title: New triple molybdates Cs3LiCo2(MoO4)4 and Rb3LiZn2(MoO4)4, filled derivatives of the Cs6Zn5(MoO4)8 type.
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-43d 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(2/3)Li(1/3))O4 tetrahedra (M = Co and Zn), having point symmetry -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 -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.
authors.affiliation: Nikolaev Institute of Inorganic Chemistry, SB Russian Academy of Sciences, Academician Lavrentiev Avenue 3, Novosibirsk 630090, Russian Federation.
authors.forename: Zoya A
authors.initials: ZA
authors.lastname: Solodovnikova
authors.forename: Sergey F
authors.initials: SF
authors.lastname: Solodovnikov
authors.forename: Evgeniya S
authors.initials: ES
authors.lastname: Zolotova