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The Cl2O2+ Cation:  Preparation and Structural Investigation of Cl2O2+SbF6- and Cl2O2+Sb2F11-

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posted on 27.04.1999 by Thomas Drews, Wolfram Koch, Konrad Seppelt
Cl2 reacts with O2+SbF6- in anhydrous HF, forming subsequently a violet, a blue, and a yellow solution. Crystals from the violet solution are identified as Cl2O2+SbF6- or Cl2O2+Sb2F11- by means of single-crystal structural determinations, Raman spectroscopy, magnetic and EPR measurements, and ab initio calculations. The cation has a planar trapezoid structure with Cl−Cl distances of 190.9(1)−191.6(5) pm, O−O distances of 118.5(11)−120.7(5) pm, and Cl−O distances of 240.8(4)−242.8(4) pm. The bonding between the two parts of the cation may be described as a π*−π* interaction, resulting in a charge transfer of about 0.6 electrons with respect to isolated Cl2+ and O2 fragments. The bonding of O2 to Cl2+ is reversible, as is shown by 18O isotope exchange. The nature of the blue solution remains unknown. Both deeply colored compounds turn into yellow Cl3+ if warmed to room temperature, especially in the presence of excess Cl2. The Cl3+ cation is symmetrical and bent with Cl−Cl = 197.23−199.44 pm and Cl−Cl−Cl = 104.51(10)−105.62(7)°.