Vanadate
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Vanadate
Orthovanadate anion.svg

In chemistry, a vanadate is a compound containing an oxoanion of vanadium generally in its highest oxidation state of +5. The simplest vanadate ion is the tetrahedral, orthovanadate, anion, which is present in e.g. sodium orthovanadate and in solutions of V2O5 in strong base (pH > 13[1]). 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.[2] There are also vanadates, such as rhodium vanadate, RhVO4, which has a statistical rutile structure where the Rh3+ and V5+ ions randomly occupy the Ti4+ positions in the rutile lattice,[3] 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 (NH4)3VF6 with the IUPAC name of ammonium hexafluoridovanadate(III).

Examples of vanadate ions

Some examples of discrete ions are

  • "orthovanadate", tetrahedral.[2]
  • "pyrovanadate", corner-shared VO4 tetrahedra, similar to the dichromate ion[2]
  • , cyclic with corner-shared VO4 tetrahedra[4]
  • , cyclic with corner-shared VO4 tetrahedra[5]
  • , corner shared VO4 tetrahedra[6]
  • , ring.[7]
  • "decavanadate", edge- and corner-shared VO6 octahedra[2]
  • , fused VO6 octahedra [8]
  • [9]

Some examples of polymeric "infinite" ions are

  • in e.g. NaVO3, sodium metavanadate[2]
  • in CaV6O16[10]
Ammonium-metavanadate-chains-3D.png
V5O14 ball and stick.png
Decavanadate polyhedra.png
metavanadate chains
V5O14
decavanadate ion

In these ions vanadium exhibits tetrahedral, square pyramidal and octahedral coordination. In this respect vanadium shows similarities to tungstate and molybdate, 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 [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 of condensations to produce polyoxovanadate ions:[2]

  • pH 9-12; ,
  • pH 4-9; , ,
  • pH 2-4; H3VO4,

Pharmacological properties

Vanadate is a potent inhibitor of certain plasma membrane ATPases, such as Na+/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] However, it does not inhibit other ATPases, such as SERCA (sarco/endoplasmic reticulum Ca2+-ATPase), actomyosin ATPase and mitochondrial ATPase.[13][14] Aureliano, Manuel; Crans, Debbie C. (2009). "Decavanadate and oxovanadates: Oxometalates with many biological activities". Journal Inorganic Biochemistry 103: 536-546. doi:10.1016/j.jinorgbio.2008.11010.

References

  1. ^ Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5
  2. ^ a b c d e f Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  3. ^ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  4. ^ Hamilton E. E.; Fanwick P.E.; Wilker J.J. (2002). "The Elusive Vanadate (V3O9)3-: Isolation, Crystal Structure, and Nonaqueous Solution Behavior". J. Am. Chem. Soc. 124 (1): 78. doi:10.1021/ja010820r.
  5. ^ G.-Y. Yang, D.-W. Gao, Y. Chen, J.-Q. Xu, Q.-X. Zeng, H.-R. Sun, Z.-W. Pei, Q. Su, Y. Xing, Y.-H. Ling and H.-Q. Jia (1998). "[Ni(C10H8N2)3]2[V4O12]·11H2O". Acta Crystallographica C. 54 (5): 616-618. doi:10.1107/S0108270197018751.CS1 maint: multiple names: authors list (link)
  6. ^ V. W. Day; Walter G. Klemperer; O. M. Yaghi (1989). "A new structure type in polyoxoanion chemistry: synthesis and structure of the anion". J. Am. Chem. Soc. 111 (12): 4518. doi:10.1021/ja00194a068.
  7. ^ 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: 71-76. doi:10.1039/B810802A.
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ Kühlbrandt, Werner (April 2004). "Biology, structure and mechanism of P-type ATPases". Nature Reviews. Molecular Cell Biology. 5 (4): 282-295. doi:10.1038/nrm1354. ISSN 1471-0072. PMID 15071553.
  12. ^ Davies, Douglas R.; Hol, Wim G.J. (2004-11-19). "The power of vanadate in crystallographic investigations of phosphoryl transfer enzymes". FEBS Letters. 577 (3): 315-321. doi:10.1016/j.febslet.2004.10.022. ISSN 0014-5793. PMID 15556602.
  13. ^ Luo D.; Nakazawa M.; Yoshida Y.; Cai J.; Imai S. (2000). "Effects of three different Ca2+ pump ATPase inhibitors on evoked contractions in rabbit aorta and activities of Ca2+ pump ATPases in porcine aorta". General Pharmacology: The Vascular System. 34 (3): 211-220. doi:10.1016/S0306-3623(00)00064-1.
  14. ^ Bowman B.J.; Slayman C.W. (1979). "The Effects of Vanadate on the Plasma Membrane ATPase of Neurospora crassa". Journal of Biological Chemistry. 254 (8): 2928-2934. PMID 155060.

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Vanadate
 



 



 
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