Reactions of Bromine Fluoride Dioxide, BrO2 F, for the Generation of the Mixed-Valent Bromine Oxygen Cations Br3 O4 + and Br3 O6. Angew Chem Int Ed Engl 2019;58:18928-18930. [PMID: 31622009 PMCID: PMC6973041 DOI: 10.1002/anie.201912271]

A reliable synthesis of unstable and highly reactive BrO₂F is reported. This compound can be converted into BrO₂⁺SbF₆⁻, BrO₂⁺AsF₆⁻_, and BrO₂⁺AsF₆⁻⋅2 BrO₂F. The latter decomposes into mixed‐valent Br₃O₄⋅Br₂⁺AsF₆⁻ with five‐, three‐, one‐, and zero‐valent bromine. BrO₂⁺ H(SO₃CF₃)₂⁻ is formed with HSO₃CF₃. Excess BrO₂F yields mixed‐valent Br₃O₆⁺OSO₃CF₃⁻ with five‐ and three‐valent bromine. Reactions of BrO₂F and MoF₅ in SO₂ClF or CH₂ClF result in Cl₂BrO₆⁺Mo₃O₃F₁₃⁻. The reaction of BrO₂F with (CF₃CO)₂O and NO₂ produces O₂Br‐O‐CO‐CF₃ and the known NO₂⁺Br(ONO₂)₂⁻. All of these compounds are thermodynamically unstable.

Structure investigations on oxygen fluorides

The solid state structures of O₂F₂ and OF₂ resemble those in the gaseous state. Attempts to isolate the proposed (O₂⁺)₂PdF₆²⁻ from O₂F in HF result in the formation of (O₂⁺H₃Pd₂F₁₂⁻)_n.

A rare example of a krypton difluoride coordination compound: [BrOF2][AsF6] x 2 KrF2

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.