Investigations Into The Electrocatalytic Synthesis And Electron Transfer Mechanism Of The Diiron Subsite Of [FeFe]-Hydrongenase Model Complex

We explores the electrocatalytic synthesis and mechanism and the electron transfer mechanism of the active site of [FeFe]-hydrogenase model complex again in this paper, which all will detailed explaining below.Re-examining electrocatalytic substitution reactions of two diiron hexacarbonyl complexes, [Fe2(μ-pdt)(CO)6] (1) (pdt=propane-1,3-dithiolate) and [Fe2(μ-padmt) (CO)6] (2) (padmt=(propylazanediyl)dimethanethiolate), reveals that the monoanion of these complexes is the catalytic species rather than their dianion. Detailed mechanisms of electrocatalytic substitution reactions for the two complexes were proposed through investigations into their electrochemistry without and with the presence of a monodentate ligand PPh3 by using a variety of cyclic voltammetric techniques and rationalised by digital simulations. Our investigations also demonstrate an alternative methodology for synthesis of substituted diiron carbonyl complexes which have been employed as models of the sub-unit of the [FeFe]-hydrogenase. Electrosynthesis requires less organic solvents, no harsh reaction conditions, and no auxiliary agents and thus environmentally more benign than chemical one, then we also use monodentate ligand PPh3 and didentate ligand ((PPh2(CH2)nPPh2(n=1,2,4)) to expand its method and discuss its mechanism.The synthesis and characterisation of some diiron hexacarbonyl complexes [Fe2(μ-SXS)(CO)6], (SXS=-S(CH2)2C(CH3)CH2OCOFc 3, (-SCH2CH2NHCOFc)2 4,-SCH2N (CH2CH2OCOFc)CH2 5), [Fe2(μ-SXS)(CO)5], (SXS=-S(CH2)2C(CH3) CH2SCH2COFc 6), [Fe2(μ-SXS)(CO)6], (SXS=(-SC6H2OCOFc)2 7, Fc= ferrocenyl group) and [Fe2(μ-SXS)(CO)6], (SXS=-SC6H4 8,-SC6H2OH), were described. By using intramolecularly integrated ferrocenyl group(s) in the complexes as an internal standard, the nature of two stepwise one-electron processes of the complexes was clearly revealed. Examining how the reduction transformed into sole one-electron process with both increasing scanning rate under Ar/CO atmosphere and lowering temperature indicated conclusively that the reduction of both complexes couples to a chemical reaction which involves CO-loss.