AMMONOTHERMAL SYNTHESIS OF COPPER NITRIDE

Tetraamine copper(II)-nitrate reacts in liquid ammonia at room temperature with copper to give tri- or diamine copper(I)-nitrate (f(T) and p(NH3)). [Cu(NH3)x]NO3 with 2 ≤ x ≤ 3 decomposes at 350 °C up to 580 °C and p(NH3) = 6 kbar in a temperature gradient within the autoclaves used to Cu3N, N2 and H2O; the nitride crystallizes in the hot zone. X-ray single-crystal investigations at room temperature and - 143 °C confirm the ReO33 type of structure: a = 3.819(1) A ̊, N = 1, Pm3m, R Rw = 0.010/0.014 with Z(F0)2)≥3σ(F0)2) = 108 but the angle of the covalent NCuN bond is 173 ° at 21 °C and 176 ° at -143 °C. Models of dynamic and static tilting of NCu6 octahedra are discussed. Cu3N forms dark crystals with a greenish lustre. It is a diamagnetic insulator. The compound is metastable at room temperature and can be handled in air without attack. It decomposes at 470 °C with an enthalpy of 83.7 kJ mol-1 to give copper and nitrogen. © 1990.