Dimethyltin(IV) complexes with zwitterionic buffers (Mes and Mops)

Abstract

Equilibrium studies in aqueous solution are reported for dimethyltin(IV) complexes of the zwitterionic buffers “Good’s buffer”, such as Mes and Mops ( L). Stoichiometry and stability constants for the complexes formed were determined at different temperature and ionic strength 0.1 M NaNO 3. The results showed the best fit of the titration curves were obtained when complexes ML, MLH −1, MLH −2, and MLH −3 were expected beside the hydrolysis products of the dimethyltin(IV) cation. The thermodynamic parameters Δ H°, Δ S° and Δ G° calculated from the temperature dependence of the formation constant of the dimethyltin(IV)–Mes complex was investigated. The effect of dioxane as a solvent on the formation constants of dimethyltin(IV)–Mes complex was discussed. The concentration distribution of the various complex species was evaluated as a function of pH. The bonding sites of the dimethyltin(IV) complexes in solid state with Mes and Mops were characterized by means of elemental analyses and FTIR. The NMR ( 1H, 13C) spectra of the DMT–Mes complex exhibits the strongly distorted octahedron geometry around tin atom. Also, thermal analyses (TGA and DTA) were discussed. Thermodynamic parameters such as activation energy ( E a), pre-exponential factor ( A), entropy of activation (Δ S ∗) and free energy of activation (Δ G ∗) have been calculated for each step, employing integral method Coats and Redfern. The reaction enthalpy (Δ H) is obtained from DTA data.