Synthesis, Structures and Electrochemical Properties of Nitro‐ and Amino‐Functionalized Diiron Azadithiolates as Active Site Models of Fe‐Only Hydrogenases

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Abstract
Complex [{(μ-SCH2)2N(4-NO2C6H4)}Fe2(CO)6] (4) was prepared by the reaction of the dianionic intermediate [(μ-S)2Fe2(CO)6]2− and N,N-bis(chloromethyl)-4-nitroaniline as a biomimetic model of the active site of Fe-only hydrogenase. The reduction of 4 by Pd-C/H2 under a neutral condition afforded complex [{(μ-SCH2)2N(4-NH2C6H4)}Fe2(CO)6] (5) in 67 % yield. Both complexes were characterized by IR, 1H and 13C NMR spectroscopy and MS spectrometry. The molecular structure of 4, as determined by X-ray analysis, has a butterfly 2Fe2S core and the aryl group on the bridged-N atom slants to the Fe(2) site. Cyclic voltammograms of 4 and 5 were studied to evaluate their redox properties. It was found that complex 4 catalyzed electrochemical proton reduction in the presence of acetic acid. A plausible mechanism of the electrocatalytic proton reduction is discussed.