Selective Activation of CCl and CF Bonds by SO^.+ Radical Cations: An Experimental and Computational Study

The activation of C-halogen bonds by the SO^{. +} radical cation is investigated in the gas phase. The CCl bond of CH₂ Cl₂ is activated by fast and effective chloride-ion transfer, whereas the CF bond of CH₂ F₂ is activated by a very slow fluoride-ion transfer. In both cases, thermodynamic and kinetic factors account for the type of process and the observed selectivity, that is, carbon-halogen versus carbon-hydrogen activation, mainly owing to the presence of the sulfur atom. The cleavage of the CCl bond of CH₂ Cl₂ by SO^{. +} is a rare example of a very effective and selective chloride-ion abstraction by a metal-free, sulfur-centred radical cation.