Equilibrium, structural and biological activity studies on organotin(IV)n+ complexes

Organotin(IV) compounds are characterized by the presence of at least one covalent C–Sn bond. The compounds contain tetravalent {Sn} centers and are classified as mono-, di-, tri-, and tetraorganotin(IV), depending on the number of alkyl (R) or aryl (Ar) moieties bound. The anions are usually Cl, F, O2, OH,–COO, or –S. It seems that the nature of the anionic group has only secondary importance in biological activity. The rapid rise in the industrial (catalyst in PVC and foam production), agricultural (fungicides and acaricides), and biological applications (wood, stone, and glass preservatives) of organotin(IV) compounds during the last few decades has led to their accumulation in the environment and, consequently, in biological systems. It is well known that organotin(IV) compounds display strong biological activity. Most organotin(IV) compounds are generally very toxic, even at low concentration. The biological activity is essentially determined by the number and nature of the organic groups bound to the central {Sn} atom. The [R3Sn(IV)]+ and [Ar3Sn(IV)]+ derivatives exert powerful toxic action on the central nervous system. Within the series of [R3Sn(IV)]+ compounds, the lower homologs (Me, Et) are the most toxic when administrated orally, and the toxicity decreases progressively from propyl (Pr) to octyl (Oc), the latter being not toxic at all towards humans.