Structures, energies and vibrational spectra of four isomers of hydrogendioxothiosulfate(IV) anion (HS2O2–) and of the related anion ClSO2–: an ab-initio molecular-orbital study

Abstract

The ground-state geometries, energies, atomic charges and vibrational wavenumbers of four isomeric forms of the HS₂O₂^– anion as well as of the related ClSO₂^– anion have been calculated at the HF/6–311G** and HF/6–311 ++ G** levels. Electron correlation has been taken into account according to second order Møller-Plesset perturbation theory (MP2). The most stable isomer of HS₂O₂^– is HSSO₂^–1 the formation of which from SO₂ and HS^– is exothermic by ca., 108 kj mol ^–1(calculated reaction energy). The analogous formation of ClSO₂^– from SO₂ and Cl^– is exothermic by 79 KJ mol^–1. Slightly less stable than 1 are HOS(S)O^–2 and HS(S)O₂^–4 and least stable is the isomer HOSSO^–3. Anions 1-3 are of C₁ symmetry and 4 as well as ClSO₂^– are of C_ssymmetry. The likely intermediates of the reaction between H₂S and SO₂ in its early stage are discussed. The calculated wavenumbers of the fundamental modes of ClSO₂^– agree well with experimental data.