inorganic compounds
The title compound, dicaesium gold(I) gold(III) hexabromide or dicaesium dibromoaurate(I) tetrabromoaurate(III), Cs2[AuIBr2][AuIIIBr4], has a distorted perovskite-type structure which is isotypic with its chloride and iodide analogues, Cs2AuIAuIIIX6 (X is Cl or I). The structure contains compressed and elongated [AuBr6] octahedra stacked alternately along the [001] and [110] directions by sharing all the corner Br− ions. The compound is also characterized by the assembly of the gold complex ions [AuIBr2]− and [AuIIIBr4]−. Structural parameters indicating the mixed-valence distortion of AuI and AuIII due to displacement of two crystallographically independent halide (X) ions from the mid-point between the two adjacent Au ions, expressed by (Au—X)/(AuX), are 0.738 (2) along the c axis and 0.799 (1) in the ab plane. These values show that the mixed-valence distortion of the title bromide is intermediate between those of the chloride and the iodide. The distortion of the title bromide from the cubic system to the tetragonal system, expressed by 21/2a/c = 0.9704 (1), is also intermediate between those of the chloride and the iodide.
inorganic compounds
Rb2[AuII2][AuIIII4], dirubidium diiodoaurate(I) tetraiodoaurate(III), has a tilted and distorted perovskite-type structure which is isotypic with its bromide analogue Rb2[AuIBr2][AuIIIBr4]. The structure contains compressed and elongated [AuI6] octahedra tilted away from each other and stacked alternately along the [001], [10] and [110] directions by sharing all the corner I- ions.