Cage and Cluster Compounds

In this section we shall deal with a few of the principal classes, choosing for each one a prototypal example with which to illustrate how symmetry considerations are brought to bear. 

Here we designate orbitals that point directly in or out of the cluster as radial and the ones mainly on the surface as tangential. 

The overall result of the foregoing analysis is that the B6 cluster itself has the following bonding MOs A x, r2jf, and TUr Since these can hold, 2, 6, and 6 electrons, respectively, a total of 14 electrons are required to occupy the 

From this simple beginning, a large body of less rigorous but useful bonding theory has been elaborated. It can be shown that for all boron clusters of the B H type which are closed polyhedra (Fig. 8.15), with n from 5 to 12, the optimum number of bonding electron pairs within the cluster is n + 1, just as we have found for B6Hg . Therefore, all of these closo boron clusters are predicted to occur as dianions, and all of them do. 

There are a number of other important boron cage compounds as well as structurally similar metal atom cluster molecules that are not closed polyhedra. Generally, these may be regarded as derived from closed polyhedra by removal of one or two vertices. The diagram below illustrates how removal of one or two vertices generates the so-called nido and arachno relatives of a closo octahedral structure. 

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R. J. Gillespie, Ring, cage, and cluster compounds of the main group elements. Chem. Soc. Rev. 1979, 315. 

Sekiguchi, Akira, and Sakurai, Hideki, Cage and Cluster Compounds of Silicon, Germanium, and Tin. 37 1... 

This chapter emphasizes cage and cluster compounds of aluminum, gallium and indium incorporating nitrogen atoms. A search of the literature reveals a number of monographs and reviews [31-33] as well as recent research articles available on this subject. Reactions of alanes and alanates with various amines leading to iminoalanes and aminoalanes have been well documented [21, 31, 34-36], In summary, there are reports on the formation of iminoalanes from Eqs. (13) to (17). 

A. Sekiguchi, H. Sakurai, "Cage and Cluster Compounds of Silicon, Germanium and Tin", Adv. Organomet. Chem. 1995, 57, 1. 

A. Sekiguchi and H. Sakurai (1995) Advances in Organometallic Chemistry, vol. 37, p. 1 - Cage and cluster compounds of silicon, germanium and tin . 

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