[C6F5Xe]+ and [C6F5XeNCCH3]+ Salts of the Weakly Coordinating Borate Anions, [BY4]− (Y = CN, C

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• 作者：Karsten Koppe ; Hermann-J. Frohn ; H&#xe9 ; l&#xe8 ; ne P. A. Mercier ; Gary J. Schrobilgen
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：April 21, 2008
• 年：2008
• 卷：47
• 期：8
• 页码：3205 - 3217
• 全文大小：2112K
• 年卷期：v.47,no.8(April 21, 2008)
• ISSN：1520-510X

文摘

New examples of [C₆F₅Xe]⁺ salts of the weakly coordinating [BY₄]⁻ (Y = CN, CF₃, or C₆F₅) anions were synthesized by metathesis of [C₆F₅Xe][BF₄] with M^I[BY₄] (M^I = K or Cs; Y = CN, CF₃, or C₆F₅) in CH₃CN at −40 °C, and were crystallized from CH₂Cl₂ or from a CH₂Cl₂/CH₃CN solvent mixture. The low-temperature (−173 °C) X-ray crystal structures of the [C₆F₅Xe]⁺ cation and of the [C₆F₅XeNCCH₃]⁺ adduct-cation are reported for [C₆F₅Xe][B(CF₃)₄], [C₆F₅XeNCCH₃][B(CF₃)₄], [C₆F₅Xe][B(CN)₄], and [C₆F₅XeNCCH₃][B(C₆F₅)₄]. The [C₆F₅Xe]⁺ cation, in each structure, interacts with either the anion or the solvent, with the weakest cation–anion interactions occurring for the [B(CF₃)₄]⁻ anion. The solid-state Raman spectra of the [C₆F₅Xe]⁺ and [C₆F₅XeNCCH₃]⁺ salts have been assigned with the aid of electronic structure calculations. Gas-phase thermodynamic calculations show that the donor–acceptor bond dissociation energy of [C₆F₅XeNCCH₃]⁺ is approximately half that of [FXeNCCH₃]⁺. Coordination of CH₃CN to [C₆F₅Xe]⁺ is correlated with changes in the partial charges on mainly Xe, the ipso-C, and N, that is, the partial charge on Xe increases and those on the ipso-C and N decrease upon coordination, typifying a transition from a 2c–2e to a 3c–4e bond.