Crystal and molecular structure of 4-fluoro-1H-pyrazole at 150 K

Abstract

Only two 4-halo-1H-pyrazole crystal structures are known to date (chloro and bromo, the structure of 4-iodo-1H-pyrazole has not been reported yet). The triclinic structure of 4-fluoro-1H-pyrazole, C3H3FN2 (P\overline{1}), reported here is not isomorphous with those of the chloro and bromo analogues (which are isomorphous, orthorhombic Pnma). To avoid sublimation during the measurement, diffraction data were collected at 150 K. Two crystallographically unique 4-fluoro-1H-pyrazole moieties linked by an N—H...N hydrogen bond are found in the asymmetric unit. Unlike the trimeric supramolecular motifs found in the structures of the chloro and bromo analogues, 4-fluoro-1H-pyrazole forms one-dimensional chains by intermolecular hydrogen bonding in the crystal.

Keywords

• pyrazole
• crystal structure
• low temperature
• hydrogen-bonding motifs