CRYSTAL AND MOLECULAR-STRUCTURE OF SODIUM PICRATE MONOHYDRATE

Na+ [C6H2(NO2)3O]- H2O, M(r) = 269.11, monoclinic, C2/m (No. 12), a = 13.065(1), b = 20.065(2), c = 3.6957(4) angstrom, beta = 90.75(1)-degrees, V = 968.7(1) angstrom 3, Z = 4, D(m) = 1.848 g cm-3 (by flotation), D(x) = 1.845 g cm-3, lambda(Cu K-alpha) = 1.54184 angstrom, mu(Cu K-alpha) = 17.5 cm-1, F(000) = 540, T = 295 K, R = 0.055, wR = 0.060 for 879 observed reflections with I greater-than-or-equal-to 2.5-sigma(I). In the structure the picrate anion has exact twofold symmetry, the water molecule has exact mirror symmetry and the two sodium cations occupy special positions on inversion centers at (0, 1/2, 0) and (1/2, 1/2, 1/2). The phenyl ring together with the four substituent N and O atoms is strictly planar, but the phenyl ring is severely distorted from hexagonal symmetry, as is commonly observed in structures containing the picrate fragment. Both sodium ions are eight-coordinated with Na(1) and Na(2) in a cubic and distorted cubic arrangement, respectively. Na(1) coordinates to four charged phenoxide O atoms and four O atoms of nitro groups, and Na(2) to four O atoms of nitro groups and four water molecules. The water molecule donates two hydrogen bonds to symmetry-related O(2) atoms of ortho nitro groups. Two symmetry-related O(3) atoms of ortho nitro groups serve as acceptors in a very unusual asymmetric bifurcated C-H . . . O hydrogen bond.