Studies of mixed-valence states in three-dimensional halogen-bridged gold compounds, Cs2Au I Au III X6(X = Cl, Br or I). Part 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)Å]. 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 AuI–AuIII mixed-valence compound Cs2Au2Br6.