No description available.

<p> This Thesis extends the fundamental chemistry of the noble-gas elements, namely, xenon and krypton. More specifically, the chemistry of Xe(IV) has been extended by the synthesis and characterization of Xe(IV) oxide and oxide fluoride derivatives. The syntheses ofXeOF2, F20XeN=CCH3, and XeOF2·nHF and their structural characterizations are described. All three compounds are endothermic and explosive at temperatures approaching 0 °C. Although Xe0F2had been previously reported, it had not been isolated as a pure compound. Xenon oxide difluoride has now been characterized in CH3CN solution by 19F, 170, and 129Xe NMR spectroscopy and XeOF2, F20XeN=CCH3, and XeOF2·nHF have been characterized in the solid-state by Raman spectroscopy. The low temperature X-ray crystal structure ofF20XeN=CCH3 reveals a long Xe-N bond trans to the Xe-0 bond and a geometrical arrangement about xenon in which the atoms directly bonded to xenon are coplanar and CH3C=N acts as a fourth ligand in the equatorial plane. The geometry about xenon is consistent with an AX2YZE2 VSEPR arrangement of bond pairs and electron lone pairs and represents a rare example of a Xe(IV)-N bond. </p> <p> The missing Xe(IV) oxide, Xe02, has been synthesized at 0 °C by hydrolysis of XeF4 in water and 2.00 M H2S04(aq) and characterized by low-temperature Raman Spectroscopy. The Raman spectra ofXe02 amend prior vibrational assignments of xenon doped Si02 and are in accordance with prior speculation that xenon depletion from the Earth's atmosphere could occur by xenon insertion at high temperatures and high pressures into Si02 in the Earth's crust. </p> <p> The XeOF3-anion has been synthesized as its Cs + and N(CH3)/ salts, and structurally characterized in the solid state bylow-temperature Raman spectroscopy. The calculated anion geometry is based on a square planar AX3YE2VSEPR arrangement with the longest Xe-F bond trans to the oxygen atom. The F-Xe-F angle is bent away from the oxygen atom to accommodate the greater spatial requirement of the oxygen double bond domain. The XeOF3-anion of the Cs + salt is fluorine-bridged in the solid-state, whereas the anion ofthe N(CH3)/ salt approximates the gas-phase anion. </p> <p> The [H(OXeF2)n][AsF6] and [FXerr(OXe1vF2)n][AsF6] (n = 1, 2) salts have been synthesized and structurally characterized in the solid state by low-temperature Raman spectroscopy. The chain length of each cation is limited to one or two OXeF2 subunits, which are oxygen-bridged and are strongly ion-paired with the AsF 6-anion. The reaction of XeOF2·xHF in superacidic HF/SbFs solvent mixtures resulted in a mixture of ([XeF3·HF][Sb2Fu])2-[HsF4][SbF6], [XeF3·HF][Sb2Fu], and [XeF3][SbF6]. The XeF/ cations in each structure are very similar, displaying T -shaped coordination of three fluorine atoms, and a short contact to the fluorine atom of HF, m ([XeF3·HF][Sb2F u])2-[H5F4][SbF6] and [XeF3·HF][Sb2Fu], or to a fluorine atom of SbF6in [XeF3][SbF6]. </p> <p> Vibrational frequency assignments for the aforementioned compounds were aided by comparison with frequencies derived from quantum-chemical calculations, by ^(18)O enrichment, and, where appropriate, by 2H enrichment. </p> <p> The syntheses and structural characterizations of [XOF2][AsF6] (X = Cl, Br), the XeF2 adduct-salts, [BrOF2][AsF6}nXeF2 (n = 1, 2), and the KrF2 adduct-salt, [BrOF2][AsF6]'2KrFz, are also described. The crystal structure of [BrOF2][AsF6] shows a positional disorder among the oxygen atom and the fluorine atoms. The low-temperature Raman spectra of [XOFz][AsF6], the complex cation salts, [BrOF2][AsF6]'nXeFz (n = 1, 2), and [BrOF2][AsF6]·2KrF2 have been assigned on the basis ofthe crystal structures and with the aid of quantum-chemical calculations. The low-temperature ( -173 °C) X -ray crystal structure of [Br0Fz][AsF6]'2KrF2 consists of isolated molecular units and represents an example of KrF2 coordinated to a main-group atom. The contact distances between bromine and fluorine atom of NgFz (Ng = Kr, Xe) is shorter in [BrOFz][AsF6]·2XeFz than in the KrFz analogue, which is attributed to the more polar nature of the Xe-F bonds. The ELF and QTAIM analyses of [BrOFz][AsF6h2-and [BrOFz][AsF6]'2XeFz were carried out and are compared with those of free BrOF/ and [BrOFz][AsF6]'2KrFz to better understand the effect of Br(V) coordination number on the localization domain of the Br(V) valence electron lone pair. </p> <p> The syntheses of FXeON160 2 and FXeoNe800) has shed light on the mechanism leading to the formation of FXeON02• Raman spectroscopy indicated the absence of 161180 isotopic scrambling among the oxygen sites of FXeON02 which was confirmed by factor-group analyses ofthe 16 isotopomeric crystallographic unit cells that result from syn-/anti-isomerization, FXe160Ne6oA180s)/FXe160Ne6os180A), among the four FXeON02 molecules of the unit cell. The intermediate oxide fluoride, O(XeF)2, was observed in the synthesis of FXeON02, providing valuable insight into the reaction pathway. A reinterpretation of the solid-state 160-and 180-enriched Raman spectra of O(XeF)z was also carried out. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

