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

摘要

The reported synthesis of the H2OF+ cation as a product of the oxidative fluorination of H2O by (XeF) (PnF6) (Pn = As, Sb) in HF solution has been reinvestigated. The system exhibits complex equilibria, producing two new Xe(II) compounds, (Xe3OF3) (PnF6) and (H3O) (PnF6)2XeF2, 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) (PnF6) 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)2XeF2 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 (sup 18)O-enrichment, while the assignments for (H3O) (AsF6)2XeF2 were confirmed by 2D- and (sup 18)O- enrichment. Quantum-chemical calculations have also been carried out for H3O+nXeF2 (n = 14), and have been used to interpret the X-ray crystal structure and vibrational spectra of (H3O) (AsF6)2XeF2. 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.