Triorganotin species

Both dialkyltins and trialkyltms inhibit oxidative metabolism, but in different ways. Triorganotin species act on the coupling ATPase, but the diorganotins act on substrate oxidation. 

While organotin species are stable in sterile environments (both aqueous as well as solid phases) and in the dark at usual environmental temperatures, the breakdown of triorganotin species occurs rapidly in sunlight and by biological action. 

The triorganotin species have been used as industrial biocides for over 30 years [117, 118]. Examples are triphenyltin hydroxide (structure 5) for fungal diseases on celery, rice, sugar beets, and coffee tricyclohexylstannyl-1,2,4-triazole (structure 6) as an acaricide for apple, pear, and citrus fruit trees bistributyltin oxide (structure 7) as a wood preservative and tributyltin-methylacrylate monomers (structure 8) polymerized with other acrylates to yield a marine antifoulant polymer that prevents the build of up barnacles, algae, and other marine animals on ships. 

In addition, organometallic forms of several metals (e.g., methylmercury, triorganotin species), which are lipophilic, are bioaccumulated by aquatic organisms much more so than inorganic forms of the metals, and some organometallic complexes are toxic to aquatic biota (see also Chapter 8, Section 2). 

The toxicity of the tetraorganotins has beenUtde studied. Available Hterature indicates that tetrabutyltin and the higher tetraalkyltins are substantially less toxic than triorganotins to mammals if taken orally (175). The high toxicity reported for tetraethyltin (LD g = 9 16 mg/kg) appears to be caused by its rapid conversion in the Hver to a triethyl tin species. 

It may, therefore, be concluded that, within a generally consistent pattern of behavior, organotins are degraded in the environment to afford nontoxic, inorganic tin species. A generalized, environmental-breakdown scheme for the commercially used tributyl- and triphenyltin derivatives (516), that is probably applicable to other triorganotins, is illustrated in Scheme 1. 

Reactions of triorganotin hydrides with amines resulted in the formation of the corresponding ditin species according to equation 4454- 56. 

Tin is thought to be an essential trace element for some species, although its precise role remains unknown. Some therapeutic uses of tin compounds have been proposed, and triorganotin carboxylates are effective bacteriocides and pesticides. Tin is, of course, an important component of a number of alloys, with copper in bronze (the Bronze age began about 3500 BC), and with lead in pewter. 

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