Organotin(IV) derivatives of mercaptosuccinic and thiodiacetic acids

Di- and tri-organotin(IV) complexes of general formula R₂SnAH, (R₃Sn)₂AH, R₂SnB, (R₃Sn)₂B (A=dianion of mercaptosuccinic acid; B=dianion of thiodiacetic acid; R=Me, Et, nPr, nBu, nOct in R₂Sn and nBu in R₃Sn) have been synthesized and characterized by elemental analysis, IR and ¹H and ¹³C NMR spectroscopy. These data support the preferential binding of sulphur over carboxylate by tin(IV) in R₂SnAH and (R₃Sn)₂AH. R₂SnAH complexes are assigned pentacoordinated bridged polymeric trigonal bipyramidal geometry whereas (R₃Sn)₂AH complexes are monomeric with trigonal bipyramidal geometry at tin arising from a bidentate carboxylate group at one tin atom and from weak bonding via Sn←O?C at the other tin atom. In R₂SnB and (R₃Sn)₂B, tin(IV) binds to two carboxylate groups in a unidentate and a bidentate manner respectively, resulting in tetracoordinated and pentacoordinated structures. Potential uses of these compounds are discussed.