Hydrolysis of methyltin(IV) trichloride in aqueous NaCl and NaNO3 solutions at different ionic strengths and temperatures

The hydrolysis of methyltin(IV) trichloride (CH3SnCl3) has been studied in aqueous NaCl and NaNO3 solutions (0 < I/mol dm−3 ≤ 1), at different temperatures (15 ≤ T/°C ≤ 45) by­potentiometric measurements (H+-glass electrode). By considering the generic hydrolytic <?tw=97.2%>reaction pCH3Sn3+ + qH2O = (CH3Sn)p(OH)q3p−q<?tw>­+ qH+ (logβpq), we have the formation of five species and logβ12 = −3.36, logβ13 = −8.99, logβ14 = −20.27 and logβ25 = −7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis constant is logβ11 = −1.5 (± 0.5). The dependence on ionic strength of logβpq is quite different in NaNO3 and NaCl solutions, and the formation at low pH values of the species CH3Sn(OH)Cl+ has been found with logβ = −1.40. Hydrolysis constants strongly depend on temperature and from the relationships logβpq = f(T), ΔH ° values have been calculated. Speciation problems of CH3Sn3+ in aqueous solution are discussed.