No description available.

The research described in this Thesis investigates the coordination chemistry of pentafluorooxotellurate(VI) (F5TeO– or “teflate”) and [PnF6]– (Pn = As, F) derivatives of mercury(II), and expands the chemistry of Ng(II) (Ng = Kr, Xe) by characterizing several NgF2 coordination complexes with mercury, and the synthesis of a new xenon(II) oxide cation. The compounds discussed herein were characterized predominately by low-temperature single-crystal X-ray diffraction and Raman spectroscopy, and were frequently complemented by quantum-chemical calculations. The chemistry of the F5TeO–group was developed for Hg(II) derivatives by investigating the Lewis acid properties of Hg(OTeF5)2. Initial efforts investigated interactions with the nitrogen base NSF3, and resulted in the coordination complexes [Hg(OTeF5)2∙N≡SF3]∞, [Hg(OTeF5)2∙2N≡SF3]2, and Hg3(OTeF5)6∙4N≡SF3 at 0oC. Although the F5TeO–group often bonds in a monodendate fashion, these less sterically saturated salts result in oxygen bridging in the solid state. In Hg3(OTeF5)6∙4N≡SF3, oxygen bridging between three metal centers by the pentafluorooxotellurate(VI) group is observed for the first time. The nature of this new bonding was further analysed computationally for Hg3(OTeF5)6∙4N≡SF3 by natural bond orbital analyses (NBO). At room temperature, reactions of Hg(OTeF5)2 with NSF3 resulted in O/F metatheses to yield related F2OSN–derivatives, namely [Hg(OTeF5)(N=SOF2)∙N≡SF3]∞ and [Hg3(OTeF5)5(N=SOF2)-∙2N≡SF3]2, accompanied by the elimination of TeF6 as confirmed by 19F NMR spectroscopy. In related work, the acceptor properties of Hg(OTeF5)2 were further investigated in its reactions with M[OTeF5] (M = [N(CH3)4]+, [N(CH2CH3)4]+, Cs+) to form a series of teflate anion salts; [N(CH2CH3)4]2[Hg(OTeF5)4], [N(CH3)4]3[Hg(OTeF5)5], [N(CH2CH3)4]3[Hg(OTeF5)5], [N(CH3)4]2[Hg2(OTeF5)6], Cs2[Hg(OTeF5)4]•Hg(OTeF5)2, and {Cs3[Hg2(OTeF5)7]•Hg(OTeF5)2}•4SO2ClF. In comparison to their halide counterparts, the less basic and more sterically demanding teflate ligands of the Hg(II) anions show less tendency to extensively bridge. The Raman spectra of the [Hg(OTeF5)4]2−, [Hg(OTeF5)5]3−, and [Hg2(OTeF5)6]2− anions were fully assigned with the aid of their calculated gas-phase vibrational frequencies. NBO analyses further probed the bonding in the anions. The [Hg(OTeF5)5]3− anion provides an unusual square-pyramidal coordination sphere around mercury and the only presently known teflate-substituted anion with a net charge of 3–. In related work, the weakly coordination anion (WCA) [Sb(OTeF5)6]– was substituted in Hg2+ salts using weakly coordinating SO2ClF solvent to give the homoleptic solvent complex, [Hg(SO2ClF)6][Sb(OTeF5)6]2. The ability of this salt to function as a precursor for other ligands was demonstrated by the reaction with the nitrogen bases NCR (R = –CH3 or –CH2CH3) which resulted in the isolation and full characterization of the corresponding homoleptic nitrile complexes [Hg(NCR)5][Sb(OTeF5)6]2ꞏ2SO2ClF. Gas-phase energy-minimized calculation of the cations aided in the vibrational assignment of the Raman spectra, whereas NBO and counterpoise corrected binding