The synthesis and crystal structures of halogenated tolans p-X–C6H4–CC–C6F5 and p-X–C6F4–CC–C6H5 (X = F, Cl, Br, I)

Abstract

A series of halogenated, partially fluorinated tolans of general formula p-X–C₆H₄–CC–C₆F₅ [X = I (1), Br (2), Cl (3), F (4)] and p-X–C₆F₄–CC–C₆H₅ [X = I (5), Br (6)] have been prepared via palladium-catalysed Sonogashira cross-coupling, or for X = Cl (7), by nucleophilic aromatic substitution reactions. The single-crystal X-ray structures of 1–3 and 5–6 have been determined. The structures reveal that the molecular packing is characterized by either arene–perfluoroarene interactions (3), or halogen–halogen interactions (isomorphous 1 and 2), or neither (isomorphous 5 and 6). The structure of 3 represents the first fully determined crystal structure of a compound that contains a halogen atom other than fluorine, in which arene–perfluoroarene interactions are present.