Li_0.17Na_5.83Mo₁₁O₃₆

The title mixed-alkali-metal molybdenium oxide, hexa­kis­(lithium/sodium) undeca­molybdate, was synthesized by solid-state reaction at 793 K. Its [Mo₁₁O₃₆]^6- framework is built up from MoO₆ octa­hedra and MoO₅ pyramids linked together by edges and vertices. The framework delimits two types of inter­secting tunnels running along [100] and [001], where the sodium and lithium ions are located. Two of the sodium ions and the lithium ion have fractional site occupancies. One of the Mo atoms has site symmetry 2, one sodium ion has site symmetry 2 and one has site symmetry -1, and the Li⁺ ion has site symmetry 2. Structural relationships between the title compound and the anatase and Na₆Mo₁₁O₃₆ structures are discussed.

Na₂MoO₂As₂O₇

Disodium molybdenum dioxide diarsenate, Na₂MoO₂As₂O₇, has been synthesized by a solid-state reaction. The structure is built up from MoAs₂O₁₂ linear units sharing corners to form a three-dimensional framework containing tunnels running along the a-axis direction in which the Na⁺ cations are located. In this framework, the As^V atoms are tetra­hedrally coordinated and form an As₂O₇ group. The Mo^VI atom is displaced from the center of an octa­hedron of O atoms. Two Na⁺ cations are disordered about inversion centres. Structural relationships between different compounds: A₂MoO₂As₂O₇ (A = K, Rb), AMOP₂O₇ (A = Na, K, Rb; M = Mo, Nb) and MoP₂O₇ are discussed.