energies give insights into the strength of the metal-ligand bonds and resulting electronic effects of these interactions. The established Lewis acidity of Hg(OTeF5)2, and known oxidative resistance of the F5TeO–group, were exploited to form rare examples of noble-gas difluoride adducts, Hg(OTeF5)2•1.5NgF2 (Ng = Xe, Kr). The isostructural complexes were fully characterized, and the KrF2 adduct provided only the second crystallographically characterized KrF2 complex and the first example of bridge coordination by KrF2¬. The chemistry of krypton was significantly extended by further exploring the little studied coordination of KrF2 with the salts Hg(PnF6)2 (Pn = As, Sb) and FHg(AsF6), leading to an important series of coordination complexes. The first homoleptic KrF2 coordination complex, [Hg(KrF2)8][AsF6]2•2HF, was thoroughly characterized by single-crystal X-ray diffraction, Raman spectroscopy, and quantum-chemical analyses. It provides the highest KrF2-to-metal ratio that is currently known for a coordination complex. The bonding was extensively analysed by NBO, calculated binding energies, energy decomposition analyses (EDA), and Extended Transition State Natural Orbitals for Chemical Valence (ETS-NOCV) analyses. This computational work suggests that both orbital interactions, which incorporate covalent bonding, and electrostatic contributions are important stabilization factors and that the 8σg (HOMO‒4) orbital and, to a lesser extent, a degenerate 4πu (HOMO) orbital, derived from free KrF2 (D∞h) are involved in adduct formation. This result helps to rationalize the observed M---F–Kr(F) coordination angles observed for most terminally coordinated NgF2 complexes. A series of related complexes with one to five KrF2 molecules per metal center were also characterized by single-crystal X-ray diffraction, namely Hg(KrF2)(HF)(AsF6)2 (1), Hg(KrF2)2(AsF6)2 (2), Hg(KrF2)3(HF)(SbF6)2 (3), [Hg(KrF2)4(HF)2(SbF6)]2[SbF6]2 (4), Hg(KrF2)5(AsF6)2 (5), Hg(KrF2)4(HF)2(AsF6)2•HF (6), FHg(μ3-FKrF)1.5(KrF2)0.5(AsF6) (7), and FHg(μ3-FKrF)0.5(KrF2)1.5(AsF6) (8). These complexes were unambiguously characterized by single-crystal X-ray diffraction which showed that the structures became more extensively linked due to bridging between mercury and the [PnF6]‒ anions as the number of coordinated KrF2 ligands decreased. While compounds (1)-(6) solely contain terminally coordinated KrF2 ligands, compound (7) also contains the second structurally characterized example of KrF2 bridging two metal centers through each of its fluorine atoms. Replacement of [AsF6]‒ by F‒ in compounds (7) and (8) also resulted in the first examples of a new bonding modality of KrF2, where only one of the fluorine atoms bridges two different metal centers. The Raman spectrum of (5) was assigned with the aid of calculated gas-phase vibrational frequencies. Natural bond orbital (NBO) analyses of [Hg(KrF2)5][AsF6]2 are consistent with coordinate covalent ligand-metal interactions. The nature of bonding for the unprecedented KrF2 bonding modality was further probed computationally with EDA and ETS-NOCV analyses and corroborate an MO description where electron density is donated from