Reactions of small molecules at transition metal sites: Studies relevant to nitrogenase, an organometallic enzyme

This article outlines some coordination chemistry of Mo, V and Fe relevant to the function of the active centre of nitrogenase, FeMoco. The focus is on work which has been carried out in the Nitrogen Fixation Laboratory, whose founding Director was Joseph Chatt, and the article is dedicated to him. The introduction sketches the properties of nitrogenase and its reductions of isocyanides, cyanide and alkynes, and interaction with carbon monoxide, which established the organometallic nature of this enzyme. A brief description of the chemistry of isolated FeMoco is given, particularly its reactions with thiols, selenols and cyanide. These reactions are discussed with respect to the structure of FeMoco. The reduction of dinitrogen (and alternative nitrogenase substrates such as isocyanides and alkynes) at metal centres is then described, leading from reactions of these substrates at metal centres with phosphine co-ligands to those metal centres with mainly sulphur ligation. The current state of knowledge of this chemistry is then discussed with respect to the likely site or sites of interaction of dinitrogen on FeMoco.