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Preparation and properties of nitrogen oxide trifluoride Passmore, Jack

Abstract

Nitrogen oxide trifluoride was prepared in trace quantities by the reaction of nitric oxide and fluorine. Low, but improved yields were obtained when nitrosyl fluoride and fluorine were heated together at 220°. It was found that (NO)₂2NiF₆ was formed by the reaction of the walls of the Monel reaction vessels, with nitrosyl fluoride, and fluorine, and that pyrolysis of this salt (in 70 p.s.i. fluorine at 350°) gave the new compound in good yield. The reactions of platinum and iridium hexafluoride with nitrosyl fluoride were investigated as routes to ONF₃. Nitrogen oxide trifluoride was colourless in the solid, liquid, and gaseous phases, melting at -161° and boiling at -87.5°. The vapour pressure was determined over the range -128° to -78°. The empirical formula was established by elemental analysis, and by determination of its molecular weight. The structural formula ONF₃ was established from the ¹⁹F n.m.r., and the infrared spectrum of the compound. Nitrogen oxide trifluoride was found to be only moderately reactive. There was no evidence that ONF₃ could be protonated by strong acids. A 1:1 adduct was formed with AsF₅. The chemical behaviour and infrared spectrum of ONF3,AsF₅ was consistent with the formulation ONF₂⁺AsF₆⁻. The empirical formula of (NO)₂^NiF₆ was established by elemental analysis. Its infrared spectrum, and magnetic susceptibility showed that it contained the (NO)⁺ and (NiF₆)²⁻ ions, and a low spin d⁶ arrangement for Ni(IV). The X-ray powder diffraction patterns of (NO)₂NiF₆ could be indexed on the basis of a hexagonal unit cell a = 5.524 Å, c = 5.097 Å, except for five diffuse lines that varied in intensity from sample to sample. Weissenberg (h k 0, h k 1,h k 2, h k 3) photographs showed two sets of reflections. One sharp strong set that could be indexed on the basis of the same hexagonal cell as the lines of the powder photograph, and a weak diffuse set of reflections that together with the strong reflections could be indexed on the hexagonal unit cell, a = 4x5.524, c = 5.097 Å. A structure determination was carried out using the strong sharp set of reflections. The diffraction data were consistent with various models, but the most likely model consisted of (NiF₆)²⁻ groups with the fluorine atoms in a regular octahedron around the nickel atom and the Ni-F bond distance equal to 1.76 Å. The N-O bond distance was very short, 0.88Å, and had associated with it regions of electron density normal to the axis defined by the nitrogen and oxygen atoms. A similar situation for the O2⁺ ion in O₂PtF₆ was reported by Ibers and Hamilton.(108) At 200° chlorine pentafluoride and iridium hexafluoride reacted to give small quantities of a yellow compound which was characterised as ClF₂⁺IrF₆⁻ from elemental analysis, magnetic susceptibility measurements, and its infrared spectrum. A structural determination was attempted from single crystal X-ray data. Preliminary results suggest that the iridium atoms form an ab face centred array, and the chlorine atoms are situated almost in the centre of the square pyramidal holes defined by the iridium atoms.

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