Preparation of some ketoorganostannanes and ketoorganochlorostannanes. Intramolecular coordination in ketoorganochlorostannanes

Abstract

Ketoorganostannanes of the structure Me 3Sn(CH 2) n COR with n = 2,3 and R = Me, Ph have been prepared by the oxidation of the corresponding alcohols, and by the reaction of the appropriate cyanoalkyltrimethylstannanes with methyl or phenyl Grignard reagents. The ketoorganostannanes have been converted to the chloro analogs Me 2Sn(Cl)(CH 2) n COR by methyl-chlorine exchange with trimethyltin chloride. The reactions with these ketones are considerably faster than that with n-butyltrimethylstannane, suggesting that intramolecular nucleophilic catalysis of an electrophilic displacement reaction occurs. Evidence that the ketoorganochlorostannanes have a structure involving intramolecular coordination between the carbonyl oxygen and the tin is provided by studies of the infrared, ultraviolet, proton and carbon-13 magnetic resonance, and Mössbauer spectra. Pyridine is shown to compete with intramolecular carbonyl in coordination to the chlorotin function, the effect being more pronounced when n = 3 than when n = 2, reflecting the greater stability of the five-membered ring complex.