Manganese(III) oxide

Manganese(III) oxide

Names
Other names dimanganese trioxide, manganese sesquioxide, manganic oxide
Identifiers
CAS Number	1317-34-6 Y
3D model (Jmol)	Interactive image
ChemSpider	14139 N
ECHA InfoCard	100.013.878
PubChem	14824
RTECS number	OP915000
InChI InChI=1S/2Mn.3O N Key: GEYXPJBPASPPLI-UHFFFAOYSA-N N InChI=1/2Mn.3O/rMn2O3/c3-1-5-2-4 Key: GEYXPJBPASPPLI-YNHMASKPAU
SMILES O=[Mn]O[Mn]=O
Properties
Chemical formula	Mn2O3
Molar mass	157.8743 g/mol
Appearance	brown or black crystalline
Density	4.5 g/cm3
Melting point	888 °C (1,630 °F; 1,161 K) (alpha form) 940 °C, decomposes (beta form)
Solubility in water	0.00504 g/100 mL (alpha form) 0.01065 g/100 mL (beta form)
Solubility	insoluble in alcohol, acetone soluble in acid, ammonium chloride
Magnetic susceptibility (χ)	+14,100·10−6 cm3/mol
Structure
Crystal structure	Cubic, cI80
Space group	Ia-3, No. 206
Thermochemistry
Std molar entropy (So298)	110 J·mol−1·K−1
Std enthalpy of formation (ΔfHo298)	−971 kJ·mol−1
Hazards
NFPA 704	0 1 0
Related compounds
Other anions	manganese trifluoride, manganese(III) acetate
Other cations	chromium(III) oxide, iron(III) oxide
Related compounds	manganese(II) oxide, manganese dioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

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

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

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

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

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

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).

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. γ-Mn₂O₃ is ferrimagnetic with a Néel temperature of 39 K.