The Sodium (Iso)Cyanurates Nax[H3-xC3N3O3]•yH2O (x=1-3, y=0, 1): A Key-Series for Understanding the Crystal Chemistry of Metal (Iso)Cyanurates

The (iso)cyanurates Na[H2C3N3O3]H2O, Na-2[HC3N3O3]H2O, Na-2[HC3N3O3], and Na-3[C3N3O3] were synthesized phase pure from Na(2)CO(3)10H(2)O, NaOH, and cyanuric acid, respectively, in aqueous solution by carefully adjusting the crystallization conditions. The crystal structures of all compounds were determined by single-crystal X-ray diffraction {Na-2[HC3N3O3]H2O: P1, a = 3.51660(10) angstrom, b = 7.8300(3) angstrom, c = 11.3966(4) angstrom, = 86.4400(10)degrees, = 85.5350(10)degrees, = 85.0720(10)degrees, Z = 2, R-1 = 0.030, wR(2) = 0.078; Na-2[HC3N3O3]: Pnma, a = 6.3409(6) angstrom, b = 12.2382(13) angstrom, c = 6.5919(7) angstrom, Z = 4, R-1 = 0.045, wR(2) = 0.079; Na-3[C3N3O3]: R3c, a = 11.7459(3) angstrom, c = 6.5286(3) angstrom, Z = 3, R-1 = 0.039, wR(2) = 0.066}. The structures show ribbons (Na[H2C3N3O3]H2O), dimers (Na-2[HC3N3O3]H2O), chains (Na-2[HC3N3O3]), or columns (Na-3[C3N3O3]) of hydrogen-bonded and parallel stacked (iso)cyanurate anions. These motifs are shown to be characteristic for certain degrees of protonation and hydration, and all (iso)cyanurate crystal structures found so far were classified accordingly. X-ray powder patterns, thermogravimetry curves, IR and UV/Vis spectra were measured for all compounds.