Hydrolysis, polymerisation, and structure of dimethyltin (IV) in aqueous solution. Molecular structure of the polymer [(SnMe2)2(OH)3]ClO4

Abstract

The hydrolysis and polymerisation equilibria of dimethyltin(IV) ion have been investigated by potentiometric measurements at 25 °C and I= 0.10 mol dm^–3(NaNO₃). Tetramer formation has been observed at high concentrations of dimethyltin(IV) ion up to 6 × 10^–2 mol dm^–3. The polymer structure of [(SnMe₂)₂(OH)₃]ClO₄ has been determined by crystal structure analysis: triclinic, space group P, a= 8.533(1), b= 9.474(1), c= 9.479(2)Å, α= 88.27(1), β= 68.97(1). γ= 74.44(1)°, Z= 2. The final R value is 0.029. The 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 distorted trigonal bipyramid with two methyl groups and one µ-hydroxo group in equatorial positions and the other two µ-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_avalues.