A metal nitride carbodiimide with a stuffed skutterudite-type structure: synthesis, crystal structure and IR spectra of (Ba6N5/6) 2[NbN4][CN2] 6

Abstract

Coppery-red, transparent single crystals of (Ba6N5/6)(2)[NbN4][CN2](6) (Im (3) over bar, no. 204, a = 1125.83(3) pm, Z = 2) are obtained by the reaction of Ba2N and ZnCN2 with the container walls of the arc-welded Nb ampoules at 1100 K. The title compound assumes a stuffed skutterudite-type structure in which edge-sharing (Ba6N5/6) Octahedra form large voids which are occupied by either [NbN4] tetrahedra or by [N=C=N](2-) units with symmetric C=N bond lengths of d = 121.8(6) pm but a bond angle deviating significantly from linearity (measured angle(N-C-N) = 175.3(9)degrees). The IR spectra corroborate this crystallographic result by the fact that all fundamental vibrations are visible in the IR spectrum [v(1) = 1262 (symmetric stretching mode); v(2) = 1957/2009 (antisymmetric stretching mode); v(3) = 611/633/653 cm(-1) (bending modes)], which is symmetry forbidden for [N=C=N](2-) units having D-infinity h symmetry but expected for the C-2v symmetry found in the title compound.