Sr₅Ge₂N₆ – A Nitridogermanate with Edge-sharing Double Tetrahedra^†

The new nitridogermanate Sr₅Ge₂N₆ was obtained as a coarsely crystalline product by Na-flux technique employing a reaction of Sr, Na, NaN₃ and GeO₂ in weld shut tantalum-tubes at temperatures up to 760 °C. The crystal structure was determined by single-crystal X-ray methods: (Sr₅Ge₂N₆, space group C2/c (no. 15), a = 1040.8(2), b = 652.08(13), c = 1356.5(3) pm, β = 100.29(3)°, V = 905.8(3)·10⁶ pm³, Z = 4, 1240 observed reflections, 61 parameters, R1 = 0.031). In the solid, there are edge-sharing [Ge₂N₆]¹⁰⁻ double tetrahedra surrounded by Sr²⁺ ions. Sr₅Ge₂N₆ was found to be isotypic with Ca₅Si₂N₆.