Hydrogen bonding in the crystal structures of the adducts between 1-phenyl-3,5-dimethylpyrazole with oxalic and perchloric acids

Abstract

The crystal structures of the title compounds have been determined from diffractometric X-ray data and refined by full-matrix least-squares to final R factors of 0.057 and 0.071 for the oxalic and perchloric adducts respectively.The space groups and cell dimensions are: (oxalic) C2/c, a = 16.516(3), b = 11.685(2), c = 12.587(3) Å, β = 107.11(2)° with Z = 4; (perchloric) Pbca, a = 16.204(3), b = 15.329(6), c = 10.296(3) Å with Z = 8.In both structures the complex is stabilized by a strong hydrogen bond between the N(2) of the 1-phenyl-3,5-dimethylpyrazole (PDMP) group and an oxygen of the acid. In the oxalic adduct the PDMP group is neutral and the N(2) atom acts as a proton acceptor, while in the perchloric complex the PDMP group is positively charged with the N(2) atom acting as a proton donor.