Coordination of KrF2 to a Naked Metal Cation, Mg2

• Published in: Angewandte Chemie International Edition Vol. 56; no. 22; pp. 6251 - 6254
• Main Authors: Lozinšek, Matic, Mercier, Hélène P. A., Brock, David S., Žemva, Boris, Schrobilgen, Gary J.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 22-05-2017
• Edition: International ed. in English
• Subjects: Anions; Cations; Chemical bonds; Coordination compounds; hypervalent compounds; Krypton; krypton difluoride; Ligands; Magnesium; Metal bonding; Metal ions; Raman spectra; Raman spectroscopy; Transition metals; X-ray crystallography
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201611534

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.
Krypton difluoride, a thermodynamically unstable and potent oxidative fluorinator, coordinates to Mg2+ to form the coordination complexes, [Mg(KrF2)4(AsF6)2] and [Mg(KrF2)4(AsF6)2]⋅2 BrF5. The complexes were characterized by low‐temperature single‐crystal X‐ray diffraction and low‐temperature Raman spectroscopy. Computational studies show that the Mg−F bonds are essentially non‐covalent, weakly electrostatic interactions.