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 <i>cis</i>-bridging between adjacent platinum(IV) centers and show that a tetrameric ring structure and <i>cis</i>-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 <i>cis</i>-chain as likely structural models of XeF₂·PtF₄.