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Abstract

The demonstration of noble-gas reactivity by Neil Bartlett’s landmark experiment, in which xenon was reacted with PtF6 to yield a compound of XePtF6 stoichiometry, represents one of the most important milestones in twentieth century inorganic chemistry. Nevertheless, the chemical nature of XePtF6 (XeF2·PtF4) remains poorly understood, and its structure has remained enigmatic. To advance the understanding of this substance, previous studies have focused on the related XeF2–MF4 systems, which have revealed a rich and diverse structural chemistry within this family of compounds.
This dissertation primarily focuses on the furthering the structural investigations of compounds in the XeF2–MF4 systems (M = Mn, Pd, Pt). A longstanding obstacle in this field has been the limited crystallinity of many phases, which have resisted crystallographic characterization by single-crystal X-ray diffraction (SCXRD). To address this challenge, these compounds were examined by 3D electron diffraction (3D ED), which required the development of a new sample transfer protocol that enabled application of the method to highly reactive and air-sensitive samples. Reinvestigation of XeF2–MnF4 system revealed three crystalline phases, namely 3XeF2·2MnF4, XeF2·MnF4, and XeF2·2MnF4, which were characterized by SCXRD, 3D ED, vibrational spectroscopy and periodic density functional theory (DFT) calculations.
The XeF2–PtF4 and XeF2–PdF4 systems were also reexplored, resulting in the crystal structure determination of XeF2·2PtF4 and XeF2·2PdF4 by 3D ED. Both phases were found to be isostructural with XeF2·2MnF4, establishing a structural link across the three systems. Periodic DFT calculations were employed to assess structural models for XeF2·PtF4, derived from experimentally established structures of XeF2–MF4 (M = Cr, Mn) analogues, identifying cis-bridged motifs, found in the crystal structures of 3XeF2·2MnF4 and XeF2·MnF4, respectively, as energetically preferred.
Reactions probing the interaction of XeF2 with both AsF5 and Lewis acidic tetrafluorides PtF4 and PdF4 in anhydrous HF (aHF) yielded amber-colored crystals of the salts [Xe2F3][MF3(XeF2)3][AsF6]2 (M = Pt, Pd) containing the previously unobserved discrete [MF3(XeF2)3]+ cations.
A reinvestigation of the XeF2–PtF5 system, which is closely linked to the first preparations of XePtF6 and related studies, was also undertaken and the compounds [Xe2F3][PtF6]·XeF2, [Xe2F3][PtF6], and [XeF][PtF6] were structurally characterized.
In addition, the role of XeF2 as a ligand to alkali-metal cations was reevaluated by examining its interactions with alkali metal hexafluoridoplatinates(V) in aHF. XeF2 was shown to coordinate Li+, Na+, and K+ as the compounds [Li(XeF2)3PtF6], [Na(XeF2)PtF6], and [K(XeF2)2PtF6] were characterized by SCXRD and Raman spectroscopy.
Finally, the behavior of XeF2·PtF4 under high-pressure and high-temperature conditions generated in a laser-heated diamond anvil cell was investigated. At pressures of 14.5 GPa, XeF2·PtF4 crystallizes upon laser heating, enabling determination of its structure for the first time. Laser heating of XeF2·PtF4 at lower pressures additionally revealed two previously unobserved polymorphs of XeF2·2PtF4, as well as a new compound, [PtF2(XeF2)4][Pt4F18].