Four diiron hexacarbonyl-complexes containing dithiolato (5), diselenolato (6), selenolato-thiolato (7) and μ²,κ³-C,O,Se-ligands (8), respectively have been prepared as [FeFe]-hydrogenase mimics.

The electrochemical reduction of the complex [Fe₂(CO)₆{µ-(SCH₂)₂GeMe₂}] (1) under N₂ and CO is reported applying cyclic voltammetry. Reduction of complex 1 in CO saturated solutions prevents the possible release of CO from the dianion 1²⁻, while the latter reacts with additional CO forming a spectroscopically uncharacterized product P1. This product undergoes a reversible redox process at E_1/2 = −0.70 V (0.2 V∙s⁻¹). In this report, the structure of the neutral complex 1, isomers of dianionic form of 1, and P1 are described applying DFT computations. Furthermore, we propose reaction pathways for H₂ production on the basis of the cyclic voltammetry of complex 1 in presence of the strong acid CF₃SO₃H.