Iron–sulfur clusters occur in many biological systems, often as components of electron transfer proteins and as the H-cluster in hydrogenase and the P-cluster and FeMo-cofactor in nitrogenase. This chapter describes significant progress made in synthetical, compositional and functional aspects of the nitrogenase-like clusters through the recent decades. New synthesized clusters were found to react with dihydrogen and proton mimicking the hydrogenase reaction S (H2 + Aox → 2H+ + Ared and 2H+ + Dred → H2 + Dox). Number of synthetic rhombic and cuboidal clusters could convert N2 to hydrazine and ammonium modeling the nitrogenase reaction. As an example of four electron mechanism of dinitrogen reduction, four nuclear complex V(II)-pyrocatechol (V(II)4) was utilized in a homogeneous reaction V(II)4N2 + V(II)4 + 8H+ → 8V(III) + 2NH3 + H2O. The Chatt Cycle, a hypothetical model for the mechanism of nitrogenase action at the atomic level based upon reactions of molybdenum compounds and scheme of the multi-stage nitrogenase process were considered.