Structural Organization and Thermal Behavior of Compounds Rb3(SbF3)(Zr2F11)·0.5H2O and Rb3(SbF3)(Zr2F11)

Abstract

Compound Rb₃(SbF₃)(Zr₂F₁₁)·0.5H₂O and its dehydration product Rb₃(SbF₃)(Zr₂F₁₁) were synthesized and their structures were studied. It was found that compound Rb₃(SbF₃)(Zr₂F₁₁)·0.5H₂O has a unique fluoride zirconate framework structure built of ring tetrameric fragments (Zr₄F₂₄) connected to each other at the vertices by bridging fluorine atoms. Inside the tetrameric fragments, ZrF₈ polyhedra are connected to each other along common edges. The zirconium framework [Zr₂F₁₁]^3– is bound by Zr–F–Sb fluoride bridges from the second coordination sphere of antimony atoms. The structure of the dehydrated compound Rb₃(SbF₃)(Zr₂F₁₁) is a three-dimensional framework consisting of infinite chains of composition [Zr₂F₁₁]^3–. The chains are formed by ZrF₇ polyhedra connected along edges and vertices and united with each other into a three-dimensional framework by fluoride bridges Zr–F–Sb from the second coordination sphere of antimony atoms. In Rb₃(SbF₃)(Zr₂F₁₁), in the temperature range 247–256 K, a reversible phase transition occurs from the partially disordered high-temperature phase α to the ordered low-temperature phase β. With the participation of fluorine atoms of the second coordination sphere and a lone pair of electrons around antimony atoms, coordination polyhedra are formed in the structures in the form of distorted (SbEF₅) and single-capped (SbEF₆) octahedra.