Synthesis and characterization of two new types of oxovanadium complexes with pyrazole as ligand

Abstract

At room temperature, two new different oxovanadium complexes with simple pyrazole (C 3 H 4 N 2 ) as ligand were synthesized. VO(pz) 4 (SO 4 )⋅ H 2 O (1) (pz: pyrazole) is a mono-nuclear oxovanadium complex with pyrazole as terminal ligands. V 2 O 2 (μ-pz)(μ-OOSO 2 )(μ-OCH 3 )(pz) 4 (2) is bi-nuclear oxovanadium complex containing three different bridges, which are pyrazolate, sulphate and methoxy, respectively. The two complexes were characterized by IR, elemental analyses, thermal analyses and X-ray diffraction. The crystal structural data of the complexes 1 and 2 are given as follows: Complex 1, orthorhombic, Pna2 1 , a = 14.547 (2) Å, b =10.895(2) Å, c =11.835(2) Å; α=β=γ=90°, V=1875.8(5) Å 3 , Z = 4, R 1 = 0.0485, W R 2 = 0.1092. Complex 2, triclinic, P1 , a =8.377(2) Å, b =9.928(2) Å, c = 16.527(3) Å, α = 85.54(3)°, β = 80.92(3)°, γ = 87.92(3)°, R 1 = 0.1461, W R 2 = 0.4444. The study of non-thermal kinetic decomposition shows that, for complex 1, the possible reaction mechanisms of the two steps are nucleation and growth n=1/3, and three-dimensional pervasion n=2, respectively, and the kinetic equations may be expressed as dα/dT = (A/β)exp(−E/RT){1/3(1−α) [−In(1−α)] −2 } and dα/dT = (A/β)exp(−E/RT){3/2(1−α) 2/3 [1−(1−α) 1/3 ] −1 }, respectively; for complex 2, the possible reaction mechanisms of the two steps are chemical reaction, and three-dimensional pervasion n=2, respectively; the kinetic equations may be expressed as dα/dT = (A/β)exp(−E/RT)[(1−α) 2 ], and dα/dT = (A/β)exp(−E/RT){3/2(1−α) 2/3 [1−(1−α) 1/3 ] −1 }, respectively.