The synthesis of a number of trialkyl- and triaryl-tin maleates, methyl maleates, and fumarates is described. The preparation of dibutylchlorotin methyl maleate and dibutyltin bis(methyl maleate) and reaction of these compounds with 2,2′-bipyridyl are discussed. Treatment of dibutyltin oxide with maleic acid gives a mixture from which three forms of dibutyltin maleate have been isolated. The structures of all these compounds are discussed with reference to their infrared spectra.