X-ray Crystal Structures of [XeF][MF6] (M = As, Sb, Bi), [XeF][M2F11] (M = Sb, Bi) and Estimated Thermochemical Data and Predicted Stabilities for Noble-Gas Fluorocati

详细信息    查看全文

• 作者：Hugh St. A. Elliott ; John F. Lehmann ; Hlne P.A. Mercier ; H. Donald Brooke Jenkins ; Gary J. Schrobilgen
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：September 20, 2010
• 年：2010
• 卷：49
• 期：18
• 页码：8504-8523
• 全文大小：1064K
• 年卷期：v.49,no.18(September 20, 2010)
• ISSN：1520-510X

文摘

The crystal structures of the xenon(II) salts, [XeF][SbF₆], [XeF][BiF₆], and [XeF][Bi₂F₁₁], have been determined for the first time, and those of XeF₂, [XeF][AsF₆], [XeF][Sb₂F₁₁], and [XeF₃][Sb₂F₁₁] have been redetermined with greater precision at −173 °C. The Bi₂F₁₁p>−p> anion, which has a structure analogous to those of the As₂F₁₁p>−p> and Sb₂F₁₁p>−p> anions, has been structurally characterized by single crystal X-ray diffraction for the first time as its XeFp>+p> salt. The fluorine bridge between the bismuth atoms is asymmetric with Bi---F_b bond lengths of 2.092(6) and 2.195(6) Å and a Bi---F_b′---Bi bridge bond angle of 145.3(3)p>op>. The XeFp>+p> cations interact with their anions by means of Xe---F_b---M bridges. Consequently, the solid-state Raman spectra of [XeF][MF₆] (M = As, Sb, Bi) were modeled as the gas-phase ion pairs and assigned with the aid of quantum-chemical calculations. Relationships among the terminal Xe−F_t and bridge Xe---F_b bond lengths and stretching frequencies and the gas-phase fluoride ion affinities of the parent Lewis acid that the anion is derived from are considered. The analogous krypton ion pairs, [KrF][MF₆] (M = As, Sb, Bi) were also calculated and compared with their previously published X-ray crystal structures. The calculated cation−anion charge separations indicate that the [XeF][MF₆] salts are more ionic than their krypton analogues and that XeF₂ is a stronger fluoride ion donor than KrF₂. The lattice energies, standard enthalpies, and free energies of formation for salts containing the NgFp>+p>, Ng₂F₃p>+p>, XeF₃p>+p>, XeF₅p>+p>, Xe₂F₁₁p>+p>, and XeOF₃p>+p> (Ng = Ar, Kr, Xe) cations were estimated using volume-based thermodynamics (VBT) based on crystallographic and estimated ion volumes. These estimated parameters were then used to predict the stabilities of noble-gas salts. VBT is used to examine and predict the stabilities of, inter alia, the salts [XeF_m][Sb_nF_5n+1] and [XeF_m][As_nF_5n+1] (m = 1, 3; n = 1, 2). VBT also confirms that XeFp>+p> salts are stable toward redox decomposition to Ng, F₂, and MF₅ (M = As, Sb), whereas the isolable krypton compounds and the unknown ArFp>+p> salts are predicted to be unstable by VBT with the ArFp>+p> salts being the least stable.