Cerium(III) chloride

Cerium(III) chloride

Cerium(III) chloride
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Names
IUPAC names Cerium(III) chloride Cerium trichloride
Other names Cerous chloride
Identifiers
CAS Number	7790-86-5 Y 18618-55-8 (heptahydrate) N
ChEBI	CHEBI:35458 Y
ChemSpider	23038 Y
Jmol 3D model	Interactive image
PubChem	24636
UNII	TH8E3IE00V N
InChI InChI=1S/Ce.3ClH/h;3*1H/q+3;;;/p-3 Y Key: VYLVYHXQOHJDJL-UHFFFAOYSA-K Y InChI=1/Ce.3ClH/h;3*1H/q+3;;;/p-3 Key: VYLVYHXQOHJDJL-DFZHHIFOAZ
SMILES [Cl-].[Cl-].[Cl-].[Ce+3]
Properties
Chemical formula	CeCl3
Molar mass	246.48 g/mol (anhydrous) 372.58 g/mol (heptahydrate)
Appearance	fine white powder
Density	3.97 g/cm3
Melting point	817 °C (1,503 °F; 1,090 K) (anhydrous) 90 °C (heptahydrate, decomposes)
Boiling point	1,727 °C (3,141 °F; 2,000 K)
Solubility in water	100 g/100 ml
Solubility	soluble in alcohol
Structure
Crystal structure	hexagonal (UCl3 type), hP8
Space group	P63/m, No. 176
Coordination geometry	Tricapped trigonal prismatic (nine-coordinate)
Vapor pressure	{{{value}}}
Related compounds
Other anions	Cerium(III) oxide Cerium(III) fluoride Cerium(III) bromide Cerium(III) iodide
Other cations	Lanthanum(III) chloride Praseodymium(III) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Cerium(III) chloride (CeCl₃), also known as cerous chloride or cerium trichloride, is a compound of cerium and chlorine. It is a white hygroscopic solid; it rapidly absorbs water on exposure to moist air to form a hydrate, which appears to be of variable composition, though the heptahydrate CeCl₃·7 H₂O is known. It is highly soluble in water, and (when anhydrous) it is soluble in ethanol and acetone.

Preparation of anhydrous CeCl₃

Simple rapid heating of the hydrate alone may cause small amounts of hydrolysis. A useful form of anhydrous CeCl₃ can be prepared if care is taken to heat the heptahydrate gradually to 140 °C (284 °F) over many hours under vacuum. This may or may not contain a little CeOCl from hydrolysis), but it is suitable for use with organolithium and Grignard reagents. Pure anhydrous CeCl₃ can be made by dehydration of the hydrate either by slowly heating to 400 °C (752 °F) with 4–6 equivalents of ammonium chloride under high vacuum, or by heating with an excess of thionyl chloride for three hours. The anhydrous halide may alternatively be prepared from cerium metal and hydrogen chloride. It is usually purified by high temperature sublimation under high vacuum.

Uses

Cerium(III) chloride can be used as a starting point for the preparation of other cerium salts, such as the Lewis acid, cerium(III) trifluoromethanesulfonate, used for Friedel-Crafts acylations. It is also used itself as a Lewis acid, for example as a catalyst in Friedel-Crafts alkylation reactions.

Luche reduction of alpha, beta-unsaturated carbonyl compounds has become a popular method in organic synthesis, where CeCl₃·7H₂O is used in conjunction with sodium borohydride. For example carvone gives only the allylic alcohol 1 and none of the saturated alcohol 2. Without CeCl₃, a mixture of 1 and 2 is formed.

Luche reduction

Another important use in organic synthesis is for alkylation of ketones, which would otherwise form enolates if simple organolithium reagents were to be used. For example, compound 3 would be expected to simply form an enolate without CeCl₃ being present, but in the presence of CeCl₃ smooth alkylation occurs:

CeCl3 directed alkylation reaction

It is reported that organolithiums work more effectively in this reaction than do Grignard reagents.

Further reading

• CRC Handbook of Chemistry and Physics (58th edition), CRC Press, West Palm Beach, Florida, 1977.