Synthesis and structural determination of ionic triphenyltin complexes of mercaptoacetic and 3-mercaptopropionic acids

Two ionic triphenyltin complexes were obtained when two thiocarboxylic acids, mercaptoacetic acid and 3-mercaptopropionic acid, were mixed with triphenyltin hydroxide in the presence of dicylcohexylamine. Their structures have been characterized by IR and multi-nuclear (1H, 13C{1H} and 119Sn{1H}) NMR spectroscopies. Coordination difference was observed between triphenyltin complexes of mercaptoacetate and 3-mercaptopropionate. The coordination assignments of the tin atoms in the two triphenyltin complexes are confirmed by X-ray crystallographic studies. In the solid state, the bidentate binding mode of mercaptoacetate ligand gives a five-coordinate ionic triphenyltin complex with a cis-trigonal-bipyramid (TBP) geometry around tin, while the tin in dicyclohexylammonium 3-mercaptopropionatotriphenylstannate was found to be four-coordinate with tetrahedral geometry around tin, as the 3-mercaptopropionate is monodentate via sulfur. Important hydrogen bonding between dicyclohexylammonium and carboxylate have been observed for both complexes.