Synthesis and characterisation of [(C(5)Me(4)R)(2)NbS2](2)M complexes (M=Fe, Co; R=Me, Et): Organometallic tetrathiometalates with niobocene ligands

Irradiation of Cp(2)* Nb(eta(2)-S-2)H (Cp* = C(5)Me(5)) la in the presence of Fe(CO)(5) gives the CO-free complex [Cp(2)* NbS2](2) Fe 2a. The core of 2a contains an FeS4 tetrahedron which is ligated by two niobocene ligands as shown by X-ray diffraction analysis. In the reaction of la or Cp(2)(x) Nb(eta(2)-S-2)H (Cp(x) = C(5)Me(4)Et) 1b with Co-2(CO)(8), compounds 3a and 3b of the same type are formed. Electrochemical studies of 2a and 3a,b show that they undergo three reversible le(-) steps. The oxidation of 3b exerts a considerable influence on its absorption spectrum. A qualitative EHMO analysis is in agreement with a strong delocalisation of electron density over the whole NbS(2)MS(2)Nb system.