Dinuclear Iron Isonitrile Complexes: Models for the Iron Hydrogenase Active Site

Reaction of Fe2(μ-S2C3H6)(CO)6 (1) with 2 equiv of t-BuNC affords a disubstitued species Fe2(μ-S2C3H6)(CN-t-Bu)2(CO)4 (2). The structure of 2 has been determined by X-ray crystallography, which shows that in the solid state
both isonitrile ligands are cis to sulfur. In solution, NMR and IR spectroscopy suggest that multiple isomers are
present. Protonation of 2 occurs at the Fe−Fe bond to give a cationic complex 3 as four different isomeric species.
Complex 3 does not react with deuterium gas (98 psi) in the absence of light. Irradiation of solutions of 3 with
visible light under D2 gas leads to formation of HD.