Rhodium (III) chloride
| Crystal structure | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
||||||||||
| __ Rh 3+ __ Cl - | ||||||||||
| General | ||||||||||
| Surname | Rhodium (III) chloride | |||||||||
| other names |
Rhodium trichloride |
|||||||||
| Ratio formula | RhCl 3 | |||||||||
| Brief description |
red solid (anhydrous), dark red solid (trihydrate) |
|||||||||
| External identifiers / databases | ||||||||||
|
||||||||||
| properties | ||||||||||
| Molar mass | 209.26 g mol −1 | |||||||||
| Physical state |
firmly |
|||||||||
| Melting point |
Decomposes at 450 ° C |
|||||||||
| solubility |
soluble (trihydrate), insoluble (anhydrous) in water |
|||||||||
| safety instructions | ||||||||||
|
||||||||||
| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||
Rhodium (III) chloride is a chemical compound made from rhodium and chlorine that is isotypic to aluminum trichloride . Rhodium trichloride is a dark red to red-brown solid that is extremely rare in nature. It is a rhodium salt of hydrochloric acid .
Extraction and presentation
Anhydrous rhodium (III) chloride results from a reaction between chlorine and rhodium at 400 to max. 800 ° C.
The trihydrate is formed from the reaction between hydrochloric acid and freshly prepared yellow rhodium (III) oxide hydrate Rh 2 O 3 · 5 H 2 O and careful drying on the steam bath.
![{\ displaystyle \ mathrm {Rh_ {2} O_ {3} \ cdot 5 \ H_ {2} O \ +6 \ HCl \ longrightarrow 2 \ [RhCl_ {3} (H_ {2} O) _ {3}] + 2 \ H_ {2} O}}](https://wikimedia.org/api/rest_v1/media/math/render/svg/7173415edc0fc353cd04d5047ca94fca2499b622)
When RhCl 3 · 3 H 2 O is heated to above 100 ° C, decomposition occurs with the formation of insoluble black rhodium (III) oxide (Rh 2 O 3 ).
properties
Physical Properties
Anhydrous rhodium (III) chloride produced at up to 700 ° C is a rose-red to brown-red amorphous powder that is insoluble in water and acids. Material produced above 700 ° C becomes clearly crystalline. From 800 ° C it sublimates into red-gold leaves. The cherry-red trihydrate with the formula [RhCl 3 (H 2 O) 3 ], on the other hand, is readily soluble in water. Anhydrous rhodium trichloride crystallizes monoclinically , space group C 2 / m (space group no. 12) with the lattice parameters a = 5.95 Å , b = 10.3 Å, c = 6.03 Å and β = 109.2 °.
Chemical properties
Anhydrous rhodium (III) chloride can be sublimed at 900 ° C. in a stream of chlorine. The color of hydrochloric acid solutions of [RhCl 3 (H 2 O) 3 ] slowly changes from red to yellow. Hydratisomeries occur:
![{\ displaystyle \ mathrm {H_ {3} [RhCl_ {6}] + 6 \ H_ {2} O \ longrightarrow \ [Rh (H_ {2} O) _ {6}] Cl_ {3} +3 \ HCl} }](https://wikimedia.org/api/rest_v1/media/math/render/svg/aa9135b2f58a493ed97a22c654dd83864c9979db)
use
In the 1960s, it was found to be useful as a catalyst for various reactions, including reactions with carbon monoxide , hydrogen, and with alkenes .
The hydrate is also used as an additive for bright and polished gold or platinum.
Individual evidence
- ↑ a b c d e f g Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 .
- ↑ a b c Entry on rhodium (III) chloride in the GESTIS substance database of the IFA , accessed on February 1, 2016(JavaScript required) .
- ^ Norman N. Greenwood, Alan Earnshaw: Chemistry of the Elements , 1st edition, Weinheim 1988, ISBN 3-527-26169-9 .
- ↑ H. Bärnighausen, BK Handa: The crystal structure of rhodium (III) chloride. In: Journal of the Less-Common Metals , 6, 1964, pp. 226-231, doi: 10.1016 / 0022-5088 (64) 90103-1 .