Structure and properties of 1,2-, 1,7-, and 1,12-dicarba-closo-dodecaboranes(12): A quantum chemical study

The molecular and electronic structures and thermodynamic parameters of 1,2-, 1,7-, and 1,12-dicarba-closo-dodecaborane(12) molecules in the singlet ground state were calculated by the Hartree-Fock, DFT, and MP2 (including B3LYP/6-311G(2d,2p) and MP2/6-311+G(d,2p) methods). The energies and character of spatial localization of the frontier MOs in o-, m-, p-carboranes(12) correlate with the changes in the configuration stabilities and reactivities in the reactions of carboranes with electrophilic and nucleophilic agents and bases. The electrostatic potential distributions in the molecules and the atomic charge distribution of hydrogen atoms correlate with the known chemical properties of carboranes(12). The thermodynamic parameters of two isomerization reactions, o-C₂B₁₀H₁₂ ⇌ m-C₂B₁₀H₁₂ and m-C₂B₁₀H₁₂ ⇌ p-C₂B₁₀H₁₂, calculated for the temperature range 298–1000 K agree with experimental data within the limits of measuring error. The values of the electron density and the Laplacian of the electron density at the (3, −1) critical points of the B-H and C-H bonds correlate with the reactivities of the title compounds. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2074–2080, December, 2006.