Iron--Molybdenum--Sulphur Clusters

The recognition that molybdenum is present in the nitrogenase enzymes as an extractable cofactor, containing iron, molybdenum and sulphur in the ratios 6-8: 1: 4-6, has stimulated investigations concerned with the synthesis and characterization of compounds containing these three elements. This paper describes the preparation and structure of complexes containing an Fe--Mo--S framework, most of these systems being classified according to whether they contain a MoS$_{4}$ group coordinated as a bidentate ligand to one or two iron atoms, or an Fe$_{3}$MoS$_{4}$ cubane-like cluster. Several physical properties of these complexes are presented, with reference to the corresponding properties of the iron--molybdenum cofactor of the nitrogenases, especially for those complexes that contain a pair of Fe$_{3}$MoS$_{4}$ cubane-like clusters.