Vanadyl sulfate

 ( Vanadium Compounds ) 

Vanadyl(IV) sulfate describes a collection of inorganic compounds of vanadium with the formula, VOSO₄(H₂O)_x where 0 ≤ x ≤ 6. The pentahydrate is common. This hygroscopic blue salt is one of the most common sources of vanadium in the laboratory, reflecting its high stability. It features the vanadyl ion, VO²⁺, which has been called the "most stable diatomic ion".

Vanadyl sulfate is an intermediate in the extraction of vanadium from petroleum residues, one commercial source of vanadium.

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Synthesis, structure, and reactions Vanadyl sulfate is most commonly obtained by reduction of vanadium pentoxide with sulfur dioxide:

From aqueous solution, the salt crystallizes as the pentahydrate, the fifth water is not bound to the metal in the solid. Viewed as a coordination complex, the ion is octahedral, with oxo, four equatorial water ligands, and a monodentate sulfate. The trihydrate has also been examined by crystallography. A hexahydrate exists below .M. Tachez, F. Theobald, G. Trouillot. Crystal data for vanadyl sulphate hexahydrate VOSO₄.6H₂O. J. Appl. Crystallogr. (1976). 9, 246 Two polymorphs of anhydrous VOSO₄ are known.

The V=O bond distance is 160 picometer, about 50 pm shorter than the V–OH₂ bonds. In solution, the sulfate ion dissociates rapidly.

Being widely available, vanadyl sulfate is a common precursor to other vanadyl derivatives, such as vanadyl acetylacetonate:

In acidic solution, oxidation of vanadyl sulfate gives yellow-coloured vanadyl(V) derivatives. Reduction, e.g. by zinc, gives vanadium(III) and vanadium(II) derivatives, which are characteristically green and violet, respectively.

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Occurrence in nature Like most water-soluble sulfates, vanadyl sulfate is only rarely found in nature. The anhydrous form occurs as pauflerite, a mineral of fumarolic origin. Hydrated forms include a hexahydrate (stanleyite), pentahydrates (minasragrite, orthominasragrite, and anorthominasragrite) and a trihydrate (bobjonesite).

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Medical research Vanadyl sulfate is a component of food supplements and experimental drugs. Vanadyl sulfate exhibits insulin-like effects.

Vanadyl sulfate has been extensively studied in the field of diabetes research as a potential means of increasing insulin sensitivity. No evidence indicates that oral vanadium supplementation improves glycaemic control. Treatment with vanadium often results in gastrointestinal side-effects, primarily diarrhea.

Vanadyl sulfate is also marketed as a health supplement, often for bodybuilding. Deficiencies in vanadium result in reduced growth in rats. Its effectiveness for bodybuilding has not been proven; some evidence suggests that athletes who take it are merely experiencing a placebo effect.

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