Nitrogenase and Its Chemical Models

Abstract

The structure of the FeMo-cofactor of nitrogenase allows us to draw conclusions about the importance of multiple contacts between dinitrogen and this polynuclear complex. Apparently, this arrangement corresponds to the maximum activation of dinitrogen and leads to the possibility of using comparatively weak reducing agents. Although there is no evidence for direct interaction of N₂ with iron atoms in cofactor, this is very likely, while vanadium and molybdenium in V- and Mo-dependent nitrogenases, respectively, stabilize the cluster and probably also regulate its redox potential. In model systems involving comparatively weak reducing agents, up to the present time, polynuclear complexes of Mo or V are the most active towards N₂. Iron-sulfur clusters are less stable and, so far, catalytic activity towards dinitrogen has been observed only in some cases with highly negative redox potentials.