Some finite groups of octahedra

Some of the simpler octahedral complexes are illustrated in Fig. 5.8 and some examples are included in the more comprehensive Table 5.3. We comment here on only a few of these complexes. 

Finite groups of octahedra of Table 5.3. Further examples of the A2X10 group of Fig. 5.8(b) include  

The A3X12 and A4X16 complexes represent the structures of the trimeric Ni and tetrameric Co acetylacetonates (Fig. 5.9) the coordination groups around the metal 

Certain elements, notably V, Nb, Ta, Mo, and W, form complex oxy-ions built from larger numbers of octahedral coordination groups. Examples are included in Table 5.3. In the heteropolyacid ions such as FWJ2O40 and 2 180 2 P atoms occupy the tetrahedral holes at the centres of the complexes. These more complex oxy-ions are described in Chapter 11. 

Of Ihe indefinitely large number of structures that could be built from octahedra sharing vertices, edges, and/or faces, a large number are already known, and a complete account of octahedral structures would cover much of the structural 

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