Rhodium(III) chloride

Rhodium(III) chloride

Names
Other names Rhodium trichloride
Identifiers
CAS Number	10049-07-7 Y 13569-65-8 (trihydrate) Y[ICSC]
3D model (Jmol)	Interactive image
ChemSpider	8096382 Y
ECHA InfoCard	100.030.138
EC Number	233-165-4
PubChem CID	24872
RTECS number	VI9290000
UNII	Q4D88MX3Z8 N
InChI InChI=1S/3ClH.Rh/h3*1H;/q;;;+3/p-3 Y Key: SONJTKJMTWTJCT-UHFFFAOYSA-K Y InChI=1S/3ClH.Rh/h3*1H;/q;;;+3/p-3 Key: SONJTKJMTWTJCT-UHFFFAOYSA-K
SMILES [Rh+3].[Cl-].[Cl-].[Cl-]
Properties
Chemical formula	RhCl3
Molar mass	209.26 g/mol
Appearance	dark red solid deliquescent
Density	5.38 g/cm3, solid
Melting point	ca. 450 °C (842 °F; 723 K)
Boiling point	717 °C (1,323 °F; 990 K)
Solubility in water	insoluble
Solubility	soluble in hydroxide and cyanide solutions, also soluble in aqua regia
Acidity (pKa)	acidic in solution
Magnetic susceptibility (χ)	−-7.5·10−6 cm3/mol
Structure
Crystal structure	Monoclinic, mS16
Space group	C12/m1, No. 12
Coordination geometry	octahedral
Thermochemistry
Std enthalpy of formation (ΔfHo298)	−234 kJ/mol
Hazards
Safety data sheet	ICSC 0746
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	>500 mg/kg (rat, oral) 1302 mg/kg (rat, oral)
Related compounds
Other anions	Rhodium(III) fluoride Rhodium(III) bromide Rhodium(III) iodide
Other cations	Cobalt(II) chloride Iridium(III) chloride
Related compounds	Ruthenium(III) chloride Palladium(II) chloride
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

Rhodium(III) chloride refers to inorganic compounds with the formula RhCl₃(H₂O)_n, where n varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of n, the material is either a dense brown solid or a soluble reddish salt. The soluble salt is widely used to prepare compounds used in homogeneous catalysis, notably for the industrial production of acetic acid.

Hydrated rhodium trichloride usually refers to compound with the approximate formula RhCl₃(H₂O)₃.¹⁰³Rh NMR spectroscopy shows that solutions of this material consist of several species, the proportions of which change with time and depend on the concentration of chloride. The relative distribution of these species determines the colour of the solutions, which can range from yellow (the hexaaquo ion) to "raspberry-red". Some of these species are [Rh(H₂O)₆]³⁺, [RhCl(H₂O)₅]²⁺, cis- and trans-[RhCl₂(H₂O)₄]⁺, and [RhCl₃(H₂O)₃]. Individual ions have been separated by ion exchange chromatography.

Anhydrous rhodium chloride crystallises with a monoclinic crystal structure, as in YCl₃ and AlCl₃. It is a dense brown solid that is insoluble in common solvents and of little value in the laboratory.

RhCl₃(H₂O)₃ is produced from salts such as Na₃RhCl₆, the latter being obtained in the purification of rhodium from the other platinum group metals such as platinum and iridium. The sodium salt is converted to H₃RhCl₆ by ion exchange chromatography. Recrystallization of this acidic salt from water affords the hydrated trichloride, sometimes called "soluble rhodium trichloride." Anhydrous RhCl₃ is prepared by reaction of chlorine with rhodium sponge metal at 200–300 °C. Above 800 °C, the anhydrous chloride reverts to Rh metal and chlorine.