[5] In the gas and liquid phase, trialkyl organothallium compounds are monomeric and planar.
Trialkyl thallium compounds can undergo alkyl exchange with itself and some acidic hydrocarbons like alkynes and cyclopentadiene.
[7] The halide atom can be substituted by nucleophiles, and the alkyl group can be abstracted by mercury acetate.
[7] Alkenes can also react with thallium(III) salts in a fashion analogous to oxymercuration to yield monoalkyl organothallium compounds.
Phenylthallium dihalides are prone to eliminating halobenzene, with the tendency increasing from chlorine to iodine, to the point that the iodide derivative is unknown.
[10] The most prominent contribution of organothallium chemistry to organic synthesis centers on thallium(III) trifluoroacetate with arenes.
Moreso than Hg(II), thallium(III) is a potent electrophile, delivering arylthallium(III) derivatives:[11] The resulting aryl thallium compounds react with nucleophiles such as halides, pseudohalides, and certain acetylides.
The first organothallium compound, diethylthallium chloride, was prepared in 1870, shortly after the discovery of the element thallium.