Synthesis, crystal structure and ion mobility in the complex fluorides of antimony (III) with the lithium cation

Abstract

Two compounds LiSb2F7 (I) and LiSbF4 (II) were synthesized from aqueous solutions of LiNO3·3H2O and Sb2O3 in the presence of HF and studied by the X-ray diffraction, IR and 7Li, 19F NMR spectroscopy. The first obtained lithium heptafluorodiantimonate(III) LiSb2F7 belongs to the orthorhombic system, the space group Pnma. The unit cell contains four formula units consisting of Sb2F7 groups. The structure is formed by Li+ cations and dimeric [Sb2F7]− complex anions.The crystal structure of lithium tetrafluorodiantimonate(III) LiSbF4 is a new structural type in the group of tetrafluoroantimonates(III) with alkali metal cations. The main structural units of LiSbF4 are SbF3E groups linked through the bridge fluorine atoms into a three-dimensional framework and the cations Li+. The compound crystal belongs to the cubic system, space group P213, and contains three formula units per the unit cell. It was found that in the temperature range 150–420K in the compound II structure there is a lithium cation transition from a rigid lattice to diffusion, while in the fluoride subsystem there are no ion motions with frequencies above 104Hz in the entire temperature range (150–450K).