Organothallium compounds. XVIII. The effect of antimony pentafluoride and fluorosulfuric acid on the thallation of polyfluoroarenes

Abstract

The polyfluoroarenes m-H₂C₆F₄, m-O₂NC₆F₄H, m- and p-BrC₆F₄H, (p-HC₆F₄)₂, C₆F₅H, 1,3,5-F₃C₆H₃ and m-FSO₂C₆F₄H have been thallated by thallic trifluoroacetate in fluorosulfuric acid in the presence of antimony pentafluoride. Substantial dithallation of m-H₂F₄ and 1,3,5-F₃C₆H₃ and slight trithallation of the latter have been achieved. The products were identified by conversion into the corresponding polyfluoroiodoarenes on reaction with aqueous sodium iodide. From the reaction with pentafluorobenzene, pentafluorophenylthallium(III) species have been characterized. 1,2,4,5-Tetrafluoro-3-methoxybenzene was thallated by thallic trifluoroacetate in 1,2-dichloroethane in the presence of boron trifluoride etherate, but C₆F₅H and p-MeC₆F₄H failed to react.