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Cadmium chloride
Identifiers
CAS number	10108-64-2 Y
EC number	233-296-7
UN number	2570
RTECS number	EV0175000
SMILES	[Cd+2].[Cl-].[Cl-]
InChI	1/Cd.2ClH/h;2*1H/q+2;;/p-2
InChI key	YKYOUMDCQGMQQO-NUQVWONBAG
ChemSpider ID	23035
Properties
Molecular formula	CdCl2
Molar mass	183.32 g/mol
Appearance	white solid, hygroscopic
Density	4.047 g/cm3 (solid)
Melting point	564 °C
Boiling point	960 °C
Solubility in water	100 g/100 mL (0 °C) 135 g/100 mL (20 °C) 147 g/100 mL (100 °C)
Solubility	soluble in acetone, alcohol insoluble in ether
Structure
Crystal structure	Rhombohedral, hr9, SpaceGroup = R-3m, No. 166
Hazards
MSDS	External MSDS
EU Index	048-008-00-3
EU classification	Carc. Cat. 2 Muta. Cat. 2 Repr. Cat. 2 Highly toxic (T+) Dangerous for the environment (N)
R-phrases	R45, R46, R60, R61, R25, R26, R48/23/25, R50/53
S-phrases	S53, S45, S60, S61
Related compounds
Other anions	Cadmium fluoride Cadmium bromide Cadmium iodide
Other cations	Zinc chloride Mercury(II) chloride Calcium chloride
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Cadmium chloride is a white crystalline compound of cadmium and chlorine, with the formula CdCl₂. It is a hygroscopic solid that is highly soluble in water and slightly soluble in alcohol. Although it is considered to be ionic, it has considerable covalent character to its bonding. The crystal structure of cadmium chloride (described below), composed of two-dimensional layers of ions, is often used as a reference for describing other crystal structures. It also has a hemipentahydrate. ^[1]

Crystal structure

Cadmium chloride forms crystals with rhombohedral symmetry. Cadmium iodide, CdI₂, has a very similar crystal structure to CdCl₂. The individual layers in the two structures are identical, but in CdCl₂ the chloride ions are arranged in a CCP lattice, whereas in CdI₂ the iodide ions are arranged in a HCP lattice.

Chemical properties

Cadmium chloride has a high solubility in water, and it dissociates into ions. A certain amount of hydrolysis to species such as [CdOH(H₂O)_x]⁺ may occur. The high solubility may be due in part to formation of complex ions such as [CdCl₄]²⁻ (i.e, CdCl₂ is a Lewis acid). With excess chloride ions in water or acetonitrile it forms mainly [CdCl₃]⁻ and the tetrahedral anion, [CdCl₄]²⁻:

CdCl₂(aq) + 2 Cl⁻(aq) → [CdCl₄]²⁻(aq)

With large cations, it is possible to isolate the trigonal bipyramidal [CdCl₅]³⁻ ion.

Preparation

Anhydrous cadmium chloride can be prepared by the action of anhydrous chlorine or hydrogen chloride gas on heated cadmium metal.

Cd(s) + 2 HCl(g) → CdCl₂(s) + H₂(g)

Hydrochloric acid may be used to make hydrated CdCl₂ from the metal, or alternatively from cadmium oxide or cadmium carbonate.

Uses

Cadmium chloride is used for the preparation of cadmium sulfide, used as "Cadmium Yellow", a brilliant-yellow pigment, which is stable to heat and sulfide fumes.

CdCl₂(aq) + H₂S(g) → CdS(s) + 2 HCl(aq)

In the laboratory, anhydrous CdCl₂ can be used for the preparation of organocadmium compounds of the type R₂Cd where R = aryl or primary alkyl. These were once used in the synthesis of ketones from acyl chlorides (see below), but nowadays they have largely been supplanted by organocopper compounds, which are much less toxic.

CdCl₂ + 2 RMgX → R₂Cd + MgCl₂ + MgX₂

R₂Cd + R'COCl → R'COR + CdCl₂

Cadmium chloride is also used for photocopying, dyeing and electroplating.

References

1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398

1. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
2. Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
3. The Merck Index, 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
4. D. Nicholls, Complexes and First-Row Transition Elements, Macmillan Press, London, 1973.
5. A. F. Wells, 'Structural Inorganic Chemistry, 5th ed., Oxford University Press, Oxford, UK, 1984.
6. 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