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-M o-S framework, most of these systems being classified according to whether they contain a MoS4 group coordinated as a bidentate ligand to one or two iron atoms, or an Fe3MoS4 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 Fe3MoS4 cubane-like clusters.