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

[Yb(NTO) 3 (H 2 O) 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 solution of ytterbium oxide. The single crystal structure was determined by a four-circle X-ray diffractometer. The crystal is monoclinic, space group C2/ c with crystal parameters of a  = 3.6931 (5)nm, b  = 0.6683(10) nm, c  = 2.5656(3) nm, β  = 130.974(5)°, V  = 4.7811(11) nm 3 , Z  = 8, μ  = 40.17 cm −1 , F (000) = 2850, D c  = 2.013 g cm −2 , and λ (Mo K α ) = 0.071073 nm. The final R is 0.0258. [Sr(NTO) 2 (H 2 O) 4 ]·2H 2 O was prepared by mixing the aqueous solution of 3-nitro-1, 2, 4-triazol-5-one and the excessive strontium 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, β  = 101.798(13)°, V  = 1.5573(4) nm 3 , Z  = 4, D c  = 1.936 g cm −3 , μ  = 35.45 cm −1 , F (000) = 912, λ (Mo K α ) = 0.071073 nm. The final R is 0.0347. Based on the results of thermal analysis, the thermal decomposition mechanism of [Yb(NTO) 3 (H 2 O) 4 ]·6H 2 O and [Sr(NTO) 2 (H 2 O) 4 ]·2H 2 O were derived. From measurements of the enthalpy of solution of [Yb(NTO) 3 (H 2 O) 4 ]·6H 2 O and [Sr(NTO) 2 (H 2 O) 4 ]·2H 2 O in water at 298.15 K, the standard enthalpy of formation, lattice energy, lattice enthalpy 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 and 67.2 kJ mol −1 , respectively.