Chlorostannate(II) Ionic Liquids: Speciation, Lewis Acidity, and Oxidative Stability

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• 作者：Matthew Currie ; Julien Estager ; Peter Licence ; Shuang Men ; Peter Nockemann ; Kenneth R. Seddon ; Ma艂gorzata Swad藕ba-Kwa艣ny ; C茅cile Terrade
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：February 18, 2013
• 年：2013
• 卷：52
• 期：4
• 页码：1710-1721
• 全文大小：563K
• 年卷期：v.52,no.4(February 18, 2013)
• ISSN：1520-510X

文摘

The anionic speciation of chlorostannate(II) ionic liquids, prepared by mixing 1-alkyl-3-methylimidazolium chloride and tin(II) chloride in various molar ratios, 蠂_SnCl2, was investigated in both solid and liquid states. The room temperature ionic liquids were investigated by ¹¹⁹Sn NMR spectroscopy, X-ray photoelectron spectroscopy, and viscometry. Crystalline samples were studied using Raman spectroscopy, single-crystal X-ray crystallography, and differential scanning calorimetry. Both liquid and solid systems (crystallized from the melt) contained [SnCl₃]^{鈭?/sup> in equilibrium with Cl鈥?/sup> when 蠂_SnCl2 < 0.50, [SnCl₃]鈭?/sup> in equilibrium with [Sn₂Cl₅]鈭?/sup> when 蠂_SnCl2 > 0.50, and only [SnCl₃]鈭?/sup> when 蠂_SnCl2 = 0.50. Tin(II) chloride was found to precipitate when 蠂_SnCl2 > 0.63. No evidence was detected for the existence of [SnCl₄]2鈥?/sup> across the entire range of 蠂_SnCl2, although such anions have been reported in the literature for chlorostannate(II) organic salts crystallized from organic solvents. Furthermore, the Lewis acidity of the chlorostannate(II)-based systems, expressed by their Gutmann acceptor number, has been determined as a function of the composition, 蠂_SnCl2, to reveal Lewis acidity for 蠂_SnCl2 > 0.50 samples comparable to the analogous systems based on zinc(II). A change of the Lewis basicity of the anion was estimated using 1H NMR spectroscopy, by comparison of the measured chemical shifts of the C-2 hydrogen in the imidazolium ring. Finally, compositions containing free chloride anions (蠂_SnCl2 < 0.50) were found to oxidize slowly in air to form a chlorostannate(IV) ionic liquid containing the [SnCl₆]2鈥?/sup> anion.}