Spectroscopy and electrical conductivity of [Au(C3S5)2]n– and [Au(C3Se5)2]n–(n= 0–1) complexes and X-ray crystal structure of [NBun4][Au(C3S5)2]

Abstract

The complexes [NBuⁿ₄][Au(C₃S₅)₂][C₃S₅^2–= 4,5-dimercapto-1,3-dithiole-2-thionate(2–)] and [NBuⁿ₄][Au(C₃Se₅)₂][C₃Se₅^2–= 4,5-di(hydroseleno)-1,3-diselenole-2-selonate(2–)] were prepared. Oxidation reactions of these complexes with iodine, [ttf]₃[BF₄]₂(ttf˙⁺= the tetrathiafulvalenium radical cation), and [Fe(cp)₂][PF₆](cp =η-C₅H₅) afforded [Au(C₃S₅)₂], [Au(C₃Se₅)₂], [ttf][Au(C₃S₅)₂], [ttf]_0.3[Au(C₃Se₅)₂], [Fe(cp)₂]_0.25[Au(C₃S₅)₂], and [Fe(cp)₂]_0.2[Au(C₃Se₅)₂], respectively. Controlled-current electrolysis of [NBuⁿ₄][Au(C₃S₅)₂] in acetonitrile containing an excess of [NBuⁿ₄][ClO₄] afforded [NBuⁿ₄]_0.22[Au(C₃S₅)₂]. The complexes [Au(C₃S₅)₂] and [Au(C₃Se₅)₂] have electrical conductivities of 5.0 × 10^–4 and 6.3 × 10^–4 S cm^–1, the ttf complexes 4.3 × 10^–3 and 3.2 × 10^–3 S cm^–1, respectively, and the other partially oxidized complexes 0.10–0.16 S cm^–1 at 25 °C for compacted pellets. Ligand-centred oxidation is believed to occur for both the [Au(C₃S₅)₂]^n– and [Au(C₃Se₅)₂]^n–(n < 1) complexes on the basis of e.s.r. and X-ray photoelectron spectra. A single-crystal X-ray analysis of [NBuⁿ₄][Au(C₃S₅)₂] revealed a crystal packing consisting of two crystallographically independent [Au(C₃S₅)₂]^– moieties with a square-planar geometry which form a one-dimensional anion chain along the c axis with some sulphur–sulphur contacts. The crystals are triclinic, space group P, with cell parameters a= 12.384(3), b= 12.258(4), c= 11.622(3)Å, α= 74.89(3), β= 90.90(2), γ= 79.59(2)°, and Z= 2. Least-squares refinement, based on 4 804 independent reflections with |F_∘| > 3σ(F), converged at R= 0.034.