Rhodium (IV) oxide

Crystal structure
__ Rh 4+      __ O 2−
General
Surname	Rhodium (IV) oxide
other names	Rhodium dioxide
Ratio formula	RhO 2
Brief description	black tetragonal crystals (pure substance) green solid (hydrate)
External identifiers / databases
CAS number 12137-27-8 (pure substance) EC number 235-237-0 ECHA InfoCard 100.032.021 PubChem 82936 Wikidata Q409279
properties
Molar mass	134.90 g mol −1
Physical state	firmly
density	7.2 g cm −3
Melting point	decomposition
solubility	almost insoluble in water, acids, alkalis and organic solvents
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Rhodium (IV) oxide , also known as rhodium dioxide , is a chemical compound of the elements rhodium and oxygen . It is a black solid; there is also a green hydrate .

Extraction and presentation

The hydrate can be obtained by oxidation of Rh ₂ (SO ₄ ) ₃ with e.g. B. ozone or by electrolysis.

${\displaystyle \mathrm {Rh_{2}(SO_{4})_{3}\longrightarrow 2\ RhO_{2}+3\ SO_{2}} }$

properties

Physical Properties

Rhodium (IV) oxide crystallizes in the tetragonal crystal system with the space group P 4 ₂ / mnm (space group no. 136) and the lattice parameters a = 448.9 pm and c = 309.0 pm, in the unit cell there are two formula units .

Chemical properties

When rhodium dioxide is heated to 850 ° C, rhodium trioxide is formed; this breaks down into the elements at 1050 ° C.

${\displaystyle \mathrm {2\ RhO_{2}\ \ {\xrightarrow[{+O_{2}}]{850^{\circ }C}}\ \ 2\ RhO_{3}\ \ {\xrightarrow[{-O_{2}}]{950^{\circ }C}}\ \ 2\ Rh} }$

literature

• O. Muller and R. Roy: Formation and stability of the platinum and rhodium oxides at high oxygen pressures and the structures of Pt ₃ O ₄ , β-PtO ₂ and RhO ₂ . In: Journal of the Less Common Metals . 16, 1968, p. 129. doi : 10.1016 / 0022-5088 (68) 90070-2 .
• RD Shannon: Synthesis and properties of two new members of the rutile family RhO ₂ and PtO ₂ . In: Solid State Communications . 6, 1968, p. 139. doi : 10.1016 / 0038-1098 (68) 90019-7 .

Individual evidence

1. ↑ ^{a b c} David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Properties of the Elements and Inorganic Compounds, pp. 4-85. ( Rhodium dioxide on webelements.com ).
2. ^ ^{A b c} Jean D'Ans, Ellen Lax: Pocket book for chemists and physicists. 3. Elements, inorganic compounds and materials, minerals, Volume 3. 4. Edition, Springer, 1997, ISBN 978-3-5406-0035-0 , p. 698 ( limited preview in Google book search).
3. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
4. ^ ^{A b} A. F. Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 , p. 1702.