both the 8σg (HOMO‒4) and a degenerate 4πu (HOMO) molecular orbital of KrF2 to LUMOs involving the 6s and 6p orbitals of each mercury atom. To further expand the chemistry of the noble-gases, the second known xenon(II) oxide, [XeOXe]2+, was synthesized from the reaction of [FXeOXe---FXeF][AsF6] and acetonitrile at low-temperatures in anhydrous HF. The cation was isolated in macroscopic quantities as its well-isolated adduct-dication [CH3CN---XeOXe---NCCH3][AsF6]2 salt and was fully characterized by single-crystal X-ray diffraction and 16/18O isotopic enrichment Raman studies. The [XeOXe]2+ adduct-cation provides an important example of σ-hole bonding by a nitrogen base to a Xe(II) atom. The nature and strength of the Xe–O and Xe–N bonds in the calculated gas-phase [XeOXe]2+ and [CH3CN---XeOXe---NCCH3]2+ cations were extensively explored using a range of quantum-chemical (QC) methods, namely, NBO, atoms in molecules (AIM), electron localization function (ELF), and molecular electrostatic potential surface (MEPS) analyses. / Thesis / Doctor of Philosophy (PhD) / The coordination chemistry of pentafluorooxotellurate(VI) (F5TeO– or “teflate”) derivatives, as well as [PnF6]– (Pn = As, Sb) salts, of mercury(II), and the chemistry of Ng(II) (Ng = Kr, Xe), are the major focuses of this Thesis. The Lewis acid properties of Hg(OTeF5)2 were investigated using the nitrogen base, NSF3, and M[OTeF5] salts (M = Cs+, N(CH3)4+, N(CH2CH3)4+) which resulted in a series of NSF3 adducts, F2S(O)N– derivatives, and several anions. Reactions of Hg(OTeF5)2 with NgF2 also provided rare examples of bridging NgF2 coordination complexes. Routes to [Sb(OTeF5)6]– salts containing weakly-solvated Hg2+ cations was developed, which provided an important synthetic precursor to explore further ligand substitution reactions at Hg2+. The relatively unexplored chemistry of krypton was further advanced by synthesizing a series of coordination complexes of KrF2 with Hg(PnF6)2 and FHg(AsF6) salts, providing rare examples of terminally coordinated and bridging KrF2 ligands, and a new coordination mode for KrF2 molecules. Advances in the chemistry of Xe(II) were also made through the synthesis and characterization of the second known, and simplest, xenon(II) oxide species. Characterization methods employed in this Thesis predominantly were single-crystal X-ray diffraction and Raman spectroscopy. Quantum-chemical calculations aided with Raman assignments, and were used to further investigate the nature of chemical bonding in the compounds that had been synthesized. The research described in this Thesis significantly contributes to and extends the chemistry of the pentafluorooxotellurate(VI) ligand, to our knowledge and understanding of the reactivity and bonding of krypton(II) and xenon(II) species, and most notably, the coordination chemistry of KrF2.

No description available.

Thesis (Ph. D.)--Catholic University of America, 1939. / Cover title. From Journal of chemical physics, v. 7, Aug. 1939.

No description available.

No description available.

Thesis (Ph. D.)--Catholic University of America, 1939. / Cover title. From Journal of chemical physics, v. 7, Aug. 1939.