Rhodium(III) iodide

Rhodium(III) iodide
Identifiers
CAS Number	15492-38-3 ;
3D model (JSmol)	Interactive image;
ChemSpider	76627;
ECHA InfoCard	100.035.913
EC Number	239-521-5;
PubChem CID	4428348;
CompTox Dashboard (EPA)	DTXSID00329389 DTXSID40403197, DTXSID00329389 ;
	InChI InChI=1S/3HI.Rh/h3*1H;/q;;;+3/p-3 Key: KXAHUXSHRWNTOD-UHFFFAOYSA-K;
	SMILES [Rh](I)(I)I;
Properties
Chemical formula	I3Rh
Molar mass	483.61890 g·mol−1
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H413
Precautionary statements	P273, P501
Related compounds
Other anions	Rhodium(III) bromide; Rhodium(III) chloride; Rhodium(III) fluoride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Rhodium(III) iodide is an inorganic compound with the formula RhI₃. It is a black solid.^[1] Some rhodium(III) iodides are used as commercial catalysts.

Structure

RhI₃ adopts same crystal structure motif as AlCl₃ and YCl₃. The structure consists of cubic close-packed iodide ions and rhodium ions filling a third of the octahedral interstices, forming a layers.^[2]

Preparation

Rhodium(III) iodide can be synthesised by the reaction of aqueous potassium iodide with rhodium(III) bromide.^[1]

RhBr₃ + 3KI → RhI₃ + 3KBr

Reactivity

Rhodium(III) iodide is only known in the anhydrous form. Unlike the other rhodium(III) halides, it does not form hydrates.^[1] The related anion [RhI₆]³⁻ was previously thought not to form^[1] but has since been prepared by diffusion of RhCl₃·3H₂O through a layer of hydroiodic acid into piperazine.^[3]

Although RhI₃ and [RhI₆]³⁻ remain laboratory curiosities, other rhodium(III) iodides have had a major impact technologically. They are catalysts used in the Monsanto process, which at one time was the dominant method for producing acetic acid, a commodity chemical. One intermediate in that cycle is [(CH₃)Rh(CO)₂I₃]⁻.^[4]

References

1 2 3 4 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1119–1120. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.
↑ Brodersen, K.; Thiele, G.; Recke, I. (1968). "Strukturuntersuchungen an Rhodiumhalogeniden". J. Less-Common Met. 14 (1): 151–152. doi:10.1016/0022-5088(68)90214-2.
↑ Bujak, Maciej (2015). "Efficient Diffusion-Controlled Ligand Exchange Crystal Growth of Isostructural Inorganic–Organic Halogenidorhodates(III): The Missing Hexaiodidorhodate(III) Anion". Cryst. Growth Des. 15 (3): 1295–1302. doi:10.1021/cg501694d.
↑ Hosea Cheung, Robin S. Tanke, G. Paul Torrence "Acetic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_045.

[G&E-1] 1 2 3 4 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1119–1120. doi:10.1016/C2009-0-30414-6. ISBN 978-0-08-037941-8.

[2] Brodersen, K.; Thiele, G.; Recke, I. (1968). "Strukturuntersuchungen an Rhodiumhalogeniden". J. Less-Common Met. 14 (1): 151–152. doi:10.1016/0022-5088(68)90214-2.

[3] Bujak, Maciej (2015). "Efficient Diffusion-Controlled Ligand Exchange Crystal Growth of Isostructural Inorganic–Organic Halogenidorhodates(III): The Missing Hexaiodidorhodate(III) Anion". Cryst. Growth Des. 15 (3): 1295–1302. doi:10.1021/cg501694d.

[4] Hosea Cheung, Robin S. Tanke, G. Paul Torrence "Acetic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_045.

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