GAS-PHASE STABILITY OF CLUSTER IONS SFM-5 AND N=1-3( (SF6)(N) WITH M=0)

The gas-phase stabilities of cluster ions SFm+(SF6)(n) with m = 0-5 we re determined by using a high pressure mass spectrometer. The bond ene rgies of SFm+(SF6)(1) were found to be less than 10 kcal/mol and to de crease with m = 0 --> 5. There appear to be rather large gaps in the b ond energies between n = 1 and 2 for the clusters SFm+(SF6)(n) with m = 0-4. The structures of SF5+, SF+ (SF6)(1), SF3+ (SF6)(1), and SF5+ ( SF6)(1) were investigated by ab inito molecular orbital calculation. F or SF5+, the D-3h geometry is found to be most stable and C-4v is a tr ansition state of the Berry pseudorotation. For the ion-molecule compl exes, the ''on-top hat'' models were found to be the most stable struc tures.