Cerium(III) chloride

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Cerium(III) chloride
Cerium(III) chloride
General
Systematic name Cerium(III) chloride
Cerium trichloride
Other names Cerous chloride
Molecular formula CeCl3
Molar mass 246.48 g/mol (anhydrous)
Appearance white solid, hygroscopic
CAS number [7790-86-5] [1]
Properties
Density and phase 3.92 g/cm3, solid
Solubility in water 100 g/100 ml (? °C)
Melting point 817 °C
Boiling point 1730 °C
Structure
Coordination
geometry		 Tricapped trigonal prismatic
(nine-coordinate)
Crystal structure UCl3 structure
Hazards
MSDS External MSDS
EU classification not listed
NFPA 704
Flash point not flammable
RTECS number  ?
Supplementary data page
Structure and
properties		 n, εr, etc.
Thermodynamic
data		 Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Related compounds
Other anions Cerium(III) fluoride
Cerium(III) bromide
Cerium(III) iodide
Other cations Lanthanum(III) chloride
Praseodymium(III) chloride
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and 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[2], though the heptahydrate CeCl3.7 H2O is known. It is highly soluble in water, and (when anhydrous) it is soluble in ethanol and acetone[4].

Contents

[edit] Preparation of anhydrous CeCl3

Simple rapid heating of the hydrate alone may cause small amounts of hydrolysis [1]. A useful form of anhydrous CeCl3 can be prepared if care is taken to heat the heptahydrate gradually to 140 °C over many hours under vacuum[4],[5],[9]. 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 with 4-6 equivalents of ammonium chloride under high vacuum[1],[6],[12], or by heating with an excess of thionyl chloride for three hours[1],[7]. The anhydrous halide may alternatively be prepared from cerium metal and hydrogen chloride [8]. It is usually purified by high temperature sublimation under high vacuum.

[edit] 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.[10]

Luche reduction[11] of alpha, beta-unsaturated carbonyl compounds has become a popular method in organic synthesis, where CeCl3.6H2O 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 or Grignard 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[5]:

CeCl3 directed alkylation reaction

It is reported[5] that organolithiums work more effectively in this reaction than do Grignard reagents.

[edit] References

  1. F. T. Edelmann, P. Poremba, in: Synthetic Methods of Organometallic and Inorganic Chemistry, (W. A. Herrmann, ed.), Vol. 6, Georg Thieme Verlag, Stuttgart, 1997.
  2. Several major manufacturers such as Alfa and Strem list their products simply as a "hydrate" with "xH2O" in the formula, but Aldrich sells a heptahydrate.
  3. CRC Handbook of Chemistry and Physics (58th edition), CRC Press, West Palm Beach, Florida, 1977.
  4. L. A. Paquette, in: Handbook of Reagents for Organic Synthesis: Reagents, Auxiliaries and Catalysts for C-C Bond Formation, (R. M. Coates, S. E. Denmark, eds.), Wiley, New York, 1999.
  5. C. R. Johnson, B. D. Tait, J. Org. Chem. 52, 281-283 (1987).
  6. M. D. Taylor, P. C. Carter, J. Inorg. Nucl. Chem. 24, 387 (1962); J. Kutscher, A. Schneider, Inorg. Nucl. Chem. Lett. 7, 815 (1971).
  7. J. H. Freeman, M. L. Smith, J. Inorg. Nucl. Chem. 7, 224 (1958).
  8. L. F. Druding, J. D. Corbett, J. Am. Chem. Soc. 83, 2462 (1961); J. D. Corbett, Rev. Chim. Minerale 10, 239 (1973).
  9. V. Dimitrov, K. Kostova, M. Genov, Tetrahedron Letters, 37, 6787 (1996).
  10. N. Mine et al., Chem. Lett., 357-360 (1986).
  11. J-L. Luche, L. Rodriguez-Hahn, P. Crabbe, J. Chem. Soc. Chem. Commun., 601-602 (1978).
  12. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.
  13. R. Anwander, in Lanthanides: Chemistry and Use in Organic Synthesis, (S. Kobayashi, ed.), Springer-Verlag, Berlin, 1999, p10-12. cerium is really cool.

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