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) less than or equal to 1) , at different temperatures (15 less than or equal to T/degrees C less than or equal to 45) by potentiometric measurements (H+-glass electrode). By co nsidering the generic hydrolytic reaction pCH(3)Sn(3+) + qH(2)O = (CH3Sn)(p )(OH)(q)(3p-q) + pH(+) (log beta(pq)), we have the formation of five specie s and log beta(12) = -3.36, log beta(13) = -8.99, log beta(14) = -20.27 and log beta(25) = -7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis c onstant is log beta(11) = -1.5 (+/- 0.5). The dependence on ionic strength of log beta(pq) is quite different in NaNO3 and NaCl solutions, and the for mation at low pH values of the species CH3Sn(OH)Cl+ has been found with log beta = -1.40. Hydrolysis constants strongly depend on temperature and from the relationships log beta(pq) = f(T), Delta H degrees values have been ca lculated, Speciation problems of CH3Sn3+ in aqueous solution are discussed. Copyright (C) 1999 John Wiley & Sons, Ltd.