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][C3S52–= 4,5-dimercapto-1,3-dithiole-2-thionate(2–)] and [NBun4][Au(C3Se5)2][C3Se52–= 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.