Capture of sulfur dioxide using sulfur oxydianions: synthesis and characterization of two novel compounds

Abstract

One mole equivalent of SO2 reversibly reacts with [N(CH3)4]2SO4(s) to give [N(CH3)4]2S2O6(s) (1) containing the [O3SOSO2]2- ion, shown by Raman and IR to be an isomer of the [O3SSO3]2- dianion. The experimental and calculated (B3PW91/6-311+G(3df)) vibrational spectra are in excellent agreement and the IR spectrum is similar to that of the isoelectronic O3ClOClO2. Crystals of [N(CH3)4]2(O2SO)2SO2•SO2 were isolated from a solution of [N(CH3)4]2SO4 in liquid SO2. The X-ray structure showed that it contained the [(O2SO)2SO2]2- dianion (2). The characterized N(CH3)4 + salts 1 and 2 are the first two members of the (SO4)(SO2)x 2- sulfur oxydianions analogous to the well-known small cation salts of the SO4(SO3)x 2- polysulfates.