The Only Iron Hydrogenase Active Site Structure And Functional Simulation - The Two-iron Aza Mercaptide Synthesis, Structure And Electrochemical Research

To construct a light-driven supramolecule composed of a biomimetic model of the hydrogenase active site and a light-harvesting component, different diiron azadithiolates were synthesized, including 1, 2, 8 and five phosphine substituted derivatives of complex 1, i.e. complexes 3, 4, 5, 6 and 7. [{(u-SCH2)2N(4-NO2C6H4)}Fe2(CO)6] (1) was p repared b y t he reaction of the d ianionic i ntermediate [(u-S)2Fe2(CO)6]2- and N, N-bis(chloromethyl)-4-nitro-aniline as a biomimetic model of the active site of Fe-only hydrogenase. The reduction of 1 by Pd-C/H2 under a neutral condition afforded complex [{(u-SCH2)2N(4-NH2C6H4)}Fe2(CO)6] (2) in 67% yield. In the solvent of n-C4H9NH2, the CO-displacement reaction of 1 took place by different phosphine ligands (PMe3. PMe2Ph and PPh3) to give five phosphine substituted complexes [{(u-SCH2)2N(4-NO2C 6H4)}Fe2(CO)5 (PPh3)2] (3), [{(u-SCH2)2N(4-NO2C6H4)}Fe2(CO)5PMe2Ph] (4), [{(u-S CH2)2N(4-NO2C6H4)} Fe2(CO)4(PMe2Ph)2] (5), [{(u-SCH2)2N(4-NO2C6H4)}Fe2(CO)5P Me3](6) and [{(u-SCH2)2N (4-NO2C6H4)}Fe2(CO)4(PMe3)2] (7). All complexes were characterized by DR, 1H & 13C NMR and MS spectra. The molecular structures of 1, 5 and 6 were determined by X-ray single crystal analysis. Cyclic voltammograms of 1, 2, 5, 6 and 7 were studied to evaluate their redox properties. The plausible mechanisms of the electrocatalytic proton reduction in the presence of HO Ac by the model complexes 1 and its phosphine substituted derivatives are discussed.