Polyfluoroarenes. Part IX. Decafluorotolan: synthesis, properties, and use as an organometallic ligand

Abstract

Di-iodoacetylene and pentafluorophenylmagnesium bromide give decafluorotolan (C₆F₅·C⋮C·C₆F₅) in good yield. The triple bond in the tolan undergoes ready catalytic hydrogenation, addition of bromine, and oxidative cleavage, but is relatively unreactive towards hydration, iodination, and carbonylation. Decafluorotolan reacts with methoxide ion in the 4- and 4′-positions, and gives a good yield of tetrakispentafluorophenylthiophen when it is heated with sulphur. Reaction of the tolan with cobalt octacarbonyl yields a complex Co₂(CO)₆(C₆F₅·C⋮C·C₆F ₅), shown by its chemical and spectroscopic properties to be similar in structure to its hydrocarbon analogue; octafluoro-4,4′-dimethoxytolan behaves similarly. Tetrakispentafluorophenylcyclopentadienone (perfluorotetracyclone) is obtained when a solution of the cobalt carbonyl complex of decafluorotolan is heated. Reaction of decafluorotolan with iron penta- or dodeca-carbonyl yields a complex Fe₂(CO)₆(C₆F₅·C⋮C·C₆F ₅)₂, together with perfluorotetracyclone.