Theoretical Study on the Regioselectivity of the B80 Buckyball in Electrophilic and Nucleophilic Reactions Using DFT-Based Reactivity Indices.

Density functional theory calculations at the B3LYP/SVP and B3LYP/6-31lG(d) levels were carried out for a series of XH3B80 complexes with X = {N, P, As, B, Al}. To probe the regioselectivity of B80, the electronic Fukui function, the molecular electrostatic potential (MEP), and the natural bond orbital (NBO) were determined. These indices were shown to provide reliable guides to predict the relative reactivities of the boron buckyball sites. Thermodynamic stabilities of the complexes formed by the reaction of B80 with nucleophiles (NH3, PH3, AsH3) and electrophiles (BH3, A1H3) are in good agreement with the prediction of regioselectivity indicated on the basis of Fukui and MEP indices. The qualitative results suggest the boron buckyball to be an amphoteric and hard molecule. It has two distinct reactive sites localized on caps and frame, which act as acids and bases, respectively. Most of the complexes are stable with formation energies comparable to that of the analogous complexes of the borane molecule, BH3BH3, BH3NH3, and BH3A1H3. The B-H-B bond characteristics of diborane are recovered in B80BH3. Exohedral complexes are more stable than endohedral complexes. The most stable complexes are those with NH3 on the caps and BH3 on the pentagonal ring of B80. [ABSTRACT FROM AUTHOR]