<p>The chemistry of Xe(II) has been significantly extended to include the first examples of a neutral Xe(II) oxide fluoride species, O(XeF)<sub>2</sub>, as well as the first nitrate derivative of Xe(II), FXeONO<sub>2</sub>. Until recently, neutral oxide fluorides were known for all formal oxidation states of xenon except Xe(II). The synthesis of the missing oxide fluoride of Xe(II), O(XeF)<sub>2</sub>, has been accomplished by reaction of the [FXeOXeFXeF][AsF<sub>6</sub>] salt with NOF and characterized by NMR spectroscopy in CH<sub>3</sub>CN solution at -78 °C and by Raman spectroscopy. Reaction of NO<sub>2</sub>F with [FXeOXeFXeF][AsF<sub>6</sub>] has provided the first structurally characterized noble-gas nitrate, FXeONO<sub>2</sub>, which slowly decomposes (-78 °C) to XeF<sub>2</sub>·N<sub>2</sub>O<sub>4</sub>. X-ray crystal structures have been determined for FXeONO<sub>2</sub>, XeF2·N<sub>2</sub>O<sub>4</sub>, and XeF2·HNO<sub>3</sub>. The preparation of the XeONO<sub>2</sub><sup>+</sup> cation was attempted by the reaction of FXeONO<sub>2</sub> with AsF<sub>5</sub> at -78 °C, but was not directly observed. It is presumed that the cation initially forms, but rapidly decomposes to give Xe, O<sub>2</sub>, and [NO<sub>2</sub>][AsF<sub>6</sub>].</p> <p>The salt, [XeOTeF<sub>5</sub>][Sb(OTeF<sub>5</sub>)<sub>6</sub>], is a strong, low-temperature oxidant capable of oxidizing halomethanes in SO<sub>2</sub>ClF solvent at -78 °C. The CCl<sub>3</sub><sup>+</sup> and CBr3<sup>+</sup> cations have been synthesized by oxidation of CCl<sub>4</sub> and CBr<sub>4</sub>, respectively. The CBr<sub>3</sub><sub></sub><sup>+</sup> cation reacts with BrOTeF<sub>5</sub>, produced in the initial redox reaction, to give CBr(OTeF<sub>5</sub>)<sub>2</sub><sup>+</sup>, C(OTeF<sub>5</sub>)<sub>3</sub><sup>+</sup> , and Br<sub>2</sub>. The XeOTeF<sub>5</sub><sup>+</sup> cation also reacts with BrOTeF<sub>5</sub> to give the Br(OTeF<sub>5</sub>)<sub>2</sub><sup>+</sup> cation. The X-ray crystal structures of [CCl<sub>3</sub>][Sb(OTeF<sub>5</sub>)<sub>6</sub>], [CBr<sub>3</sub>][Sb(OTeF<sub>5</sub>)<sub>6</sub>]•SO<sub>2</sub>ClF, and [C(OTeF5)3][Sb(OTeF5)6]·3SO<sub>2</sub>ClF have been determined and show that the carbocations are trigonal planar about the central atom.</p> <p>Reactions of chlorofluoro-and bromofluoromethanes with [XeOTeF<sub>5</sub>][Sb(OTeF<sub>5</sub>)<sub>6</sub>] have also been investigated in SO<sub>2</sub>ClF solvent by <sup>13</sup>C and <sup>19</sup>F NMR spectroscopy at -80 °C. The CFCl<sub>2</sub><sup>+</sup> and CFCl(OTeF<sub>5</sub>)<sup>+</sup> cations are among the carbocations that have been obtained by reactions of CFCl<sub>3</sub> and CF<sub>2</sub>Cl<sub>2</sub> with XeOTeF<sub>5</sub><sup>+</sup>. The CF<sub>2</sub>Br<sup>+</sup> cation is an intermediate in the reaction of XeOTeF<sub>5</sub><sup>+</sup> with CF<sub>2</sub>Br<sub>2</sub>, undergoing rapid halogen exchange with CF<sub>2</sub>Br<sub>2</sub> to form CFBr<sub>2</sub><sup>+</sup> and CF<sub>3</sub>Br. The CFBr<sub>2</sub><sup>+</sup> cation undergoes further halogen exchange over several hours to form the CBr<sub>3</sub><sup>+</sup> cation and CF<sub>3</sub>Br. Although the highly electrophilic CF<sub>3</sub><sup>+</sup> cation has not been isolated by the reaction of CF<sub>3</sub>Br with XeOTeF<sub>5</sub><sup>+</sup>,<sup> 13</sup>C and <sup>19</sup>F NMR spectroscopy indicates the CF<sub>3</sub><sup>+</sup> cation reacts with BrOTeF<sub>5</sub> to form F<sub>3</sub>CBrOTeF<sub>5</sub><sup>+</sup> and/or abstracts an OTeF<sub>5</sub> group from the Sb(OTeF<sub>5</sub>)<sub>6</sub><sup>- </sup>anion to yield CF<sub>3</sub>OTeF<sub>5</sub> and, ultimately, [SbBr<sub>4</sub>][Sb(OTeF<sub>5</sub>)<sub>6</sub>].</p> <p>The synthesis of C(OTeF<sub>5</sub>)<sub>4</sub> has been accomplished by reaction of CBr4 with Br0TeF5 in SO<sub>2</sub>ClF solution, and has been fully characterized by NMR spectroscopy, Raman spectroscopy, and single-crystal X-ray diffraction, and its geometric parameters have been compared with those of the isoelectronic B(OTeF<sub>5</sub>)<sub>4</sub><sup>-</sup>anion in order to assess the symmetry of the E(OTe)<sub>4</sub><sup>-/0</sup> (E = B, C) subgroup.</p> / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/14167 |
| Date | January 2007 |
| Creators | Moran, Matthew D. |
| Contributors | Schrobilgen, Gary J., Chemistry |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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