Hydrolysis, Solvation, and Reduction of SO3, S2O6, ClO3(OH), Cl2O7, and ArO4Relating Chemical Properties to the Instability of SO, ClO, and ArO Groups
journal contributionposted on 07.12.2001, 00:00 by J. R. Tobias Johnson, Itai Panas
Successive water addition to the mononuclear species SO3(g) and ClO3(OH)(g) and ArO4(g), as well as the binuclear clusters S2O6(g) and Cl2O7(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 SO, ClO, and ArO bonds. This instability causes the acidity displayed by water solutions of SO2(OH)2 and ClO3(OH) and makes the Cl and Ar systems prone to O2(g) evolution. The latter system is also reduced directly by water, while the reduction of SO2(OH)2 to H2S requires a reducing agent of equivalent power to H2. Three water ligands are necessary to produce nanoscale deprotonation of SO2(OH)2 and ClO3(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.