Octahedral geometry hexanuclear clusters

However this approach is not so easy to handle when the complexity of clusters increases for instance, Rh6(CO)i6, Co6(CO)i6, Ir6(CO)i6 share 86 electrons in the valence shell, which according to the noble gas rule formalism, would result in 11 metal-metal bonds. Since there is no simple geometry to accommodate 11 metal-metal bonds using 6 metal atoms, it is not surprising to observe an octahedral geometry with 12 metal-metal bonds. In this case the molecular clusters have an excess of two electrons which are located in bonding orbitals [2, 7]. If one increases the number of electrons in the hexanuclear frame, for example by introducing a carbon... 

Hexanuclear Organometallic Clusters. Although the octahedral arrangement of metal atoms is the most representative one for hexanuclear cluster compounds, a number of other geometries have also been observed. The structural characteristics of a selected group of hexanuclear compounds are briefly described in Table 2.6. The different types of structures found for these clusters are illustrated schematically in Fig. 2.25. 

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