This review summarizes the study of the formation of SO2 -X- , SOCl2 -X- , SOBr2 -X- , SO2 Cl2 -X- complexes (X- = Cl- , Br- , I- , and SCN- ) in pure and mixed solvents of acetonitrile and dimethylsulfoxide over the past 30 years. Spectrometry (290nm-380nm) was the principal technique used for the investigation, since the enthalpies of formation Δ Hfo of the above complexes are low ( -6.03  -22.51 kJ/mol ). The stability of the complexes depend on the nature of the solvent, acceptor properties of the sulfur compounds, the donor properties of the halide ions and the temperature of the reaction. Also, it was found that the extent of the iodide ion replacement reactions by the other halide depends on the nature of the solvent and the halide ions. SO2 -I- + X- → SO2 -X- + I- The structures of SO2 -X- compounds are pyramidal, with X- at the top of the pyramid, the S atom at the center, and the angle depends on the nature of the halide ion.

This review summarizes the study of the formation of SO2 -X- , SOCl2 -X- , SOBr2 -X- , SO2 Cl2 -X- complexes (X- = Cl- , Br- , I- , and SCN- ) in pure and mixed solvents of acetonitrile and dimethylsulfoxide over the past 30 years. Spectrometry (290nm-380nm) was the principal technique used for th...