SYNTHESIS AND PROPERTIES OF NEW MIXED-HALIDE DERIVATIVES OF IRON-SULFIDE DIMERS - CRYSTAL-STRUCTURE OF (ET(4)N)(2)[FE2S2CL2BR2]

The synthesis and characterization of the new mixed-halide clusters (E t(4)N)(2)[Fe2S2Cl4-Br-n(n)] (n = 2, 3), together with an improved synt hesis of (Et(4)N)(2)[Fe2S2Br4] and the crystal and molecular structure of (Et(4)N)(2)[F2S2Cl2Br2], are reported here. The structure consists of [Fe2S2Cl2Br2] dianions, with a pseudo-tetrahedral symmetry around each iron atom. A disorder problem precludes precise identification of the locations of the chloride and bromide ligands. A syn (or anti) co nformation is however considered to be most likely, for steric hindran ce reasons and on the basis of Mossbauer data. The Mossbauer, magnetic susceptibility, cyclic voltammetry and UV/Vis properties of the new c lusters remain similar to those of the parent single-type halide clust ers. These new clusters are interesting precursors for complexes with mixed thiolate and non-thiolate coordination at the iron sites.