[Li(NTO)(H2O)2] was prepared by mixing the aqueous solution of 3-nitro-1, 2, 4-triazol-5-one (NTO) and lithium hydroxide. The crystal structure of [Li(NTO)(H2O)2] was determined by single crystal diffraction analysis. The crystal is monoclinic, space group P21/n with crystal parameters of α=0.742 0(2)nm, b=0.344 9(1)nm, c=2.490 6(3)nm, β=94.89(1)α, Z=4, Dc=1.799g. cm 3, V=0.635nm3, μ=l.591cm-1, F(000)=392. The finaIR is 0.051. TheMNDOMOcalculation shows that the coordinate bonds of title compound possess certain extent of covalent character. 02 atom of NTO anion is bonded to Li atom; the nitro group will be lost first when NTO is decomposed.

The single crystal of cobalt compound of 3-nitro-1,2,4-triazol-5-one (NTO) ([Co(H2O)6](NTO)2•2H2O) was prepared and the crystal structure has been determined by a four-circle X-ray diffractometer. The compound is monoclinic with space group Cc and unit cell parameters of a=2.3163 (2)nm, b=0.6451 (1) nm, c=1.4123 (1)nm, β=123.96 (1)◦, V=1.7504 (3)nm3 and Z=4. Based on the thermal analysis, the thermal decomposition mechanism of [Co(H2O)6](NTO)2•2H2O has been derived. From measurements of the enthalpy of solution in water at 298.15 K, the standard enthalpy of formation, lattice enthalpy and lattice energy have been determined as −(2594.7±4.5), −2753.19, and −2718.19 kJ mol−1, respectively.

H[Pr(NTO)4(H2O)4]-2H2O was prepared by mixing the aqueous solution of lithium 3-nitro-1,2,4-triazol-5-onate and the dilute nitric acid solution of Pr6O11. The single crystal structure has been determined by a four-circle X-ray diffractometer. The crystal is triclinic, space group P1 with crystal parameters of a=1.0463(10)nm, b=1.0484(10)nm, c=1.1474(10)nm,α=99.10(10)0, β=96. 96(10)0, r=97.65(10)0, V=1.2186(2)nm3, Z-2, Dc-2.088g-cmÿ3, u=21.17 cmÿ1, F(0 0 0)540. The final R is 0.0206. Based on the thermal analysis, the thermal decomposition mechanism of H[Pr(NTO)4(H2O)4]-2H2O has been derived. From measurements of the enthalpy of solution in water of H[Pr(NTO)4(H2O)4]-2H2O at 298.15 K, the standard enthalpy of formation, lattice energy and lattice enthalpy have been determined as ÿ(2884.1 8.9), ÿ5443.25 and ÿ5473.25 kJ molÿ1, respectively.