Abstract
Single crystals of NbF4, niobium(IV) tetra-fluoride, were synthesized by disproportionation of Nb2F5 at 1273 K in a sealed niobium tube, extracted and studied by single-crystal X-ray diffraction. Previous reports on the crystal structure of NbF4 were based on X-ray powder diffraction data and the observed isotypicity to SnF4 [Gortsema & Didchenko (1965 ▸). Inorg. Chem. 4, 182-186; Schäfer et al. (1965 ▸). J. Less Common Met. 9, 95-104]. The data obtained from a single-crystal X-ray diffraction study meant the atomic coordinates could now be refined as well as their anisotropic displacement parameters, leading to a significant improvement of the structural model of NbF4. In the structure, the Nb atom is octahedron-like surrounded by six F atoms of which four are bridging to other NbF6 octa-hedra, leading to a layer structure extending parallel to the ab plane.
Highlights
Single crystals of NbF4, niobium(IV) tetrafluoride, were synthesized by disproportionation of Nb2F5 at 1273 K in a sealed niobium tube, extracted and studied by single-crystal X-ray diffraction
Previous reports on the crystal structure of NbF4 were based on X-ray powder diffraction data and the observed isotypicity to SnF4 [Gortsema & Didchenko (1965)
The first synthesis of niobium tetrafluoride was reported by Schäfer and co-workers by reduction of niobium pentafluoride with niobium metal (Schäfer et al, 1964)
Summary
The first synthesis of niobium tetrafluoride was reported by Schäfer and co-workers by reduction of niobium pentafluoride with niobium metal (Schäfer et al, 1964). The obtained products were reported as dark-blue or black powders, respectively We obtained green NbF4 single crystals among a green powder. It is reported to be soluble in hydrochloric acid, sulfuric acid or hydrogen fluoride (Schäfer et al, 1965). The compound disproportionates under vacuum above 623 K to NbF5 and a fluoride of which the compositions were reported as NbF2.37 (Schäfer et al, 1965) or NbF3 (Gortsema & Didchenko, 1965). In a sealed niobium ampoule NbF4 disproportionates at 825 K to NbF5 and Nb2F5 (Chassaing & Bizot, 1980). & Didchenko, 1965, Schäfer et al, 1965). Magnetic measurements show that NbF4 orders antiferromagnetic in contrast to the other niobium tetrahalides which are reported to be diamagnetic (Chassaing & Bizot, 1980)
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