhC(S)double bond; length as m-dashC(S)Ph]Fe2(CO)65. Complex 5 was characterized by X-ray crystallography. The formation of complexes 4 and 5 was unexpected since it involved a fragmentation of the organic ligand 1 during its reaction with Fe2(CO)9. The electrochemical studies of 1, complexes 2 and 3 were undertaken in order to get information about the chemical behaviors of the intermediates generated by electron transfer. The results of cyclic voltammetry studies of 2 and 1 suggested that the reaction of 1 with Fe2(CO)9 involved two competitive reactions: (i) a thermal reaction which led to the expected compounds 2 and 3 and (ii) an electron transfer reaction involving a fragmentation of starting ligand 1 led to the unexpected complex 5. The required electrons may be provided by iron during the thermal decay of complexes 2 or 3 or Fe2(CO)9.