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Ca[LiAlN2]: A Quaternary Nitridoaluminate



Ca[LiAlN2] was synthesized from LiAlH4, LiN3, calcium, and lithium metal as fluxing agent in welded-shut tantalum crucibles at 900 °C. The compound crystallizes in the form of transparent colorless platelets that undergo hydrolysis in air and under moisture. The crystal structure [P21/c (no. 14), a = 5.7587(12) Å, b = 6.8773(14) Å, c = 5.7960(12) Å, β = 90.28(3)°, Z = 4] was solved from single-crystal X-ray diffraction data and was confirmed with Rietveld refinement methods and lattice-energy calculations (Madelung part of lattice energy, MAPLE). Ca[LiAlN2] forms layers of edge- and vertex-sharing AlN4 tetrahedra isotypic with LiCaGaN2. Li+ ions are positioned in tetrahedral voids within the [Al2N2N4/2] layers resulting in a highly condensed structure of Al- and Li-centered polyhedra.

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