A new oxynitride compound of molybdenum, Na3MoO3N -: Synthesis via the azide route and structure

The new oxynitride compound of molybdenum, Na3MoO3N was prepared via the azide route. Its crystal structure was solved and refined from X-ray powder data (orthorhombic, Pmn2(1), a = 724.63(1), b = 624.98(1), c = 563.86(1) pm, R-p: 9.04 %; R-wp: 9.83 %). The structure consists of isolated [MoO3N](3-) tetrahedra which are separated by Na+ cations, also in a tetrahedral coordination. It is isostructural to Na3WO3N which is a lower symmetry derivative of the Cu3AsS4 structure. Due to the small difference in the scattering lengths of nitrogen and oxygen, we were unable to distinguish between fully ordered, fully disordered, or partially ordered anions. However, from the positive SHG responses, we can deduce the acentric space group being the correct one and based on the lattice energy calculations, we have been able to identify the position most probably being occupied by nitrogen.