Santamaría-Pérez David, Vegas Angel
Instituto de Química-Física Rocasolano, CSIC, C/Serrano 119, E-28006 Madrid, Spain.
Acta Crystallogr B. 2003 Jun;59(Pt 3):305-23. doi: 10.1107/s0108768103005615. Epub 2003 May 23.
The structures of 94 ternary aluminates are reinterpreted on the basis of the Zintl-Klemm concept and Pearson's generalized octet rule. In aluminates of highly electropositive metals such as alkali, alkaline-earth and rare-earth metals, the Al atoms form three-dimensional skeleta which can be interpreted as if the Al atoms were behaving as Zintl polyanions, adopting the structure of either main-group elements or Zintl polyanions showing the same connectivity. The O atoms are then located close to both the hypothetical two-electron bonds and the lone pairs, giving rise to a tetrahedral coordination. When more electronegative elements, such as W or Si, are present in the compound, the electron transfer towards the Al atoms does not take place. In this case, aluminium behaves as a base, transferring its electrons to the more electronegative atoms and the coordination sphere of aluminium becomes octahedral. In some compounds the Al atoms clearly show amphoteric character so that some Al atoms act as donors (bases) and hence are octahedrally coordinated, whereas others behave as acceptors (acids), adopting a tetrahedral coordination. From this it is concluded that the coordination sphere of aluminium is not a function of the ionic radius of the Al(3+) cations, but it depends on the nature of the other cations accompanying them in the structure. The networks formed by these aluminates are, in many instances, similar to those of the binary oxides of the main-group elements. For this reason, a systematic survey of these oxides is also reported. Compounds such as stuffed cristobalites and trydimites and also perovskites are examples of this new interpretation. Perovskites are then reinterpreted as a stuffed pseudo-TeO(3) structure. Other families of compounds such as silicates and phosphates are susceptible to a similar interpretation. This study provides additional examples of how cations recognize themselves in spite of being embedded in an oxygen matrix.
基于津特耳-克莱姆概念和皮尔逊广义八隅体规则，对94种三元铝酸盐的结构进行了重新诠释。在碱金属、碱土金属和稀土金属等高电正性金属的铝酸盐中，铝原子形成三维骨架，这可以解释为铝原子表现得如同津特耳多阴离子，采用主族元素的结构或具有相同连接性的津特耳多阴离子的结构。然后，氧原子位于假设的双电子键和孤对电子附近，形成四面体配位。当化合物中存在电负性更强的元素，如钨或硅时，电子不会向铝原子转移。在这种情况下，铝表现为碱，将其电子转移给电负性更强的原子，铝的配位球变为八面体。在一些化合物中，铝原子明显表现出两性特征，因此一些铝原子充当供体（碱），从而呈八面体配位，而其他铝原子则充当受体（酸），采用四面体配位。由此得出结论，铝的配位球不是Al(3+)阳离子离子半径的函数，而是取决于结构中与其相伴的其他阳离子的性质。这些铝酸盐形成的网络在许多情况下与主族元素的二元氧化物的网络相似。因此，还报道了对这些氧化物的系统研究。诸如填充方石英和鳞石英以及钙钛矿等化合物就是这种新诠释的例子。然后将钙钛矿重新诠释为填充的类TeO(3)结构。其他化合物家族，如硅酸盐和磷酸盐，也易于进行类似的诠释。这项研究提供了更多例子，说明阳离子如何在嵌入氧基质的情况下识别自身。
