Rhodium(III) oxide

Identifiers

CAS Number

* 12036-35-0 Y

3D model (JSmol)

* Interactive image

EC Number |

* 234-846-9

PubChem CID

* 159409

UNII |

* 6PYI3777JI Y

InChI

* InChI=1S/3O.2Rh/q3*-2;2*+3

SMILES

* [O-2].[O-2].[O-2].[Rh+3].[Rh+3]

Properties

Chemical formula

| Rh2O3
Molar mass | 253.8092 g/mol
Appearance  | dark grey odorless powder
Density | 8.20 g/cm3
Melting point |  1,100 °C (2,010 °F; 1,370 K) (decomposes)

Solubility in water

| insoluble
Solubility | insoluble in aqua regia

Magnetic susceptibility (χ)

| +104.0·10−6 cm3/mol
Structure[1]

Crystal structure

| hexagonal (corundum)

Space group

| R3c

Lattice constant

a = 512.7 pm (hexagonal setting), c = 1385.3 pm (hexagonal setting)

Hazards
GHS pictograms |
GHS Signal word | danger

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Rhodium(III) oxide (or Rhodium sesquioxide) is the inorganic compound with the formula Rh2O3. It is a gray solid that is insoluble in ordinary solvents.

## Contents

* 1 Structure
* 2 Production
* 3 Physical properties
* 4 Catalytic properties
* 5 See also
* 6 References

## Structure

Rh2O3 has been found in two major forms. The hexagonal form adopts the corundum structure. It transforms into an orthorhombic structure when heated above 750 °C.[1]

## Production

Rhodium oxide can be produced via several routes:

* Treating RhCl3 with oxygen at high temperatures.[3]
* Rh metal powder is fused with potassium hydrogen sulfate. Adding sodium hydroxide results in hydrated rhodium oxide, which upon heating converts to Rh2O3.[4]
* Rhodium oxide thin films can be produced by exposing Rh layer to oxygen plasma.[5]
* Nanoparticles can be produced by the hydrothermal synthesis.[6]

## Physical properties

Rhodium oxide films behave as a fast two-color electrochromic system: Reversible yellow ↔ dark green or yellow ↔ brown-purple color changes are obtained in KOH solutions by applying voltage ~1 V.[7]

Rhodium oxide films are transparent and conductive, like indium tin oxide (ITO) - the common transparent electrode, but Rh2O3 has 0.2 eV lower work function than ITO. Consequently, deposition of rhodium oxide on ITO improves the carrier injection from ITO thereby improving the electrical properties of organic light-emitting diodes.[5]

## Catalytic properties

Rhodium oxides are catalysts for hydroformylation of alkenes,[8] N2O production from NO,[9] and the hydrogenation of CO.[10]

## See also

* Rhodium
* Rhodium(IV) oxide
* Rhodium-platinum oxide

## References

1. ↑ 1.0 1.1 Coey, J. M. D. (1970-11-01). "The crystal structure of Rh2O3". Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry (International Union of Crystallography (IUCr)) 26 (11): 1876–1877. doi:10.1107/s0567740870005022. ISSN 0567-7408.
2. ↑ GHS: Alfa Aesar 011814 SDS (Feb 2021)
3. ↑ H. L. Grube (1963). "The Platinum Metals". in G. Brauer. Handbook of Preparative Inorganic Chemistry, 2nd Ed.. NY: Academic Press. p. 1588.
4. ↑ Wold, Aaron; Arnott, Ronald J.; Croft, William J. (1963). "The Reaction of Rare Earth Oxides with a High Temperature Form of Rhodium(III) Oxide". Inorganic Chemistry (American Chemical Society (ACS)) 2 (5): 972–974. doi:10.1021/ic50009a023. ISSN 0020-1669.
5. ↑ 5.0 5.1 Kim, Soo Young; Baik, Jeong Min; Yu, Hak Ki; Kim, Kwang Young; Tak, Yoon-Heung; Lee, Jong-Lam (2005-08-15). "Rhodium-oxide-coated indium tin oxide for enhancement of hole injection in organic light emitting diodes". Applied Physics Letters (AIP Publishing) 87 (7): 072105. doi:10.1063/1.2012534. ISSN 0003-6951. Bibcode: 2005ApPhL..87g2105K. https://scholarworks.unist.ac.kr/handle/201301/7384.
6. ↑ Mulukutla, Ravichandra S.; Asakura, Kiyotaka; Kogure, Toshihiro; Namba, Seitaro; Iwasawa, Yasuhiro (1999). "Synthesis and characterization of rhodium oxide nanoparticles in mesoporous MCM-41". Physical Chemistry Chemical Physics (Royal Society of Chemistry (RSC)) 1 (8): 2027–2032. doi:10.1039/a900588i. ISSN 1463-9076. Bibcode: 1999PCCP....1.2027M.
7. ↑ Gottesfeld, S. (1980). "The Anodic Rhodium Oxide Film: A Two-Color Electrochromic System". Journal of the Electrochemical Society (The Electrochemical Society) 127 (2): 272. doi:10.1149/1.2129654. ISSN 0013-4651.
8. ↑ Pino, P.; Botteghi, C. (1977). "Aldehydes from olefins: cyclohexanecarboxaldehyde". Organic Syntheses 57: 11. doi:10.15227/orgsyn.057.0011.
9. ↑ Mulukutla, Ravichandra S; Shido, Takafumi; Asakura, Kiyotaka; Kogure, Toshihiro; Iwasawa, Yasuhiro (2002). "Characterization of rhodium oxide nanoparticles in MCM-41 and their catalytic performances for NO–CO reactions in excess O2". Applied Catalysis A: General (Elsevier BV) 228 (1–2): 305–314. doi:10.1016/s0926-860x(01)00992-9. ISSN 0926-860X.
10. ↑ Watson, P; Somorjai, G. A. (1981). "The hydrogenation of carbon monoxide over rhodium oxide surfaces". Journal of Catalysis (Elsevier BV) 72 (2): 347–363. doi:10.1016/0021-9517(81)90018-x. ISSN 0021-9517. https://escholarship.org/uc/item/861193km.

