Xenon Trioxide Adducts of O-Donor Ligands; [(CH3)2CO]3XeO3, [(CH3)2SO]3(XeO3)2, (C5H5NO)3(XeO3)2, and [(C6H5)3PO]2XeO3

Oxygen coordination to the Xe(VI) atom of XeO₃ was observed in its adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction and Raman spectroscopy. Unlike solid XeO₃, which detonates when mechanically or thermally shocked, the solid [(C₆H₅)₃PO]₂XeO₃, [(CH₃)₂SO]₃(XeO₃)₂, and (C₅H₅NO)₃(XeO₃)₂ adducts are insensitive to mechanical shock, but undergo rapid deflagration when ignited by a flame. Both [(C₆H₅)₃PO]₂XeO₃ and (C₅H₅NO)₃(XeO₃)₂ are air-stable whereas [(CH₃)₂SO]₃(XeO₃)₂ slowly decomposes over several days and [(CH₃)₂CO]₃XeO₃ undergoes adduct dissociation at room temperature. The xenon coordination sphere of [(C₆H₅)₃PO]₂XeO₃ is a distorted square pyramid which provides the first example of a five-coordinate XeO₃ adduct. The xenon coordination spheres of the remaining adducts are distorted octahedra comprised of three Xe---O secondary contacts that are approximately trans to the primary Xe–O bonds of XeO₃. Quantum-chemical calculations were used to assess the Xe---O adduct bonds, which are predominantly electrostatic σ-hole bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the xenon atoms.