Thermodynamic criteria for aromaticity of cluster molecules and ions

A new approach to the estimation of the aromaticity of the cluster closo-sy stems (molecules and ions) is described. It is based on the calculation of the thermodynamic parameters using the structural-thermodynamic model of th e key compounds involved in the disproportionation reactions and the subseq uent use of these parameters for the quantitative estimation of the energy of aromatic stabilization. This approach was applied to describe the aromat icity of the closo-borane ions B12H122- and B12F122-. The B-12 clusters in these ions were shown to differ strongly in aromaticity. Fluorination of th e B-12 cluster reduces its aromaticity nearly by half because of the decrea se in the degree of delocalization of the skeletal (B-12) electrons.