Synthesis and structural studies on di-oxovanadium(V) complexes of N(4)-substituted pyrazole based thiosemicarbazones

Three mononuclear cis-dioxovanadium(V) complexes of tridentate thiosemicarbazones derived from 5-methyl-3-formylpyrazole (MPA) and N(4)-methyl/ethyl/dimethyl thiosemicarbazide have been synthesized and characterized. Single crystal X-ray analyses were performed with [VO2L1] (1), [VO2L2] (2) and [VO2L3] (3), where L1, L2 and L3 denote the [1 + 1] thiosemicarbazone mono-anions derived from MPA and N(4)-substituted methyl/ethyl/dimethyl thiosemicarbazide respectively. In all the complexes the vanadium atom is in a distorted square pyramidal geometry with a N2SO2 chromophore. The interesting finding in the work is that in complexes 1 and 2, the thioimine nitrogen unusually participates in coordination whereas in 3 it is the azomethine nitrogen (quite usual) which is involved in the coordination process.

cis-Dioxo vanadium(V) complexes (1–3) of three different tridentate thiosemicarbazone ligands synthesized from 5-methyl-3-formylpyrazole and N(4)-substituted thiosemicarbazides have been prepared and structurally characterized. All the three complexes have square pyramidal geometry. In 2, two asymmetric units appreciably differ in their conformations. In 1 and 2, the pyrazolyl N, the thioimine N (quite unusual) and the thiolato S of the corresponding tridentate ligand molecule coordinate to the vanadium atom whereas in 3, the respective ligand utilizes the azomethine nitrogen (usual) instead of the thioimine nitrogen to coordinate the vanadium atom along with the other two donor sites.Figure optionsDownload as PowerPoint slide