Tetraphenylphosphonium-ikosioctabromooctaantimonat(III), (PPh4)4Sb8Br28 / Tetraphenylphosphonium Ikosioctabromooctaantimonate(III), (PPh4)4Sb8Br28
The title compound was obtained by the reaction of PPh4Br, Sb2Se3, and bromine in dichloromethane. Its crystal structure was determined by X-ray diffraction. Crystal data: a = 1249.1(2), b = 1307.8(2), c = 2152.3(4) pm, α = 102.93(2), β = 100.83(2), γ = 100.42(2)°, Z = 2, triclinic, space group P1̄. (PPh4)4Sb8Br28 is isotypic with (PPh4)4Sb8I28. The Sb8Br284- ion can be taken as the association product of eight SbBr3 molecules with four Br− ions. Each Sb atom has a distorted octahedral coordination with three shorter (252 to 274 pm) and three longer (300 to 353 pm) Sb-Br bonds. The octahedra share common edges in two parallel rows of four octahedra each. The arrangement of the 28 bromine atoms corresponds to a section of a closest packing of spheres.