Edge-sharing SiN4 tetrahedra in the highly condensed nitridosilicate BaSi7N10

The novel nitridosilicate BaSi7N10 was obtained by the reaction of barium metal with Si(NH)(2) in a special high-frequency furnace at 1650 degrees C. The single-crystal structure determination (a = 687.29(3), b = 671.29(3), c = 963.28 (4) pm, beta = 106.269(3)degrees, Pc, Z = 2, R1 = 0.0497, wR2 = 0.0924) reveals a network structure of connected SiN4 tetrahedra. BaSi7N10 is the first nitridosilicate with both corner and edge-sharing SiN, tetrahedra. Unlike the situation in normal oxosilicates, vertex-sharing of SIN, tetrahedra is not exclusively favored over edge-sharing. With a Si:N molar ratio of 7:10, BaSi7N10 is the most highly condensed multinary nitridosilicate known and has almost the same degree of condensation as binary Si3N4.