Studies of mixed-valence states in three-dimensional halogen-bridged gold compounds, Cs2AuIAuIIIX6(X = Cl, Br or I). Part 1. Synthesis, X-ray powder diffraction, and electron spin resonance studies of CsAu0.6Br2.6

Abstract

A new non-stoichiometric mixed-valence compound CsAu_0.6Br_2.6 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 Au^I–Au^III mixed-valence compound Cs₂Au₂Br₆.