Noble gas supported boron-pentagonal clusters BNg: exploring the structures and bonding.

A novel type of trivalent BNg five-membered cational species BNg(Ng = He~Rn, n = 1~5) has been found and investigated theoretically using the B3LYP and MP2 methods with the def2-QZVPPD and def2-TZVPPD basis sets. The geometry, harmonic vibrational frequencies, bond energies, charge distribution, bond nature, aromaticity, and energy decomposition analysis of these structures were reported. The calculated B-Ng bond energy is quite large (the averaged bond energy is in the range of 209.2~585.76 kJ mol) for heavy rare gases and increases with the Ng atomic number. The analyses of the molecular wavefunction show that in the BNg compounds of heavy Ng atoms Ar~Rn, the B-Ng bonds are of typical covalent character. Nuclear independent chemical shifts display that both B and BNg(n=1~5) have obvious aromaticity. Energy decomposition analysis shows that these BNg compounds are mainly stabilized by the σ-donation from the Ng valence p orbital to the B LUMO. These findings offer valuable clues toward the design and synthesis of new stable Ng-containing compounds.