Using pendant ferrocenyl group(s) as an intramolecular standard to probe the reduction of diiron hexacarbonyl model complexes for the sub-unit of [FeFe]-hydrogenase

The synthesis and characterisation of two diiron hexacarbonyl complexes [Fe 2 (SXS)(CO) 6 ], 1 (SXS   =   (( − SCH 2 ) 2 C(CH 3 )CH 2 OCOFc, Fc   =   ferrocenyl group) and 2 (SXS   =   ( − SCH 2 CH 2 NHCOFc) 2 ), 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 coupled with a chemical reaction was clearly demonstrated. 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.