W₅Br₁₂·BiBr₃ Cluster Phases with Different Crystal Structures

A mixture of two structurally different cluster phases I and II with the general chemical formula W₅Br₁₂·BiBr₃ is obtained as a product of the WBr₆ reduction reaction with elemental bismuth at 280 °C. The elemental composition of the mixture is determined by the energy-dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectrometry. For the single crystals selected from a mixture of phases I and II their crystal structures are determined, and the powder X-ray diffraction analysis is performed for the polycrystalline mixture. In the crystal structure of I, square-pyramidal cluster fragments are bridged by bromine atoms into infinite chains by the W–Br^a–a–W interaction. In the structure of II, BiBr₃ (W–{Br^aBiBrBr^a}–W) molecules incorporate into the chain instead of the bridging bromine atom.