SYNTHESIS AND CHARACTERIZATION 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 pres ence of Fe(CO)(5) gives the CO-free complex [Cp(2) NbS2](2) Fe 2a. Th e core of 2a contains an FeS4 tetrahedron which is ligated by two niob ocene 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(C O)(8), compounds 3a and 3b of the same type are formed. Electrochemica l studies of 2a and 3a,b show that they undergo three reversible le(-) steps. The oxidation of 3b exerts a considerable influence on its abs orption spectrum. A qualitative EHMO analysis is in agreement with a s trong delocalisation of electron density over the whole NbS(2)MS(2)Nb system.