ELECTRONIC-STRUCTURE OF THE IRON-MOLYBDENUM AND ALTERNATIVE COFACTORSOF NITROGENASES - A COMPARISON AND ITS CONSEQUENCES

The electronic structure of idealized structural models [H(3)MFe(3)S(3 ){mu(2)-S}3Fe4S3H](n-) with 3m (C-3) symmetry for the FeMo-, FeV-, and FeFe-cofactors of the three nitrogenase systems known (2 M = Mo and n = 1, 3 M = V and n = 2, 4 M = Fe and n = 2) has been investigated usi ng the EHMO and SCCC-EHMO methods, respectively. On the basis of MO an alysis the similarities and differences between these model clusters w ill be discussed. Special attention will be focused on the possible fu nction of the heterometal center of these model clusters (Mo, V, and F e) as well as the binding of dinitrogen to the cofactor models.