High-Pressure Reactivity of Kr and F2—Stabilization of Krypton in the +4 Oxidation State

• Main Authors: Dominik Kurzydłowski, Magdalena Sołtysiak, Aleksandra Dżoleva, Patryk Zaleski-Ejgierd
• Format: Article
• Language: English
• Published: MDPI AG 2017-10-01
• Series: Crystals
• Subjects: krypton; fluorine; high-pressure; Density Functional Theory; phase transitions; noble gas chemistry; molecular crystals, fluorides
• Online Access: https://www.mdpi.com/2073-4352/7/11/329

Since the synthesis of the first krypton compound, several other Kr-bearing connections have been obtained. However, in all of them krypton adopts the +2 oxidation state, in contrast to xenon which forms numerous compounds with an oxidation state as high as +8. Motivated by the possibility of thermodynamic stabilization of exotic compounds with the use of high pressure (exceeding 1 GPa = 10 kbar), we present here theoretical investigations into the chemistry of krypton and fluorine at such large compression. In particular we focus on krypton tetrafluoride, KrF4, a molecular crystal in which krypton forms short covalent bonds with neighboring fluorine atoms thus adopting the +4 oxidation state. We find that this hitherto unknown compound can be stabilized at pressures below 50 GPa. Our results indicate also that, at larger compressions, a multitude of other KrmFn fluorides should be stable, among them KrF which exhibits covalent Kr–Kr bonds. Our results set the stage for future high-pressure synthesis of novel krypton compounds.