Acta Crystallographica Section C

Crystal Structure Communications

Volume 62, Part 1 (January 2006)

inorganic compounds

Acta Cryst. (2006). C62, i6-i8 [ doi:10.1107/S0108270105037121 ]

New triple molybdates Cs₃LiCo₂(MoO₄)₄ and Rb₃LiZn₂(MoO₄)₄, filled derivatives of the Cs₆Zn₅(MoO₄)₈ type

Z. A. Solodovnikova, S. F. Solodovnikov and E. S. Zolotova

Abstract: Two new isotypic triple molybdates, namely tricesium lithium dicobalt tetrakis(tetraoxomolybdate), Cs₃LiCo₂(MoO₄)₄, and trirubidium lithium dizinc tetrakis(tetraoxomolybdate), Rb₃LiZn₂(MoO₄)₄, crystallize in the non-centrosymmetric cubic space group I $\overline{4}$ 3d and adopt the Cs₆Zn₅(MoO₄)₈ structure type. In the parent structure, the Zn positions have 5/6 occupancy, while they are fully occupied by statistically distributed M²⁺ and Li⁺ cations in the title compounds. In both structures, all corners of the (M_2/3Li_1/3)O₄ tetrahedra (M = Co and Zn), having point symmetry $\overline{4}$ , are shared with the MoO₄ tetrahedra, which lie on threefold axes and share corners with three (M,Li)O₄ tetrahedra to form open mixed frameworks. Large alkaline cations occupy distorted cuboctahedral cavities with $\overline{4}$ symmetry. The mixed tetrahedral frameworks in the structures are close to those of mayenite (12CaO·7Al₂O₃) and the related compounds 11CaO·7Al₂O₃·CaF₂, wadalite (Ca₆Al₅Si₂O₁₆Cl₃) and Na₆Zn₃(AsO₄)₄·3H₂O, but the terminal vertices of the MoO₄ tetrahedra are directed in opposite directions along the threefold axes compared with the configurations of Al(Si)O₄ or AsO₄ tetrahedra. The cation arrangements in Cs₃LiCo₂(MoO₄)₄, Rb₃LiZn₂(MoO₄)₄ and Cs₆Zn₅(MoO₄)₈ repeat the structure of Y₃Au₃Sb₄, being stuffed derivatives of the Th₃P₄ type.

Formula: Cs₃LiCo₂(MoO₄)₄ and Rb₃LiZn₂(MoO₄)₄


	Structure factor file (CIF format) (36.2 kbytes) [ doi:10.1107/S0108270105037121/iz1066Isup2.hkl ] Contains datablock I

	Structure factor file (CIF format) (33.2 kbytes) [ doi:10.1107/S0108270105037121/iz1066IIsup3.hkl ] Contains datablock II

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