Fe–S complexes containing five-membered heterocycles: novel models for the active site of hydrogenases with unusual low reduction potential

Abstract

Three biomimetic 2Fe2S complexes [{(µ-SCH₂)₂NCH₂(2-C₄H₃O)}](Fe₂(CO)₆) (6a), [{(µ-SCH₂)₂ NCH₂(2-C₄H₃S)}](Fe₂(CO)₆) (6b) and [{(µ-SCH₂)₂NCH₂(5-Br-2-C₄H₂S)}Fe₂(CO)₆] (6c) were prepared as models for the active site of Fe-only hydrogenase by the convergent process from [(µ-S₂)Fe₂(CO)₆] and N,N-bis(hydromethyl)-2-furan and thiophene. The structures of these complexes were identified spectroscopically and crystallographically. The electrochemical behavior of the complexes 6a and 6c was unique as they showed catalytic proton reduction with a low reduction potential at −1.13 and −1.09 V vs Fc/Fc⁺, respectively, in the presence of HClO₄.