CS-5[NA(W4N10)] - THE FIRST FRAMEWORK NITRIDOTUNGSTATE(VI)

Cs-5[Na{W4N10}] was prepared from a mixture of NaNH2, CsNH2 and tungst en powder (molar ratio 1:10:4) at 700 degrees C in autoclaves. After t he reaction is finished the nitride is embedded in an alkali metal mat rix. Dark red crystals were isolated by washing out the alkali metal w ith liquid ammonia at room temperature. The structure of Cs-5[Na{W4N10 }] was solved by X-ray single crystal data: I4(1) (No. 80), Z = 4, a = 13.926(3) Angstrom, c = 8.723(3) Angstrom, Z(F-o(2)) greater than or equal to 3 sigma(F-o(2))= 1535, Z(Variables)= 63, R/R(w) = 0.040/0.052 . The compound is highly sensitive against moisture giving oxotungstat es and ammonia. It contains a framework of tetrahedra (3)(infinity)[WN N3/21.5-]. Sodium shares four terminal nitrogen ligands. Including sod ium a distorted, beta-cristobalite type arrangement (3)(infinity)[Na{W 4N10}(5-)] results. It contains caesium in all interstices formed by t welve nitrogen ligands in so-called Friauf polyhedra.