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

A novel type of trivalent BNg five-membered cational species BNg(Ng = HeRn, n = 15) 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 209.2585.76 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 ArRn, 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.