Diversity in Nitridosilicate Chemistry: The Nitridoalumosilicate Ca-4(AlSiN5) and the Nitridosilicate Silicide Ca12Si4[SiN4]

Single crystals of the calcium nitridoalumosilicate Ca-4(AlSiN5) and the nitridosilicate silicide Ca12Si4[SiN4] were grown from sodium flux. Ca-4(AlSiN5) crystallizes in the noncentrosymmetric space group Pna2(1) and presents a framework of AlN4 and SiN4 tetrahedra sharing vertices. Ca12Si4[SiN4] crystallizes in P (1) over bar. Its crystal structure features mutually isolated nitridosilicate tetrahedra [(SiN4)-N-IV](8-) next to Si4- Zintl anions, with silicon both in its highest and lowest possible oxidation state. Crystals of the isotypic compound Sr12Ge4[GeN4] were obtained, but the crystal structure could not be satisfactorily refined due to unsolved twinning issues.