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UBC Theses and Dissertations

High-valent fluorides and oxyfluorides. Beaton, Stephen Peter

Abstract

A new compound of iodine (VII), IOF . was prepared pure in bulk quantities by the reaction of IF₇ with H₂O or SiO₂, followed by the removal of IF₇ from the resulting IF₇ /IOF₅ mixture with SbF₅ . IOF₅ was characterized by its infrared and ¹⁹F n.m.r. spectra, both of which confirmed the expected C₄v symmetry for the molecule. Since our studies indicated that previous work on IF₇ was carried out with samples containing IOF₅ , IF₇ was reinvestigated, using ¹⁹F n.m.r. and infrared spectroscopy to establish its stereochemistry. The infrared spectrum suggested a high symmetry, likely D₅h, for IF₇ while the ¹⁹F n.m.r. spectrum showed that rapid intramolecular rearrangement occurred in the liquid phase. Vapour pressure-temperature data were obtained for both IF₇ and IOF₅ ; these suggested that neither IF₇ nor IOF₅ was associated in the liquid or solid states. Some comments have been made on the acid-base behaviour of IF₇ and IOF₅ . IOF₅ shows no tendency to act as either a fluoride ion donor or acceptor, but IF₇ in addition to acting as a donor to AsF₅ and SbF₅ may show acceptor properties, previously unrecorded. The acid-base adduct IF₇ .AsF₅ was characterized by its structure, determined from X-ray powder data; and infrared spectrum as the ionic salt, IF⁺₆AsF⁻₆. The results of magnetic measurements on XeF₆ have been presented and have been suggested to be inconsistent with the hypothesis that XeF₆ is a molecule with a non-octahedral ground state and a low-lying triplet state. The reactions of ONF with the third transition series hexafluorides, and with ReF₇, ReOF₅ and OsOF₅ were studied, along with the reactions of NO with ReF₇ , ReOF₅ and ReF₆. The results confirmed the trend of increasing oxidizing power across the series from tungsten to platinum, established previously in these laboratories. The decreasing tendency to form higher coordinate anions and the variation in anion sizes across the series has been noted, and these have been shown to be consistent with the trend of oxidizing power. The reaction of ONF with IrF₆and PtF₆ has provided the first example of a fluorine elimination reaction: ONF + MF₆→NOMF₆ + F₂(+ ONF₃). The existence of fluorine as a reaction product was conclusively proven and comments on the mechanism of the reaction have been made. The ONF-PtF₆ reaction also provided the first synthetic route to the preparation of pure NO⁺PtF⁻₆. Infrared spectroscopic, magnetic susceptibility, and X-ray powder data have been given for this salt. The experimental evidence is consistent with the formulation of the compound as a derivative of platinum (v). The magnetic data for HOPtF₆, along with the data for O₂PtF₆, has been used to derive magnetic moments for the dioxygenyl cation, O⁺₂. The volumes of the O⁺₂ and NO⁺ cations have been compared.

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