Synthesis and Structural Characterization of Lanthanide Containing Polyoxoanions Functionalized by Peroxo Groups, and Investigation of Their Catalytic Properties

我们建议合成一种新型的稀土中心取代的多氧钨酸盐，其末端的水配体被过氧基取代。到目前为止，还没有任何这样的物种被发现。我们还将研究这类新的多金属氧酸盐(POMS)的均相和非均相氧化催化性能。我们将研究稀土离子与各种水溶性多钨酸盐前驱体的相互作用，然后使用过氧化氢对其进行官能化。我们最初的重点将放在已知的稀土多金属有机化合物的官能化上，例如我们的小组最近发表的壮观的含有100-钨锗酸盐[Ce20Ge10W100O376(H2O)4(H2O)30]56的20-Ce-Ce。21这个物种总共有30个末端水配体与20个Ce中心相关，因此是一个很好的带有过氧基的官能化候选者。通过单晶X-射线衍射、FTIR、TGA-DSC、多核核磁共振(如183W、31P、29Si)和元素分析对所合成的新型稀土过氧POMS进行了表征。雅各布斯大学还将进行初步催化试验(例如，基于过氧化氢的烯烃氧化)。将稀土元素引入到空位的多钨骨架中，已经得到了几种在发光、磁性和Lewis酸型催化方面具有有趣性质的多金属有机化合物。由于其较大的尺寸和配位数，与3D过渡金属相比，稀土离子不能完全插入到空位的POM前驱体的空位上，通常导致两个或更多末端、空间可及和不稳定的水配体。这又允许这些水分子被有机配体(包括手性的)或与其他POM片段配位，从而形成非常大的离散的分子结构或扩展的框架。29另一方面，目前还没有报道过稀土过氧磷的报道。我们认为这种多金属有机化合物应该存在，因为侧向-过氧桥联稀土配位络合物的形成是众所周知的。

We propose to synthesize novel polyoxotungstates substituted by lanthanide centers for which the terminal aqua ligands have been substituted by peroxo groups. To date no such species are known at all. We will also investigate the homogeneous and heterogeneous oxidation catalysis properties of this novel subclass of polyoxometalates (POMs). We will investigate the interaction of lanthanide ions with a variety of water-soluble polytungstate precursors, followed by functionalization using aqueous hydrogen peroxide. Our initial focus will be on the functionalization of known lanthanide-POMs, e.g. the spectacular 20-cerium containing 100- tungstogermanate [Ce20Ge10W100O376(OH)4(H2O)30]56- published very recently by our group.21 This species has a total of 30 terminal aqua ligands associated with the 20 cerium centers and hence represents a good candidate for functionalization with peroxo groups. Our novel lanthanide-peroxo-POMs will be characterized as usual by single-crystal X-ray diffraction, FTIR, TGA-DSC, multinuclear NMR (e.g. 183W, 31P, 29Si) and elemental analysis. The preliminary catalytic tests (e.g. peroxide-based oxidation of olefins) will also be carried out at Jacobs University. Incorporation of lanthanides into lacunary polytungstate frameworks has already resulted in several POMs with interesting properties in the areas of luminescence, magnetism, and Lewis acid-type catalysis. Due to their larger size and coordination number, compared to 3d transition metals, lanthanide ions cannot be fully inserted into the vacant sites of the lacunary POM precursors, usually resulting in 2 or more terminal, sterically accessible and labile water ligands. This in turn allows for substitution of those water molecules by organic ligands (incl. chiral ones) or for coordination to other POM fragments leading to very large discrete, molecular architectures or extended frameworks. To date some peroxo-POMs are known and they are very good oxidation catalysts.29 On the other hand, no lanthanide-peroxo-POMs have ever been reported. We believe that such POMs should exist, as formation of side-on -peroxo bridged lanthanide based coordination complexes are well known.30