5 , NH(n-Pr), NH(n-Bu), NH(i-Bu)) has been synthesized using a low-temperature method. Their structures have been characterized by IR, Mössbauer and NMR spectroscopies. In the solid state, an unsymmetrical chelation of the dithiocarbamate ligand was found in all the compounds synthesized. The observation of two Sn-S distances in the compounds was confirmed in the crystal structure of tricyclohexyltin N-n-butyldithiocarbamate. In solution, the compounds were found to exhibit distorted tetrahedral structures. The insecticidal activities of the title compounds were screened against the second larval instar of the Anopheles stephensi Liston and Aedes aegypti (L.) mosquitoes. Results from the screening studies indicated that the triorganotin dithiocarbamates were effective larvicides against both species of larvae. However, there were no significant activity differences between the triphenyltin and tricyclohexyltin derivatives. A quantitative structure-activity relationship was also developed for the An. stephensi.

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A series of tris-(para-substitutedphenyl)tins (X − C 6 H 4 ) 3 SnY, where X = Cl, F, CH 3 and SCH 3 and Y = Cl, OH and OAc, was synthesized. The structures of the compounds were primarily characterized by Mössbauer spectroscopy. Based on the spectroscopic data, the chloride derivatives were determined to be four-coordinated monomers and the acetate and hydroxide compounds were found to be fivecoordinated polymers. The compounds were screened against the second larval instar of the Anopheles stephensi and Aedes aegypti mosquitoes. For the An. stephensi larvae, the compounds that had the highest toxicity were those that contained a single atom substituent on the phenyl ring, and the least effective compounds contained the SCH 3 substituent. Toxicity was more dependent on the ring substituent than on the anion attached to the tin atom. Quantitative structure-activity relationships could be generated between the toxicity of the compounds and the surface area of the molecule, indicating that the toxicity was related to the size of the substituent on the ring. In the case of the Ae. aegypti, the toxicity was also more dependent on the ring substituent than on the anion group. However, the size of the substituent on the ring was not found to be the dominant factor in the toxicity of these compounds.

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The 14 triorganotin compounds that were screened against the brine shrimp, Artemia salina, were least effective against the first nauplii stage (24 h). This was attributed to the presence of a yolk membrane which reduced the contact between the triorganotin compounds and the organism. The data indicated that the species responsible for the toxicity is primarily the hydrated triorganotin cation. However, the anion X group may also play a minor role in the toxicity of these compounds. The observed order of activity for the triorganotins does not parallel their hydrophobicities, indicating that other factors must be involved in the toxicity mechanism.