Cerium(III) chloride - Misplaced Pages

Cerium(III) chloride (CeCl₃), also known as cerous chloride or cerium trichloride, is a compound of cerium and chlorine. It is a white hygroscopic salt; it rapidly absorbs water on exposure to moist air to form a hydrate, which appears to be of variable composition, though the heptahydrate CeCl₃·7H₂O 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. Soxhlet extraction of CeCl₃ with thf gives CeCl₃(thf)_1.04.

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.

Organic synthesis

Cerium(III) chloride is a reagent in several procedures used in organic synthesis. 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.

It can also deprotect MEM group to alcohol in the presence of other acetal protecting groups (e.g. THP.)

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:

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

References

Several great producers such as Alfa and Strem list their products simply as a "hydrate" with "xH₂O" in the formula, but Aldrich sells a heptahydrate.
^ Paquette, L. A. (1999). Coates, R. M.; Denmark, S. E. (eds.). Handbook of Reagents for Organic Synthesis: Reagents, Auxiliaries and Catalysts for C-C Bond Formation. New York: Wiley. ISBN 0-471-97924-4.
^ Edelmann, F. T.; Poremba, P. (1997). Herrmann, W. A. (ed.). Synthetic Methods of Organometallic and Inorganic Chemistry. Vol. VI. Stuttgart: Georg Thieme Verlag. ISBN 3-13-103021-6.
^ Johnson, C. R.; Tait, B. D. (1987). "A cerium(III) modification of the Peterson reaction: methylenation of readily enolizable carbonyl compounds". Journal of Organic Chemistry. 52 (2): 281–283. doi:10.1021/jo00378a024. ISSN 0022-3263.
Dimitrov, Vladimir; Kostova, Kalina; Genov, Miroslav (1996). "Anhydrous cerium(III) chloride — Effect of the drying process on activity and efficiency". Tetrahedron Letters. 37 (37): 6787–6790. doi:10.1016/S0040-4039(96)01479-7.
Taylor, M. D.; Carter, P. C. (1962). "Preparation of anhydrous lanthanide halides, especially iodides". Journal of Inorganic and Nuclear Chemistry. 24 (4): 387–391. doi:10.1016/0022-1902(62)80034-7.
Kutscher, J.; Schneider, A. (1971). "Notiz zur Präparation von wasserfreien Lanthaniden-Haloge-niden, Insbesondere von Jodiden". Inorg. Nucl. Chem. Lett. 7 (9): 815. doi:10.1016/0020-1650(71)80253-2.
Greenwood, N. N.; Earnshaw, A. (1984). Chemistry of the Elements. New York: Pergamon Press. ISBN 0-08-022056-8.
Freeman, J. H.; Smith, M. L. (1958). "The preparation of anhydrous inorganic chlorides by dehydration with thionyl chloride". Journal of Inorganic and Nuclear Chemistry. 7 (3): 224–227. doi:10.1016/0022-1902(58)80073-1.
Druding, L. F.; Corbett, J. D. (1961). "Lower Oxidation States of the Lanthanides. Neodymium(II) Chloride and Iodide". Journal of the American Chemical Society. 83 (11): 2462–2467. doi:10.1021/ja01472a010. ISSN 0002-7863.
Corbett, J. D. (1973). "Reduced Halides of the Rare Earth Elements". Rev. Chim. Minérale. 10: 239.
Hirneise, Lars; Buschmann, Dennis A.; Maichle-Mössmer, Cäcilia; Anwander, Reiner (2022). "Cerium Fluorenyl Complexes Including CC Coupling Reactions". Organometallics. 41 (8): 962–976. doi:10.1021/acs.organomet.2c00029. S2CID 248065310.
Mine, Norioki; Fujiwara, Yuzo; Taniguchi, Hiroshi (1986). "Trichlorolanthanoid (LnCl₃)-catalyzed Friedel-Crafts alkylation reactions". Chemistry Letters. 15 (3): 357–360. doi:10.1246/cl.1986.357.
Paquette, Leo A.; Sabitha, G.; Yadav, J. S.; Scheuermann, Angelique M.; Merchant, Rohan R. (2021). "Cerium(III) Chloride". Encyclopedia of Reagents for Organic Synthesis. pp. 1–15. doi:10.1002/047084289X.rc041.pub3. ISBN 9780471936237.
Luche, Jean-Louis; Rodriguez-Hahn, Lydia; Crabbé, Pierre (1978). "Reduction of natural enones in the presence of cerium trichloride". Journal of the Chemical Society, Chemical Communications (14): 601–602. doi:10.1039/C39780000601.

Preparation of anhydrous CeCl3

Uses

Organic synthesis

References

Further reading

Preparation of anhydrous CeCl₃