Electrochemical, Spectroscopic, and Computational Study of Bis(μ-methylthiolato)diironhexacarbonyl: Homoassociative Stabilization of the Dianion and a Chemically Reversible Reduction/Reoxidation Cycle

The redox characteristics of (μ-SMe)2Fe2(CO)6 from the 1+ to 2– charge states are reported. This [2Fe-2S] compound is related to the active sites of [FeFe]-hydrogenases but notably without a linker between the sulfur atoms. The 1+ charge state was studied both by ionization in the gas phase by photoelectron spectroscopy and by oxidation in the solution phase by cyclic voltammetry. The adiabatic ionization is to a cation whose structure features a semibridging carbonyl, similar to the structure of the active site of [FeFe]-hydrogenases in the same oxidation state. The reduction of the compound by cyclic voltammetry gives an electrochemically irreversible cathodic peak, which often suggests disproportionation or other irreversible chemical processes in this class of molecules. However, the return scan through electrochemically irreversible oxidation peaks that occur at potentials around 1 V more positive than the reduction led to the recovery of the initial neutral compound. The dependence of the CVs on sca...