Dialkyltin exchange reaction

The exchange reaction between the Sn-O bond in dialkyltin oxides, R2SnO, and the SnCl bond in organotin halides is discussed in Section 12.4. 

The Ligand Exchange Reaction of Some Dialkyltin Dimercaptides and Dicarboxylates with Dialkyltin Dichlorides... 

The existence of a ligand exchange reaction between dialkyltin dimercaptides and dicarboxylates (typical poly(vinyl chloride) stabilizers) and dialkyltin dichlorides is demonstrated by 1H and 13C NMR. Dibenzyl- and dibutyltin dimercaptides undergo the reaction instantaneously and quantitatively at 25° C to yield dialkylchlorotin mercaptides. Dialkyltin dicarboxylates and dimethyltin dimercaptides appear to participate in an equilibrium exchange reaction with dialkyltin dichlorides in which the individual components are not identifiable by NMR at 25°C. These results are discussed as they pertain to poly(vinyl chloride) stabilization. 

These exchange reaction phenomena may be general for all types of organotin PVC stabilizers. In the cases where an equilibrium exchange reaction is observed (dimethyltin dimercaptides and dialkyltin dicar-boxylates), the equilibrium at PVC processing temperatures may be far toward the dialkylchlorotin species and thus the mechanism is still operative. 

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