THE STRUCTURE AND LEWIS ACIDITY OF SOME TRIORGANOTIN CARBOXYLATES

A series of tributyltin carboxylates and one triphenyltin carboxylate were prepared by reaction of the tin oxide with the appropriate carbox ylic acid. The tin-119 chemical shift of each compound in chloroform a nd, for the solid carboxylates, in the solid state was determined. A c omparison 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 polymer ic species in the solid state. The Lewis acidity of the compounds towa rd triethylphosphine oxide (TEPO) was determined by recording the P-31 chemical shift in a mixture of the carboxylate and TEPO in toluene as a function of concentration. Predominant 1 : 1 adduct formation was o bserved with equilibrium constants ranging from 5 to 320. The magnitud e of the constant can be explained by the electronic effects of the su bstituents surrounding the tin.