Noble-gas difluoride complexes of mercury(II): the syntheses and structures of Hg(OTeF5)2·1.5NgF2 (Ng = Xe, Kr) and Hg(OTeF5)2.

The synthesis of high-purity Hg(OTeF5)2 has resulted in its structural characterization in the solid state by Raman spectroscopy and single-crystal X-ray diffraction (XRD) and in solution by (19)F NMR spectroscopy. The crystal structure of Hg(OTeF5)2 (-173 °C) consists of discrete Hg(OTeF5)2 units having gauche-conformations that interact through long Hg---O and Hg---F intramolecular contacts to give a chain structure. The Lewis acidity of Hg(OTeF5)2 toward NgF2 (Ng = Xe, Kr) was investigated in SO2ClF solvent and shown to form stable coordination complexes with NgF2 at -78 °C. Both complexes were characterized by low-temperature Raman spectroscopy (-155 °C) and single-crystal XRD. The complexes are isostructural and are formulated as Hg(OTeF5)2·1.5NgF2. The Hg(OTeF5)2 units of Hg(OTeF5)2·1.5NgF2 also have gauche-conformations and are linked through bridging NgF2 molecules, also resulting in chain structures. These complexes represent the only examples of coordination compounds where NgF2 coordinates to mercury in a neutral covalent compound and the only example of mercury coordinated to KrF2. Moreover, the Hg(OTeF5)2·1.5KrF2 complex is the only KrF2 complex known to contain a bridging KrF2 ligand. Energy-minimized gas-phase geometries and vibrational frequencies for the model compounds, [Hg(OTeF5)2]3 and [Hg(OTeF5)2]3·2NgF2, were obtained and provide good approximations of the local environments of Hg(OTeF5)2 and NgF2 in the crystal structures of Hg(OTeF5)2 and Hg(OTeF5)2·1.5NgF2. Assignments of the Raman spectra of Hg(OTeF5)2 and Hg(OTeF5)2·1.5NgF2 are based on the calculated vibrational frequencies of the model compounds. Natural bond orbital analyses provided the associated bond orders, valencies, and natural population analysis charges.