Experimental gas-phase high-pressure equilibrium determinations of Delta H degrees(rxn) and Delta S degrees(rxn) for the reactions : C-C4H8S+ + c-C4H8S reversible arrow [c-C4H8S therefore c-SC4H8](+), c-C5H10S+ + c-SC4H8 reversible arrow [c-C5H10S therefore c-SC4H8](+) and c-C5H10S+ + c-SC5H10 reversible arrow [c-C5H10S therefore c-SC5H10](+) have been carried out. The product ions of these reactions are examples of species which may contain two-center three-electron (2c-3e) sulfur-sulfur bends. The heats of reaction result in the following bond enthalpies for the 2c-3e bonded adducts : 115 kJ/mol for [c-C4H8S therefore c-SC4H8](+), 108 kJ/mol for [c-C5H10S therefore c-SC4H8](+), and 106 kJ/mol for [c-C5H10S therefore c-SC5H10](+) while the entropies of reaction are -119, -109, and -112 J/mol K, respectively. Metastable and collision induced dissociation (CID) spectra provide experimental evidence of the atomic connectivity and of the 2c-3e bonds. Metastable cleavage of the S therefore S 2c-3e bonds appear to occur with no reverse activation barriers and to result in small average kinetic energy releases. In the unsymmetric ion [c-C5H10S therefore c-SC4H8](+), both ionic moieties are observed but the intensity is greater for retention of the charge on the larger ring, c-C5H10S+. Cleavage of the S therefore S 2c-3e bonds by CID of the adducts yields the most intense product ions. Reaction of [c-C4H8S](+) with c-C2H4S entailed a ring expansion with incorporation of a sulfur atom to produce [c-C4H8S2](+). However, in a similar experiment, no expansion occurred when c-C5H10S+ and c-C2H4S reacted. In addition, no expansion reaction was observed for either [c-C4H8S](+) or [c-C5H10S](+) reacting with c-C3H6S.