Cerium(III) chloride (CeCl3), also known as cerous chloride or cerium trichloride, is a compound ofcerium andchlorine. It is a whitehygroscopic salt; it rapidly absorbs water to formhydrates, which may be of variable composition.The hexa- and heptahydrate CeCl3·7H2O are known.[1] All forms are highly soluble inwater, and the anhydrous derivative is soluble inethanol andacetone.[2][3]
Simple rapid heating of the hydrate alone may cause small amounts ofhydrolysis.[4]
A useful form ofanhydrous CeCl3 can be prepared if care is taken to heat the heptahydrate gradually to 140 °C (284 °F) over many hours under vacuum.[2][5][6] This may or may not contain a little CeOCl fromhydrolysis, but it is suitable for use withorganolithium andGrignard 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 ofammonium chloride under high vacuum,[4][7][8][9] or by heating with an excess ofthionyl chloride for three hours.[4][10] The anhydroushalide may alternatively be prepared fromcerium metal andhydrogen chloride.[11][12] It is usually purified by high temperature sublimation under high vacuum. Soxhlet extraction ofCeCl3 with thf givesCeCl3(thf)1.04.[13]
Cerium(III) chloride is a reagent in several procedures used in organic synthesis.[15]Luche reduction[16] of alpha, beta-unsaturated carbonyl compounds has become a popular method inorganic synthesis, where CeCl3·7H2O is used in conjunction withsodium borohydride. For example,carvone gives only the allylicalcohol1 and none of thesaturatedalcohol2. Without CeCl3, a mixture of1 and2 is formed.
It can also deprotectMEM group to alcohol in the presence of other acetal protecting groups (e.g.THP.)
Another important use inorganic synthesis is for alkylation ofketones, which would otherwise formenolates if simpleorganolithium reagents were to be used. For example, compound3 would be expected to simply form an enolate without CeCl3 being present, but in the presence of CeCl3 smooth alkylation occurs:[5]
It is reported that organolithium reagents work more effectively in this reaction than doGrignard reagents.[5]
^Boatner, L. A.; Neal, J. S.; Ramey, J. O.; Chakoumakos, B. C.; Custelcean, R. (2013). "The observation of scintillation in a hydrated inorganic compound: CeCl3·6H2O".Applied Physics Letters.103 (14).doi:10.1063/1.4823707.
^abPaquette, 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.ISBN0-471-97924-4.
^Boatner, L. A.; Wisniewski, D.; Neal, J. S.; Ramey, J. O.; Kolopus, J. A.; Chakoumakos, B. C.; Wisniewska, M.; Custelcean, R. (2008). "Single-crystal CeCl3(CH3OH)4: A new metal-organic cerium chloride methanol adduct for scintillator applications".Applied Physics Letters.93 (24).doi:10.1063/1.3049137.
^abcEdelmann, F. T.; Poremba, P. (1997). Herrmann, W. A. (ed.).Synthetic Methods of Organometallic and Inorganic Chemistry. Vol. VI. Stuttgart: Georg Thieme Verlag.ISBN3-13-103021-6.
^abcJohnson, 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.ISSN0022-3263.
^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.ISBN0-08-022056-8.
^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.
^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.ISBN9780471936237.
^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.
_2.png)
