Structural considerations in the chemistry of noble gases

The structures of noble gas compounds provide insight into the bonding between noble gas atoms and various ligands and into the electronic environment of the bound noble gas atoms. Structural knowledge of the free molecules is thus important in advancing theories of chemical bonding. Structures inferred from infrared, raman, visible, and ultraviolet spectroscopy, microwave spectroscopy, electron diffraction, Moessbauer measurements, nuclear magnetic resonance, x-ray and neutron diffraction, electric deflection, and thermodynamic measurements are compared for self-consistency and with theoretical calculations and predictions. The structure of XeF6 has proved particularly elusive. Most physical measurements indicate that XeF6 is not octahedral and that the F--Xe--F bond angles are not 900. However, electric and magnetic deflection of molecular beams of XeF6 have shown the absence of a static dipole moment and of significant electronic paramagnetism. Weakly bound noble gas molecules have been formed in hypersonic nozzles and examined using the molecular beam electric deflection techniques.