STUDIES OF MIXED-VALENCE STATES IN 3-DIMENSIONAL HALOGEN-BRIDGED GOLD COMPOUNDS, CS2AUIAUIIIX6 (X = CL, BR OR I) .1. SYNTHESIS, X-RAY-POWDER DIFFRACTION, AND ELECTRON-SPIN-RESONANCE STUDIES OF CSAU0.6BR2.6

A new non-stoichiometric mixed-valence compound CsAu0.6Br2.6 has been prepared, and its powder X-ray diffraction profile, ESR spectra, and electrical conductivity determined. From its empirical formula the average valence of Au is +2.67. Powder diffraction data indicate that the compound has a cubic perovskite structure [cubic lattice, space group Pm3m, a = 5.462(2) angstrom]. This means that the AuBr6 octahedra are crystallographically equivalent. ESR measurements show the existence of a +II formal oxidation state for Au. The conductivity is four orders of magnitude higher than that of the Au(I)-Au(III) mixed-valence compound Cs2Au2Br6.