[FeFe] Hydrogenase: 2‐Propanethiolato‐Bridged {FeFe} Systems as Electrocatalysts for Hydrogen Production in Acetonitrile‐Water

AbstractDiiron bis(monothiolato)‐bridged hydrogenase mimics [Fe2(μ‐SiPr)2(CO)6] A (iPr=isopropyl) and their phosphine derivatives [Fe2(μ‐SiPr)2(CO)5(L1/2)] and [Fe2(μ‐SiPr)2(CO)4(L3)] {tricyclohexylphosphine (L1, PCy3) 1, triphenylphosphine (L2, PPh3) 2 and cis‐1,2‐bis(diphenylphosphino)ethylene (L3, dppv) 3} have been synthesized and investigated for electrocatalytic proton reduction activity in CH3CN−H2O. Based on the FTIR data (red‐shift), the electron‐donating ability of the phosphines followed the order: dppv>PCy3>PPh3 (average shift value with respect to complex A was 61 (1), 51 (2) and 80 (3) cm−1). From CV measurements, it was seen that the catalytic reduction potential (acetic acid as proton source) shifted considerably towards positive potentials (anodic shift) on changing the solvent from pure CH3CN to CH3CN−H2O (4 : 1 v/v). An increase in the percentage of water in CH3CN led to the decomposition of complexes 1 and 3. Though complexes A and 2 were stable in CH3CN−H2O (3 : 2 v/v), no improvement in electrocatalytic currents was observed.