# Vol. 39 Issue 1

##### Maaz A. Ali and Hussin A. M. Ahmed

Over the last ten years charge-transfer complexes of the type $\mathrm{SO}_{2}-\mathrm{X}^{-}, \mathrm{SOCl}_{2}-\mathrm{X}^{-}$, $\mathrm{SOBr}_{2}-\mathrm{X}^{-}, \mathrm{SO}_{2} \mathrm{Cl}_{2}-\mathrm{X}^{-}, \mathrm{SeO}_{2}-\mathrm{X}^{-}$and $\mathrm{SeOCl}_{2}-\mathrm{X}^{-}\left(\mathrm{X}^{-}=\mathrm{Cl}, \mathrm{Br}, \mathrm{I}\right.$ and $\left.\mathrm{SCN}\right)$ were identified and their thermodynamic parameters determined in MeCN, DMSO and their mixtures over the temperatures $10-35^{\circ} \mathrm{C}$. The stability constants in the $\mathrm{MeCN}$ DMSO mixed solvents pointed to the existence of solute-solvent and solvent-solvent interactions (Salama and Wasif $1971,1973,1975$ and b, 1978, 1980). Solute solvent interactions were shown to exist (Salama and Wasif 1971, 1973, 1975a) and in fact account for the change in stability constants of the above complexes in MeCN and DMSO by solvation of halide ligands and adduct formation between solvent molecules and sulphur acceptor molecules. The present work aims to confirm the existence of solvent-solvent interactions predicted earlier (Salama and Wasif 1978, 1980).