Ba9Ge3N10: A New Ternary Nitride Containing Isolated Planar Triangular Anions of [GeN3](5-)

Abstract

A new nitride, Ba9Ge3N10, was obtained as single crystals from constituent elements in molten Na. It crystallizes in space group R-3c (No. 167) with a = 7.9399(2) angstrom, c = 17.282(1) angstrom, and Z = 2. It contains the first example of isolated nitridometallate anions of GeN35- in perfect planar triangular shape. Ge-N bond length is 1.786(8) angstrom, which is significantly shorter than any known Ge-N bonds, ranging from 1.84 angstrom to 1.95 angstrom. Valence bond model suggests partial multiple bonding character of the Ge-N bond, which is the first example of such bonding configuration for Ge-N bond. N-centered polyhedral perspective suggests the structure of Ba9Ge3N10 can be conceived as the cationic framework of [Ba9Ge3N9](3+), whose 1/3 of the octahedral interstitial sites are occupied by N3- anions.