Abstract: Two newmonomeric complexes of oxovanadium(IV), VO[HB(pz)3](pzH)(C6H5COO) (1) and VO[HB(3,5-Me2pz)3](3,5-Me2pzH)(C6H5COO) (2) (HB(pz)3: hydrotris(pyrazolyl)borate; pzH: pyrazole; HB(3,5-Me2pz)3: hydrotris (3,5-dimethylpyrazolyl)borate; 3,5-Me2pzH: 3,5-dimethyl pyrazole) were synthesized from the reaction of VOSO4·nH2O with corresponding ligands. The complexes were characterized by elemental analysis, IR spectrum, and single crystal X-ray diffraction. The electronic structures and the bonding characteristics of both complexes were analyzed using ab initio calculations. Calculation results show that the structure of complex 2 is more stable than that of complex 1. The atomic net charge distribution in the molecular system indicates obvious covalent interaction between the coordinated atoms and vanadium. These results are consistent with the structural analyses of these complexes.

Key words: Oxovanadiumcomplex, Poly(pyrazolyl)borate,  Crystal structure, Quantumchemistry