Oxovanadium(IV) pyrazolyl carboxylic acid complexes: synthesis, crystal structures of [VO(pzH)(HMPA)2]2 · 4H2O (1) and VO(OH)(dmpzH)2(C6H5COO) (2) (H2MPA = 5-methyl-1H-pyrazole-3-carboxylic acid, pzH = pyrazole, dmpzH = 3,5-dimethyl pyrazole)

Abstract

Two new monomeric complexes of oxovanadium(IV), [VO(pzH)(HMPA)2]2 · 4H2O (1) and VO(OH)(dmpzH)2(C6H5COO) (2) (H2MPA = 5-methyl-1H-pyrazole-3-carboxylic acid, pzH = pyrazole, dmpzH = 3,5-dimethyl pyrazole), have been synthesized from reaction of VOSO4 · nH2O with respective ligands. The compounds were characterized by elemental analysis, IR spectra and X-ray diffraction. Structural analysis of 1 and 2 gave the following parameters: 1, monoclinic, P2(1)/n, a = 11.1729(13) Å, b = 23.965(3) Å, c = 13.5591(15) Å, β = 99.969(2)°, V = 3575.8(7) Å3, Z = 4; 2, orthorhombic, Pbcn, a = 13.197(4) Å, b = 15.898(5) Å, c = 18.192(6) Å, V = 3817(2) Å3, Z = 8. In each complex the vanadium is a distorted tetragonal bipyramid, which is typical for oxovanadium(IV) complexes. In both complexes, inter- and intra-molecular hydrogen bonds are also discussed. Complex 1 exists as an infinite chain along the b-axis by intermolecular hydrogen bonds. In addition, thermal analysis and quantum chemistry calculations were performed for analyzing the stability of the complexes.