Recently, the hydrolysis of nerve agents by Lewis acid catalysts has attracted considerable attention. The development of molecular catalysts, such as polyoxometalates (POMs) with Lewis acidic sites, is helpful to improve degradation efficiency and understand the catalytic mechanism at a molecular level. Herein, two novel Keggin-type POMs, namely, mono-Sc-substituted K₄[Sc(H₂O)PW₁₁O₃₉]·22H₂O·2(CH₃COOK) (1) and di-Sc-substituted Na₇[Sc₂(CH₃COO)₂PW₁₀O₃₈]·10H₂O·2CH₃COONa (2), have been successfully synthesized and thoroughly characterized by routine techniques. To our knowledge, 1 and 2 represent the first example of discrete Sc-substituted Keggin clusters. Compared with the reported Sc-containing POMs, 1 and 2 exhibit relatively good solubility and stability in aqueous solution, as evidenced by ³¹P nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. The two Sc-substituted POMs can effectively catalyze the hydrolytic decontamination of dimethyl 4-nitrophenyl phosphate (DMNP), a nerve agent simulant, at near-neutral pH. Notably, the catalytic performance of 2 (conversion: 97%) is much better than that of 1 (conversion: 28%). It is found that the different coordination environment of Sc is the key factor to impact their activity. Mechanistic studies including the control experiments and spectroscopy analysis (¹³C nuclear magnetic resonance spectroscopy and electrospray ionization mass spectrometry) show that under the turnover conditions the coordinated acetate dissociates from 2 and the exposed coordinatively unsaturated Sc center is more active than the water-coordinated Sc in 1 for binding with DMNP.

中文翻译：

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单和双Sc取代的Keggin多金属氧酸盐：有效的路易斯酸催化剂，用于神经制剂模拟水解和机理研究。

最近，路易斯酸催化剂对神经活性剂的水解引起了极大的关注。分子催化剂的开发，例如具有路易斯酸性位点的多金属氧酸盐（POM），有助于提高降解效率并了解分子水平的催化机理。在此，两种新颖的Keggin型POM，即单-Sc-取代的K ₄ [Sc（H ₂ O）PW ₁₁ O ₃₉ ]·22H ₂ O·2（CH ₃ COOK）（1）和双-Sc-取代的Na ₇ [Sc ₂（CH ₃ COO）₂ PW ₁₀ O ₃₈ ]·10H ₂ O·2CH ₃COONa（2）已成功合成，并通过常规技术进行了全面表征。据我们所知，1和2代表离散的Sc取代Keggin簇的第一个例子。与报道的含Sc的POM相比，1和2在水溶液中具有相对较好的溶解度和稳定性，如³¹ P核磁共振波谱和傅立叶变换红外光谱所证明的。两个Sc取代的POM可以在接近中性的pH值下有效催化神经毒剂模拟物二甲基4-硝基苯基磷酸二甲酯（DMNP）的水解去污。值得注意的是2的催化性能（转化率：97％）比1（转化率：28％）要好得多。发现Sc的不同协调环境是影响其活动的关键因素。包括控制实验和光谱分析（¹³ C核磁共振波谱和电喷雾电离质谱）在内的机理研究表明，在周转条件下，乙酸根离子从2上解离，暴露的配位不饱和Sc中心比水配位的Sc更活泼。在1与DMNP结合。