:Vanadate
{{Short description|Coordination complex of vanadium}}
In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes {{chem2|[V(CN)6](3-)}} and {{chem2|[V2Cl9](3-)}} are referred to as hexacyanovanadate(III) and nonachlorodivanadate(III), respectively.
A simple vanadate ion is the tetrahedral orthovanadate anion, {{chem2|VO4(3−)}} (which is also called vanadate(V)), which is present in e.g. sodium orthovanadate and in solutions of vanadium pentoxide in strong base (pH > 13{{Cotton&Wilkinson6th}}). 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.{{Greenwood&Earnshaw}} There are also vanadates, such as rhodium vanadate, {{chem2|RhVO4}}, which has a statistical rutile structure where the {{chem2|Rh(3+)}} and {{chem2|V(5+)}} ions randomly occupy the {{chem2|Ti(4+)}} positions in the rutile lattice,Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications {{ISBN|0-19-855370-6}} 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 {{chem2|[NH4]3[VF6]}} with the IUPAC name of ammonium hexafluoridovanadate(III).
Examples of oxovanadate ions
Some examples of discrete ions are
- {{chem2|VO4(3−)}} "orthovanadate", tetrahedral.
- {{chem2|V2O7(4−)}} "pyrovanadate", corner-shared {{chem2|VO4}} tetrahedra, similar to the dichromate ion
- {{chem2|V3O9(3−)}}, cyclic with corner-shared {{chem2|VO4}} tetrahedra{{cite journal|title = The Elusive Vanadate (V3O9)3−: Isolation, Crystal Structure, and Nonaqueous Solution Behavior|author1=Hamilton E. E. |author2=Fanwick P.E. |author3=Wilker J.J. |journal = J. Am. Chem. Soc.|volume = 124|issue = 1|doi = 10.1021/ja010820r|pmid=11772064 |year = 2002|pages = 78–82 }} [https://figshare.com/articles/The_Elusive_Vanadate_V_sub_3_sub_O_sub_9_sub_sup_3-_sup_Isolation_Crystal_Structure_and_Nonaqueous_Solution_Behavior/3634506 Supplementary Information].
- {{chem2|V4O12(4−)}}, cyclic with corner-shared {{chem2|VO4}} tetrahedra{{cite journal|title = [Ni(C10H8N2)3]2[V4O12]·11H2O|author = 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|doi = 10.1107/S0108270197018751|year = 1998|journal = Acta Crystallographica C|volume = 54|pages = 616–618|issue = 5| bibcode=1998AcCrC..54..616Y }}
- {{chem2|V5O14(3−)}}, corner shared {{chem2|VO4}} tetrahedra{{cite journal|title = A new structure type in polyoxoanion chemistry: synthesis and structure of the {{chem|V|5|O|14|3−}} anion|author1=V. W. Day |author2-link=Walter G. Klemperer |author2=Walter G. Klemperer |author3=O. M. Yaghi |journal = J. Am. Chem. Soc.|doi = 10.1021/ja00194a068|year = 1989|volume = 111|pages = 4518|issue = 12}}
- {{chem2|V6O18(6−)}}, ring.{{cite journal|title = Vanadium polyoxoanion-bridged macrocyclic metal complexes: from one-dimensional to three-dimensional structures|author1=Guang-Chuan Ou. |author2=Long Jiang |author3=Xiao-Long Feng |author4=Tong-Bu Lu|journal = Dalton Transactions|doi = 10.1039/B810802A|year = 2009|volume = 1|issue= 1|pages = 71–76|pmid=19081973 |s2cid=35209358 }}
- {{chem2|V10O28(6−)}} "decavanadate", edge- and corner-shared {{chem2|VO6}} octahedra
- {{chem2|V12O32(4−)}}
- {{chem2|V13O34(3−)}}, fused {{chem2|VO6}} octahedra {{cite journal|title = Tridecavanadate, [V13O34]3−, a new high-potential isopolyvanadate|author1=Hou D. |author2=Hagen K.D. |author3=Hill C.L. |journal = J. Am. Chem. Soc.|doi = 10.1021/ja00040a061|year = 1992|volume = 114|pages = 5864|issue = 14}}
- {{chem2|V18O42(12−)}}{{cite journal|title = Polyoxovanadates: High-Nuclearity Spin Clusters with Interesting Host–Guest Systems and Different Electron Populations. Synthesis, Spin Organization, Magnetochemistry, and Spectroscopic Studies|author1=Müller A. |author2=Sessoli R. |author3=Krickemeyer E. |author4=Bögge H. |author5=Meyer J. |author6=Gatteschi D. |author7=Pardi L. |author8=Westphal J. |author9=Hovemeier K. |author10=Rohlfing R. |author11=Döring J |author12=Hellweg F. |author13=Beugholt C. |author14=Schmidtmann M. |journal = Inorg. Chem.|doi = 10.1021/ic9703641|year = 1997|volume = 36|pages = 5239|issue = 23}}
Some examples of polymeric "infinite" ions are
- {{chem|[VO|3|]|n|n−}} in e.g. {{chem2|NaVO3}}, sodium metavanadate
- {{chem|[V|3|O|8|]|n|n−}} in {{chem2|CaV6O16}}{{cite journal|title = On a new calcium vanadate: synthesis, structure and Li insertion behaviour|author1=Jouanneau, S. |author2=Verbaere, A. |author3=Guyomard, D. |journal = Journal of Solid State Chemistry|doi = 10.1016/S0022-4596(02)00164-0|year = 2003|volume = 172|issue=1 |pages = 116–122|bibcode = 2003JSSCh.172..116J }}
| align="center" class="wikitable" style="margin:1em auto;" | Image:V5O14 ball and stick.png | Image:decavanadate polyhedra.png |
| {{center|metavanadate chains}}
|{{center|{{chem2|V5O14}}}} |{{center|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 {{chem2|VO4(3−)}} 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 {{chem2|[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:
- pH 9–12: {{chem2|HVO4(2−)}}, {{chem2|V2O7(4−)}}
- pH 4–9: {{chem2|H2VO4−}}, {{chem2|V4O12(4−)}}, {{chem2|HV10O28(5−)}}
- pH 2–4: {{chem2|H3VO4}}, {{chem2|H2V10O28(4−)}}
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.
