Clusters of the Heavier Croup 13 Elements

Ceroid Linti, Hansgeorg Schnockel, Werner Uhl and Nils Wiberg 

A metal atom cluster as defined by Cotton [1] is still a very broad term, because non-metal atoms can also be part of the cluster core. In this chapter mainly two types of metal atom clusters are presented the polyborane analogous polyhedral and the metalloid clusters E Rr of group 13 elements E. The structures and bonding of the polyhedral clusters with n r are similar to those in the well-known polyboranes. 

In a metalloid cluster [2] more metal-metal bonds than metal-ligand bonds are involved, which means n r. The largest structurally characterized compounds of this type contain 77 A1 or 84 Ga atoms, respectively [3, 4], Metal-metal bonds dominate these clusters and the framework of the resulting metal-metal bonds exhibits a geometry similar to the bulk metal itself. With respect to the Greek word ei8o (idea, prototype) the suffix -oid indicates that the bulk metal element is actually visible in the metal atom core of the metalloid or more generally, elementoid clusters. 

We will first comment on metal-metal bonds (see Section 2.3.2) and then discuss (see Section 2.3.3) the polyhedral clusters [6], followed by the second central subject, the metalloid clusters in Section 2.3.4 (for recently published reviews see e.g., Refs. [7-11]). 

In part, the success with this chemistry of group 13 is based on a technique 

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