Structures and bond energies of the noble gas complexes NgBeO (NgAr, Kr, Xe)

The geometries, vibrational frequencies and NgBeO bond dissociation energies are calculated for the title compounds using quantum chemical methods. The electronic structure of the molecules is investigated with the help of the topological analysis of the electron density distribution. At the MP4 level of theory using effective core potentials for the noble gases and large valence basis sets (quadruple-zeta for Ng, triple-zeta for Be and O, three d and one f type polarization functions), the bond strengths D₀ are predicted after correcting for the BSSE to be 12.6 for XeBeO, 9.3 for KrBeO and 6.7 kcal mol^-1 for ArBeO. The NgBeO bond of ArBeO and KrBeO is caused by induced dipole interactions, but the XeBeO bond has small covalent contributions. The shift of the BeO stretching frequency towards higher wave numbers upon formation of the noble gas complexes is in agreement with the observed blue-shift of the compounds.