Chemistry:Magnesium cyanide

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Magnesium cyanide
Other names
  • Magnesium dicyanide
  • Magnesium(II) cyanide
3D model (JSmol)
Molar mass 76.34 g/mol
Appearance White solid
Melting point 500 °C (932 °F; 773 K) (decomposes)
Reacts to form magnesium hydroxide
Solubility in ammonia Slightly soluble
Related compounds
Other anions
Magnesium thiocyanate
Other cations
Calcium cyanide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Magnesium cyanide is a chemical compound with the formula Mg(CN)2. It is a toxic white solid. It has been theorized that it is a nitrile compound, but it has been disproved.[1] If heated to 500 °C, it decomposes to magnesium nitride.[2]


The first attempt to prepare magnesium cyanide was attempted in 1924. It was attempted by reacting a solution of hydrogen cyanide in water with magnesium metal:[2]

HCN + Mg → Mg(CN)2 + H2

The instant it was formed, it reacted with water to form magnesium hydroxide. To avoid this problem, instead of using water as the reaction medium, pure ammonia was used at -30 °C. This formed magnesium cyanide ammoniate, which in turn was heated to 180 °C to produce magnesium cyanide. Then, the ammoniate was then heated to 180 °C which decomposed back to magnesium cyanide.[3] Other methods are possible, such as the decomposition of magnesium ferricyanide in an electric carbon tube, which produces iron carbide as a byproduct.[2]


Magnesium cyanide reacts with silver nitrate to form magnesium silver cyanide, with the formula MgAg2(CN)4. When this compound is heated it produces hydrogen cyanide gas and magnesium hydroxide, which meant it could not be used as a pathway for the production of magnesium cyanide. When silver nitrate reacts with magnesium cyanide, it also produces another magnesium silver cyanide, with the formula MgAg(CN)3.[2]


  1. Kapp, Jürgen; Schleyer, Paul v. R. (1996). "M(CN)2 Species (M = Be, Mg, Ca, Sr, Ba): Cyanides, Nitriles, or Neither?" (in en). Inorg. Chem. (ACS Publications) 35 (8): 2247–2252. doi:10.1021/ic9511837. PMID 11666420. 
  2. 2.0 2.1 2.2 2.3 Fr. Fichter; Richard Suter (1924). "Über Magnesiumcyanid" (in German). Helvetica (Wiley) 5 (3): 396–400. doi:10.1002/hlca.19220050311. 
  3. A. R. Frank, R. B. Booth, American Cyanamid Co., US Patent 2419931, 1947.