* v
* t
* e

Rhodium compounds

Rh(0)|

| Organorhodium(0) compounds|

* [Rh6(CO)16]
* [Rh4(CO)12]

|

Rh(I)|

* [RhCl(PPh3)3]

| Organorhodium(I) compounds|

* [(C8H12)RhCl]2
* [(C8H14)2)RhCl]2
* [(CO)2)RhCl]2
* [HRh(CO)(PPh3)3]

|

Rh(II)|

* Rh2(CH3CO2)4

| Organorhodium(II) compunds|

* [Rh(C5H5)2]

|

Rh(III)|

* RhCl3
* Rh2O3
* YbRh2Si2
* [Rh(NH3)5Cl]Cl2

| Organorhodium(III) compunds|

* [Cp*RhCl2]2

|

Rh(IV)|

* RhO2

Rh(V)|

* XeRhF6

Rh(VI)|

* RhF6

* v
* t
* e

Oxides

Mixed oxidation states|

* Antimony tetroxide (Sb2O4)
* Cobalt(II,III) oxide (Co3O4)
* Europium(II,III) oxide (Eu3O4)
* Iron(II,III) oxide (Fe<sub>3O4)
* Lead(II,IV) oxide (Pb3O4)
* Manganese(II,III) oxide (Mn3O4)
* Silver(I,III) oxide (Ag2O2)
* Triuranium octoxide (U3O8)
* Carbon suboxide (C3O2)
* Mellitic anhydride (C12O9)
* [[Chemistry:Praseodymium(III,IV) Praseodymium(III,IV) oxide]] (Pr6O11)
* Terbium(III,IV) oxide (Tb4O7)

+1 oxidation state|

* Copper(I) oxide (Cu<sub>2O)
* Caesium oxide (Cs2O)
* Dicarbon monoxide (C2O)
* Dichlorine monoxide (Cl2O)
* Gallium(I) oxide (Ga2O)
* Lithium oxide (Li2O)
* Potassium oxide (K2O)
* Rubidium oxide (Rb2O)
* Silver oxide (Ag2O)
* Thallium(I) oxide (Tl2O)
* Sodium oxide (Na2O)
* Water (hydrogen oxide) (H2O)

+2 oxidation state|

* Aluminium(II) oxide (AlO)
* Barium oxide (BaO)
* Beryllium oxide (BeO)
* Cadmium oxide (CdO)
* Calcium oxide (CaO)
* Carbon monoxide (CO)
* Chromium(II) oxide (CrO)
* Cobalt(II) oxide (CoO)
* Copper(II) oxide (CuO)
* Europium(II) oxide (EuO)
* Germanium monoxide (GeO))
* Iron(II) oxide (FeO)
* Lead(II) oxide (PbO)
* Magnesium oxide (MgO)
* Manganese(II) oxide (MnO)
* Mercury(II) oxide (HgO)
* Nickel(II) oxide (NiO)
* Nitric oxide (NO)
* Palladium(II) oxide (PdO)
* Silicon monoxide (SiO)
* Strontium oxide (SrO)
* Sulfur monoxide (SO)
* Disulfur dioxide (S2O2)
* Thorium monoxide (ThO)
* Tin(II) oxide (SnO)
* Titanium(II) oxide (TiO)
* Vanadium(II) oxide (VO)
* Zinc oxide (ZnO)

