通过六电子还原过程在 Keggin 型多金属氧酸盐中形成异金属金属-金属键,Inorganic Chemistry

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通过六电子还原过程在 Keggin 型多金属氧酸盐中形成异金属金属-金属键
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2023-01-30 , DOI: 10.1021/acs.inorgchem.2c03769
Clément Falaise ₁ , Gabrielle Mpacko Priso ₁ , Nathalie Leclerc ₁ , Mohamed Haouas ₁ , Emmanuel Cadot ₁

Affiliation

多金属氧酸盐 (POM) 代表了一类很有前途的分子电子库。然而，它们的多电子还原会产生复杂的物理化学现象，必须充分理解这些现象才能将其用于未来的储能设备。在此，我们展示了原型 Keggin 型 POM [Si(W ^VI₂ Mo ^VI O ₁₀ )(W ^VI₃ O ₁₀ ) ₃ ] ^4–在水溶液中的本体电解导致六电子还原衍生物 [Si (W ^IV₂ Mo ^IV O ₇ (H ₂ O) ₃ )(W ^VI₃ O₁₀ ) ₃ ] ^4–（标记为SiW ₁₁ Mo-VI'），其中混合金属三元组充当六个电子和六个质子的存储单元。X 射线衍射分析和多核核磁共振（¹⁸³ W 和⁹⁵ Mo）研究表明，这种富含电子的物质代表了在附加中心之间含有异金属金属-金属键的 POM 的第一个例子。这种富含电子的 POM 可以通过多电子事件进一步还原，而其完全氧化可恢复氧化母离子的结构。值得注意的是， SiW ₁₁ Mo-VI'的形成与完全基于 W 的类似物观察到的相比，这是一个快速聚类过程的结果，表明混合金属 Mo/W POM 中金属-金属键的形成得到促进，因为反应速率不受缓慢歧化步骤的限制. 最后，我们使用基于非离子表面活性剂浊点测量的方法评估SiW ₁₁ Mo-VI'的超分子特性。该研究表明，聚类过程对 POM 的溶液行为具有显着影响，由于水合壳的局部结构化效应，取消了其超离液特性。这些基本结果为使用混合金属 POM 的大量电子存储特性的应用铺平了道路。

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Making Heterometallic Metal–Metal Bonds in Keggin-Type Polyoxometalates by a Six-Electron Reduction Process

Polyoxometalates (POMs) represent a promising class of molecular electron reservoirs. However, their multielectron reduction gives rise to intricate physical–chemical phenomena that must be fully understood for their future use in energy-storage devices. Herein, we show that bulk electrolysis of the archetypal Keggin-type POM [Si(W^VI₂Mo^VIO₁₀)(W^VI₃O₁₀)₃]^4– in aqueous solution leads to the six-electron-reduced derivative [Si(W^IV₂Mo^IVO₇(H₂O)₃)(W^VI₃O₁₀)₃]^4– (notated SiW₁₁Mo-VI′) in which the mixed-metal triad acts as a storage unit for six electrons and six protons. X-ray diffraction analysis and multinuclear NMR (¹⁸³W and ⁹⁵Mo) studies reveal that this electron-rich species represents the first example of POMs containing heterometallic metal–metal bonds between addenda centers. This electron-rich POM can be further reduced through multielectronic events, while its full oxidation restores the structure of the oxidized parent ion. Remarkably, the formation of SiW₁₁Mo-VI′ results from a fast clustering process compared to that observed for the entirely W-based analogue, revealing that the formation of metal–metal bonds in the mixed-metal Mo/W POM is facilitated because the reaction rate is not limited by a slow disproportionation step. Last, we evaluate the supramolecular properties of SiW₁₁Mo-VI′ using a method based on the cloud-point measurement of a nonionic surfactant. This investigation demonstrates that the clustering process has dramatic consequences on the solution behavior of the POM, canceling its superchaotropic character due to a local structuring effect of the hydration shell. These fundamental results pave the way for applications using the massive electron-storage properties of mixed-metal POMs.

更新日期：2023-01-30

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