Polyhedral skeletal electron pair theory transition metal clusters

Development of the concept of the chemical bond from hydrogen to cluster compounds Limitations of the polyhedral skeletal electron pair theory in organometallic cluster chemistry examples in tri- and tetrametallic systems Electron-count versus structural arrangement in clusters based on a cubic transition metal core with bridging main group elements... 

It became necessary to develop new approaches for predicting electron closed-shell structures, and ideas came from Williams, Wade, Mingos, and Rudolph, which now make up the polyhedral skeletal electron pair theory (PSEPT). The bonding in clusters can sometimes be described in terms of edge-localized, two-center two-electron bonds. Thus, through the formation of element-element bonds, the atoms of a polyhedron can acquire an effective inert gas configuration (8 valence electrons for a main group element and 18 for a transition metal atom). 

Platinum clusters generally do not agree with the electronic requirements of transitions metal clusters established by the polyhedral Skeletal Electron Pair Theory. These clusters generally possess fewer electrons than expected from this theory. 

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