Potentiometric determination of stability constants and thermodynamic data for dimethyltin(IV) dichloride complexes with iminobis(methylphosphonic acid) in water and dioxane-water mixtures

The interaction of dimethyltin(IV) (DMT) with iminobis(methylphosphonic acid) (IDP) was investigated at 25 A degrees C and ionic strength 0.1 mol dm(-3) NaCl using the potentiometric technique. The formation constants of the complexes formed in solution were calculated using the non-linear least-squares program MINIQUAD-75. The stoichiometry and stability constants for the complexes formed are reported. The results showed the formation of 110, 111, 112, 11-1, and 11-2 for DMT-IDP complexes. The concentration distribution of the various complex species was evaluated. The effect of dioxane as a solvent on the hydrolysis of DMT and both the protonation and the formation constants of DMT complexes with IDP was discussed. The thermodynamic parameters Delta HA degrees and Delta SA degrees were calculated from the temperature dependence of the equilibrium constants. The effect of ionic strength on the hydrolysis of DMT, the protonation of IDP, and the formation constants of DMT-IDP complexes was also discussed.