Diiron models for the active site of Fe-only hydrogenase with terminal organosulfur ligation: Synthesis, structures and electrochemistry

Diiron model complexes (μ-SCH2CH2CH2S)Fe2(CO)5L with thioether-substitution, L = S(CH2CH3)2 (2), S(CH2CH3)(CH2CH2Cl) (3), S(CH2CH3)(C6H5) (4), or sulfoxide-substitution, L = SO(CH2CH2CH3)2 (5), SO(CH3)2 (6), were synthesized as active site analogues of Fe-only hydrogenase. The organosulfur ligands were introduced into the diiron centers via moderately stable intermediates following two routes. The X-ray crystallographic structures of complexes 2–6 show the apical positions of terminal organosulfur ligands. The electrochemical behaviors of the model complexes were investigated, especially for the interesting properties of the derivative of 6 which is proposed to be the first model with weak donor ligand similar to CO.