Hydrolysis, Solvation, and Reduction of SO3, S2O6, ClO3(OH), Cl2O7, and ArO4Relating Chemical Properties to the Instability of SO, ClO, and ArO Groups

Successive water addition to the mononuclear species SO 3 (g) and ClO 3 (OH)(g) and ArO 4 (g), as well as the binuclear clusters S 2 O 6 (g) and Cl 2 O 7 (g), is studied by means of quantum chemistry. A large basis set effect is observed for the S−O, Cl−O, and Ar−O bond distances, as well as for redox energetics. While the 6-311+G(d,p) basis set is enough for O and H atoms, S, Cl, and Ar require the 6-311+G(3df) set for an accurate description. Given this combination of basis sets, B3LYP is found to give very good results of equal quality to high-level methods. The dominating chemical feature that is monitored is the instability of the S O, Cl O, and Ar O bonds. This instability causes the acidity displayed by water solutions of SO 2 (OH) 2 and ClO 3 (OH) and makes the Cl and Ar systems prone to O 2 (g) evolution. The latter system is also reduced directly by water, while the reduction of SO 2 (OH) 2 to H 2 S requires a reducing agent of equivalent power to H 2 . Three water ligands are necessary to produce nanoscale deprotonation of SO 2 (OH) 2 and ClO 3 (OH). The hydrolytic cleavage of the S−O−S and Cl−O−Cl bridges is exothermic by 23−30 kJ/mol, which explains the sensitivity to excess of water displayed by these polymers.