Synthesis, structural characterization and spectroscopy studies of new oxovanadium(IV, V) complexes with hydrazone ligands

The reaction of vanadyl acetoacetonate, VO(acac) 2 , with 2-hydroxybenzaldehyde hydrazone in ethanol gave the mononuclear oxovanadium(IV) complex [VO(salh 1 ) 2 ]( 1 ). However, when the hydrazides 3-hydroxy-2-naphthoic acid hydrazide (h 2 ) and 5-phenylisoxazole-3-carboxylicacidhydrazide (h 3 ) were used, the mononuclear oxoethoxovanadium(V) complexes [VO(acanh 2 )(OEt)] ( 2 ) and [VO(acanh 3 )(OEt)] ( 3 ) were isolated, respectively. The reaction with benzene-1,4-dicarbohydrazide (h 4 ) in a water–ethanol solution gave polynuclear {[VO( l -EtO) 2 ]( l -acanh 4 )} n ( 4 ). The complexes were characterized by elemental analysis, IR, UV–Vis and 51 V NMR spectra. Magnetic susceptibility measurements indicated the +5 vanadium oxidation state in 2 , 3 and 4 and +4 in 1 . X-ray single crystal diffraction studies revealed that the vanadium(V) center has a distorted square pyramidal geometry in 2 and 3 , and a distorted octahedral geometry in 4 , with an O 3 N coordination environment around the V(V) acceptor center. Complex 4 is a polymeric compound with dihydrazide ligand as a linker and each two vanadium ions are connected via two l -ethoxo bridges