Studies of mixed-valence states in three-dimensional halogen-bridged gold compounds, Cs2AuIAuIIIX6, (X = Cl, Br or I). Part 2. X-Ray photoelectron spectroscopic study

Abstract

The mixed-valence states in Cs₂Au^IAu^IIIX₆(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 CsAu_0.6Br_2.6 the oxidation state of Au is considered to be almost homogeneous.