THE DIXENON(1+) CATION - FORMATION IN THE CONDENSED PHASES AND CHARACTERIZATION BY ESR, UV-VISIBLE, AND RAMAN-SPECTROSCOPY

The redox chemistry of the couple formed bv XeF+ and elemental xenon gives rise to a green intermediate. This is formed, for example, from XeF+Sb2F11- in antimony pentafluoride solution, irreversibly under the action of various reducing agents (e.g. H2O, Pb, Hg, S02, PF3, or SbF3) or reversibly under the action of xenon gas, and while an overpressure of xenon is maintained, it is long-lived at ambient temperatures. The product has been characterized by a combination of ESR, UV-visible, and Raman spectroscopies, enrichment in Xe-136 or Xe-129 playing a crucial role in establishing that the carrier of the green coloration is the dixenon(l+) cation, Xe2+. Quantitative studies of the UV-visible and Raman spectra of antimony pentafluoride solutions imply that the reversible formation of Xe2+ takes place in accordance with the equilibrium 3Xe + XeF+Sb2F11- + 2SbF5 reversible 2Xe2+Sb2F11-, although a secondary equilibrium finds the Xe2+ bound in a complex with an excess of the oxidant: Xe2+Sb2F11- + XeF+Sb2F11-reversible Xe2+Sb2F11-.XeF+Sb2F11-. The spectroscopic properties of Xe2+ are discussed in relation to those of the isoelectronic species I2- and to the results of previous theoretical calculations. Of the media investigated to date antimony pentafluoride seems to be unique in its ability to support the Xe2+ cation in appreciable concentrations at normal temperatures.