XeF2 Coordination Complexes of the [BrO2]+ Cation, [O2Br(FXeF) n ][AsF6] (n = 1, 2) and [O2Br(FXeF)2][SbF6]; Their Syntheses and Structural Characterizations

The syntheses and structural characterizations of the first XeF₂ coordination complexes of the [BrO₂]⁺ cation are described. The reactions of [BrO₂][PnF₆] (Pn = As, Sb) with XeF₂ in anhydrous HF solvent yield the salts [O₂Br(FXeF)_n][AsF₆] (n = 1, 2) and [O₂Br(FXeF)₂][SbF₆], which were characterized by low-temperature (LT) Raman spectroscopy and single-crystal X-ray diffraction (SCXRD). The XeF₂ ligands and [PnF₆]^- coordinate to the Lewis acidic [BrO₂]⁺ cation through primarily electrostatic Br^V---F_Xe σ-hole bonds that result from coordination of the F atoms into regions of high positive electrostatic potential on the Br(V) atom and have bond trajectories that avoid the stereoactive valence electron lone-pair of Br(V). The complexes and their structural characterizations by LT Raman spectroscopy and SCXRD significantly extend the coordination chemistry of Br(V) and provide rare examples of a noble-gas difluoride coordinated to a strong oxidant main-group Lewis acid center.