Hydrothermal Crystal Growth and Structure Determination of Double Hydroxides LiSb(OH)₆, BaSn(OH)₆, and SrSn(OH)₆

Colorless single crystals of LiSb­(OH)6, SrSn­(OH)6, and BaSn­(OH)6, which are useful as precursors for the synthesis of LiSbO3, SrSnO3, and BaSnO3, were synthesized by a low-temperature hydrothermal method using a Teflon-lined autoclave at 380 K. The crystal structures were determined by single-crystal X-ray diffraction measurements. LiSb­(OH)6 crystallizes in the trigonal space group P3̅1m with a = 5.3812(3)­A, c = 9.8195(7)­A, V = 246.25(3)­A3, Z = 2. In this layered structure, [Li2Sb­(OH)6]+ and [Sb­(OH)6]− layers are alternately stacked along the c-direction. The [Li2Sb­(OH)6]+ layer can be regarded as a cation-ordered CdCl2 layer. The [Sb­(OH)6)]− layer is built up from isolated [Sb­(OH)6]− octahedra, which are linked to each other via hydrogen bonding within the layer. BaSn­(OH)6 and SrSn­(OH)6 crystallize with monoclinic P21/n space group symmetry. The monoclinic structure possesses a CsCl-type packing of Ba2+/Sr2+ cations and [Sn­(OH)6]2– anions. The [Sn­(OH)6]2– polyhedra are connected to each other through hydrogen bonding to form a three-dimensional framework. The factors that favor these hitherto unknown crystal structures are discussed using a structure map that compares various M­(OH)3 and M′M″(OH)6 compounds.