Cadmium chloride is a white crystalline compound of cadmium and chloride, with the formula CdCl2. This salt is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. The crystal structure of cadmium chloride (described below), is a reference for describing other crystal structures. Also known are CdCl2•H2O and the hemipentahydrate CdCl2•2.5H2O.[2]
Structure
Anhydrous
Anhydrous cadmium chloride forms a layered structure consisting of octahedral Cd2+ centers linked with chloride ligands. Cadmium iodide, CdI2, has a similar structure, but the iodide ions are arranged in a HCP lattice, whereas in CdCl2 the chloride ions are arranged in a CCP lattice.[8][9]
Hydrates
The anhydrous form absorbs moisture from the air to form various hydrates. Three of these hydrates have been examined by X-ray crystallography.
Chemical properties
Cadmium chloride dissolves well in water and other polar solvents. It is a mild Lewis acid.[8]
CdCl2 + 2 Cl− → [CdCl4]2−
Solutions of equimolar cadmium chloride and potassium chloride give potassium cadmium trichloride.[13]With large cations, it is possible to isolate the trigonal bipyramidal [CdCl5]3− ion.
Cadmium metal is soluble in molten cadmium chloride, produced by heating cadmium chloride above 568 °C. Upon cooling, the metal precipitates.[14]
The anhydrous salt can also be prepared from anhydrous cadmium acetate using hydrogen chloride or acetyl chloride.[15]
Industrially, it is produced by the reaction of molten cadmium and chlorine gas at 600 °C.[14]
The monohydrate, hemipentahydrate, and tetrahydrate can be produced by evaporation of the solution of cadmium chloride at 35, 20, and 0 °C respectively. The hemipentahydrate and tetrahydrate release water in air.[10][11][12]
In the laboratory, anhydrous CdCl2 can be used for the preparation of organocadmium compounds of the type R2Cd, where R is an aryl or a primary alkyl. These were once used in the synthesis of ketones from acyl chlorides:[16]
CdCl 2 + 2 RMgX → R 2Cd + MgCl 2 + MgX 2
R 2Cd + 2R'COCl → 2R'COR + CdCl 2
Such reagents have largely been supplanted by organocopper compounds, which are much less toxic.
^ a bSeidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). New York: D. Van Nostrand Company. p. 169.
^ a b c d"Cadmium Chloride - CdCl2". chem.uwimona.edu.jm. Mona, Jamaica: The University of the West Indies. Retrieved 2014-06-25.
^ a b cSigma-Aldrich Co., Cadmium chloride. Retrieved on 2014-05-23.
^ a bN. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
^A. F. Wells, Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
^ a bH. Leligny; J. C. Monier (1974). "Structure cristalline de CdCl2.H2O" [Crystal structure of CdCl2.H2O]. Acta Crystallographica B (in French). 30 (2): 305–309. doi:10.1107/S056774087400272X.
^ a bH. Leligny; J. C. Monier (1975). "Structure de CdCl2.2,5H2O" [Structure of CdCl2.2,5H2O]. Acta Crystallographica B (in French). 31 (3): 728–732. doi:10.1107/S056774087500369X.
^ a bH. Leligny; J. C. Monier (1979). "Structure de dichlorure de cadmium tétrahydraté" [Structure of cadmium dichloride tetrahydrate]. Acta Crystallographica B (in French). 35 (3): 569–573. doi:10.1107/S0567740879004179.
^F. Wagenknecht; R. Juza (1963). "Potassium cadmium chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. p. 1095.
^ a b c dKarl-Heinz Schulte-Schrepping; Magnus Piscator (2000). "Cadmium and Cadmium Compounds". Ullmann's Encyclopedia of Industrial Chemistry (6th ed.). p. 472. doi:10.1002/14356007.a04_499. ISBN 9783527306732.
^F. Wagenknecht; R. Juza (1963). "Cadmium chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY, NY: Academic Press. pp. 1093–4.
^J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
External links
International Chemical Safety Card 0116
IARC Monograph "Cadmium and Cadmium Compounds"
National Pollutant Inventory - Cadmium and compounds
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