Hydrogenases are enzymes that catalyze the reversible conversion of protons to mol. hydrogen. The active site of the [Fe-Fe]-hydrogenases (the H-cluster) can provide the required potential for this reaction using iron in low oxidn. states. Since it has been recognized that the H-cluster may contain low-spin Fe(I), monovalent iron has become a focus of bio-organometallic synthetic chem. In spite of its intriguing implication in hydrogenogenesis, the electronic structure of low-spin Fe(I) is unknown. The high asymmetry of the dinuclear site in the H-cluster stabilizes the elusive Fe(I)Fe(II...
