New extraction procedure for protonated polyoxometalates prepared in aqueous-organic solution and characterisation of their catalytic ability
New extraction procedure for protonated polyoxometalates prepared in aqueous-organic solution and characterisation of their catalytic ability
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DOI：
10.1016/j.apcata.2014.07.032
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发表时间：
2014-09
影响因子：
5.5
通讯作者：
T. Ueda;Keisuke Yamashita;A. Onda
中科院分区：
文献类型：
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作者：
T. Ueda;Keisuke Yamashita;A. Onda
虽然在水-有机溶液中制备的多金属有机化合物具有有趣的化学性质，并且可能是有效的催化剂，但用常规的萃取方法不能将它们以质子化的形式分离出来。本研究通过改进和优化萃取条件，建立了一种分离水-有机混合溶液中质子化POMS[S2VxM18−xO62](4+x)−和[AsVxM12−xO40](3+x)−(M=3Mo，W；x=0-2)的新方法。用红外光谱和拉曼光谱对分离的质子化多酸进行了表征，并用Hammett指示剂测量了它们的酸度。H4S2W18O62、H5S2VW17O62、H4S2Mo18O62和H3As2W18O62的酸性强于H3PW12O40。考察了它们在多种有机反应中的催化性能，包括片呐醇重排、与苯甲醛和乙二醇合成缩醛以及苯甲醚与丙酮酸乙酯的Friedel-Craft酰化反应。与H3PM12O40和H4SiM12O40(M=1Mo，W)等市售POMS相比，它们表现出更强的催化能力。
Although POMs prepared in aqueous-organic solutions have been reported to exhibit interesting chemical properties and may be efficient catalysts, they could not be isolated in their protonated form using the normal extraction method. In this study, a new procedure of isolating protonated POMs, [S2VxM18−xO62](4+x)−and [AsVxM12−xO40](3+x)−(M = Mo, W;x= 0–2), which were prepared in an aqueous-organic mixed solution, was developed by modifying and optimising the extraction conditions. Isolated protonated POMs were characterised using IR and Raman spectroscopy, and their acidity was measured using a Hammett indicator. The acidity of H4S2W18O62, H5S2VW17O62, H4S2Mo18O62, and H3As2W18O62was stronger than that of H3PW12O40. Their catalytic ability was investigated in multiple types of organic reactions, including pinacol rearrangement, acetal formation with benzaldehyde and ethylene glycol, and the Friedel-Crafts acylation of anisole with ethyl pyruvate. They exhibited greater catalytic ability than commercially available POMs such as H3PM12O40and H4SiM12O40(M = Mo, W).