Ollide ions

The 1,2- and 1,7-isomers are susceptible to degradation with strong base, which removes one boron atom from each of the cages. In the 1,2-isomers either the 3- or 6-boron atom is removed while for the 1,7-isomers either the 2- or 3-boron atom is removed. The boron atoms capable of extraction in each isomer are adjacent to both heteroatoms. These boron atoms are the most electron-deficient and the most susceptible to nucleophilic base attack. The 11-atom fragments are not normally isolated as the ollide ions themselves but in a protonated form (i.e., 1,2-B9C2H12-). The extra protons are easily removed with base prior to metal complexation. The ollide ions discussed in this section may well exist as open-face icosahedral fragments (Fig. 2). This point has not been definitely determined yet and an alternative... 

If the ollide ions are or can rearrange to open icosahedral species (Fig. 2), the open face of these structures would have the characteristics of the cyclopentadienide ion. The five nearly equivalent sp3 atomic orbitals pointing toward the missing apex of the ollide ion should yield five 7r-type molecular orbitals which correspond to the Al, the two j, and the two E2 molecular orbitals of the C5H5 ion. This type of ligand would then be expected to form sandwich-bonded complexes similar to the metallocenes. 

Since systematic nomenclature for the B9C2Hf j" ion and its complexes is rather unwieldy, the trivial name dicarbollide ion has been proposed. This is derived from the Spanish word olla meaning pot, in view of the shape of the 11-particle icosahedral fragment. The unknown parent ollide ion would beBuHjf. 

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