Redetermination of the crystal structure of 3,5-dimethylpyrazolium β-octamolybdate tetrahydrate

The title compound, (C5H9N2)4[Mo8O26]·4H2O, was reported previously from a room-temperature data collection from which only the metal atoms could be refined anisotropically [FitzRoy et al. (1989). Inorg. Chim. Acta, 157, 187-194]. The current redetermination at 180(2)K models all the non-H atoms with anisotropic displacement parameters and fully describes the supramolecular N - H⋯O and O - H⋯O hydrogen-bonded network connecting the 3,5-dimethylpyrazolium cations, the water molecules of crystallization and the β-octamolybdate anion. All H atoms involved in the three-dimensional hydrogen-bonding network could be located from difference Fourier maps, with the exception of those of one disordered water molecule, firstly seen in this structural report [refined over two distinct locations with site-occupancy factors of 0.65(2) and 0.35(2)]. The complete β-octamolybdate anion is generated by a crystallographic inversion centre