{{Cite journal|last=Kühlbrandt|first=Werner|date=April 2004|title=Biology, structure and mechanism of P-type ATPases|journal=Nature Reviews. Molecular Cell Biology|volume=5|issue=4|pages=282–295|doi=10.1038/nrm1354|issn=1471-0072|pmid=15071553|s2cid=24927167 }}{{Cite journal|date=2004-11-19|title=The power of vanadate in crystallographic investigations of phosphoryl transfer enzymes|journal=FEBS Letters|language=en|volume=577|issue=3|pages= 315–321|doi= 10.1016/j.febslet.2004.10.022|pmid = 15556602|issn= 0014-5793|last1=Davies|first1=Douglas R.|last2=Hol|first2=Wim G.J.|doi-access=free}} It also inhibits skeletal muscle actomyosin MgATPase activity{{cite journal|last1 = Goodno|first1 = C.C.|last2 = Taylor|first2 = E.W.|date = 1982|title = Inhibition of actomyosin ATPase by vanadate|journal = Proceedings of the National Academy of Sciences USA|volume = 79| issue=1 |pages = 21–25|doi = 10.1073/pnas.79.1.21| pmid=6459580 | pmc=345653 | bibcode=1982PNAS...79...21G |doi-access=free}} and calcium activated force generation by actomyosin in the intact skeletal muscle contractile apparatus.{{cite journal|last1 = Wilson|first1 = G.J.|last2 = Shull|first2 = S.E.|last3 = Cooke|first3 = R.|date = 1995|title = Inhibition of muscle force by vanadate|journal = Biophysical Journal|volume = 68|issue = 1|pages = 216–226|doi = 10.1016/S0006-3495(95)80177-3| pmid=7711244 | pmc=1281679 | bibcode=1995BpJ....68..216W |doi-access=free}} However, it does not inhibit other ATPases, such as SERCA (sarco/endoplasmic reticulum Ca2+-ATPase) or mitochondrial ATPase.{{cite journal|title = Effects of three different Ca2+ pump ATPase inhibitors on evoked contractions in rabbit aorta and activities of Ca2+ pump ATPases in porcine aorta|author1=Luo D. |author2=Nakazawa M. |author3=Yoshida Y. |author4=Cai J. |author5=Imai S. |journal = General Pharmacology: The Vascular System|doi=10.1016/S0306-3623(00)00064-1|pmid=11120383 |year = 2000|volume = 34|pages = 211–220|issue = 3}}{{cite journal|title = The Effects of Vanadate on the Plasma Membrane ATPase of Neurospora crassa|author1=Bowman B.J. |author2=Slayman C.W. |journal = Journal of Biological Chemistry|pmid = 155060|year = 1979|volume = 254|pages = 2928–2934|issue = 8|doi=10.1016/S0021-9258(17)30163-1 |doi-access=free }}{{cite journal|last1 = Aureliano |first1 = Manuel |last2 = Crans |first2 = Debbie C. |year = 2009 |title = Decavanadate ({{chem|V|10|O|28|6−}}) and oxovanadates: Oxometalates with many biological activities |url=https://www.sciencedirect.com/science/article/pii/S0162013408002882 |journal = Journal of Inorganic Biochemistry |volume = 103 |issue = 4 |pages = 536–546 |doi = 10.1016/j.jinorgbio.2008.11.010 |pmid = 19110314 |issn=0162-0134|url-access = subscription }}