Vanadium(II) sulfate

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| ImageFile = V(aq)6SO4.png

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| Section1 = {{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 13566-06-8

| PubChem1 = 166848

| PubChem1_Comment = anhydrous

| PubChem2 = 22613976

| PubChem2_Comment = heptahydrate

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = IO5B4EXJYI

| SMILES = [V+2].[O-]S([O-])(=O)=O

| SMILES_Comment = anhydrous

| SMILES1 = [OH2+][V-4]([OH2+])([OH2+])([OH2+])([OH2+])[OH2+].[O-]S(=O)(=O)[O-]

| SMILES1_Comment = hexahydrate

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| Section2 = {{Chembox Properties

| V=1|O=10|H=12|S=1

| MolarMass =

| Appearance = violet solid

| Density = 1.910 g/cm³

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| Section3 = {{Chembox Hazards

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Vanadium(II) sulfate describes a family of inorganic compounds with the formula VSO₄(H₂O)_x where 0 ≤ x ≤ 7. The hexahydrate is most commonly encountered. It is a violet solid that dissolves in water to give air-sensitive solutions of the aquo complex. The salt is isomorphous with [Mg(H₂O)₆]SO₄. Compared to the V–O bond length of 191 pm in [V(H₂O)₆]³⁺, the V–O distance is 212 pm in the [V(H₂O)₆]SO₄. This nearly 10% elongation reflects the effect of the lower charge, hence weakened electrostatic attraction.{{cite journal|title = Synthesis and Characterization of Four Vanadium(II) Compounds, Including Vanadium(II) Sulfate Hexahydrate and Vanadium(II) Saccharinates|last1 = Cotton|first1 = F. A.|authorlink1 = F. Albert Cotton|last2 = Falvello|first2 = L. R.|last3 = Llusar|first3 = R.|last4 = Libby|first4 = E.|last5 = Murillo|first5 = C. A.|last6 = Schwotzer|first6 = W.|journal = Inorganic Chemistry|year = 1986|volume = 25|issue = 19|pages = 3423–3428|doi = 10.1021/ic00239a021}}

The heptahydrate has also been crystallized. The compound is prepared by electrolytic reduction of vanadyl sulfate in sulfuric acid.{{cite book|last1 = Kranz|first1 = M.| title=Inorganic Syntheses |year = 1963|chapter = Vanadium(II) Sulfate|series = Inorganic Syntheses|volume = 7|pages = 94–96|doi = 10.1002/9780470132388.ch29|isbn = 978-0-470-13238-8}} The crystals also feature [V(H₂O)₆]²⁺ centers but with an extra water of crystallization. The salt is isomorphous with ferrous sulfate heptahydrate.{{cite journal|title = Neutron and X-Ray Structural Characterization of the Hexaaquavanadium(II) Compound V(SO₄)·7H₂O|last1 = Cotton|first1 = F. A.|last2 = Falvello|first2 = L. R.|last3 = Murillo|first3 = C. A.|last4 = Pascual|first4 = I.|last5 = Schultz|first5 = A. J.|last6 = Tomas|first6 = M.|journal = Inorganic Chemistry|year = 1994|volume = 33|issue = 24|pages = 5391–5395|doi = 10.1021/ic00102a009}} A related salt is vanadous ammonium sulfate, (NH₄)₂V(SO₄)₂·6H₂O, a Tutton's salt isomorphous with ferrous ammonium sulfate.{{cite journal|last1 = Montgomery|first1 = H.|first2 = B.|last2 = Morosin |first3 = J. J.|last3 = Natt|first4 = A. M.|last4 = Witkowska|first5 = E. C.|last5 = Lingafelter|year = 1967|title = The crystal structure of Tutton's salts. VI. Vanadium(II), iron(II) and cobalt(II) ammonium sulfate hexahydrates|journal = Acta Crystallographica|volume = 22|issue = 6|pages = 775–780|doi = 10.1107/S0365110X67001550|doi-access = free| bibcode=1967AcCry..22..775M }}