Vanadium(IV) sulfate
Encyclopedia
Vanadyl sulfate, VOSO4, is a well known inorganic compound
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 of vanadium. This very hygroscopic blue solid 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, a major commercial source of vanadium. Vanadyl sulfate is a component of some food supplements and drugs. Vanadyl compounds mimic the effects of insulin, although humans seem to have no dietary
Dietary mineral
Dietary minerals are the chemical elements required by living organisms, other than the four elements carbon, hydrogen, nitrogen, and oxygen present in common organic molecules. Examples of mineral elements include calcium, magnesium, potassium, sodium, zinc, and iodine...

 requirement for vanadium.

Synthesis, structure, and reactions

Vanadyl sulfate is most commonly obtained by reduction of vanadium pentoxide
Vanadium(V) oxide
Vanadium oxide is the chemical compound with the formula V2O5. Commonly known as vanadium pentoxide, this brown/yellow solid is the most stable and common compound of vanadium. Upon heating it reversibly loses oxygen...

 with sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

:
V2O5 + 7 H2O + SO2 + H2SO4 → 2 [V(O)(H2O)4]SO4

From aqueous solution, the salt crystallizes as the pentahydrate
Water of crystallization
In crystallography, water of crystallization or water of hydration or crystallization water is water that occurs in crystals. Water of crystallization is necessary for the maintenance of crystalline properties, but capable of being removed by sufficient heat...

, the fifth water is not bound to the metal in the solid. Viewed as a coordination complex, the ion is octahedral
Octahedral molecular geometry
In chemistry, octahedral molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are symmetrically arranged around a central atom, defining the vertices of an octahedron...

, with oxo, four equatorial water ligands, and a monodentate sulfate. The V=O bond distance is 160 pm in length, 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
Vanadyl acetylacetonate
Vanadyl acetylacetonate is the chemical compound with the formula VO2. This blue-green coordination complex consists of the vanadyl group, VO2+, bound to two acetylacetonate anions, acac−. Like other charge-neutral acetylacetonates, this complex is soluble in organic solvents.-Synthesis:The...

:
[V(O)(H2O)4]SO4 + C5H8O2
Acetylacetone
Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The less stable tautomer is a diketone formally named pentane-2,4-dione. The more common tautomer is the enol form. The pair of tautomers rapidly interconvert and are treated as a single...

  + Na2CO3 → [V(O)(C5H7O2)2 + Na2SO4 + 4 H2O + CO2


In acidic solution, oxidation of vanadyl sulfate gives yellow-coloured vanadyl(V) derivatives. Reduction, e.g. by zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

, gives vanadium(III) and vanadium(II) derivatives, which are characteristically green and violet, respectively.

Occurrence in nature

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