Three New Lanthanum Oxoantimonate(III) Halides: Synthesis and Crystal Structure of La5Cl3[SbO3]4, La2Sb12O19Br4 and La2Sb12O19I4

It was possible to synthesize colorless single crystals of La5Cl3[SbO3](4) (block-shaped) as well as La2Sb12O19Br4 and La2Sb12O19I4 (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 beta 3 = 90.007(2)degrees for Z = 2. This layered compound contains isolated psi(1)-tetrahedral [SbO3](3-) units, square hemiprisms [LaO8](13-), and antiprisms [LaO4Cl4](9-). La2Sb12O19Br4 and La2Sb12O19I4 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)(infinity){[Sb12O19](2-)} are present, which consist mainly of [SbO4](5-) and few [Sb03]3- units with stereochemically active electronic lone pairs at their Sb3+ centers. Within these socalled "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 La2Sb12O19I4, and La5Cl3[SbO3](4) was structurally compared with the isostoichiometric, but not isotypic La5F3[SFO3](4).