In chemistry, a vanadate is an anionic

coordination complex A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...

vanadium Vanadium is a chemical element; it has Symbol (chemistry), 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 ...

. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest

oxidation state In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...

of +5. The complexes and are referred to as hexacyanovanadate(III) and nonachlorodivanadate(III), respectively. A simple vanadate ion is the tetrahedral orthovanadate anion, (which is also called vanadate(V)), which is present in e.g. sodium orthovanadate and in solutions of in strong base ( pH > 13). Conventionally this ion is represented with a single double bond, however this is a resonance form as the ion is a regular tetrahedron with four equivalent oxygen atoms. Additionally a range of polyoxovanadate ions exist which include discrete ions and "infinite" polymeric ions. There are also vanadates, such as rhodium vanadate, , which has a statistical

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at vis ...

structure where the and ions randomly occupy the positions in the rutile lattice, that do not contain a lattice of cations and balancing vanadate anions but are mixed oxides. In chemical nomenclature when vanadate forms part of the name, it indicates that the compound contains an anion with a central vanadium atom, e.g. ammonium hexafluorovanadate is a common name for the compound with the

IUPAC name In chemical nomenclature, a preferred IUPAC name (PIN) is a unique name, assigned to a chemical substance and preferred among all possible names generated by IUPAC nomenclature. The "preferred IUPAC nomenclature" provides a set of rules for choos ...

of ammonium hexafluoridovanadate(III).

Examples of oxovanadate ions

Some examples of discrete ions are * "orthovanadate", tetrahedral. * "pyrovanadate", corner-shared tetrahedra, similar to the dichromate ion *, cyclic with corner-shared tetrahedra *, cyclic with corner-shared tetrahedra *, corner shared tetrahedra *, ring. * "decavanadate", edge- and corner-shared octahedra * *, fused octahedra * Some examples of polymeric "infinite" ions are * in e.g. , sodium metavanadate * in In these ions vanadium exhibits tetrahedral, square pyramidal and octahedral coordination. In this respect vanadium shows similarities to

tungstate In chemistry, a tungstate is a Chemical compound, compound that contains an oxyanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is , "orthotungstate". Many other tungstates belong to a large group of polyatomi ...

and

molybdate In chemistry, a molybdate is a compound containing an oxyanion with molybdenum in its highest oxidation state of +6: . Molybdenum can form a very large range of such oxyanions, which can be discrete structures or polymeric extended structures, ...

, whereas chromium however has a more limited range of ions.

Aqueous solutions

Dissolution of vanadium pentoxide in strongly basic aqueous solution gives the colourless ion. On acidification, this solution's colour gradually darkens through orange to red at around pH 7. Brown hydrated V2O5 precipitates around pH 2, redissolving to form a light yellow solution containing the ion. The number and identity of the oxyanions that exist between pH 13 and 2 depend on pH as well as concentration. For example, protonation of vanadate initiates a series of

condensation Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor ...

s to produce polyoxovanadate ions: *pH 9–12: , *pH 4–9: , , *pH 2–4: ,

Pharmacological properties

Vanadate is a potent inhibitor of certain plasma membrane

ATPase ATPases (, Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, ATP hydrolase, adenosine triphosphatase) are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion or ...

s, such as Na⁺/K⁺-ATPase and Ca²⁺-ATPase (

PMCA The plasma membrane Ca2+ ATPase (PMCA) is a transport protein in the plasma membrane of cell (biology), cells that functions as a calcium pump to remove calcium (Ca2+) from the cell. PMCA function is vital for regulating the amount of Ca2+ with ...

). Acting as a transition-state analog of

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

, vanadate undergoes nucleophillic attack by water during phosphoryl transfer, essentially "trapping"

P-type ATPase The P-type ATPases, also known as E1-E2 ATPases, are a large group of evolutionarily related ion and lipid pumps that are found in bacteria, archaea, and eukaryotes. P-type ATPases are α-helical bundle primary transporters named based upon thei ...

s in their phosphorylated E2 state. It also inhibits skeletal muscle

actomyosin Myofilaments are the three protein filaments of myofibrils in muscle cells. The main proteins involved are myosin, actin, and titin. Myosin and actin are the ''contractile proteins'' and titin is an elastic protein. The myofilaments act toget ...

MgATPase activity and calcium activated force generation by actomyosin in the intact skeletal muscle contractile apparatus. However, it does not inhibit other ATPases, such as

SERCA SERCA, or sarcoplasmic/endoplasmic reticulum Ca2+-ATPase, or SR Ca2+-ATPase, is a calcium ATPase-type P-ATPase. Its major function is to transport calcium from the cytosol into the sarcoplasmic reticulum. Function SERCA is a P-type ATPase. It ...

(sarco/

endoplasmic reticulum The endoplasmic reticulum (ER) is a part of a transportation system of the eukaryote, eukaryotic cell, and has many other important functions such as protein folding. The word endoplasmic means "within the cytoplasm", and reticulum is Latin for ...

Ca²⁺-ATPase) or mitochondrial ATPase.

References

{{Vanadium compounds Transition metal oxyanions Oxometallates