Evidence for [18-Crown-6 Na]2[S2O4] in Methanol and Dissociation to Na2S2O4 and 18-Crown-6 in the Solid State; Accounting for the Scar

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• 作者：Pablo J. Bruna ; Scott Greer ; Jack Passmore ; J. Mikko Rautiainen
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：February 21, 2011
• 年：2011
• 卷：50
• 期：4
• 页码：1491-1497
• 全文大小：871K
• 年卷期：v.50,no.4(February 21, 2011)
• ISSN：1520-510X

文摘

[18-Crown-6 Na]₂S₂O₄ complex was prepared in methanol solution but dissociates into 18-Crown-6 _(s) and Na₂S₂O_{4 (s)} on removal of the solvent. Evidence for complexation in methanol is supported by a quantitative mass analysis and the dissociation in the solid state by vibrational spectroscopy and powder X-ray diffraction. These observations are accounted for by investigating the energetics of complexation in solution and dissociation in the solid state using calculated density functional theory (DFT) gas phase binding enthalpies and free energies combined with conductor-like screening model (COSMO) solvation energies and lattice enthalpy and free energy terms derived from volume based thermodynamics (VBT). Our calculations show that complexation of alkali metal dianion salts to crown ethers are much less favorable than that of the corresponding monoanion salts in the solid state and that the formation of alkali metal crown complexes of stable simple oxy-dianion (e.g., CO₃^{2鈭?/sup>, SO₄2鈭?/sup>) salts is unlikely. The roles of complexation with 18-Crown-6 and ion pair formation in the process of dissolution of Na₂S₂O₄ to methanol are discussed.}