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
摘要:
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.
Studies of mixed-valence states in three-dimensional halogen-bridged gold compounds, Cs2Au I Au III X6, (X = Cl, Br or I). Part 2. X-Ray photoelectron spectroscopic study
The mixed-valence states in Cs2Au(I)Au(III)X6 (X = Cl, Br or I) were systematically studied by X-ray photoelectron spectroscopy of the Au 4f region for the first time. The gold valence states in halogeno complexes of Au(I) and Au(III) were also studied. In Cs2Au2X6 the difference between the oxidation state of Au(I) and that of Au(III) decreases as the covalency of the -Au(I)-X-Au(III)-X- bonds increases in the order X = Cl < Br < I, because the charge-transfer interaction between Au(I) and Au(III) through the bridging halogen becomes stronger in this order. In the non-stoichiometric CsAu0.6Br2.6 the oxidation state of Au is considered to be almost homogeneous.
Wells, H. L.; Wheeler, H. L., Zeitschrift fur anorganische Chemie, 1892, vol. 2, p. 304 - 310