Cs5[Na{W4N10}]: The first framework nitridotungstate(VI)

Article abstract of DOI:10.1002/zaac.19966220522

Cs₅[Na{W₄N₁₀}] was prepared from a mixture of NaNH₂, CsNH₂ and tungsten powder (molar ratio 1:10:4) at 700°C in autoclaves. After the reaction is finished the nitride is embedded in an alkali metal matrix. Dark red crystals were isolated by washing out the alkali metal with liquid ammonia at room temperature. The structure of Cs₅[Na{W₄N₁₀}] was solved by X-ray single crystal data: I4₁ (No. 80), Z = 4, a = 13.926(3) A, c = 8.723(3) A, Z(F_o²) ≥ 3σ(F_o²) = 1535, Z(Variables) = 63, R/R_w = 0.040/0.052. The compound is highly sensitive against moisture giving oxotungstates and ammonia. It contains a framework of tetrahedra _∞³[WNN_3/2^1.5-]. Sodium shares four terminal nitrogen ligands. Including sodium a distorted, β-cristobalite type arrangement _∞³[Na{W₄N₁₀}^5-] results. It contains caesium in all interstices formed by twelve nitrogen ligands in so-called Friauf polyhedra. Johann Ambrosius Barth 1996.