Hypomanganate

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Trivalent anion

title: "Hypomanganate" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["manganese(v)-compounds", "transition-metal-oxyanions"] description: "Trivalent anion" topic_path: "general/manganese-v-compounds" source: "https://en.wikipedia.org/wiki/Hypomanganate" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Trivalent anion ::

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

Hypomanganates are usually bright blue. Potassium hypomanganate is the best known salt, but sodium hypomanganate , barium hypomanganate , and the mixed potassium-barium salt is also known. and brownmillerite.

History

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

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.

The anion is a bright blue species with a visible absorption maximum at wavelength λmax = 670 nm (ε = 900 dm3 mol−1 cm−1).

Stability

Hypomanganate is unstable towards disproportionation to manganate(VI) and manganese dioxide: The estimated electrode potentials at pH 14 are: :MnO + e− MnO E = +0.27 V :MnO + e− + 2 H2O MnO2 + 4 OH− E = +0.96 V However, the reaction is slow in very alkaline solutions (with OH− concentration above 5–10 mol/L).

The disproportionation is believed to pass through a protonated intermediate, with the acid dissociation constant for the reaction HMnO MnO + H+ being estimated as pKa = 13.7 ± 0.2. However, K3MnO4 has been cocrystallized with Ca2Cl(PO4), allowing the study of the UV–visible spectrum of the hypomanganate ion.

Preparation

Hypomanganates may be prepared by the careful reduction of manganates with sulfite, hydrogen peroxide or mandelate.

Hypomanganates can also be prepared by the solid state method under flow near 1000 °C.

Uses

The strontium vanadate fluoride compound, with hypomanganate substituted for some vanadate units, has been investigated for potential use in near infrared lasers.

The barium salt has interesting magnetic properties.

Related compounds

In theory, hypomanganate would be the conjugate base of hypomanganic acid . This acid cannot be formed because of its rapid disproportionation, but its third acid dissociation constant has been estimated by pulse radiolysis techniques: :HMnO MnO + H+ pKa = 13.7 ± 0.2

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

References

References

  1. 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. {{doi. 10.1016/S0925-8388(96)02461-9
  2. The anion can replace [[phosphate]] {{chem. PO. 4. 10.1006/jssc.1999.8394
  3. 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 {{doi. 10.1016/0022-4596(70)90064-2
  4. 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 {{chem. Ba. 2. In. 2-''x''. Mn. ''x''. O. 5+''x''" ''Inorganic Chemistry'', volume 52, issue 3, pages 1349-1357. {{doi. 10.1021/ic3020332
  5. Herrman Lux (1946): "[http://zfn.mpdl.mpg.de/data/1/ZfN-1946-1-0281.pdf Über Salze des fünfwertigen Mangans]." ''Zeitschrift für Naturforschung'', volume 1, pages 281-283.
  6. (2014). "Synthesis, Crystal Structure, and Magnetic Properties of the Oxometallates KBaMnO4 and KBaAsO4". Solid State Sciences.
  7. {{Greenwood&Earnshaw1st
  8. (1956). "Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions". J. Chem. Soc..
  9. (1993). "Reduction of manganate(VI) by mandelic acid and its significance for development of a general mechanism of oxidation of organic compounds by high-valent transition metal oxides". J. Am. Chem. Soc..
  10. {{Cotton&Wilkinson4th
  11. {{RubberBible62nd
  12. "Manganese – compounds – standard reduction potentials". WebElements.
  13. (1979). "Rate of the MnO4−/MnO42− and MnO42−/MnO43− electrode reactions in alkaline solutions at solid electrodes". Electrochim. Acta.
  14. (1995). "Studies of Manganate(V), -(VI), and -(VII) Tetraoxyanions by Pulse Radiolysis. Optical Spectra of Protonated Forms". Inorg. Chem..
  15. (1956). "Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions". J. Chem. Soc..
  16. (1989). "Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds". J. Am. Chem. Soc..
  17. 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. {{doi. 10.1063/1.359585
  18. Ba. 3. Mn. 2. O. 8". ''Physics Review B'', volume 77, page 134406 {{doi. 10.1103/PhysRevB.77.134406

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