Preparation, crystal structure, thermal decomposition mechanism and thermodynamical properties of [Yb(NTO)(3)(H2O)(4)]center dot 6H(2)O and [Sr(NTO)(2)(H2O)(4)]center dot 2H(2)O

[Yb(NTO)(3)(H2O)(4)]. 6H(2)O was prepared by mixing the aqueous solution of lithium 3-nitro-1, 2, 4-triazol-5-onate and the dilute nitric acid solutio n of ytterbium oxide. The single crystal structure was determined by a four -circle X-ray diffractometer. The crystal is monoclinic, space group C2/c w ith crystal parameters of a = 3.6931 (5)nm, b = 0.6683(10) nm, c = 2.5656(3 ) nm, beta = 130.974(5)degrees, V = 4.7811(11) nm(3), Z = 8, mu = 40.17 cm( -1), F(000) = 2850, D-c = 2.013 g cm(-2), and lambda(MoKalpha,) = 0.071073 nm. The final R is 0.0258. [Sr(NTO)(2)(H2O)4]. 2H(2)O was prepared by mixin g the aqueous solution of 3-nitro-l, 2, 4-triazol-5-one and the excessive s trontium carbonate. The single crystal structure: was determined by a four- circle X-ray diffractometer. The crystal is monoclinic, space group P2(1)/c with crystal parameters of a = 1.1034(1) nm; b - 2.2742(2) nm, c = 0.63398 (9) nm, beta = 101.798(13)degrees, V = 1.5573(4) nm(3), Z = 4, D-c = 1.936 g cm(-3), mu = 35.45 cm(-1), F(000) = 912, lambda(MoKalpha) = 0.071073 nm. The final R is 0.0347. Based on the results of thermal analysis, the therma l decomposition mechanism of [Yb(NTO)(3)(H2O)(4)]. 6H(2)O and [Sr(NTO)(2)(H 2O)(4)]. 2H(2)O were derived. From measurements of the enthalpy of solution of [Yb(NTO)(3)(H2O)(4)]. 6H(2)O and [Sr(NTO)(2)(H2O)(4)]. 2H(2)O in water at 298.15 K, the standard enthalpy of formation, lattice energy, lattice en thalpy and standard enthalpy of dehydration have been determined as -(3853. 3 +/- 6.8) and - (2545.2 +/- 4.7), -4596 and -2114, -4631 and -2136, 391 an d 67.2 kJ mol(-1), respectively. (C) 1999 Elsevier Science B.V. All rights reserved.