In chemistry, avanadate is an anioniccoordination complex ofvanadium. Often vanadate refers to oxoanions ofvanadium, most of which exist in its highestoxidation state of +5. The complexes[V(CN)6]3− and[V2Cl9]3− are referred to as hexacyanovanadate(III) and nonachlorodivanadate(III), respectively.
A simple vanadate ion is the tetrahedral orthovanadate anion,VO3−4 (which is also called vanadate(V)), which is present in e.g.sodium orthovanadate and in solutions ofV2O5 in strong base (pH > 13[1]). Conventionally this ion is represented with a single double bond, however this is aresonance 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.[2] There are also vanadates, such as rhodium vanadate,RhVO4, which has a statisticalrutile structure where theRh3+ andV5+ ions randomly occupy theTi4+ positions in the rutile lattice,[3] that do not contain a lattice of cations and balancing vanadate anions but aremixed 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[NH4]3[VF6] with theIUPAC name of ammonium hexafluoridovanadate(III).
In these ions vanadium exhibits tetrahedral, square pyramidal and octahedral coordination. In this respect vanadium shows similarities totungstate andmolybdate, whereas chromium however has a more limited range of ions.
Dissolution of vanadium pentoxide in strongly basic aqueous solution gives the colourlessVO3−4 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[VO2(H2O)4]+ 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 ofcondensations to produce polyoxovanadate ions:[2]
Vanadate is a potent inhibitor of certain plasma membraneATPases, such asNa+/K+-ATPase and Ca2+-ATPase (PMCA). Acting as a transition-state analog of phosphate, vanadate undergoes nucleophillic attack by water during phosphoryl transfer, essentially "trapping" P-type ATPases in their phosphorylated E2 state.[11][12] It also inhibits skeletal muscle actomyosin MgATPase activity[13] and calcium activated force generation by actomyosin in the intact skeletal muscle contractile apparatus.[14] However, it does not inhibit other ATPases, such asSERCA (sarco/endoplasmic reticulum Ca2+-ATPase) or mitochondrial ATPase.[15][16][17]
^Guang-Chuan Ou.; Long Jiang; Xiao-Long Feng; Tong-Bu Lu (2009). "Vanadium polyoxoanion-bridged macrocyclic metal complexes: from one-dimensional to three-dimensional structures".Dalton Transactions.1 (1):71–76.doi:10.1039/B810802A.PMID19081973.S2CID35209358.
^Hou D.; Hagen K.D.; Hill C.L. (1992). "Tridecavanadate, [V13O34]3−, a new high-potential isopolyvanadate".J. Am. Chem. Soc.114 (14): 5864.doi:10.1021/ja00040a061.
^Müller A.; Sessoli R.; Krickemeyer E.; Bögge H.; Meyer J.; Gatteschi D.; Pardi L.; Westphal J.; Hovemeier K.; Rohlfing R.; Döring J; Hellweg F.; Beugholt C.; Schmidtmann M. (1997). "Polyoxovanadates: High-Nuclearity Spin Clusters with Interesting Host–Guest Systems and Different Electron Populations. Synthesis, Spin Organization, Magnetochemistry, and Spectroscopic Studies".Inorg. Chem.36 (23): 5239.doi:10.1021/ic9703641.
^Jouanneau, S.; Verbaere, A.; Guyomard, D. (2003). "On a new calcium vanadate: synthesis, structure and Li insertion behaviour".Journal of Solid State Chemistry.172 (1):116–122.Bibcode:2003JSSCh.172..116J.doi:10.1016/S0022-4596(02)00164-0.
