Organothallium compounds. XIV. Thermal decomposition of some Polyfluorobenzoatobis(polyfluorophenyl)thallium(III) compounds

Abstract

The organothallium carboxylates, R₂TIO₂CR (R = C₆F₅, p-MeOC₆F₄, p-HC₆F₄, m-HC₆F₄ or o-HC₆F₄), prepared by reactions of appropriate halogenobis(polyfluorophenyl)thallium(III) compounds and sodium carboxylates, are considered to have associated structures with bridging carboxylate groups. Thermal decomposition of R₂TlO₂CR (R = C₆F₅, p-MeOC₆F₄ or p-HC₆F₄ or m-HC₆F₄) in boiling pyridine resulted in decarboxylation and formation of the corresponding tris(polyfluorophenyl)thallium compounds, which were isolated in analytically pure form as the complexes R₃Tl(diox) (R = C₆F₅, p-HC₆F₄ or m-HC₆F₄; diox = 1,4-dioxan) and R₃Tl(bpy) (R = C₆F₅ or p-MeOC₆F₄; bpy = 4,4'-bipyridyl). However, no decomposition was observed when R = o-HC₆F₄. The ease of decarboxylation decreased in the sequence R = C₆F₅ > p-MeOC₆F₅ ≥ p-HC₆F₄ ≈ m-HC₆F₄ S o-HC₆F₄, and a possible mechanism is discussed. Pyrolysis of R₂TIO₂CR (R = C₆F₅, p-MeOC₆F₄, p-HC₆F₄, m-HC₆F₄ or o-HC₆F₄) at 310° under nitrogen in the absence of a solvent gave tris(polyfluorophenyl)thallium compounds (R = C₆F₅, p-MeOC₆F₄, p-HC₆F₄ or m-HC₆F₄), isolated as the dioxan complexes, thallous fluoride and polyfluorobiphenyls and polyfluoropolyphenyls. In addition, decafluorobenzophenone was obtained when R = C₆F₅, methyl fluoride when R = p-MeOC₆F₄ and the corresponding tetrafluorobenzene C₆H₂F₄ when R = p-HC₆F₄, m-HC₆F₄ or o-HC₆F₄. Chlorobis(2,3,5,6-tetrafluoro-4-methoxyphenyl)thallium(III) was prepared by reaction of thallic chloride with 2,3,5,6-tetrafluoro-4-methoxyphenyllithium, which was obtained from 2,3,5,6-tetra- fluoroanisole and butyllithium.