NEW TETRAPNICTIDOMETALLATES OF SILICON, G ERMANIUM, TIN, AND TANTALUMWITH THE NA6ZNO4 STRUCTURE

The tetrapnictidometallates(IV) Na(3)M(3)E(IV)X(4) (M = Na/Ca, Na/Sr, Na/Eu; E = Si, Ge, Sn and X = P, As) were prepared from NaX, M'X (M' = Ca, Sr, Eu) and elemental E in tantalum ampoules at temperature of 12 70 K. The tetrapnictidotantalates(V) Na-3(Na2Eu)TaP4 and Na-3(Na2Eu)Ta As4 were formed by a reaction with the walls of the ampoule. All compo unds crystallise hexagonal in the Na6ZnO4 structure type hP22 (P6(3)mc , no. 186; Z = 2) with polar orientated tetrahedron anions [SiX(4)](8- ), [GeX(4)](8-), [SnX(4)](8-) and [TaX(4)](7-). The average bondlength s are: (d) over bar(Si-P) = 230.4 pm; (d) over bar(Si-As) = 239.9 pm; (d) over bar(Ge-P) = 237.1 pm; (d) over bar(Ge-As) = 247.8 pm; (d) ove r bar(Sn-P) = 252.3 pm; (d) over bar(Sn-As) = 261.4 pm; (d) over bar(T a-P) = 238.3 pm; (d) over bar(Ta-As) = 247.4 pm.