The Cl2O2+ cation:: Preparation and structural investigation of Cl2O2+SbF6- and Cl2O2+Sb2F11-

Cl-2 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 pi*-pi* interaction, resulting in a charge transfer of about 0.6 electrons with respect to isolated Cl-2(+) and O-2 fragments. The bonding of O-2 to Cl-2(+) is reversible, as is shown by O-18 isotope exchange. The nature of the blue solution remains unknown. Both deeply colored compounds rum into yellow Cl-3(+) if warmed to room temperature, especially in the presence of excess Cl-2. The Cl-3(+) cation is symmetrical and bent with Cl-Cl = 197.23-199.44 pm and Cl-Cl-Cl = 104.51(10)-105.62(7)degrees.