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_cyanide_A.jpg) | |
| Names | |
|---|---|
| IUPAC name Copper(I) cyanide | |
| Other names Cuprous cyanide, copper cyanide, cupricin | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.008.076 |
| EC Number |
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| RTECS number |
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| UNII | |
| UN number | 1587 |
| |
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| 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 product (Ksp) | 3.47×10−20[2] |
| Solubility | insoluble inethanol, cold diluteacids; soluble inNH3,KCN |
| Structure | |
| monoclinic | |
| Hazards | |
| GHS labelling: | |
  | |
| Danger | |
| H300,H310,H330,H410 | |
| P260,P262,P264,P270,P271,P273,P280,P284,P301+P310,P302+P350,P304+P340,P310,P320,P321,P322,P330,P361,P363,P391,P403+P233,P405,P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 1 mg/m3 (as Cu)[3] |
REL (Recommended) | TWA 1 mg/m3 (as Cu)[3] |
IDLH (Immediate danger) | TWA 100 mg/m3 (as Cu)[3] |
| Safety data sheet (SDS) | Oxford MSDS |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Copper(I) cyanide (cuprous cyanide) is aninorganic compound with the formula CuCN. This off-white solid occurs in twopolymorphs; impure samples can be green due to the presence of Cu(II) impurities. The compound is useful as acatalyst, in electroplating copper, and as areagent in the preparation ofnitriles.[4]
Copper cyanide is acoordination polymer. It exists in two polymorphs both of which contain -[Cu-CN]- chains made from linear copper(I) centres linked bycyanidebridges. In the high-temperature polymorph, HT-CuCN, which is isostructural withAgCN, the linear chains pack on a hexagonal lattice and adjacent chains are off set by +/- 1/3c, Figure 1.[5] 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.[6]
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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.[7]
Cuprous cyanide is commercially available and is supplied as the low-temperature polymorph. It can be prepared by the reduction ofcopper(II) sulfate with sodium bisulfite at 60 °C, followed by the addition ofsodium cyanide to precipitate pure LT-CuCN as a pale yellow powder.[8]
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 treatingcopper(II) sulfate withsodium cyanide, in this redox reaction, copper(I) cyanide forms together withcyanogen:[9]
Because this synthetic route producescyanogen, 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 apseudohalide. It also explains whycupric cyanide (copper(II) cyanide, Cu(CN)2), has not been synthesised.
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. These complexes contrast with those of silver and gold cyanides, which form [M(CN)2]− ions in solution.[10] The coordination polymer KCu(CN)2 contains [Cu(CN)2]− units, which link together forming helical anionic chains.[11]
Copper cyanide is also soluble in concentrated aqueous ammonia, pyridine and N-methylpyrrolidone.
Cuprous cyanide is used forelectroplating copper.[4]
CuCN is a prominent reagent inorganocopper chemistry. It reacts withorganolithium reagents to form "mixed cuprates" with the formulas Li[RCuCN] and Li2[R2CuCN]. The use of CuCN revolutionized the deployment of simpler organocopper reagents of the type CuR and LiCuR2, the so-calledGilman reagents. In the presence of cyanide, these mixed cuprates are more readily purified and more stable.
The mixed cuprates Li[RCuCN] and Li2[R2CuCN] function as sources of the carbanions R−, but with diminished reactivity compared to the parent organolithium reagent. Thus they are useful for conjugate additions and some displacement reactions.
CuCN also forms silyl and stannyl reagents, which are used as sources of R3Si− and R3Sn−.[12]
CuCN is used in the conversion of aryl halides to nitriles in theRosenmund–von Braun reaction.[13]
CuCN has also been introduced as a mild electrophilic source of nitrile under oxidative conditions, for instance secondary amines[14] as well as sulfides and disulfides[15] have been efficiently cyanated using this methodology. This last methodology has been then introduced in a domino 3 component reaction, leading to 2-aminobenthiazoles.[16]
