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Abstract

The chemistry of noble-gas compounds is fundamentally important because it challenges concepts of reactivity and bonding, providing also valuable insight in the valence shell electron pair repulsion model of molecular structure. However, the synthesis and handling of these compounds is a difficult task, which places their rich chemistry beyond the reach of most laboratories.
To broaden access to noble-gas chemistry, mechanochemistry has been introduced as a viable method for synthesis of noble-gas compounds. It has been demonstrated that compounds containing the xenon in the oxidation state +1/2, +2, and +4 can be readily prepared using commercially available equipment, with purities comparable to those obtained through classical synthetic routes.
Reaction of NCCN with [XeF][AsF6] has been investigated for the first time and it enabled the synthesis of [FXeNCCNXeF][AsF6]2, which represents the first example of a bis-[XeF]+-coordinated nitrogen base. This compound converts to [XeNC(F)C(F)NXe][AsF6]2 at room temperature. The [XeNC(F)C(F)NXe]2+ cation contains the first example of C=N−Xe bonding modality and exhibits a σ-hole on the xenon atoms. The presence of a σ-hole in the cation was exploited for the synthesis of the adduct-cations [RCN∙∙∙XeNC(F)C(F)NXe∙∙∙NCR][AsF6]2 (R = CH3, H), which feature rare examples of an N−Xe−N linkage.
To investigate the propensity of XeF2 to act as a hydrogen-bond donor, the salt cocrystals (RC(OH)NH2)[AsF6]∙XeF2 (R = CF3, C2F5, C3F7) were prepared and crystallographically characterized at low temperature. These represent the first crystallographically characterized examples of NH∙∙∙FXeF hydrogen bonds. Additionally, the crystal structures of hemiprotonated amide salts (CF3CONH2)2H[AsF6] and (C3F7CONH2)2H[AsF6], as well as the salt cocrystal H3O[AsF6]∙2CF3CONH2 were elucidated.
Protonated decafluorobenzophenone, (C6F5)2COH+, isolated as a (C6F5)2COH+[AsF6]−, as well as (C6F5)2CO∙AsF5 adduct have been synthesized and crystallographically characterized for the first time, with latter representing a rare case of ketone acting as a ligand toward AsF5. In both compounds, the geometry of (C6F5)2CO moiety is perturbed relative to that of the neutral molecule.
The hydrostatic properties of several oxidatively resistant fluorinated liquids have been investigated under high pressure. They have been shown to be truly hydrostatic up to 1.7 GPa and remain nearly hydrostatic even at 4 GPa, making them suitable for high-pressure studies of noble-gas compounds.
Finally, high-pressure studies of XeF6 and XeF2∙XeF4 have been carried out. XeF6 has been found to form a one-dimensional polymer already above 1 GPa. XeF2∙XeF4 undergoes structural changes at lower pressures, as indicated by Raman spectroscopy.
Overall, the results of this thesis demonstrate the richness of the chemistry of noble-gas compounds over the large temperature and pressure range and show that many new insights can be gained by introducing novel methodologies in the chemistry of so-called inert gases.