Dioxovanadium(V) complexes with N,N,O-donor monoanionic ligands: Synthesis, structure and properties

Abstract

Dioxovanadium(V) complexes having the general formula [VO 2(phsalR)] have been synthesized in 52–63% yields by reacting one mole equivalent each of VOSO 4 · 5H 2O, 4-R-2-(pyridin-2-yl-hydrazonomethyl)-phenols (HphsalR, where R = H, OCH 3, Cl, Br and NO 2) and N(C 2H 5) 3 in water–acetonitrile (1:1.3) mixture. The complexes have been characterized by elemental analysis, magnetic susceptibility and spectroscopic (IR, UV–Vis, NMR and EPR) measurements. The physical properties of the complexes are consistent with the +5 oxidation state of the metal ion in them. The X-ray structure of a representative complex, [VO 2(phsal)] (R = H) has been determined. The metal centre in [VO 2(phsal)] is in square-pyramidal N 2O 3 coordination sphere. The monoanionic pyridine-N, imine-N and phenolate-O donor phsal − and one of the two oxo groups form the N,N,O,O basal plane and the other oxo group satisfies the fifth apical coordination site. This square-pyramidal molecules form weakly associated dimeric units due to the participation of the oxo group at the basal plane in the V–O–V bridge formation. The structure of [VO 2(phsal)] 2 can be described as two edge-shared VN 2O 4 octahedra. In the crystal lattice, these dimeric units form infinite one-dimensional chain structure via intermolecular N–H⋯O V hydrogen bonding interaction.