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

Abstract

Diiron model complexes (μ-SCH 2CH 2CH 2S)Fe 2(CO) 5L with thioether-substitution, L = S(CH 2CH 3) 2 ( 2), S(CH 2CH 3)(CH 2CH 2Cl) ( 3), S(CH 2CH 3)(C 6H 5) ( 4), or sulfoxide-substitution, L = SO(CH 2CH 2CH 3) 2 ( 5), SO(CH 3) 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.