Equilibrium and kinetic studies of the stannate(IV)-polyol reaction

  • Jolocam Mbabazi Department of Chemistry, Makerere University, P.O. Box 7062, Kampala, Uganda
  • John Wasswa Department of Chemistry, Makerere University, P.O. Box 7062, Kampala, Uganda
  • Muhammad Ntale Department of Chemistry, Makerere University, P.O. Box 7062, Kampala, Uganda
Keywords: Hexahydroxystannate(IV), Polyol, Stability constants, Conductimetric method, Mechanism

Abstract

The stability constants of 1:1 stannate(IV)-polyol complexes in aqueous media have been determined using a conductimetric technique. The constants are fairly large, and lie in the range 5.3-123.0 for the ten ligands investigated. These values were subsequently used in conjunction with kinetic data to postulate a mechanism involving the species Sn(OH)5- as intermediate in the formation of the chelates. The stannate(IV)-polyol reaction, though taking place at higher pH values, is acid-catalysed and follows first-order kinetics in the oxyanion, but at large ligand-oxyanion mole ratios the reaction exhibits zero-order rate dependence on the polyol. These features taken together are consistent with a unimolecular nucleophilic substitution on the oxyanion.

 

KEY WORDS: Hexahydroxystannate(IV), Polyol, Stability constants, Conductimetric method, Mechanism

 

 

Bull. Chem. Soc. Ethiop. 2010, 24(3), 447-456.

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