Quantum chemical study of thiosulfinic acids and their anions

The electronic and geometrical structures of thiosulfinic acids, RSSOH, 1, (1a, R = H; 1b, R = CH3; 1c, R = t-C4H9; 1d, R = C6H5; 1e, R = F) and their anions have been investigated by the ab initio and density functional methods. The calculations show that the stability of the thiolo-tautomers of 1, RS(O)SH, and the thiono-tautomers, RS(S)OH, is almost the same in the gas phase, the energy of the thiolo-tautomers being slightly lower. The tautomers of 1 having the thiosulfone structure, RS(O)(S)H, were found to be the least stable. The thiosulfinate anions show ambident character with the negative charge dispersed over terminal O and S atoms and are stabilized by electronegative substituents.