Coordination of KrF2 to a Naked Metal Cation, Mg2+

Examples of coordination compounds in which KrF₂ functions as a ligand are very rare. In contrast, XeF₂ provides a rich coordination chemistry with a variety of main-group and transition metal cations. The reactions of Mg(AsF₆ )₂ and KrF₂ in HF or BrF₅ solvent have afforded [Mg(KrF₂ )₄ (AsF₆ )₂ ] and [Mg(KrF₂ )₄ (AsF₆ )₂ ]⋅2 BrF₅ , respectively, the first examples of a metal cation ligated by KrF₂ . Their X-ray crystal structures and Raman spectra show that the KrF₂ ligands and [AsF₆ ]^- anions are F-coordinated to a naked Mg²⁺ cation. Quantum-chemical calculations are consistent with essentially non-covalent ligand-metal bonding. These compounds significantly extend the XeF₂ -KrF₂ analogy and the limited chemistry of krypton by introducing a new class of coordination compound in which KrF₂ functions as a ligand towards a naked metal cation.