Ba2Na(CN2)(CN)(3), a novel cyanamide cyanide with interpenetrating substructures

Ba2Na(CN2)(CN)(3) was obtained by the reaction of Ba2N with melamine and NaCN at 700 degrees C. The compound was structurally characterized by single-crystal;stal X-ray investigations (<Fd(3)over bar m>, a = 1518.8(3) pm, Z = 16). In the crystal structure the Ba ions form a cubic close packed arrangement, the Na+ and the CN22- ions occupy the octahedral interstices. The CN- ions are located within the close packed BB2+ layers. The unit cell of Ba2Na(CN2)(CN)(3) contains two interpenetrating substructures of the zinc-blende structure type, building up a variant of NaTl. A reversible phase transition has been observed during cooling of the compound. Whereas the Ba-2(CN2)(CN)(3) sublattice remains nearly unaffected in this process, the Na+ ions of the low-temperature phase are statistically distributed on two crystallographic positions.