THE CRYSTAL-STRUCTURES OF THE ISOTYPIC COMPOUNDS BA3[MON4] AND BA3[WN4]

The isotypic ternary compounds Ba3[MoN4] and Ba3[WN4] were prepared by reaction of the transition metals with barium (Ba3N2, resp.) under nitrogen. The crystal structures were determined by single crystal X-ray diffraction: Ba3[MoN4] (Ba3[WN4]): Pbca; Z = 8; a = 1083.9(3) pm (1091.8(3) pm), b = 1030.3(3) pm (1037.5(3) pm), c = 1202.9(3) pm (1209.2(4) pm). The structures contain isolated tetrahedral anions [MN4]6- (M = Mo, W) which are arranged in form of slightly distorted hexagonal layers and which are stacked along [0 1 0] with the sequence (... AB ...). Two of the three Ba atoms are situated between, the third one is placed within the layers of [MN4]-groups. In this way the structures can be derived from the Na3As structure type.