Crystal Structures of XeF2·2PtF4 and XeF2·2PdF4 Determined by 3D Electron Diffraction and Structural Models of XePtF6

Although the demonstration of noble-gas reactivity represents one of the most significant breakthroughs of 20th-century inorganic chemistry, the first noble-gas compound, XePtF₆ (XeF₂·PtF₄), lacks comprehensive structural characterization, and its structure remains to be elucidated. In this study, the XeF₂–PtF₄ and XeF₂–PdF₄ systems were reexplored, resulting in the crystal structure determination of XeF₂·2PtF₄ and XeF₂·2PdF₄ by 3D electron diffraction, marking the first successful structural characterization of compounds from these systems. Both compounds are isostructural with the previously characterized XeF₂·2MnF₄, featuring corrugated zigzag double-chain motifs formed by interconnected octahedral fluoridometallate(IV) units. Periodic density functional theory calculations were employed to evaluate the structural models of XeF₂·PtF₄, which were derived from experimentally determined crystal structures of XeF₂–MF₄ (M = Cr, Mn) analogues. The results reveal a preference for cis-bridging between adjacent platinum(IV) centers and show that a tetrameric ring structure and cis-chain polymorph, modeled after the crystal structure of XeF₂·MnF₄ and XeF₂-deficient 3XeF₂·2MnF₄, respectively, emerge as energetically favored. The results of this study thus provide a direct structural link between platinum, palladium, and manganese analogues in the XeF₂–MF₄ systems and highlight the tetrameric ring structure and cis-chain as likely structural models of XeF₂·PtF₄.

3D electron diffraction was employed to elucidate the structures of XeF₂·2PtF₄ and XeF₂·2PdF₄, representing the first crystal structures obtained from the XeF₂−MF₄ (M = Pt, Pd) systems, which include the hitherto poorly characterized first noble-gas compound, XePtF₆ (XeF₂·PtF₄). Structural models for XeF₂·PtF₄ were also evaluated by periodic density functional theory calculations, predicting that tetrameric ring and cis-chain structures, derived from XeF₂·MnF₄ and 3XeF₂·2MnF₄, respectively, are the most energetically favorable.