The synthesis and crystal structures of halogenated tolans p-X-C6H4-C[triple bond]C-C6F5 and p-X-C6F4-C[triple bond]C-C6H5(X=F, Cl, Br, I)

A series of halogenated, partially fluorinated tolans of general formula p-X-C6H4-C[triple bond]C-C6F5[X=I (1), Br (2), Cl (3), F (4)] and p-X-C6F4-C[triple bond]C-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 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.