| Abstract
| - A series of dinuclear complexes, (μ-SRS)Fe2(CO)6 (R = −CH2CH2−, −CH2CH2CH2−, −CH2−C6H4−CH2−; edt, pdt, and o-xyldt, respectively) has been examined for specific characteristics that mightrelate to structural similarity with the active site of Fe-only hydrogenases. Variable-temperature proton NMRstudies display the fluxionality of the iron−dithiocyclohexane unit in (μ-pdt)Fe2(CO)6 while in the (μ-o-xyldt)Fe2(CO)6 compound, the bridge is fixed. Temperature-dependent 13C NMR spectral studies establishintramolecular CO site exchange localized on discrete Fe(CO)3 units in all complexes, which is influenced bysteric effects of the μ-SRS unit. Kinetic studies of intermolecular CO/CN- ligand-exchange reactions establishassociative or Ia mechanisms in sequential steps to form the dicyano dianion, (μ-SRS)[Fe(CO)2(CN)]2= with100% selectivity. Theoretical calculations (DFT) of transition states in the intramolecular site-exchange processeslead to a rationale for the interesting cooperativity in the CN-/CO intermolecular ligand-exchange process.The hinge motion of the three light atom S-to-S bridge is related to a possible heterolytic H2 activation/production process in the enzyme.
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