proposed herein are bis - trialkylstannyl derivatives of chlorinated polycyclic dicarboxylic acids , of the general formula ## str1 ## wherein r is a lower alkyl , r &# 39 ;= h , ch 3 , n = 0 , 1 , which are obtained by a condensation reaction of anhydrides of the respective dicarboxylic acids with hexaalkyldistannoxanes r 3 snosnr 3 , wherein r is a lower alkyl , in the medium of an organic solvent . the resulting compounds exhibit antifouling activity and represent active components of coatings intended to protect ships &# 39 ; bottoms and the submerged parts of various hydraulic structures against fouling . antifouling polymer coatings containing said compounds are more effective and durable , and over five and more years prevent biomasses of marine organisms of vegetal and animal origin from accumulating on the surface .