Gas-phase stability of cluster ions SF m (+) (SF 6) n with m = 0-5 and n = 1-3

The gas-phase stabilities of cluster ions SF m (+) (SF6) n with m = 0-5 were determined by using a high pressure mass spectrometer. The bond energies of SF m (+) (SF6)1 were found to be less than 10 kcal/mol and to decrease with m = 0 → 5. There appear to be rather large gaps in the bond energies between n = 1 and 2 for the clusters SF m (+) (SF6) n with m = 0-4. The structures of SF 5 (+) , SF(+) (SF6)1 SF 3 (+) (SF6)1 and SF 5 (+) (SF6)1, were investigated by ab initio molecular orbital calculations. For SF 5 (+) , the D 3h geometry is found to be most stable and C 4v is a transition state of the Berry pseudorotation. For the ion-molecule complexes, the "on-top hat" models were found to be the most stable structures.