Cobalt(II) cyanide

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Cobalt(II) cyanide
CAS number 542-84-7 YesY
20427-11-6 (dihydrate)
26292-31-9 (trihydrate)
PubChem 68336
ChemSpider 61631 YesY
Jmol-3D images Image 1
Molecular formula Co(CN)2
Molar mass 110.968 g/mol (anhydrous)
147.00 g/mol (dihydrate)
165.02 g/mol (trihydrate)
Appearance deep-blue powder
hygroscopic (anhydrous)
reddish-brown powder (dihydrate)
Density 1.872 g/cm3 (anhydrous)
Melting point 280 °C (anhydrous)
Solubility in water insoluble[1]
Solubility dihydrate
degraded with dissolution by NaCN, KCN, NH4OH, HCl
Related compounds
Other anions Cadmium chloride,
Cadmium iodide
Other cations Zinc cyanide,
Calcium cyanide,
Magnesium cyanide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Cobalt(II) cyanide is the inorganic compound with the formula Co(CN)2. It is coordination polymer that has attracted intermitant attention over many years in the area of inorganic synthesis and homogeneous catalysis.


Cobalt(II) cyanide has been used as a precursor to cobalt carbonyl.[2]


The trihydrate salt is obtained as a reddish brown precipitate by adding potassium cyanide to a cobalt salt solution.:[3]

CoCl2(H2O)6 + 2 KCN → Co(CN)2 + 2 KCl + 6 H2O

Hydrated Co(CN)2 dissolves in the presence of excess potassium cyanide, forming a red solution of K4Co(CN)6. This material further oxidizes to yellow K3Co(CN)6.


  1. ^ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3. 
  2. ^ Heinz W. Sternberg, Irving Wender, Milton Orchin Cobalt Tetracarbonyl Hydride: (Cobalt Hydrocarbonyl) Inorganic Syntheses, 1957, vol. V, p. 192. doi:10.1002/9780470132364.ch55
  3. ^ John H. Bigelow, "Potassium Hexacyanocobaltate(III)" Inorganic Syntheses, 1946, Volume I1, p. 225.