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, VO43− 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[edit]
Some examples of discrete ions are
- VO43− "orthovanadate", tetrahedral.[2]
- V2O74− "pyrovanadate", corner shared VO4 tetrahedra similar to dichromate ion[2]
- V3O93− cyclic with corner shared VO4 tetrahedra [4]
- V4O124− cyclic with corner shared VO4 tetrahedra [5]
- V5O143− corner shared VO4 tetrahedra [6]
- V10O286− "decavanadate", edge and corner shared VO6 octahedra[2]
- V12O324−[2]
- V13O343− fused VO6 octahedra [7]
- V18O4212−[8]
Some examples of polymeric “infinite” ions are
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In these ions vanadium exhibits tetrahedral, square pyramidal and octahedral coordination. In this respect vanadium shows similarities to tungstate and molybdate, chromium however has a more limited range of ions.
Aqueous solutions[edit]
Dissolution of vanadium pentoxide in strongly basic aqueous solution gives the colourless VO43− 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; HVO42−, V2O74−
- pH 4–9; H2VO4−, V4O124−, HV10O285−
- pH 2–4; H3VO4, H2V10O284−
Pharmacological properties[edit]
Vanadate is a potent inhibitor of certain plasma membrane ATPases, such as Na+/K+-ATPase and Ca2+-ATPase (PMCA). However, it does not inhibit other ATPases, such as SERCA (sarco/endoplasmic reticulum Ca2+-ATPase), actomyosin ATPase and mitochondrial ATPase.[10][11]
References[edit]
- ^ 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
- ^ a b c d e f g Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- ^ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
- ^ 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.
- ^ 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. doi:10.1107/S0108270197018751.
- ^ V. W. Day, Walter G. Klemperer, O. M. Yaghi (1989). "A new structure type in polyoxoanion chemistry: synthesis and structure of the V5O143− anion". J. Am. Chem. Soc. 111 (12): 4518. doi:10.1021/ja00194a068.
- ^ 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: 116. Bibcode:2003JSSCh.172..116J. doi:10.1016/S0022-4596(02)00164-0.
- ^ 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.
- ^ 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.