Chemistry of Group IV Metal Ion-Containing Polyoxometalates
Chemistry of Group IV Metal Ion-Containing Polyoxometalates
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DOI：
10.1002/ejic.201000712
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发表时间：
2011
影响因子：
2.3
通讯作者：
K. Nomiya;Yoshitaka Sakai;Satoshi Matsunaga
中科院分区：
文献类型：
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作者：
K. Nomiya;Yoshitaka Sakai;Satoshi Matsunaga
本文对含IV族金属离子（TiIV， ZrIV和HfIV）的多金属氧酸盐（pom）的化学性质进行了重点综述，介绍了我们自己研究的一个方面。本文分几节介绍了由不同的孔位化合物与TiIV、ZrIV和HfIV原子反应制备的聚甲醛的合成、结构和固/溶态行为，并将其分为Keggin和Dawson聚甲醛族。由于TiIV的离子半径（0.75 A）接近WVI的离子半径（0.74 A）， TiIV原子可以很好地嵌入POM的单腔位，而比TiIV原子大的ZrIV和HfIV原子（0.85-0.86 A）则不能嵌入POM的单腔位。因此，POM的单空位作为TiIV原子的氧供体五齿配体，而它作为ZrIV和HfIV原子的四齿配体。POM中的TiIV原子具有六坐标几何结构，而ZrIV和HfIV原子由于其较大的离子半径而具有更高的配位数（6,7和8）。因此，大多数ti取代Keggin POMs被分离为由共享角的Ti-O-Ti键形成的低聚物，而含有Zr/Hf的Keggin/Dawson POMs通常被分离为夹在两个空位的POMs之间的二、三、四-Zr/Hf簇阳离子，其簇阳离子由共享边的M(OH)2M （M = Zr, Hf）键形成。这些化合物在ph依赖条件下表现出完全不同的行为。ti取代的二聚体和单体之间的ph依赖性相互转化与含Zr/ hf的Dawson POMs完全相反。ti取代的Dawson POM低聚物倾向于碱水解生成单体，而含Zr/ hf的Dawson POM低聚物倾向于酸水解生成单体。在含IV族金属离子的pom中，Zr/Hf原子的功能非常相似，但与Ti原子的行为却截然不同。
The chemistry of Group IV metal ion (TiIV, ZrIV and HfIV)-containing polyoxometalates (POMs) is presented as a sharply focused microreview, introducing an aspect of our own research. The synthesis, structure, and solid/solution state behavior of the POMs, which are prepared by the reactions of various lacunary species of POMs with TiIV, ZrIV and HfIV atoms, are described in several sections, classified with Keggin and Dawson POM families. Because of the ionic radius of TiIV (0.75 A), close to that of WVI (0.74 A), the TiIV atom can fit nicely into the mono-lacunary site of the POM, but ZrIV and HfIV atoms (0.85–0.86 A), larger than TiIV atom, do not fit into the mono-lacunary site of the POM. Thus, the mono-lacunary site of the POM acts as the oxygen-donor pentadentate ligand to the TiIV atom, whereas it acts as the tetradentate ligand to ZrIV and HfIV atoms. The TiIV atom in the POM takes on six-coordinate geometry, whereas the ZrIV and HfIV atoms have higher coordination numbers (6, 7 and 8) due to their larger ionic radii. Consequently, most Ti-substituted Keggin POMs are isolated as oligomers formed by corner-sharing Ti–O–Ti bonds, whereas Zr/Hf-containing Keggin/Dawson POMs are usually isolated as di-, tri-, tetra-Zr/Hf cluster cations sandwiched between two lacunary POMs, the cluster cations of which are formed by edge-sharing M(OH)2M (M = Zr, Hf) bonds. These compounds show quite different behavior under pH-dependent conditions. The pH-dependent interconversion between the dimeric and monomeric species of Ti-substituted Dawson POMs is quite an opposite tendency from those of Zr/Hf-containing Dawson POMs. The Ti-substituted Dawson POM oligomers have a tendency to undergo base hydrolysis to give monomers, whereas the Zr/Hf-containing Dawson POM oligomers have a tendency to undergo acid hydrolysis to provide monomers. In the Group IV metal ion-containing POMs, the Zr/Hf atoms function very similarly to each other, but show quite different behavior from the Ti atom.