Potassium hypomanganate

Potassium hypomanganate
Names
IUPAC names
potassium manganate(V)
potassium tetraoxidomanganate(3−)
Properties[1]
K3MnO4
Molar mass 236.23 g mol−1
Appearance bright blue solid
UV-vis (λmax) 670 nm
(ε = 900 dm3 mol−1 cm−1)
Related compounds
Other anions
 Potassium manganate
Potassium permanganate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Potassium hypomanganate, K3MnO4, also known as potassium manganate(V), is a bright blue salt and a rare example of a manganese(V) compound. It is formed:

MnO−
4 + SO2−
3 + H2O → MnO3−
4 + SO2−
4 + 2 H+
2 MnO2−
4 + H2O2 + 2 OH− → 2 MnO3−
4 + O2 + 2 H2O
2 MnO2−
4 + C
8H
7O−
3 + 2 OH− → 2 MnO3−
4 + C
8H
5O−
3 + 2 H2O
2 MnO2 + 3 OH− → MnO3−
4 + MnO(OH) + H2O

The hypomanganate anion is unstable with respect to disproportionation in all but the most alkaline of solutions:[2][3] estimated electrode potentials at pH 14 are[5][6][7]

MnO2−
4 + e− ⇌ MnO3−
4   E = +0.27 V
MnO3−
4 + e− + 2 H2O ⇌ MnO2 + 4 OH−   E = +0.96 V

The disproportionation is believed to pass through a protonated intermediate,[7] with the acid dissociation constant for the reaction HMnO2−
4 ⇌ MnO3−
4 + H+ being estimated as pKa = 13.7 ± 0.2.[8] However, K3MnO4 has been cocrystallized with Ca2Cl(PO4), allowing the study of the UV–visible spectrum of the hypomanganate ion.[2][9]

References

  1. 1 2 Lee, Donald G.; Chen, Tao (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., 115 (24): 11231–36, doi:10.1021/ja00077a023.
  2. 1 2 3 4 Cotton, F. Albert; Wilkinson, Geoffrey (1980), Advanced Inorganic Chemistry (4th ed.), New York: Wiley, p. 746, ISBN 0-471-02775-8.
  3. 1 2 Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 1221–22. ISBN 0-08-022057-6..
  4. ↑ Lee, Donald G.; Chen, Tao (1989), "Oxidation of hydrocarbons. 18. Mechanism of the reaction between permanganate and carbon-carbon double bonds", J. Am. Chem. Soc., 111 (19): 7534–38, doi:10.1021/ja00201a039.
  5. ↑ Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. D-134. ISBN 0-8493-0462-8..
  6. ↑ Manganese – compounds – standard reduction potentials, WebElements, retrieved 2010-06-26.
  7. 1 2 Sekula-Brzezińska, K.; Wrona, P. K.; Galus, Z. (1979), "Rate of the MnO4−/MnO42− and MnO42−/MnO43− electrode reactions in alkaline solutions at solid electrodes", Electrochim. Acta, 24 (5): 555–63, doi:10.1016/0013-4686(79)85032-X.
  8. ↑ Rush, J. D.; Bielski, B. H. J. (1995), "Studies of Manganate(V), -(VI), and -(VII) Tetraoxyanions by Pulse Radiolysis. Optical Spectra of Protonated Forms", Inorg. Chem., 34 (23): 5832–38, doi:10.1021/ic00127a022.
  9. ↑ Carrington, A.; Symons, M. C. R. (1956), "Structure and reactivity of the oxy-anions of transition metals. Part I. The manganese oxy-anions", J. Chem. Soc.: 3373–80, doi:10.1039/JR9560003373.
This article is issued from Wikipedia - version of the 6/23/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.