The [2+2] cycloaddition product of perhalogenated cyclopentadienyl cations: structural characterization of salts of the [C10Cl10]2+ and [C10Br10]2+ dications.

Abstract

Instead of monomeric cyclopentadienyl cations, the low-temperature reaction of hexachloro- and hexabromocyclo-pentadiene (C5Cl6 and C5Br6) with powerful Lewis acids SbF5 and AsF5 in SO2ClF yields salts of perhalogenated dications [C10Cl10][Sb3F16]2 and [C10Br10][As2F11]2 which are characterized via single crystal X-ray diffraction and NMR spectroscopy. Additionally, this reactivity is rationalized by quantum-chemical calculations.