Sr(Mg3Ge)N4 and Sr(Mg2Ga2)N4: New isostructural Mg-containing quaternary nitrides with nitridometallate anions of [(Mg3Ge)N4]2−∞3 and [(Mg2Ga2)N4]2−∞3 in a 3D-network structure

Two new isostructural Mg-containing quaternary nitrides, Sr(Mg3Ge)N4 and Sr(Mg2Ga2)N4, were obtained as single crystals from their constituent elements in molten Na. Sr(Mg3Ge)N4 and Sr(Mg2Ga2)N4 both crystallize in space group I4/m (No. 87) with a = 8.316(1), c = 3.398(1) Å, Z = 2, and a = 8.2925(7), c = 3.3585(5) Å, Z = 2, respectively. The two compounds are isoelectronic, with two Ga3+ in Sr(Mg2Ga2)N4 replaced by one Mg2+ and one Ge4+ in Sr(Mg3Ge)N4. Condensed nitridometallate anions, [(Mg3Ge)N4]2−∞3 and [(Mg2Ga2)N4]2−∞3, form a 3D-network structure with basket-shaped cavities, which are occupied by the Sr2+ counter-cations. Each Sr2+ coordinates to eight N in a symmetric, near cubic conformation, with all Sr–N bond lengths of 2.86 Å.

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