New Unsymmetrical Oxovanadium(IV) Complexes of Mixed‐Donor Amido and Oxo Ligands

Abstract The novel, unsymmetrical, mixed‐donor, tetradentate amido, and oxo complexes of V(IV) of the general formula VOL x were synthesized by a nontemplate method and characterized by physico‐chemical methods. The ligands were prepared by a two‐stage aldol condensation reaction in the molar ratio 1:1 of 2‐hydroxybenzaldehyde, 2′‐hydroxyacetophenone, or 2′,4′‐dihydroxyacetophenone and 1,2‐diaminopropane of the general formula HA x (x = 1–3) as precursors. The tetradentate mixed donor ligands of the general formula H2L x (x = 1–6) were obtained by condensation reaction of precursors with appropriate ketone or aldehyde. The synthesis of the ligand system, described here, is an efficient and easy method with the advantages of high yield, selectivity, and short reaction times. Only a brown polymeric form was obtained for VOL2 and green monomeric forms were obtained for VOL x , x = 1, 3–5, while in the presence of strong field ligands only monomeric forms were obtained. These observations suggest that monomeric forms of oxovanadium(IV) complexes exhibit a coordination number of five with N2O3 donor sets and the polymeric form exhibits a coordination number of six with N2O4 donor sets. Analytical data, 1H NMR, IR, UV–VIS spectra, and elemental analyses confirm the nature of the products.