Coordination of XeF₂ to Fluoridometal Cations: The Adduct Cations [PtF₃(XeF₂)₃]⁺ and [PdF₃(XeF₂)₃]

Crystals of the double salts [Xe₂F₃][MF₃(XeF₂)₃][AsF₆]₂ (M = Pd, Pt), prepared from anhydrous HF solutions, were characterized by low-temperature single-crystal X-ray diffraction and Raman spectroscopy. The crystal structures reveal that the compounds contain the hitherto unobserved [MF₃(XeF₂)₃]⁺ adduct cations, which differ from all previously identified examples of XeF₂ coordination to a metal(IV) center in their mononuclear and cationic nature, as well as in the coordination of multiple XeF₂ ligands to a single metal(IV) center. Quantum-chemical calculations were performed to gain insight into the bonding and electronic structure of the [MF₃(XeF₂)₃]⁺ adduct cations, with the optimized gas-phase geometries showing good agreement with the experimental solid-state structures. The characterized [MF₃(XeF₂)₃]⁺ adduct cations markedly extend the chemistry of XeF₂-MF₄ systems and represent rare, crystallographically characterized examples of XeF₂ coordination to Pt^IV and Pd^IV, a feature also believed to occur in the structure of the first discovered noble-gas compound, XePtF₆. Moreover, the [MF₃(XeF₂)₃]⁺ cations constitute the first examples of a new class of XeF₂ coordination compounds, which are characterized by XeF₂ ligation to a fluoridometal [MF_x]ⁿ⁺ cation, thereby enabling further expansion of the coordination chemistry of noble-gas fluorides.