NA2K13[W7N19] THE FIRST NITRIDO TUNGSTATE(VI) WITH LAYERS OF CORNER-SHARING NITROGEN TETRAHEDRA AROUND TUNGSTEN

Mixtures of NaNH2, KNH2 and tungsten powder (molar ratio 1:5:1) react in autoclaves at 700 degrees C to N2K13[W7N19] and alkali metals. Dark red crystals are isolated by extracting the alkali metals with liquid ammonia. The structure was determined based on single crystal X-ray d ata. Na2K13[W7N19]: P1, Z = 2, a = 6.726(3) Angstrom, b = 12.505(4) An gstrom, c = 19.347(3) Angstrom, alpha = 90.63(2)degrees, beta = 94.21( 2)degrees, gamma = 100.27(3)degrees. Each tungsten atom has four nitro gen ligands. These form tetrahedra which are connected to layers by co rner sharing. Three of seven inequivalent tetrahedra share two-[WN2N2/ 2]-and the remaining four tetrahedra share three corners-[WNN3/2]-with other tetrahedra. This results in layers (2)(infinity)[(WN2N2/2)(3)(W NN3/2)(4)(15-)]. Within the layers all sodium and five of 13 potassium atoms are located whilst the other potassium atoms connect the layers .