Potentiometric Studies on Binary Complexes of Catecholic Compounds with Organotin (IV) Cations

potentiometric studies are performed in aqueous solution in order to characterize the interaction of dimethyltin (IV) [DMT] and Trimethyltin (IV) [TMT] cation with catecholic ligands. Experiments are performed at three different temperatures (20C, 30C and 40C) and at three ionic strengths ( = 0.05, 0.10 and 0.15 M). The analysis of stability constant (log) and stability order of investigated metal-ligand species [MHL, ML, ML (OH) and ML (OH) 2] are obtained by using computer programme SCOGS (stability constants of generalized species). The complex species formed are water soluble in the experimental pH range (3.0-10.5). Thermodynamic stability constants along with thermodynamic parameters i. e. standard free energy change (-G) enthalpy change (-H) and entropy change (-S) are calculated for all the systems. The thermodynamic stabilities of DMT species are found to be more than TMT (IV) species. High stability of 4-methylcatechol complexes is attributed to greater basicity.