Three new lanthanum oxoantimonate(III) halides : synthesis and crystal structure of La5Cl3[SbO3]4, La2Sb12O19Br4 and La2Sb12O19I4

Abstract

It was possible to synthesize colorless single crystals of La5Cl3[SbO3]4 (block-shaped) as well as La2Sb12O19Br4 and LaSb12O19I4 (both needle-shaped), representing three new compounds from the system of lanthanum oxoantimonate(III) halides, which have not been described in the literature before. La5Cl3[SbO3]4 crystallizes in the monoclinic space group P2/c with the lattice parameters a = 895.82(5) pm, b = 564.28(3) pm, c = 1728.19(9) pm, and β = 90.007(2)° for Z = 2. This layered compound contains isolated ψ1-tetrahedral [SbO3]3- units, square hemiprisms [LaO8]13-, and antiprisms [LaO4Cl4]9-, La2Sb12O19Br4 and LaSb12O19I4 crystallize isotypically in the orthorhombic space group Pnma with a = 3184.69(19) pm, b = 417.78(3) pm, c = 1019.85(6) pm for the bromide and a = 3215.08(19) pm, b = 419.94(3) pm, c = 1062.89(6) pm for the iodide. Instead of isolated [SbO3]3- anions, semi-tubular features 1∞{[Sb12O19]2-} are present, which consist mainly of [SbO4]5- and few [SbO3]3- units with stereochemically active electronic lone pairs at their Sb3+ centers. Within these so-called “double-halfpipes”, La3+ is surrounded by nine oxygen atoms as [LaO9]15- polyhedron without any contact with X- anions. Single-crystal Raman measurements were performed for La5Cl3[SbO3]4 and LaSb12O19I4, and La5Cl3[SbO3]4 was structurally compared with the isostoichiometric, but not isotypic La5F3[SbO3]4.