Copper(I) cyanide
Encyclopedia
Copper cyanide in an inorganic compound
with the formula CuCN. This off-white solid occurs in two polymorph
s; 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 nitrile
s.
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. 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.
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.
to precipitate pure LT-CuCN as a pale yellow powder.
On addition of sodium bisulphite the copper sulphate 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 togther with cyanogen
:
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 sulphate 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.
which link together forming helical anionic chains.
Copper cyanide is also soluble in 0.88 aqueous ammonia, pyridine and N-methylpyrrolidone.
, for example in the regioselective and stereoselective allylation and conjugate addition of N-Boc-2-lithiopyrrolidine and N-Boc-2-lithiopiperidine, or the copper cyanide catalyzed palladium coupling of α-lithio amines and aryl iodides.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula CuCN. This off-white solid occurs in two polymorph
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
s; 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
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
in the preparation of nitrile
Nitrile
A nitrile is any organic compound that has a -C≡N functional group. The prefix cyano- is used interchangeably with the term nitrile in industrial literature. Nitriles are found in many useful compounds, one example being super glue .Inorganic compounds containing the -C≡N group are not called...
s.
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 cyanideCyanide
A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....
bridges
Bridging ligand
A bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually restricted to small ligands such as pseudohalides or to ligands that are...
. In the high-temperature polymorph, HT-CuCN, which is isostructural with AgCN
Silver cyanide
Silver cyanide is the chemical compound with the formula AgCN. This white solid forms upon treatment of solutions containing Ag+ with cyanide. This precipitation step is used in some schemes to recover silver from solution...
, the linear chains pack on a hexagonal lattice and adjacent chains are off set by +/- 1/3 c, Figure 1. 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.
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.
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 bisulphite at 60 °C, followed by the addition of sodium cyanideSodium cyanide
Sodium cyanide is an inorganic compound with the formula NaCN. This highly toxic colorless salt is used mainly in gold mining but has other niche applications...
to precipitate pure LT-CuCN as a pale yellow powder.
- 2 CuSO4 + NaHSO3 + H2O + 2 NaCN → 2 CuCN + 3 NaHSO4
On addition of sodium bisulphite the copper sulphate 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
Sodium cyanide
Sodium cyanide is an inorganic compound with the formula NaCN. This highly toxic colorless salt is used mainly in gold mining but has other niche applications...
, in this redox reaction, copper(I) cyanide forms togther with cyanogen
Cyanogen
Cyanogen is the chemical compound with the formula 2. It is a colorless, toxic gas with a pungent odor.The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups — analogous to diatomic halogen molecules, such as Cl2, but far less oxidizing...
:
- 2 CuSO4 + 4 NaCN → 2 CuCN + (CN)2 + 2 Na2SO4
Because this synthetic route produces cyanogen
Cyanogen
Cyanogen is the chemical compound with the formula 2. It is a colorless, toxic gas with a pungent odor.The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups — analogous to diatomic halogen molecules, such as Cl2, but far less oxidizing...
, 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 sulphate 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-, these ions are trigonal planar and tetrahedral respectively. This is in contrast to both silver and gold cyanides which form [M(CN)2]- ions in solution. The coordination polymer KCu(CN)2 contains [Cu(CN)2]- unitswhich link together forming helical anionic chains.
Copper cyanide is also soluble in 0.88 aqueous ammonia, pyridine and N-methylpyrrolidone.
Applications
Cuprous cyanide is used for electroplating copper. The compound is useful reagent in organic synthesisOrganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
, for example in the regioselective and stereoselective allylation and conjugate addition of N-Boc-2-lithiopyrrolidine and N-Boc-2-lithiopiperidine, or the copper cyanide catalyzed palladium coupling of α-lithio amines and aryl iodides.