Existence of the halocarbonyl and trifluoromethyl cations in the condensedphase

Experimental and theoretical studies show that neither CF3+ nor FCO+ can be stabilized in the condensed phase with presently known Lewis acids. In the case of ClCO+, stabilization with SbF6- was also not possible, but Sb3F15 possesses sufficient acidity to abstract a fluoride ion from ClFCO in the f ormation of ClCO+Sb3F16-. This salt was fully characterized, providing the first well-established proof for the existence of a halocarbonyl cation in the condensed phase. Theoretical calculations and thermochemical cycles wer e used to corroborate our experimental findings, demonstrating that is poss ible to predict correctly whether a molecule with three different donor sit es, such as ClFCO, will form an oxygen-coordinated donor-acceptor adduct or undergo either F- or Cl- abstraction,Furthermore, a method is described fo r extending natural bond orbital (NBO) analyses to systems containing two d ifferent types of competing, p(pi) back-donating ligands.