Copper(I) cyanide

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Copper(I) cyanide
Alpha-CuCN-unit-cell-CM-3D-balls.png
Names
IUPAC name
Copper(I) cyanide
Other names
Cuprous cyanide, copper cyanide, cupricin
Identifiers
544-92-3 YesY
ChemSpider 10543 YesY
EC Number 208-883-6
Jmol 3D model Interactive image
PubChem 11009
RTECS number GL7150000
  • InChI=1S/CN.Cu/c1-2;/q-1;+1 YesY
    Key: DOBRDRYODQBAMW-UHFFFAOYSA-N YesY
  • InChI=1/CN.Cu/c1-2;/q-1;+1
    Key: DOBRDRYODQBAMW-UHFFFAOYAI
  • [Cu+].[C-]#N
Properties
CuCN
Molar mass 89.563 g/mol
Appearance off-white / pale yellow powder
Density 2.92 g/cm3[1]
Melting point 474 °C (885 °F; 747 K)
negligible
Solubility insoluble in ethanol, cold dilute acids;
soluble in NH4OH, KCN
Structure
monoclinic
Vapor pressure {{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
YesY verify (what is YesYN ?)
Infobox references

Copper(I) cyanide is an inorganic compound with the formula CuCN. This off-white solid occurs in two polymorphs; impure samples can be green due to the presence of Cu(II) impurities. The compound is useful as a catalyst, in electroplating copper, and as a reagent in the preparation of nitriles.[2]

Structure

Copper cyanide is a coordination polymer. It exists in two polymorphs both of which contain -[Cu-CN]- chains made from linear copper(I) centres linked by cyanide bridges. In the high-temperature polymorph, HT-CuCN, which is isostructural with AgCN, the linear chains pack on a hexagonal lattice and adjacent chains are off set by +/- 1/3 c, Figure 1.[3] In the low-temperature polymorph, LT-CuCN, the chains deviate from linearity and pack into rippled layers which pack in an AB fashion with chains in adjacent layers rotated by 49 °, Figure 2.[4]

  • Figure 1: The structure of HT-CuCN showing the chains running along the c axis. Key: copper = orange and cyan = head-to-tail disordered cyanide groups.

  • Figure 2: The structure of LT-CuCN showing sheets of chains staking in an ABAB fashion. Key copper = orange and cyan = head-to-tail disordered cyanide groups.

LT-CuCN can be converted to HT-CuCN by heating to 563 K in an inert atmosphere. In both polymorphs the copper to carbon and copper to nitrogen bond lengths are ~1.85 Å and bridging cyanide groups show head-to-tail disorder.[5]

Preparation

Cuprous cyanide is commercially available and is supplied as the low-temperature polymorph. It can be prepared by the reduction of copper(II) sulfate with sodium bisulfite at 60 °C, followed by the addition of sodium cyanide to precipitate pure LT-CuCN as a pale yellow powder.[6]

2 CuSO4 + NaHSO3 + H2O + 2 NaCN → 2 CuCN + 3 NaHSO4

On addition of sodium bisulfite the copper sulfate solution turns from blue to green, at which point the sodium cyanide is added. The reaction is performed under mildly acidic conditions. Copper cyanide has historically been prepared by treating copper(II) sulfate with sodium cyanide, in this redox reaction, copper(I) cyanide forms together with cyanogen:[7]

2 CuSO4 + 4 NaCN → 2 CuCN + (CN)2 + 2 Na2SO4

Because this synthetic route produces cyanogen, uses two equivalents of sodium cyanide per equivalent of CuCN made and the resulting copper cyanide is impure it is not the industrial production method. The similarity of this reaction to that between copper sulfate and sodium iodide to form copper(I) iodide is one example of cyanide ions acting as a pseudo halide. It also explains why copper(II) cyanide, Cu(CN)2, has not been synthesised.

Reactions

Copper cyanide is insoluble in water but rapidly dissolves in solutions containing CN− to form [Cu(CN)3]2− and [Cu(CN)4]3−, which exhibit trigonal planar and tetrahedral coordination geometry, respectively. This is in contrast to both silver and gold cyanides which form [M(CN)2]− ions in solution.[8] The coordination polymer KCu(CN)2 contains [Cu(CN)2]− units which link together forming helical anionic chains.[9]

Copper cyanide is also soluble in 0.88 aqueous ammonia, pyridine and N-methylpyrrolidone.

Applications

Cuprous cyanide is used for electroplating copper.[2] The compound is useful reagent in organic synthesis, for example in the regioselective and stereoselective allylation and conjugate addition of N-Boc-2-lithiopyrrolidine and N-Boc-2-lithiopiperidine,[10] or the copper cyanide catalyzed palladium coupling of α-lithio amines and aryl iodides.[11]

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 H. Wayne Richardson "Copper Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a07_567
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.; Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Housecroft, Catherine E.; Sharpe, Alan G. (2008) Inorganic Chemistry (3rd ed.), Pearson: Prentice Hall. ISBN 978-0-13-175553-6.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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