Studies on oxovanadium (IV) oxalate hydrates

Abstract

The oxalato complexes, VOC₂O₄·2H₂O and VOC₂O₄·4H₂O, are described. Their magnetic moments correspond to one unpaired electron showing the tetravalency of vanadium. They are monomeric in aqueous solution. Thermal studies suggest VO₂ formation when the compounds are decomposed. Infrared spectra reveal covalent bonding between the vanadium and the oxalate group and the coordinated water. The tetrahydrate has also some lattice held water. The weak band at 780 mμ and a shoulder at 600 mμ are due to d ↔ d transitions and the absorption in the ultra violet is due to charge transfer within the VO²⁺ group. The dihydrate is assigned a stable five co-ordinated pyramidal structure; while the tetrahydrate, a distorted octahedron with one water molecule loosely bound along the V-O axis and the other outside the co-ordination sphere.