HYDROLYSIS, POLYMERIZATION, AND STRUCTURE OF DIMETHYLTIN(IV) IN AQUEOUS-SOLUTION - MOLECULAR-STRUCTURE OF THE POLYMER [(SNME2)2(OH)3]CLO4

The hydrolysis and polymerisation equilibria of dimethyltin(IV) ion ha ve been investigated by potentiometric measurements at 25-degrees-C an d I = 0.10 mol dm-3 (NaNO3). Tetramer formation has been observed at h igh concentrations of dimethyltin(IV) ion up to 6 x 10(-2) mol dm-3. T he polymer structure of [(SnMe2)2(OH)3]ClO4 has been determined by cry stal structure analysis: triclinic, space group P1BAR, a = 8.533(1), b = 9.474(1), c = 9.479(2) angstrom, alpha = 88.27 (1 ), beta = 68.97 ( 1 ), gamma = 74.44 (1 )-degrees, Z = 2. The final R value is 0.029. Th e polymer consists of five-co-ordinate tin(IV) units with di- and mono hydroxo bridging. The co-ordination geometry of the tin unit is a dist orted trigonal bipyramid with two methyl groups and one mu-hydroxo gro up in equatorial positions and the other two mu-hydroxo groups in axia l positions. The species formed by hydrolysis have been characterised on the basis of the molecular structure in the crystals and are discus sed together with their pK(a) values.