Isolation, structure and spectroscopic properties of [Re2(C3S5)5]2– complexes and electrical conductivities of their oxidized species

Abstract

Salts of the dianion [Re₂(C₃S₅)₅]^2–[C₃S₅^2–= 4,5-disulfanyl-1,3-dithiole-2-thionate(2–)] with PPh₄⁺1, NEt₄⁺2 and NBuⁿ₄⁺3 were prepared. A single-crystal X-ray analysis of 1 revealed that the dinuclear anion containing a Re–Re single bond and two Re–S–Re bridges involving the C₃S₅ ligands contains distorted-octahedral co-ordination geometries around both metal atoms and that the anions are associated into a dimeric form through sulfur–sulfur contacts, being further arranged into a chain through other such contacts. Redox potentials of the [Re₂(C₃S₅)₅]^2– anion were determined by cyclic voltammetry. Complexes 1 and 2 were oxidized by iodine, [Fe(C₅H₅)₂][PF₆], and [ttf]₃[BF₄]₂(ttf˙⁺= the tetrathiafulvalenium radical cation) or current-controlled electrolysis to yield species [ttf][Re₂(C₃S₅)₅], [PPh₄]_x- and [NEt₄]_y-[Re₂(C₃S₅)₅](x,y= 0.1–0.65). They behave as semiconductors with electrical conductivities of 2.0 × 10^–3–4.9 × 10^–2 S cm^–1 for compacted pellets at room temperature. The electronic states of the oxidized complexes are discussed on the basis of electronic absorption, IR, ESR as well as X-ray photoelectron spectra.