Facile preparation of an α-Keggin-type [H3W12O40]5− complex: Does it exist in aqueous solution?
Facile preparation of an α-Keggin-type [H3W12O40]5− complex: Does it exist in aqueous solution?
复制标题
轻松制备 α-Keggin 型 [H3W12O40]5− 络合物：它存在于水溶液中吗？
DOI：
10.1016/j.poly.2010.06.002
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发表时间：
2010
期刊：
影响因子：
2.6
通讯作者：
K. Eda
中科院分区：
文献类型：
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作者：
S. Himeno;Kiyomi Nakajima;K. Eda
研究了α-Keggin结构的[H_2W_(12)O_(40)]_6-−和[H_3W_(12)O_(40)]_5-−络合物在水溶液中的形成过程。[H_3W_(12)O_(40)]_6-−的形成是通过在−117ppm处出现183W的核磁共振线来确定的，但在可及的pH范围内没有发现[H_3W_(12)O_(40)]_5−存在的证据。在WV溶液中加入(CH3)4N+(Me4N+)直接析出(Me4N)6[H_2W_12O_(40)]盐。另一方面，较大的Bu4N+阳离子的加入会析出(Bu4N)4.5H0.5[H3W12O40]盐，因为在结晶过程中或在固态时形成的裸质子可能会进入Keggin壳层生成[H3W12O40]5−。这一解释是基于这样一个事实，即在酸化的水溶液中，[H3W12O40]6−不会自发转化为[H3W12O40]5−。根据它们的伏安性质，开发了一种简单的诊断标准来区分[H3W12O40]6−和[H3W12O40]5−。
The formation processes of α-Keggin-type [H2W12O40]6−and [H3W12O40]5−complexes were investigated in aqueous WVI(0.05–0.50M) solutions. The formation of [H2W12O40]6−was ascertained by the appearance of a183W NMR line at −117ppm, but no evidence was found for the existence of [H3W12O40]5−in the solution at the accessible pH range. The addition of (CH3)4N+(Me4N+) to the WVIsolution directly precipitated the (Me4N)6[H2W12O40] salt. On the other hand, the addition of the larger Bu4N+cation precipitates the (Bu4N)4.5H0.5[H3W12O40] salt, because a naked proton formed during the crystallization process or in the solid state may enter into the Keggin shell to produce [H3W12O40]5−. This explanation is based on the fact that [H2W12O40]6−is not spontaneously converted into [H3W12O40]5−in acidified aqueous solution. On the basis of their voltammetric properties, a simple diagnostic criterion was developed to distinguish between [H2W12O40]6−and [H3W12O40]5−.