The Existence of Argon Difluoride: Is There Any Reason for Optimism? (pp. 257-264)
Authors: Carol A. Deakyne, Kathleen F. Edwards, Maja Ponikvar-Svet, and Joel F. Liebman
Abstract: We begin with admitted pessimism. XeF2 is stable relative to decomposition to Xe + F2, and a fortiori, relative to the atoms Xe + 2F. KrF2 is thermodynamically stable relative to the atoms but not to Kr + F2. Quantum chemical calculations show HeF2 and NeF2 are metastable but nonetheless atomically unbound. What about ArF2? All reported attempts that would logically be successful in synthesis of ArF2do not do so. Isoelectronic reasoning using atomic ionization potentials explains the stability of noble gas difluorides: XeF2 > KrF2 > ArF2 > NeF2 > HeF2. However, there are other inter-row comparisons in the periodic table. For example, high oxidation state species from 4th row elements are generally less stable in a thermodynamic sense than their isoelectronic 3rd and 5th row counterparts: AsCl5 < PCl5, SbCl5; SeO42–< SO42–, TeO42–, BrO4– < ClO4–, IO4–. So, maybe KrF2 is thermodynamically less stable than both ArF2 and XeF2. An analysis using the recently enunciated trichotomy of “convenience, anthropocentrism and folksonomy” strongly suggests the need for new studies on ArF2.