The preparation and crystal structure of 5SbF3·3SbF5

Abstract

5SbF₃·3SbF₅ was prepared by the reduction of SbF₃·SbF₅ or SbF₅ with a stoicheiometric amount of PF₃ in arsenic trifluoride solution. A single-crystal X-ray diffraction study of 5SbF₃·SbF₅ shows that it is orthorhombic, space group Pnma with cell dimensions, a= 19.187(9), b= 15.890(2), c= 15.713(3)Å, and Z= 8. The structure was refined to a final R of 0.057 for 3 718 reflections. The structure consists of a three-dimensional cross-linked polymeric (Sb₅F₁₂)_n³ⁿ⁺ cation and SbF₃^– anions with significant cation–anion interactions. The polymeric cation can be viewed as being built of strongly interacting Sb₂F₅⁺, SbF₃, and Sb₂F₃³⁺ units. The various configurations of Sb₂F₅⁺ cations are described and discussed. The planar eclipsed Sb₂F₃³⁺ cation has not been observed in other binary fluorides of antimony. The geometries of the fluorine atoms in the several co-ordination spheres about the various antimony(III) species are described. A rationale is advanced for the existence of a variety of polymeric antimony(III) fluorocations formed between SbF₃ and SbF₅, in contrast to AsF₃ and SbF₅ which form an adduct that can be described as AsF₂⁺SbF₆^–. The Raman spectrum of 5SbF₃·3SbF₅ is reported.