| Abstract: | It has long been appreciated that mercaptoester/Cl exchange equilibria in mono- and dialkyltin mercaptoester/chlorides are important in understanding the stabilization of PVC by alkyltin mercaptoesters (1–3). More recently, IR studies have demonstrated the existence of similar equilibria in mixed mono-/dialkyltin systems; it has been suggested that these exchange reactions may be the source of synergism in the mixed mono-/dialkytin mercaptoester stabilizers (4). The ability to study these systems by IR and NMR methods is based upon the phenmenon of carbonyl to Sn coordination in these compounds and its sensitivity to molecular environment, principally the electronegativity of the tin atom. Our previous studies have now been extended to include estertin (β-carboalkoxyethyltin) mercaptoesters and mercaptoester/chlorides. In contrast to the simple alkyltin systems, the position of the respective mercaptoester/Cl exchange equilibria are dominated by carbonyl to Sn coordination from the ester group of the β-carboalkoxyethyl moiety. Based on the same phenomenon of carbonyl to tin coordination, the nature of alkyl- and estertin mercaptoesters containing alkyltin sulfides has been looked at to a very limited extent. |
