VOLUME CONJUGATION IN ELECTRON-DEFICIENT POLYHEDRAL MOLECULES

The character of the chemical bond in electron-deficient polyhedral molecules (such as the isomers of dicarbaclosododecaborane and the dodecaborane dianion) has been investigated on the basis of a detailed analysis of the distribution of valence electron density over molecular space. The main electron charge is shown to reside within the sphere inscribed in the polyhedron limited by the network atoms. A significant proportion of the electron density is found at the centre of this sphere. It is concluded that the network atoms are maintained in position by the attraction of the spatial charge distributed within the sphere. All the valence electrons contribute to this distribution, and the new concept of volume conjugation is proposed to characterize this unusual type of bond. © 1979.