Transthallation of anisole and chlorobenzene by phenylthallium(III) bis(trifluoroacetate)

Abstract Phenylthallium(III) bis(trifluoroacetate) (PhTlX2) reacts with excess of anisole at 70‐80°, yielding mainly the three isomeric anisylphenylthallium(III) compounds (o‐, m‐, p‐AnPhTlX). Monoanisylthallium(III) derivatives (o‐, m‐, p‐AnTlX2) are obtained only in the presence of excess of HX. The slow transthallation reaction of chlorobenzene requiring the presence of HX leads to the o‐, m‐, p‐ClC6H4TlX2 isomers rather than to diarylthallium(III) compounds. The three isomeric anisylphenylthallium(III) compounds (o‐, m‐, p‐AnPhTlX) readily undergo exchange and isomerization reactions with anisole in the presence ‐ or more slowly in the absence ‐ of HX. Similar processes were observed with chlorobenzene but only in the presence of HX. (p‐Chlorophenyl)phenylthallium(III) trifluoroacetate is much less reactive, both towards anisole and chlorobenzene. With long reaction times the systems approach equilibrium distributions, which are approximately the same as those found for the prolonged direct thallation of the aromatic compounds. Tentative mechanistic interpretations include three different modes of formation of arylthallium bonds and draw a parallel between thallation, mercuration and plumbylation.