The synthesis of [BrOF(2)][AsF(6)] x 2 KrF(2), its structural characterization, and bonding are described in this study. Although several KrF(2) adducts with transition metal centers have been previously reported, none have been crystallographically characterized. The solid-state Raman spectrum of [BrOF(2)][AsF(6)] x 2 KrF(2) has been assigned with the aid of quantum-chemical calculations. The low-temperature (-173 degrees C) X-ray crystal structure of [BrOF(2)][AsF(6)] x 2 KrF(2) consists of isolated molecular units and represents an example of KrF(2) coordinated to a main-group atom. The coordination geometry around the BrOF(2)(+) cation renders the free valence electron lone pair more compact than in free BrOF(2)(+). The KrF(2) ligands are coordinated trans to the fluorine atoms of BrOF(2)(+) with the AsF(6)(-) anion coordinated trans to oxygen. The quantum theory of atoms in molecules (QTAIM) and electron localization function (ELF) analyses have been carried out in order to define the nature of the bonding in the complex. A significant amount of charge (0.25 e) is transferred to BrOF(2)(+) from the two KrF(2) ligands (0.10 e each) and from the AsF(6)(-) anion (0.05 e). Significant polarization also occurs within the KrF(2) ligands, which enhances the anionic characters of the fluorine bridges. The interaction energy is mostly governed by the electrostatic interaction of the positively charged bromine atom with the surrounding fluorine atoms.

The syntheses and structural characterizations of the [XOF(2)][AsF(6)] (X = Cl, Br) salts and the XeF(2) adduct-salts, [BrOF(2)][AsF(6)].nXeF(2) (n = 1, 2), are described. Although the [XOF(2)][AsF(6)] salts have been known for some time, their crystal structures had not been reported until the present study. The crystal structure of [BrOF(2)][AsF(6)] shows a positional disorder among the oxygen atom and the fluorine atoms. Both ClOF(2)(+) and BrOF(2)(+) have pseudo-octahedral coordination with a primary tripodal coordination sphere consisting of an oxygen atom and two fluorine atoms and a secondary coordination sphere consisting of three long contacts to fluorine atoms of different AsF(6)(-) anions. The low-temperature Raman spectra of [XOF(2)][AsF(6)] have been assigned on the basis of the crystal structures and with the aid of quantum-chemical calculations using [XOF(2)][AsF(6)](3)(2-) as a model for the crystallographic environment of XOF(2)(+). Several examples of XeF(2) coordinated through fluorine to transition metal centers are known, but no crystallographically characterized examples of XeF(2) coordinated to a nonmetal center other than xenon are known. The complex cation salts, [BrOF(2)][AsF(6)].nXeF(2) (n = 1, 2), were synthesized, and their Raman spectra have been assigned with the aid of quantum-chemical calculations. Although the structure of [BrOF(2)][AsF(6)].2XeF(2) is similar to that of the recently reported krypton analogue, notable differences occur. The contact distances between bromine and the fluorine atoms of NgF(2) (Ng = Kr, Xe) are shorter in [BrOF(2)][AsF(6)].2XeF(2) than in the KrF(2) analogue, which is attributed to the more polar natures of the Xe-F bonds. Unlike [BrOF(2)][AsF(6)].2KrF(2), which has been shown in the prior study to be stable in HF solution at room temperature, [BrOF(2)][AsF(6)].2XeF(2) enters into a dissociative equilibrium in which fluoride ion abstraction by BrOF(2)(+) occurs to give Xe(2)F(3)(+) and BrOF(3). The ELF and QTAIM analyses of [BrOF(2)][AsF(6)](3)(2-) and [BrOF(2)][AsF(6)].2XeF(2) were carried out and are compared with those of [BrOF(2)][AsF(6)].2KrF(2) and for free BrOF(2)(+) to better understand the effect of Br(V) coordination number on the localization domain of the Br(V) valence electron lone pair.