+3 oxidation state|

* Aluminium oxide (Al<sub>2O3)
* Antimony trioxide (Sb2O3)
* Arsenic trioxide (As2O3)
* Bismuth(III) oxide (Bi2O3)
* Boron trioxide (B2O3)
* Cerium(III) oxide (Ce2O3)
* Dibromine trioxide (Br2O3)
* Chromium(III) oxide (Cr2O3)
* Dinitrogen trioxide (N2O3)
* Dysprosium(III) oxide (Dy2O3)
* Erbium(III) oxide (Er2O3)
* Europium(III) oxide (Eu2O3)
* Gadolinium(III) oxide (Gd2O3)
* Gallium(III) oxide (Ga2O3)
* Holmium(III) oxide (Ho2O3)
* Indium(III) oxide (In<sub>2O3)
* Iron(III) oxide (Fe2O3)
* Lanthanum oxide (La2O3)
* Lutetium(III) oxide (Lu2O3)
* Manganese(III) oxide (Mn2O3)
* Neodymium(III) oxide (Nd2O3)
* Nickel(III) oxide (Ni2O3)
* Phosphorus trioxide (P4O6)
* Praseodymium(III) oxide (Pr2O3)
* Promethium(III) oxide (Pm2O3)
* Rhodium(III) oxide (Rh2O3)
* [[Chemistry:Samarium(III) Samarium(III) oxide]] (Sm2O3)
* Scandium oxide (Sc2O3)
* Terbium(III) oxide (Tb2O3)
* Thallium(III) oxide (Tl2O3)
* Thulium(III) oxide (Tm2O3)
* Titanium(III) oxide (Ti2O3)
* Tungsten(III) oxide (W2O3)
* Vanadium(III) oxide (V2O3)
* Ytterbium(III) oxide (Yb2O3)
* Yttrium(III) oxide (Y2O3)

+4 oxidation state|

* Americium dioxide (AmO2)
* Carbon dioxide (CO2)
* Carbon trioxide (CO3)
* Cerium(IV) oxide (CeO2)
* Chlorine dioxide (ClO2)
* Chromium(IV) oxide (CrO<sub>2)
* Dinitrogen tetroxide (N2O4)
* Germanium dioxide (GeO<sub>2)
* [[Chemistry:Hafnium(IV) Hafnium(IV) oxide]] (HfO2)
* Lead dioxide (PbO2)
* Manganese dioxide (MnO2)
* Neptunium(IV) oxide (NpO2)
* Nitrogen dioxide (NO2)
* Osmium dioxide (OsO2)
* Plutonium(IV) oxide (PuO2)
* Praseodymium(IV) oxide (PrO2)
* Protactinium(IV) oxide (PaO2)
* Rhodium(IV) oxide (RhO2)
* Ruthenium(IV) oxide (RuO<sub>2)
* Selenium dioxide (SeO2)
* Silicon dioxide (SiO2)
* Sulfur dioxide (SO2)
* Tellurium dioxide (TeO<sub>2)
* [[Chemistry:Terbium(IV) Terbium(IV) oxide]] (TbO2)
* Thorium dioxide (ThO2)
* Tin dioxide (SnO2)
* Titanium dioxide (TiO<sub>2)
* Tungsten(IV) oxide (WO2)
* Uranium dioxide (UO2)
* Vanadium(IV) oxide (VO2)
* Zirconium dioxide (ZrO2)

+5 oxidation state|

* Antimony pentoxide (Sb2O5)
* Arsenic pentoxide (As2O5)
* Dinitrogen pentoxide (N2O5)
* Niobium pentoxide (Nb2O5)
* Phosphorus pentoxide (P2O5)
* Protactinium(V) oxide (Pa2O5)
* Tantalum pentoxide (Ta2O5)
* Vanadium(V) oxide (V2O5)

+6 oxidation state|

* Chromium trioxide (CrO3)
* Molybdenum trioxide (MoO3)
* Rhenium trioxide (ReO3)
* Selenium trioxide (SeO3)
* Sulfur trioxide (SO3)
* Tellurium trioxide (TeO3)
* Tungsten trioxide (WO3)
* Uranium trioxide (UO3)
* Xenon trioxide (XeO3)
* Iridium trioxide (IrO3)

+7 oxidation state|

* Dichlorine heptoxide (Cl2O7)
* Manganese heptoxide (Mn2O7)
* [[Chemistry:Rhenium(VII) Rhenium(VII) oxide]] (Re2O7)
* Technetium(VII) oxide (Tc2O7)

+8 oxidation state|

* Osmium tetroxide (OsO4)
* Ruthenium tetroxide (RuO4)
* Xenon tetroxide (XeO4)
* Iridium tetroxide (IrO4)
* Hassium tetroxide (HsO4)

Related|

* Oxocarbon
* Suboxide
* Oxyanion
* Ozonide
* Peroxide
* Superoxide

Oxides are sorted by oxidation state. Category:Oxides

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