The structure and Lewis acidity of some triorganotin carboxylates

Abstract

A series of tributyltin carboxylates and one triphenyltin carboxylate were prepared by reaction of the tin oxide with the appropriate carboxylic acid. The tin-119 chemical shift of each compound in chloroform and, for the solid carboxylates, in the solid state was determined. A comparison of the solution (109–157 ppm) and solid state shifts (−53 to +45 ppm) indicates that the compounds exist primarily as monomeric 4-coordinate species in solution and as 5-coordinate, presumably polymeric species in the solid state. The Lewis acidity of the compounds toward triethylphosphine oxide (TEPO) was determined by recording the 31P chemical shift in a mixture of the carboxylate and TEPO in toluene as a function of concentration. Predominant 1 : 1 adduct formation was observed with equilibrium constants ranging from 5 to 320. The magnitude of the constant can be explained by the electronic effects of the substituents surrounding the tin.