Samarium(III) chloride

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Samarium(III) chloride
Samarium(III)_chloride_hexahydrate
UCl3 without caption.png
Identifiers
CAS number 10361-82-7 (anhydrous) YesY, 13465-55-9 (hexahydrate)
ChemSpider 55428 YesY
Jmol-3D images Image 1
Properties
Molecular formula SmCl3
Molar mass 256.76 g/mol (anhydrous)
364.80 g/mol (hexahydrate)
Appearance pale yellow solid (anhydrous)

cream-coloured solid (hexahydrate)

Density 4.46 g/cm3 (anhydrous)

2.383 g/cm3 (hexahydrate)

Melting point 682 °C
Boiling point decomposes
Solubility in water 92.4 g/100 mL (10 °C)
Structure
Crystal structure hexagonal, hP8
Space group P63/m, No. 176
Coordination
geometry
Tricapped trigonal prismatic
(nine-coordinate)
Hazards
Main hazards Irritant
Related compounds
Other anions Samarium(III) oxide
Other cations Promethium(III) chloride, Europium(III) chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Samarium(III) chloride, also known as samarium trichloride, is an inorganic compound of samarium and chloride. It is a pale yellow solid that rapidly absorbs water to form a hexahydrate, SmCl3.6H2O.[1] The compound has few practical applications but is used in laboratories for research on new compounds of samarium.

Structure[edit]

Like several related chlorides of the lanthanides and actinides, SmCl3 crystallises in the UCl3 motif. The Sm3+ centres are nine-coordinate, occupying trigonal prismatic sites with additional chloride ligands occupying the three square faces.

Preparation and reactions[edit]

SmCl3 is prepared by the "ammonium chloride" route, which involves the initial synthesis of (NH4)2[SmCl5]. This material can be prepared from the common starting materials at reaction temperatures of 230 °C from samarium oxide:[2]

10 NH4Cl + Sm2O3 → 2 (NH4)2[SmCl5] + 6 NH3 + 3 H2O

The pentachloride is then heated to 350-400 °C resulting in evolution of ammonium chloride and leaving a residue of the anhydrous trichloride:

(NH4)2[SmCl5] → 2 NH4Cl + SmCl3

It can also be prepared from samarium metal and hydrogen chloride.[3][4]

2 Sm + 6 HCl → 2 SmCl3 + 3 H2

Aqueous solutions of samarium(III) chloride can be prepared by dissolving metallic samarium or samarium carbonate in hydrochloric acid.

Samarium(III) chloride is a moderately strong Lewis acid, which ranks as "hard" according to the HSAB concept. Aqueous solutions of samarium chloride can be used to prepare samarium trifluoride:

SmCl3 + 3 KF → SmF3 + 3 KCl

Uses[edit]

Samarium(III) chloride is used for the preparation of samarium metal, which has a variety of uses, notably in magnets. Anhydrous SmCl3 is mixed with sodium chloride or calcium chloride to give a low melting point eutectic mixture. Electrolysis of this molten salt solution gives the free metal.[5]

In laboratory[edit]

Samarium(III) chloride can also be used as a starting point for the preparation of other samarium salts. The anhydrous chloride is used to prepare organometallic compounds of samarium, such as bis(pentamethylcyclopentadienyl)alkylsamarium(III) complexes.[6]

References[edit]

  1. ^ F. T. Edelmann, P. Poremba (1997). W. A. Herrmann, ed. Synthetic Methods of Organometallic and Inorganic Chemistry 6. Stuttgart: Georg Thieme Verlag. 
  2. ^ Meyer, G. (1989). "The Ammonium Chloride Route to Anhydrous Rare Earth Chlorides-The Example of YCl3". Inorganic Syntheses 25: 146–150. doi:10.1002/9780470132562.ch35. ISBN 978-0-470-13256-2. 
  3. ^ L. F. Druding, J. D. Corbett (1961). J. Am. Chem. Soc. 83 (11): 2462. doi:10.1021/ja01472a010. 
  4. ^ J. D. Corbett (1973). Rev. Chim. Minerale 10: 239. 
  5. ^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. ISBN 0-08-022057-6. 
  6. ^ G. A. Molander, E. D. Dowdy (1999). Shu Kobayashi, ed. Lanthanides: Chemistry and Use in Organic Synthesis. Berlin: Springer-Verlag. pp. 119–154. ISBN 3-540-64526-8.