Dimers [Al2N6]12- and Chains 1 ∞[AlN4/2 3-] in the Crystal Structures of Ca6[Al2N6] and Ba3[Al2N4]

Pale yellow transparent single crystals of Ca6[Al2N6] (P21/c, No. 14, a = 693.7(3), b = 614.9(3), c = 987.1(5) pm, ß = 94.01(5)°; Z = 4) and colourless transparent single crystals of Ba3[Al2N4] (Pnna, No. 52, a = 617.9(2), b = 1005.2(4), c = 1023.0(4) pm; Z = 4) were obtained from reactions of mixtures of the representative metals with nitrogen at Tmax = 1000 °C. The crystal structure of Ca6[Al2N6] contains isolated units [Al2N6]12- built of two edge-sharing tetrahedra. Ba3[Al2N4] is an isotype of Sr3[Al2N4]. The crystal structure contains infinite chains 1 ∞ [AlN4/2 3-] of trans edge-sharing tetrahedra.