Disproportionation reactions within the series of coordinated monoorganostannanes

Interaction of monoorganotin trichlorides (RSnCl3, R = Ph, Vin, All, Bn and c-Pr) with O-TMS-amides of 2-hydroxycarboxylic acids afforded a number of mononuclear and binuclear organotin complexes (2a–j). These organotin complexes disproportionate into diorganostannanes and inorganic coordination compounds containing two O,O-chelated ligands (3a–c). All the complexes were characterized by multinuclear NMR spectroscopy in solution and X-ray diffraction in crystalline state (2a, 2b, 2j, 3b, 3c). It was found that disproportionation reaction proceeded only for very well dissolved substances in concentrated solutions upon heating. The tendency for disproportionation depends on the nature of a substituent and decreases as follow: Vin ≈ Allyl > Bn > Ph ≈ c-Pr >> Alk. It is believed that the key step of the mechanism of disproportion reaction is a ligand exchange, which is possible only in the case of binuclear complexes acting as intermediate compounds.