A barium germanium nitride, Ba₃Ge₂N₂, containing ¹_∞| Ge^2- and GeN^4-₂ anions

Single crystals of a ternary nitride, Ba₃Ge₂N₂, were synthesized by the reaction of Ba and Ge with N from NaN₃ in a Na melt by slow cooling from 750°C. The structure, as determined by single crystal X-ray diffraction, is monoclinic, space group P2₁/m with Z = 2, and has lattice parameters a = 9.6196(6), b = 4.0466(2), c = 10.1337 Å, β = 113.553(4)°. The structure consists of angular nitridometallate anions of [GeN₂]^4- and prisms of [Ba₃Ge]⁴⁺ condensed in one dimension to form zigzag Zintl anions ¹_∞| Ge^2-. The Ge-N bond length in the [GeN₂]^4- anions (1.88 Å) is similar to those found in linear MN^z-₂ anions, while the Ge-Ge bond in the Ge^2- chains (2.50 Å) is only slightly larger than in elemental Ge (2.45 Å).