Structural Types, Electron Counts, and Isolobal Units

Structural Types, Electron Counts, and Isolobal Units 

The discovery of metallacarboranes was of major importance not only for carborane chemistry, but also for organometallic and cluster chemistry in 

The structures of the products (Fig. 3.20) show that the iron atom effectively plugs the gap created by removal of a BI cationic unit from the closo carborane. As this BH unit was one of the two that were adjacent to the two carbon atoms, the nido carborane anion [C2B9Hii]2 coordinates to the metal 

A third approach notes the relationship between the anion [(q -CsHs) Fe(q5-C2B9Hii)]2 and the parent carborane from which it is derived, C2B10H12. An anionic [(q5-C5H5)Fe] unit in the former replaces a neutral BH unit in the latter. The capacities of these two units, [(CsHsjFe] and BH, to participate in cluster bonding are similar. Each can function as a source of two electrons, and three AOs, for use in skeletal bonding. Not only are the numbers of their frontier orbitals the same, but so are their lobal characteristics they are isolobal (Fig. 3.21).The metal unit can effectively supply a radially oriented Pzdz. hybrid orbital and two pd p.xL i,P-,d., ) hybrid orbitals to bond to the nido 

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