Gas-phase nucleophilic reactions in SO2F2: experiment and theory

The gas-phase ion-molecule reactions of simple anions (HO−, CH3O−, NH2−) with SO2F2 proceed with rate constants close to the collision limit. The energy surface for the OH−/SO2F2 reaction has been characterized by ab initio calculations using basis functions adapted for a pseudopotential and corrected for anionic systems by the generator coordinate method (GCM) at the QCISD(T)/(ECP/TZV/GCM) level. The calculations indicate that reaction occurs by initial addition of the anion to SO2F2 to form a hypervalent sulfur species. The high efficiency of the reaction is associated with a low energy barrier separating the initial adduct from the product side ion-neutral complex.