Abstract

The evolution of the use of the 14/4n series method has resulted in the discovery of skeletal numbers. The skeletal numbers have rendered the testing of the 18-and 8-electron rules much easier and faster. In the same way, they have been very useful in simplifying the categorization of clusters, the prediction of shapes, and the matching of isolobal fragments. Furthermore, the skeletal numbers have made it possible to tentatively assign ligands to individual skeletal elements in such way that the 18- or 8-electron rule is obeyed. Thus, skeletal numbers can be utilized as a simple guide in analyzing and understanding clusters.

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