Cadmium cyanide

Cadmium cyanide is an inorganic compound with the formula Cd(CN)2. It is a white crystalline compound that is used in electroplating.[2] It is very toxic, along with other cadmium and cyanide compounds.

Cadmium cyanide
Names
IUPAC name
Cadmium(II) cyanide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.027
UNII
Properties
Cd(CN)2
Molar mass 164.45 g/mol
Appearance white cubic crystals
Density 2.226 g/cm3
1.71 g/100 mL (15 °C)
2.2 g/100 mL (20 °C)
Solubility slightly soluble in alcohol
dissolves in alkali, metal cyanides and hydroxides
-54.0·10−6 cm3/mol
Hazards
NIOSH (US health exposure limits):
PEL (Permissible)
 [1910.1027] TWA 0.005 mg/m3 (as Cd)[1]
REL (Recommended)
 Ca[1]
IDLH (Immediate danger)
 Ca [9 mg/m3 (as Cd)][1]
Related compounds
Other anions
 Cadmium chloride,
Cadmium iodide
Other cations
 Zinc cyanide,
Calcium cyanide,
Magnesium cyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation and structure

Cadmium cyanide is prepared commercially by treating cadmium hydroxide with hydrogen cyanide:[3]

Cd(OH)2 + 2 HCN → Cd(CN)2 + 2 H2O

It can also be generated from tetracyanocadmate:

[Cd(CN)4]2− + CdCl2 → 2 Cd(CN)2 + 2 Cl−
Structure of the clathrate consisting of cadmium cyanide host and carbon tetrachloride guest, Cd(CN)2.CCl4. Blue = Cd(CN)2 framework, gray = C, green = disordered Cl.

Cadmium cyanide and zinc cyanide adopt similar structures.[4] As such, each metal has tetrahedral coordination sphere. Cyanide ligands interconnect pairs of metal centers. Two of the resulting diamondoid structures are interpenetrated. The structure is related to that of cristobalite, a polymorphs of SiO2. This structural similarity of cadmium dicyanide and cristobalite was foundational in the development of mineralomimetic chemistry: "the build-up of mineral-like structures using materials that never give stable minerals."[5]

Reactions and uses

It is used as an electrolyte for electrodeposition of thin metallic cadmium coatings on metal to protect against corrosion.

Like zinc cyanide, cadmium cyanide is fairly soluble in water, which is unusual for transition metal cyanides. The solubility increases with the additional cyanide, this reaction proceeding via "[Cd(CN)3]−" and [Cd(CN)4]2−. With acids, its solutions evolve hydrogen cyanide. When it is crystallizes in the presence of certain small molecules, it forms clathrates.[4]

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0087". National Institute for Occupational Safety and Health (NIOSH).
  2. Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3.
  3. Karl-Heinz Schulte-Schrepping, Magnus Piscator "Cadmium and Cadmium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2007 Wiley-VCH, Weinheim. doi:10.1002/14356007.a04_499.
  4. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  5. Iwamoto, Toschitake; Nishikiori, Shin-ichi; Kitazawa, Takafumi; Yuge, Hidetaka (1997). "Mineralomimetic chemistry as a modern aspect of co-ordination chemistry". Journal of the Chemical Society, Dalton Transactions (22): 4127–4136. doi:10.1039/A702539D..


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