Ba5[CrN4]N: Das erste Nitridochromat(V)

Ba₅CrN₄]N: The First Nitridochromate(V) Ba₅CrN₄]N is prepared by reaction of mixtures of Li₃N, Ba₃N₂ and CrN/Cr₂N (1 : 1) (molar ratio Li : Ba : Cr = 3 : 5 : 1) in tantalum crucibles at 700°C with flowing nitrogen (1 atm) within a period of 48 h. After cooling down to room temperature (60°C/h) black-shining single crystals of the ternary phase with a platy habit are obtained (monoclinic, C2/m; a = 1054.0(2) pm, b = 1170.9(3) pm, c = 937.7(2) pm, b? = 110,79(2)°; Z = 4). The crystal structure contains isolated complex anions Cr^VN₄]^7? which nearly satisfy the ideal tetrahedral symmetry (Cr? N pm]: 2 × 175.3(4), 2 × 175.8(5); N? Cr? N °]: 106.8(2), 109.5(2), 2 × 109.9(2), 2 × 110,3(2)). The coordination sphere for each of the terminal nitride functions of the complex anions is completed by five neighbouring Ba²⁺ ions (distorted CrBa₅ octahedra). The octahedra are connected via common CrBa₂ faces as well as CrBa edges thereby forming condensed tetrameric octahedral groups. The isolated nitride ions which are also present in the crystal structure of Ba₅CrN₄]N are in an octahedral environment of Ba²⁺ ions. The presence of a d¹-System (Cr(V)) is confirmed by magnetic susceptibility data.