Английская Википедия:Hypomanganate

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Шаблон:Short description

In chemistry, hypomanganate, also called manganate(V) or tetraoxidomanganate(3−), is a trivalent anion (negative ion) composed of manganese and oxygen, with formula Шаблон:Chem.

Hypomanganates are usually bright blue.[1][2] Potassium hypomanganate Шаблон:Chem is the best known salt, but sodium hypomanganate Шаблон:Chem, barium hypomanganate Шаблон:Chem, and the mixed potassium-barium salt Шаблон:Chem is also known.[3] The anion can replace phosphate Шаблон:Chem in synthetic variants of the minerals apatite[4][5] and brownmillerite.[6]

History

The manganate(V) anion was first reported in 1946 by Hermann Lux, who synthesized the intensely blue sodium hypomanganate by reacting sodium oxide Шаблон:Chem and manganese dioxide Шаблон:Chem in fused sodium nitrite Шаблон:Chem at 500 °C.[7][3] He also crystalized the salt from strong (50%) sodium hydroxide solutions as the decahydrate Шаблон:Chem·10Шаблон:Chem.

Structure and properties

Manganate(V) is a tetrahedral oxyanion structurally similar to sulfate, manganate, and permanganate. As expected for a tetrahedral complex with a d2 configuration, the anion has a triplet ground state.[3]

The anion is a bright blue species[1] with a visible absorption maximum at wavelength λmax = 670 nm (ε = Шаблон:Nowrap).[8][9]

Stability

Hypomanganate is unstable towards disproportionation to manganate(VI) and manganese dioxide:[10][1] The estimated electrode potentials at pH 14 are:[11][12][13]

MnOШаблон:Su + e− Шаблон:Eqm MnOШаблон:Su   E = +0.27 V
MnOШаблон:Su + e− + Шаблон:Nowrap Шаблон:Eqm MnO2 + Шаблон:Nowrap   E = +0.96 V

However, the reaction is slow in very alkaline solutions (with OH− concentration above 5–10 mol/L.[1][7]

The disproportionation is believed to pass through a protonated intermediate,[13] with the acid dissociation constant for the reaction HMnOШаблон:Su Шаблон:Eqm MnOШаблон:Su + H+ being estimated as pKa = Шаблон:Nowrap.[14] However, K3MnO4 has been cocrystallized with Ca2Cl(PO4), allowing the study of the UV–visible spectrum of the hypomanganate ion.[10][15]

Preparation

Hypomanganates may be prepared by the careful reduction of manganates with sulfite,[1] hydrogen peroxide[16] or mandelate.[9]

Hypomanganates can also be prepared by the solid state method under Шаблон:O2 flow near 1000 °C.[3][4][5] [6] They can be prepared also via low temperature routes such as hydrothermal synthesis or flux growth.[3] It is produced by dissolving manganese dioxide in molten sodium nitrite.[17]

Uses

The strontium vanadate fluoride Шаблон:Chem compound, with hypomanganate substituted for some vanadate units, has been investigated for potential use in near infrared lasers.[18]

The barium salt Шаблон:Chem has interesting magnetic properties.[19]

Related compounds

In theory, hypomanganate would be the conjugate base of hypomanganic acid Шаблон:Chem. This acid cannot be formed because of its rapid disproportionation, but its third acid dissociation constant has been estimated by pulse radiolysis techniques:[14]

HMnOШаблон:Su Шаблон:Eqm MnOШаблон:Su + H+   pKa = Шаблон:Nowrap

Cyclic esters of hypomanganic acid are thought to be intermediates in the oxidation of alkenes by permanganate.[9]

See also

References

Шаблон:Reflist

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Разное

  1. ↑ 1,0 1,1 1,2 1,3 1,4 Шаблон:Greenwood&Earnshaw1st.
  2. ↑ D. Reinen, W. Rauw, U. Kesper, M. Atanasov, H. U Güdel, M. Hazenkamp, and U. Oetliker (1997): "Colour, luminescence and bonding properties of tetrahedrally coordinated chromium(IV), manganese(V) and iron(VI) in various oxide ceramics" Journal of Alloys and Compounds, volume 246, issue 1-2, pages 193-208. Шаблон:Doi
  3. ↑ 3,0 3,1 3,2 3,3 3,4 Шаблон:Cite journal
  4. ↑ 4,0 4,1 K. Dardenne, D. Vivien, and D. Huguenin (1999): "Color of Mn(V)-substituted apatites A10((B, Mn)O4)6F2, A = Ba, Sr, Ca; B= P, V". Journal of Solid State Chem.istry, volume 146, issue 2, pages 464-472. Шаблон:Doi
  5. ↑ 5,0 5,1 Grisafe, D.A. and Hummel, F.A. (1970): "Pentavalent ion substitutions in the apatite structure, part A: Crystal chemistry". Journal of Solid State Chemistry, volume 2, issue 2, pages 160-166 Шаблон:Doi
  6. ↑ 6,0 6,1 P. Jiang, J. Li, A. Ozarowski, A. W. Sleight, and M. A, Subramanian (2013): "Intense turquoise and green colors in brownmillerite-type oxides based on Mn5+ in Шаблон:Chem" Inorganic Chemistry, volume 52, issue 3, pages 1349-1357. Шаблон:Doi
  7. ↑ 7,0 7,1 Herrman Lux (1946): "Über Salze des fünfwertigen Mangans." Zeitschrift für Naturforschung, volume 1, pages 281-283.
  8. ↑ Шаблон:Citation
  9. ↑ 9,0 9,1 9,2 Шаблон:Citation.
  10. ↑ 10,0 10,1 Шаблон:Cotton&Wilkinson4th.
  11. ↑ Шаблон:RubberBible62nd.
  12. ↑ Шаблон:Citation.
  13. ↑ 13,0 13,1 Шаблон:Citation.
  14. ↑ 14,0 14,1 Шаблон:Citation.
  15. ↑ Шаблон:Citation.
  16. ↑ Шаблон:Citation.
  17. ↑ Шаблон:Cite journal
  18. ↑ L. D. Merkle, Y. Guyot, and B. H. T. Chai (1995): "Spectroscopic and laser investigations of Mn5+:Sr5(VO4)3F". Journal of Applied Physics, volume 77, issue 2, pages 474-480. Шаблон:Doi
  19. ↑ M. B. Stone, M. D. Lumsden, Y. Qiu, E. C. Samulon, C. D. Batista, and I. R. Fisher (2008): "Dispersive magnetic excitations in the S=1 antiferromagnet Шаблон:Chem". Physics Review B, volume 77, page 134406 Шаблон:Doi
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