Decavanadate Structure
   HOME

TheInfoList



OR:

Sodium decavanadate describes any member of the family of
inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
s with the formula Na6 10O28H2O)n. These are sodium salts of the orange-colored decavanadate anion 10O28sup>6−. Numerous other decavanadate salts have been isolated and studied since 1956 when it was first characterized.


Preparation

The preparation of decavanadate is achieved by acidifying an aqueous solution of ortho- vanadate: :10 Na3 O4 + 24 HOAc → Na6 10O28 + 12 H2O + 24 NaOAc The formation of decavanadate is optimized by maintaining a pH range of 4–7. Typical side products include metavanadate, O3sup>−, and hexavanadate, 6O16sup>2−, ions.


Structure

The decavanadate ion consists of 10 fused VO6 octahedra and has D2h symmetry. The structure of Na6 10O28·18H2O has been confirmed with X-ray crystallography. The decavanadate anions contains three sets of equivalent V atoms (see fig. 1). These include two central VO6 octahedra (Vc) and four each peripheral tetragonal-pyramidal VO5 groups (Va and Vb). There are seven unique groups of oxygen atoms (labeled A through G). Two of these (A) bridge to six V centers, four (B) bridge three V centers, fourteen of these (C, D and E) span edges between pairs of V centers, and eight (F and G) are peripheral. The oxidation state of
vanadium Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pas ...
in decavanadate is +5.


Acid-base properties

Aqueous vanadate (V) compounds undergo various self-condensation reactions. Depending on pH, major vanadate anions in solution include VO2(H2O)42+, VO43−, V2O73−, V3O93−, V4O124−, and V10O286−. The anions often reversibly
protonate In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, ...
. Decavanadate forms according to this equilibrium: :H3V10O283− ⇌ H2V10O284− + H+ :H2V10O284− ⇌ HV10O285− + H+ :HV10O285−(aq) ⇌ V10O286− + H+ The structure of the various protonation states of the decavanadate ion has been examined by 51V NMR spectroscopy. Each species gives three signals; with slightly varying chemical shifts around −425, −506, and −523 ppm relative to
vanadium oxytrichloride Vanadium oxytrichloride is the inorganic compound with the formula VOCl3. This yellow distillable liquid hydrolyzes readily in air. It is an oxidizing agent. It is used as a reagent in organic synthesis. Samples often appear red or orange o ...
; suggesting that rapid proton exchange occurs resulting in equally symmetric species. The three protonations of decavanadate have been shown to occur at the bridging oxygen centers, indicated as B and C in figure 1. Decavanadate is most stable in pH 4–7 region. Solutions of vanadate turn bright orange at pH 6.5, indicating the presence of decavanadate. Other vanadates are colorless. Below pH 2.0, brown V2O5 precipitates as the hydrate. :V10O286− + 6H+ + 12H2 ⇌ 5V2O5


Potential uses

Decavanadate has been found to inhibit phosphoglycerate mutase, an enzyme which catalyzes step 8 of
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...
. In addition, decavandate was found to have modest inhibition of ''
Leishmania ''Leishmania'' is a parasitic protozoan, a single-celled organism of the genus '' Leishmania'' that are responsible for the disease leishmaniasis. They are spread by sandflies of the genus ''Phlebotomus'' in the Old World, and of the genus '' ...
tarentolae'' viability, suggesting that decavandate may have a potential use as a topical
inhibitor Inhibitor or inhibition may refer to: In biology * Enzyme inhibitor, a substance that binds to an enzyme and decreases the enzyme's activity * Reuptake inhibitor, a substance that increases neurotransmission by blocking the reuptake of a neurotra ...
of protozoan parasites.


Related decavanadates

Many decavanadate salts have been characterized. NH4+, Ca2+, Ba2+, Sr2+, and group I decavanadate salts are prepared by the acid-base reaction between V2O5 and the oxide, hydroxide, carbonate, or hydrogen carbonate of the desired positive ion. :6 NH3 + 5 V2O5 + 3 H2O ⇌ (NH4)6 10O28 Other decavanadates: :(NH4)6 10O28·6H2O :K6 10O28·9H2O :K6 10O28·10H2O :Ca3 10O28·16H2O :K2Mg2 10O28·16H2O :K2Zn2 10O28·16H2O :Cs2Mg2 10O28·16H2O :Cs4Na2 10O28·10H2O :K4Na2 10O28·16H2O :Sr3 10O28·22H2O :Ba3 10O28·19H2O : C6H5)4P3V10O28·4CH3CN :Ag6 10O28·4H2O Naturally occurring decavanadates include: :Ca3V10O28·17 H2O (
Pascoite Pascoite is a mineral with formula Ca3V10O28·17H2O that is red-orange to yellow in color. It was discovered in the Pasco Province of Peru, for which it is named, and described in 1914. Description Crystals of pascoite, which occur in granular cr ...
) :Ca2Mg(V10O28)·16H2O (
Magnesiopascoite Magnesiopascoite is a bright orange mineral with formula Ca2Mg(V10O28)·16H2O. It was discovered in the U.S. state of Utah and formally described in 2008. The mineral's name derives from its status as the magnesium analogue of pascoite. Descripti ...
) :Na4Mg(V10O28)·24H2O (
Huemulite Huemulite is a mineral with formula Na4Mg(V10O28)·24H2O that is yellow to orange in color. It was first discovered in Argentina in 1959 and described in 1966. The mineral is named for the Huemul mine in which it was discovered. Occurrence and pr ...
)


References

{{reflist Vanadates Sodium compounds