Novel hydrogen bonding in crystalline tetra-n-butylammonium salts of catechol halides

The crystal structures of [N(n-C4H9)4] [catechol … Cl] (1) and [N(n-C4H9)4] [catechol … Br] (2) have been determined by X-ray analysis which showed that the two structures are isomorphous, with the orthorhombic space group Pbca, Z = 8. The cell dimensions and final R-values are: (1) a = 15.323(2), b = 16.166(2), c = 19.713(2) Å, R = 0.048 for 1361 observed reflections; (2) a = 15.432(1), b = 16.244(2), c = 19.824(1) Å, R = 0.041 for 1958 observed reflections. The crystal structures consist of discrete tetra-n-butylammonium cations and catechol halide anions. Catechol forms two strong hydrogen bonds to a single halide ion giving a pattern of hydrogen bonding unique for such systems.