The small binding energies of the negative cluster ions: SF 5−(SF 6) 1, SF 6−(SF 6) 1 and F −(SF 6) n ( n = 1 and 2), in the gas phase

Abstract

The gas-phase clustering reactions of SF 5 −, SF 6 − and F − ions with SF 6 were measured using a high-pressure mass spectrometer. The bond energies of SF 5 −(SF 6) 1 and SF 6 −(SF 6) 1 were estimated to be ⩽2.3 kcal/mol. The bond energies of F −(SF 6) n with n = 1 and 2 were determined to be 5.4 and ≈4.1 kcal/mol, respectively. This result indicates that the SF 6 molecule is the weakest electrophilic reagent toward F − ever reported. This is mainly due to the exchange repulsion between the negative ions and fluorine atoms surrounding the reactive S atom. The structure of the cluster ion F −(SF 6) 1 whose binding energy was surrrisingly small was investigated by ab initio MO calculations.