XeOF₂, F₂OXeN≡CCH₃, and XeOF₂·nHF:  Rare Examples of Xe(IV) Oxide Fluorides

The syntheses of XeOF₂, F₂OXeN⋮CCH₃, and XeOF₂·nHF and their structural characterizations are described in this study. All three compounds are explosive at temperatures approaching 0 °C. Although XeOF₂ had been previously reported, it had not been isolated as a pure compound. Xenon oxide difluoride has now been characterized in CH₃CN solution by ¹⁹F, ¹⁷O, and ¹²⁹Xe NMR spectroscopy. The solid-state Raman spectra of XeOF₂, F₂OXeN⋮CCH₃, and XeOF₂·nHF have been assigned with the aid of ¹⁶O/¹⁸O and ¹H/²H enrichment studies and electronic structure calculations. In the solid state, the structure of XeOF₂ is a weakly associated, planar monomer, ruling out previous speculation that it may possess a polymeric chain structure. The geometry of XeOF₂ is consistent with a trigonal bipyramidal, AX₂YE₂, VSEPR arrangement that gives rise to a T-shaped geometry in which the two free valence electron lone pairs and Xe−O bond domain occupy the trigonal plane and the Xe−F bond domains are trans to one another and perpendicular to the trigonal plane. Quantum mechanical calculations and the Raman spectra of XeOF₂·nHF indicate that the structure likely contains a single HF molecule that is H-bonded to oxygen and also weakly F-coordinated to xenon. The low-temperature (−173 °C) X-ray crystal structure of F₂OXeN⋮CCH₃ reveals a long Xe−N bond trans to the Xe−O bond and a geometrical arrangement about xenon in which the atoms directly bonded to xenon are coplanar and CH₃C⋮N acts as a fourth ligand in the equatorial plane. The two fluorine atoms are displaced away from the oxygen atom toward the Xe−N bond. The structure contains two sets of crystallographically distinct F₂OXeN⋮CCH₃ molecules in which the bent Xe−N−C moiety lies either in or out of the XeOF₂ plane. The geometry about xenon is consistent with an AX₂YZE₂ VSEPR arrangement of bond pairs and electron lone pairs and represents a rare example of a Xe(IV)−N bond.