Magnetism and structure of polymeric oxovanadium(IV) acetate and other polymeric oxovanadium(IV) complexes

Over 20 years have passed since the discovery that the magnetic interaction of a pair of Cu²⁺ ions could produce an abnormal EPR spectrum for copper(II) acetate monohydrate and the confirmation of this by an outline X-ray crystallographic determination of the molecular structure to be the dimer CU₂(H₂O)₂(CH₃CO₂)₄. Since then there have been many studies of the synthesis, properties, and bonding of copper(II) carboxylates and their complexes. This review summarizes these results and correlates the information provided by different techniques. Besides the many dimers, the Cu²⁺ ion forms a number of other polynuclear structures containing carboxylate groups. These are also surveyed here as are the studies on polynuclear carboxylates of other elements. Most of the work has been carried out on d-block transition elements, but appropriate compounds of f-block or nontransition elements are also included. The review is restricted to clusters containing bridging carboxylate groups, but is not confined to molecules in which carboxylates are the only bridging groups.

The preparation and properties of oxovanadium(IV) acetate, propionate and pivalate are described. In the reaction of the acetate with triphenylphosphine in thionyl chloride, [ClPPh₃]₂VCl₆ is formed. The reactions between vanadium(III) halides and acetic or propionic acids yield carboxylates of the general formula V₃(OH)(OCOR)₈; under mild conditions VCl(OCOCH₃)₂ can be isolated. The structures of the compounds are discussed in the light of their spectroscopic properties.

The title compound, which contains vanadyl oxo-bridges, has a magnetic moment of 1.78 BM at 295°K and obeys the Curie-Weiss Law (θ=−7°) over the range 95–295°K. The implications of this observation for possible mechanisms of spin-spin coupling in magnetically anomalous oxovanadium(IV) compounds are discussed.