Hydrolysis of the mixed-ligand dimethyltin(ethoxy)ethanesulfonate, [Me2Sn(OEt)(OSO2Et)](n) (1a) in moist hexane proceeds via disproportionation and partial cleavage of Sn-C and S-C bonds to afford a novel oxo-/hydroxo-organotin cluster of the composition [(Me2Sn)(MeSn)(4)(OSO2Et)(2)(OH)(4)(O)(2)(SO3)(2)] (1) bearing both mono- and dimethyltin fragments and in situ generated sulfite (SO32-) anion in the structural framework. On the other hand, similar reactions with analogous mixed ligand diorganotin precursors, [R2Sn(OR1)(OSO2R1)](n) (R=n-Bu, R-1=Et (2a); R=Et, R-1=Me (3a)), result in the formation of tetranuclear diorganotin clusters, [{(n-Bu2Sn)(2)(OH)(OSO2Et)}](2) (2) and [(Et2Sn)(4)(OH)(O)(2)(OSO2Me)(3)] (3), respectively. The activation of the Sn-C or S-C bond is not observed in these cases. These findings provide a preliminary insight into the unusual reactivity of la under hydrolytic conditions.