A new krypton complex – experimental and computational investigation of the krypton sulphur pentafluoride cation, [KrSF5]+, in the gas phase

The gas-phase reactions of noble gas (Ng) cations, namely Kr⁺ and Xe⁺, with SF₆ were investigated experimentally by Fourier transform ion cyclotron resonance mass spectrometry and computationally using RI-MP2 and BCCD(T) methods. The study revealed a new interaction between Kr⁺ and neutral SF₆ that gave rise to a new cationic, weakly bound complex of Kr, [KrSF₅]⁺, although the major reaction channel was dissociative electron transfer to yield SF₅⁺ and {Kr, F}. Experimental studies examined the formation and stability of the new species and computational studies addressed the energetics of the reaction and indicated that [KrSF₅]⁺ is stable by ca. 1 kcal mol⁻¹. The same computational approach was used to examine the reaction of Xe⁺ with SF₆ and showed it to be thermodynamically unfavourable by ca. 35 kcal mol⁻¹, confirming the non-observation of reaction in the mass spectrometry experiments. An analysis of the bonding in [KrSF₅]⁺ clearly showed that it is a non-covalently bound species, while in its presumed precursor [KrSF₆]⁺ a partially covalent Kr–F bond is present.