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 SnOC 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.