Oxygen coordination to the Xe(VI) atom of XeO<sub>3</sub> was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO<sub>3</sub>, which detonates when mechanically or thermally shocked, the solid [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub>, [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub>,<sub> </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3 </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> are air-stable whereas [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> slowly decomposes over several days and [(CH<sub>3</sub>)<sub>2</sub>CO]<sub>3</sub>XeO<sub>3</sub> undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub> is a distorted square pyramid which provides the first example of a five-coordinate XeO<sub>3</sub> adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO<sub>3</sub>. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.
<p></p><p>Molten mixtures of XeF<sub>6</sub> and Cr<sup>VI</sup>OF<sub>4</sub> in 1:1 and 1:2 molar ratios undergo reduction to Cr(V) and Cr(IV) by means of F<sub>2</sub> elimination to form [XeF<sub>5</sub>][Xe<sub>2</sub>F<sub>11</sub>][Cr<sup>V</sup>OF<sub>5</sub>]∙2Cr<sup>VI</sup>OF<sub>4</sub> and [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>IV</sup>F<sub>6</sub>]∙2Cr<sup>VI</sup>OF<sub>4</sub>, respectively, as shown by low-temperature (LT) single-crystal X-ray diffraction (SCXRD). A LT Raman spectroscopic study of an equimolar mixture of solid XeF<sub>6</sub> and CrOF<sub>4</sub> and its melt showed that [Cr<sup>VI</sup>OF<sub>5</sub>]<sup>–</sup> is formed as an intermediate. Reaction of [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>IV</sup>F<sub>6</sub>]∙2Cr<sup>VI</sup>OF<sub>4</sub> with XeF<sub>6</sub> in a melt gave [Xe<sub>2</sub>F<sub>11</sub>]<sub>2</sub>[Cr<sup>IV</sup>F<sub>6</sub>] and [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]. Their LT crystal structures revealed that [XeF<sub>5</sub>]<sup>+</sup> and [Xe<sub>2</sub>F<sub>11</sub>]<sup>+</sup> are coordinated to their respective [CrF<sub>6</sub>]<sup>2−</sup> and [Cr<sub>2</sub>O<sub>2</sub>F<sub>8</sub>]<sup>2−</sup> anions by means of Xe---F–Cr bridges to form infinite chain structures. The reactions of a 1:1 molar ratio of XeF<sub>6</sub> and CrOF<sub>4</sub> in anhydrous hydrogen fluoride (aHF) and in mixed CFCl<sub>3</sub>/aHF solvents yielded [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]∙2HF and a mixture of [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]∙2HF and [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]∙2XeOF<sub>4</sub>, respectively. The SCXRD structures of the latter and aforementioned salts provide the first X-ray structures of [CrOF<sub>5</sub>]<sup>2–</sup> and [Cr<sub>2</sub>O<sub>2</sub>F<sub>8</sub>]<sup>2–</sup>. The [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]∙2XeOF<sub>4</sub> and [XeF<sub>5</sub>][Xe<sub>2</sub>F<sub>11</sub>][Cr<sup>V</sup>OF<sub>5</sub>]∙2Cr<sup>VI</sup>OF<sub>4</sub> salts were also characterized by LT Raman spectroscopy. Quantum-chemical calculations were carried out to obtain the energy-minimized, gas-phase geometries and vibrational frequencies for [Cr<sup>VI</sup>OF<sub>5</sub>]<sup>–</sup>, [XeF<sub>5</sub>]<sub>2</sub>[Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]∙2XeOF<sub>4</sub>, [Cr<sup>V</sup><sub>2</sub>O<sub>2</sub>F<sub>8</sub>]<sup>2–</sup>, [XeF<sub>5</sub>][Xe<sub>2</sub>F<sub>11</sub>][Cr<sup>V</sup>OF<sub>5</sub>]∙2Cr<sup>VI</sup>OF<sub>4</sub>, [Cr<sup>V</sup>OF<sub>5</sub>]<sup>2–</sup>, and to aid in the assignments of their vibrational frequencies.</p><br><p></p>
Oxygen coordination to the Xe(VI) atom of XeO<sub>3</sub> was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO<sub>3</sub>, which detonates when mechanically or thermally shocked, the solid [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub>, [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub>,<sub> </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3 </sub>and (C<sub>5</sub>H<sub>5</sub>NO)<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> are air-stable whereas [(CH<sub>3</sub>)<sub>2</sub>SO]<sub>3</sub>(XeO<sub>3</sub>)<sub>2</sub> slowly decomposes over several days and [(CH<sub>3</sub>)<sub>2</sub>CO]<sub>3</sub>XeO<sub>3</sub> undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C<sub>6</sub>H<sub>5</sub>)<sub>3</sub>PO]<sub>2</sub>XeO<sub>3</sub> is a distorted square pyramid which provides the first example of a five-coordinate XeO<sub>3</sub> adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO<sub>3</sub>. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.
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