Octahedral coordination structures, edge-sharing

Many more structures are known in which vertices and edges of octahedral coordination groups are shared, and models of several of them are described in MSIC. A relatively simple example is the AX3 framework formed from edge-sharing pairs of octahedra which are further linked to form the 3D framework of Fig. 5.33. This framework is the basis of the structure of one form of KSb03 and of KBiOj,... 

The structure of the decavanadate ion [Vi0O28]6 is well established. Vanadium-51 NMR spectroscopic studies have shown that the structure in solution corresponds to that in the solid state (2). Numerous X-ray studies have shown that it consists of an arrangement of 10 edge-shared V06 octahedra with approximate D2h symmetry (Fig. 7). All vanadium atoms have distorted octahedral geometry and the oxygen atoms fall into seven categories, ranging from terminal to six coordinate. 

The block iron silicate Si2 xFex Fe3ijFe 05(0H)4, cronstedtite, is representative of several mixed-valent minerals. Its structure consists of alternate layers of comer-shared tetrahedra and edge-shared octahedra. The tetrahedra Si " and Fe ions are coordinated by four oxide ions, the octahedral Fe " and Fe " ions share three common oxide ions with tetrahedral-site layers on one side and on the other are coordinated by three hydroxyl ions that hydrogen bond to the next tetrahedral-site layer. Mossbauer data at 35 K are able to resolve distinguishable Fe " and Fe " ions on the octahedral sites but in the range 300 < T < 500 K a rapid (t), < 10 s) charge transfer was found ... 

In the dinuclear complexes two octahedrally coordinated metal ions are bound together by one, two, or three hydroxide ions by sharing a corner, an edge, or a face, as shown in structures 1-3. These mono-, di-, and trihydroxo-bridged binuclear structures are known for... 

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