Zinc cyanide

Zinc cyanide
Identifiers
CAS number 557-21-1
PubChem 11186
ChemSpider 10713 Y
RTECS number ZH1575000
Jmol-3D images Image 1
Properties
Molecular formula C2N2Zn
Molar mass 117.444 g/mol
Appearance white powder
Density 1.852 g/cm3, solid
Melting point

800 °C (decomposes)
Solubility in water 0.00005 g/100 mL (20 °C)
Solubility attacked by alkalies, KCN, ammonia
Hazards
EU classification not listed
NFPA 704
0
4
2
LD50 100 mg/kg, rat (intraperitoneal)
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Zinc cyanide is the inorganic compound with the formula Zn(CN)2. It is a white solid that is used mainly for electroplating zinc but also has more specialized applications for the synthesis of organic compounds.

Contents

Structure, properties, synthesis

The structure features the zinc in the familiar tetrahedral coordination environment, all linked by bridging cyanide ligands. The structure consists of two "interpenetrating" structures. Such motifs are sometimes called "expanded diamondoid" structures because the interconnecting atoms are tetrahedral but instead of being directly linked as in diamond, the atoms are separated by additional bonds. Some forms of SiO2 adopts a similar structures, wherein the tetrahedral Si centres are linked by oxides. The cyanide group shows head to tail disorder with any zinc atom having between 1 and 4 carbon neighbours, and the remaining being nitrogen atoms. It shows one of the largest negative coefficents of thermal expansion (exceeding the previous record holder, zirconium tungstate).

Typical for an inorganic polymer, Zn(CN)2 is insoluble in most solvents. The solid dissolves in, or more precisely, is degraded by, aqueous solutions of basic ligands such as hydroxide, ammonia, and additional cyanide to give anionic complexes.

Zn(CN)2 is fairly easy to make because combining aqueous solutions of cyanide and zinc ions. For commercial applications, some effort is made to avoid halide impurities by using zinc acetates.[1] Zinc cyanide is a byproduct of certain gold extraction methods. To isolate gold from aqueous gold cyanide, some procedures call for the addition of zinc:

2 [Au(CN)2]- + Zn → 2 Au + Zn(CN)2 + 2 CN-

Applications

The main application of Zn(CN)2 is for electroplating of zinc from aqueous solutions containing additional cyanide.[1]

Organic synthesis

Zn(CN)2 is employed as a catalyst for the cyanosilylation of aldehydes and ketones.[2]

It is also used to introduce the formyl group in organic synthesis. 2-Hydroxy-1-naphthaldehyde has been prepared from 2-naphthol, zinc cyanide, and anhydrous hydrogen chloride.[3][4]

References

  1. ^ a b Ernst Gail, Stephen Gos, Rupprecht Kulzer, Jürgen Lorösch, Andreas Rubo and Manfred Sauer "Cyano Compounds, Inorganic" Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim, 2004. doi:10.1002/14356007.a08_159.pub2
  2. ^ Rasmussen J. K., Heilmann S. M. (1990), "In situ Cyanosilylation of Carbonyl Compounds: O-Trimethylsilyl-4-Methoxymandelonitrile", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv7p0521 ; Coll. Vol. 7: 521 
  3. ^ Adams R., Levine I. (1923). "Simplification of the Gattermann Synthesis of Hydroxy Aldehydes". J. Am. Chem. Soc. 45 (10): 2373–77. doi:10.1021/ja01663a020. 
  4. ^ Fuson R. C., Horning E. C., Rowland S. P., Ward M. L. (1955), "Mesitaldehyde", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv3p0549 ; Coll. Vol. 3: 549