Manganese(III) oxide

Manganese(III) oxide
Other names dimanganese trioxide, manganese sesquioxide, manganic oxide
Identifiers
CAS number	1317-34-6 Y
PubChem	14827
RTECS number	OP915000
Properties
Molecular formula	Mn2O3
Molar mass	157.8743 g/mol
Appearance	brown or black crystalline
Density	4.50 g/cm3
Melting point	940 °C (decomp)
Solubility in water	insoluble
Solubility	insoluble in alcohol, acetone soluble in acid
Structure
Crystal structure	Cubic, cI80[1]
Space group	Ia-3, No. 206
Related compounds
Other anions	manganese trifluoride, manganese(III) acetate
Other cations	chromium(III) oxide, iron(III) oxide
Related compounds	manganese(II) oxide, manganese dioxide
Hazards
NFPA 704	0 1 0
Y oxide (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Manganese(III) oxide is the chemical compound of formula Mn₂O₃.

Preparation and chemistry

Heating MnO₂ in air at below 800°C α-Mn₂O₃ is produced (higher temperatures produce Mn₃O₄).^[2] γ-Mn₂O₃ can be produced by oxidation followed by dehydration of manganese(II) hydroxide.^[2] Many preparations of nano-crystalline Mn₂O₃ have been reported, for example syntheses involving oxidation of Mn^II salts or reduction of MnO₂.^[3][4][5]

Manganese (III) oxide is formed by the redox reaction in an alkaline cell:

2 MnO₂ + Zn → Mn₂O₃ + ZnO

Manganese (III) oxide Mn₂O₃ must not be confused with MnOOH manganese (III) oxohydroxide. Contrary to Mn₂O₃, MnOOH is a compound that decomposes at about 300°C to form MnO₂.^[6]

Structure

Mn₂O₃ is unlike many other transition metal oxides in that it does not adopt the corundum (Al₂O₃) structure.^[2] Two forms are generally recognized, α-Mn₂O₃ and γ-Mn₂O₃,^[7] although a high pressure form with the CaIrO₃ structure has been reported too.^[8]

α-Mn₂O₃ has the cubic bixbyite structure, which is an example of a C-type rare earth sesquioxide (Pearson symbol cI80, space group Ia3, #206). The bixbyite structure has been found to be stabilised by the presence of small amounts of Fe³⁺, pure Mn₂O₃ has an orthorhombic structure (Pearson symbol oP24,space group Pbca, #61).^[9]

γ-Mn₂O₃ has a structure related to the spinel structure of Mn₃O₄ where the oxide ions are cubic close packed. This is similar to the relationship between γ-Fe₂O₃ and Fe₃O₄.^[7] γ-Mn₂O₃ is ferrimagnetic with a Neel temperature of 39 K.^[10]

References

1. ^ Otto H.H., Baltrasch R., Brandt H.J. (1993). "Further evidence for Tl3+ in Tl-based superconductors from improved bond strength parameters involving new structural data of cubic Tl2O3". Physica C 215: 205. doi:10.1016/0921-4534(93)90382-Z. 
2. ^ ^{a b c} Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
3. ^ Shuijin Lei, Kaibin Tang, Zhen Fang, Qiangchun Liu, Huagui Zheng (2006). "Preparation of α-Mn₂O₃ and MnO from thermal decomposition of MnCO₃ and control of morphology". Materials Letters 60: 53. doi:10.1016/j.matlet.2005.07.0. 
4. ^ Zhong-Yong Yuan, Tie-Zhen Ren, Gaohui Du, Bao-Lian Su (2004). "A facile preparation of single-crystalline α-Mn₂O₃ nanorods by ammonia-hydrothermal treatment of MnO₂". Chemical Physics Letters 389: 83. doi:10.1016/j.cplett.2004.03.064. 
5. ^ Navin Chandra, Sanjeev Bhasin, Meenakshi Sharma and Deepti Pal (2007). "A room temperature process for making Mn₂O₃ nano-particles and γ-MnOOH nano-rods". Materials Letters 61: 3728. doi:10.1016/j.matlet.2006.12.024. 
6. ^ Thomas Kohler, Thomas Armbruster, Eugen Libowitzky (1997). "Hydrogen Bonding and Jahn-Teller Distortion in Groutite,α-MnOOH, and Manganite,γ-MnOOH, and Their Relations to the Manganese Dioxides Ramsdellite and Pyrolusite". Journal of Solid State Chemistry 133: 486–500. doi:10.1006/jssc.1997.7516. 
7. ^ ^{a b} Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
8. ^ High Pressure Phase transition in Mn₂O₃ to the CaIrO₃-type Phase Santillan, J.; Shim, S. American Geophysical Union, Fall Meeting 2005, abstract #MR23B-0050
9. ^ Geller S. (1971). "Structure of α-Mn₂O₃, (Mn_0.983Fe_0.017)₂O₃ and (Mn_0.37Fe_0.63)₂O₃ and relation to magnetic ordering". Acta Cryst B27: 821. doi:10.1107/S0567740871002966. 
10. ^ Kim S. H, Choi B. J ,Lee G.H., Oh S. J., Kim B., Choi H. C., Park J, Chang Y. (2005). "Ferrimagnetism in γ-Manganese Sesquioxide (γ−Mn₂O₃) Nanoparticles". Journal of the Korean Physical Society 46 (4): 941.