High-pressure stabilization of open-shell bromine fluorides

• Published in: Physical chemistry chemical physics : PCCP Vol. 26; no. 3; pp. 1762 - 1769
• Main Authors: Dalsaniya, Madhavi H, Upadhyay, Deepak, Jan Kurzyd owski, Krzysztof, Kurzyd owski, Dominik
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 17.01.2024
• Subjects: Bromine; Fluorides; Fluorine; High pressure; Molecular orbitals; Phase transitions
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/d3cp05020c

Halogen fluorides are textbook examples of how fundamental chemical concepts, such as molecular orbital theory or the valence-shell electron-repulsion (VSEPR) model, can be used to understand the geometry and properties of compounds. However, it is still an open question whether these notions are applicable to matter subject to high pressure (>1 GPa). In an attempt to gain insight into this phenomenon, we present a computational study on the phase transitions and reactivity of bromine fluorides at pressures of up to 100 GPa ( 10 6 atm). We predict that at a moderately high pressure of 15 GPa, the bonding preference in the Br/F system should change considerably with BrF 3 becoming thermodynamically unstable and two novel compounds emerging as stable species: BrF 2 and BrF 6 . Calculations indicate that both these compounds contain radical molecules while being non-metallic. We propose a synthetic route for obtaining BrF 2 which does not require the use of highly reactive elemental fluorine. Finally, we show how molecular orbital diagrams and the VSEPR model can be used to explain the properties of compressed bromine fluorides. Open-shell BrF 2 and BrF 6 are predicted to become thermodynamically stable at high pressure. Bromine difluoride should form a molecular crystal containing (BrF 2 ) 3 trimers held by a 3e-3c bond.