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

Abstract

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 BrV---FXe 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.