Symmetrization of Bromobis(polyfluorophenyl)thallium(III) compounds with copper powder

Reaction of bromobis(polyfluorophenyl)thallium(III) compounds, R2TlBr (R = C6F5, p-HC6F4, m-HC6F4 or 3,5-H2C6F3) and (C6F5)2TlOH, with copper powder in boiling 1,4-dioxan (diox) or diethyl ether gave the corresponding tris(polyfluorophenyl)thallium(III) compounds, which were isolated as the complexes R3Tl,diox. By contrast, the derivatives R2TlBr (R = o- HC6F4, 3,6-H2C6F3 or Ph) failed to react, and (C6F5)2TlBr was decomposed by copper powder in boiling toluene yielding decafluorobiphenyl. Formation of tris(polyfluorophenyl)thallium(III) compounds is considered to occur via polyfluorophenylcopper(I) intermediates. Treatment of (C6F5)2TlBr with pentafluorophenylcopper in dioxan gave (C6F5)3Tl,diox. The new bromobis-(polyfluorophenyl)thallium(III) compounds, R2TIBr (R = p-HC6F4, m-HC6F4, o-HC6F4, 3,5-H2C6F3 or 3,6- H2C6F3), were prepared by reaction of thallic chloride with the appropriate Grignard reagents.