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 have been investigated by potentiometric measurements at 25-degrees-C and I = 0.10 mol dm-3 (NaNO3). Tetramer formation has been observed at high concentrations of dimethyltin(IV) ion up to 6 x 10(-2) mol dm-3. The polymer structure of [(SnMe2)2(OH)3]ClO4 has been determined by crystal 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. The polymer consists of five-co-ordinate tin(IV) units with di- and monohydroxo bridging. The co-ordination geometry of the tin unit is a distorted trigonal bipyramid with two methyl groups and one mu-hydroxo group in equatorial positions and the other two mu-hydroxo groups in axial positions. The species formed by hydrolysis have been characterised on the basis of the molecular structure in the crystals and are discussed together with their pK(a) values.