Ba2[Ni3N2]: A low-valent nitridonickelate - Synthesis, crystal structure, and physical properties

Abstract

The ternary alkaline-earth nitridonickelate Ba2[Ni 3N2] (Ba2[Ni12- Ni 0N2]) was prepared by the reaction of mixtures of Ba 2N and Ni in nitrogen gas of ambient back-pressure at 1173K. The crystal structure determined by X-ray single-crystal and powder diffraction methods as well as from neutron diffraction data at various temperatures between 2 and 298 K is orthorhombic (Cmca (no. 64), 298 K: a = 715.27(18) pm, b = 1032.99(21) pm, c = 740.12(20) pm) and provides the first example of a nitridonickelate with a two-dimensional complex anion. The Ni(2) atom is described with a split position and the corresponding superstructure variants are investigated by theoretical full-potential nonorthogonal local-orbital calculations (FPLO). The average oxidation state of Ni in Ba2[Ni 3N2] is +0.67, the lowest average value observed in nitridonickelates so far. Investigations of the physical properties demonstrate that Ba2[Ni3N2] acts as a "poor" metal with a large resistivity of ≈2.7 mΩ at 300 K and exhibits low-dimensional magnetism with antiferromagnetic ordering at T≈ 90 K. XAS spectra correspond with lowvalent Ni states. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.