Thermochemistry of the reactions of F+(P-3) and F+(D-1) with hydrogen sulphide: A molecular orbital study

The potential energy surfaces (PESs) of the reactions of F+ in its P-3 ground state and in its D-1 first excited state with H2S have been studied by means of G2 and complete-basis set high-level ab initio techniques. Singlet- and triplet-state cations present important differences regarding their relative stabilities and bonding characteristics. The former are covalently bound compounds while the latter are weakly bound species. The triplet PES is consistent with the experimental evidence which show that HS+ and S+ are the only products of the reaction between F+(P-3) and H2S. The reaction of H2S with F+(D-1) would yield the two possible protonated forms of thiohypofluorous acid, the sulphur protonated species being the most stable. However, also in this case, the formation of HS+ and S+ as products of the reaction cannot be discarded. The estimated heats of formation for the most stable FSH2+ singlet- and triplet-state cations are 173 +/- 1.5 and 191 +/- 5 kcal mol(-1) respectively.