STUDIES OF MIXED-VALENCE STATES IN 3-DIMENSIONAL HALOGEN-BRIDGED GOLD COMPOUNDS, CS2AUIAUIIIX6 (X = CL, BR OR I) .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.