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

The reported synthesis of the H2OF+ cation as a product of the oxidative fluorination of H2O by [XeF][PnF(6)] (Pn = As, Sb) in HF solution has been reinvestigated. The system exhibits complex equilibria, producing two new Xe(II) compounds, [Xe3OF3][PnF(6)] and [H3O][PnF(6)]center dot 2XeF(2), refuting the original claim for the synthesis of the H2OF+ cation. Both compounds have been isolated and characterized by vibrational spectroscopy and single-crystal X-ray diffraction. The X-ray crystal structures of the [Xe3OF3][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 [H3O][AsF6]center dot 2XeF(2) adduct contains XeF2 molecules that interact with the H3O+ cations. The vibrational assignments for the Xe3OF3+ cation have been made with the aid of quantum-chemical calculations and were confirmed by O-18-enrichment, and the assignments for [H3O][AsF6]center dot 2XeF(2) were confirmed by D-2- and O-18-enrichment. Quantum-chemical calculations have also been carried out for H3O+center dot nXeF(2) (n = 1-4) and have been used to interpret the X-ray crystal structure and vibrational spectra of [H3O][AsF6]center dot 2XeF(2). The energy-minimized geometries and vibrational frequencies for HOF and H2OF+ have been calculated, further disproving the original report of the H2OF+ cation. Both FXeOH and FXeOH2+ have also been computed and are viable intermediates in the proposed equilibria between XeF+ and H2O that lead to the Xe3OF3+ cation.