ISOLATED NI6(NH2)12 UNITS IN NICKEL(II) AMIDE

Amorphous Ni(NH2)2 is obtained by the reaction of NiBr2 or [Ni(NH3)3](SCN)2 with KNH2 in liquid NH3. Starting with the amorphous compound, single crystals of Ni(NH2)2 were grown from ammonia in autoclaves (p less-than-or-equal-to 1.5 kbar) at temperatures of 100 less-than-or-equal-to T less-than-or-equal-to 150-degrees-C within two weeks by chemical transport with KNH2 via an amidoniccolate(II)d. X-ray investigations gave the following data for Ni(NH2)2: Pm3, Z = 18, a = 10.825(6) angstrom, rho(X-ray) = 2.137 g cm-3, R/R(W) = 0.032/0.035 with w = 1 N((F0(2) greater-than-or-equal-to 1.5-sigma (F0(2))) = 170 N(Variables) = 42 The diamagnetic, deep-red-coloured compound contains isolated Ni octahedra with d(Ni...Ni) = 2.85 angstrom surrounded by amide ions forming a cubo-octahedron. These Ni6(NH2)12-groups occupy the edges of the cubic-unit-cell-like oxygen in the ReO3 structure type. FTIR spectroscopic measurements indicate at most weak N-H...N bridge bonds between the Ni6(NH2)12 groups. Thermochemical investigations on Ni(NH2)2 show, that the amide forms no ammoniate in liquid NH3; furthermore the small temperature region for the existence of Ni3N2(110 less-than-or-equal-to T less-than-or-equal-to 150-degrees-C) has been verified.