On the XeF⁺/H₂O System: Synthesis and Characterization of the Xenon(II) Oxide Fluoride Cation, FXeOXeFXeF⁺

The reported synthesis of the H(2)OF(+) cation as a product of the oxidative fluorination of H(2)O by [XeF][PnF(6)] (Pn = As, Sb) in HF solution has been reinvestigated. The system exhibits complex equilibria, producing two new Xe(II) compounds, [Xe(3)OF(3)][PnF(6)] and [H(3)O][PnF(6)] x 2 XeF(2), refuting the original claim for the synthesis of the H(2)OF(+) cation. Both compounds have been isolated and characterized by vibrational spectroscopy and single-crystal X-ray diffraction. The X-ray crystal structures of the [Xe(3)OF(3)][PnF(6)] salts contain the Z-shaped FXeOXeFXeF(+) cation, which represents the first example of an isolated Xe(II) oxide fluoride. The crystal structure of the [H(3)O][AsF(6)] x 2 XeF(2) adduct contains XeF(2) molecules that interact with the H(3)O(+) cations. The vibrational assignments for the Xe(3)OF(3)(+) cation have been made with the aid of quantum-chemical calculations and were confirmed by (18)O-enrichment, and the assignments for [H(3)O][AsF(6)] x 2 XeF(2) were confirmed by (2)D- and (18)O-enrichment. Quantum-chemical calculations have also been carried out for H(3)O(+) x nXeF(2) (n = 1-4) and have been used to interpret the X-ray crystal structure and vibrational spectra of [H(3)O][AsF(6)] x 2 XeF(2). The energy-minimized geometries and vibrational frequencies for HOF and H(2)OF(+) have been calculated, further disproving the original report of the H(2)OF(+) cation. Both FXeOH and FXeOH(2)(+) have also been computed and are viable intermediates in the proposed equilibria between XeF(+) and H(2)O that lead to the Xe(3)OF(3)(+) cation.