Copper hydride
Names | |
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IUPAC name
Copper hydride
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Other names
Copper(I) hydride
Cuprous hydride Hydridocopper(I) Cuprane poly[cuprane(1)] | |
Identifiers | |
3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.229.864 |
EC Number |
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PubChem CID
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CompTox Dashboard (EPA)
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Properties | |
CuH | |
Molar mass | 64.554 g·mol−1 |
Melting point | 100 °C (212 °F; 373 K)[1] |
Hazards | |
GHS labelling: | |
Warning | |
H228, H315, H319, H335 | |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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TWA 1 mg/m3 (as Cu)[2] |
REL (Recommended)
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TWA 1 mg/m3 (as Cu)[2] |
IDLH (Immediate danger) |
TWA 100 mg/m3 (as Cu)[2] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Copper hydride is inorganic compound with the chemical formula CuHn where n ~ 0.95.[3] It is a red solid, rarely isolated as a pure composition, that decomposes to the elements.[4] Copper hydride is mainly produced as a reducing agent in organic synthesis and as a precursor to various catalysts.[5]
History
In 1844, the French chemist
Chemical properties
Structure
In copper hydride, elements adopt the
The CuH consists of a core of CuH with a shell of water and this may be largely replaced by ethanol. This offers the possibility of modifying the properties of CuH produced by aqueous routes.[10] While all methods for the synthesis of CuH result in the same bulk product, the synthetic path taken engenders differing surface properties. The different behaviors of CuH obtained by aqueous and nonaqueous routes can be ascribed to a combination of very different particle size and dissimilar surface termination, namely, bonded hydroxyls for the aqueous routes and a coordinated donor for the nonaqueous routes.[11]
Chemical reactions
CuH generally behaves as a source of H–. For instance, Wurtz reported the double displacement reaction of CuH with hydrochloric acid:[12]
- CuH + HCl → CuCl +H
2
When not cooled below −5 °C (23 °F), copper hydride decomposes, to produce hydrogen gas and a mixture containing elemental copper:
- 2 CuH → xCu•(2-x)CuH + ½x H
2 (0 < x < 2)
Solid copper hydride is the irreversible autopolymerisation product of the molecular form, and the molecular form cannot be isolated in concentration.
Production
Copper does not react with hydrogen even on heating,[13] thus copper hydrides are made indirectly from copper(I) and copper(II) precursors. Examples include the reduction of copper(II) sulfate with sodium hypophosphite in the presence of sulfuric acid,[1] or more simply with just hypophosphorous acid.[14] Other reducing agents, including classical aluminium hydrides can be used.[15]
- 4 Cu2+ + 6 H3PO2 + 6 H2O → 4 CuH + 6 H3PO3 + 8 H+
The reactions produce a red-colored precipitate of CuH, which is generally impure and slowly decomposes to liberate hydrogen, even at 0 °C.[14]
- 2 CuH → 2 Cu + H2
This slow decomposition also takes place underwater,
A new synthesis method has been published in 2017 by Lousada et al.[18] In this synthesis high purity CuH nanoparticles have been obtained from basic copper carbonate, CuCO3·Cu(OH)2.[18] This method is faster and has a higher chemical yield than the copper sulfate based synthesis and produces nanoparticles of CuH with higher purity and a smaller size distribution. The obtained CuH can easily be converted to conducting thin films of Cu. These films are obtained by spraying the CuH nanoparticles in their synthesis medium into some insulating support. After drying, conducting Cu films protected by a layer of mixed copper oxides are spontaneously formed.
Reductive sonication
Copper hydride is also produced by reductive sonication. In this process, hexaaquacopper(II) and hydrogen(•) react to produce copper hydride and oxonium according to the equation:
- [Cu(H2O)6]2+ + 3 H• → 1/n (CuH)n + 2 [H3O]+ + 4 H2O
Hydrogen(•) is obtained in situ from the homolytic sonication of water. Reductive sonication produces molecular copper hydride as an intermediate.[7]
Applications in Organic Synthesis
Phosphine- and NHC-copper hydride species have been developed as reagents in organic synthesis, albeit of limited use.
Chiral phosphine-copper complexes catalyze hydrosilation of ketones and esters with low enantioselectivities.[23] An enantioselective (80 to 92% ee) reduction of prochiral α,β-unsaturated esters uses Tol-BINAP complexes of copper in the presence of PMHS as the reductant.[24] Subsequently, conditions have been developed for the CuH-catalyzed hydrosilylation of ketones[25] and imines[26] proceeding with excellent levels of chemo- and enantioselectivity.
The reactivity of LnCuH species with weakly activated (e.g. styrenes, dienes) and unactivated alkenes (e.g. α-olefins) and alkynes has been recognized[27] and has served as the basis for several copper-catalyzed formal hydrofunctionalization reactions.[28][29][30]
"Hydridocopper"
The diatomic species CuH is a gas that has attracted the attention of spectroscopists. It polymerises upon being condensed. A well-known oligomer is octahedro-hexacuprane(6), occurring in Stryker's reagent. Hydridocopper has acidic behavior for the same reason as normal copper hydride. However, it does not form stable aqueous solutions, due in part to its autopolymerisation, and its tendency to be oxidised by water. Copper hydride reversibly precipitates from pyridine solution, as an amorphous solid. However, repeated dissolution affords the regular crystalline form, which is insoluble. Under standard conditions, molecular copper hydride autopolymerises to form the crystalline form, including under aqueous conditions, hence the aqueous production method devised by Wurtz.
Production
Molecular copper hydride can be formed by reducing
Amorphous copper hydride is also produced by anhydrous reduction. In this process copper(I) and tetrahydroaluminate react to produce molecular copper hydride and triiodoaluminium adducts. The molecular copper hydride is precipitated into amorphous copper hydride with the addition of diethyl ether. Amorphous copper hydride is converted into the Wurtz phase by annealing, accompanied by some decomposition.[31]
History
Hydridocopper was discovered in the vibration-rotation emission of a hollow-cathode lamp in 2000 by Bernath, who detected it at the University of Waterloo. It was first detected as a contaminant while attempting to generate NeH+ using the hollow-cathode lamp.[33][34] Molecular copper hydride has the distinction of being the first metal hydride to be detected in this way. (1,0) (2,0) and (2,1) vibrational bands were observed along with line splitting due to the presence of two copper isotopes, 63Cu and 65Cu.[35][36]
The A1Σ+-X1Σ+ absorption lines from CuH have been claimed to have been observed in sunspots and in the star
In vapour experiments, it was found that copper hydride is produced from the elements upon exposure to 310 nanometre radiation.[4]
- Cu + H2 ↔ CuH + H•
However, this proved to be unviable as a production method as the reaction is difficult to control. The activation barrier for the reverse reaction is virtually non-existent, which allows it to readily proceed even at 20 Kelvin.
Other copper hydrides
- A binary dihydride (CuH
2) also exists, in the form of an unstable reactive intermediate in the reduction of copper hydride by atomic hydrogen.
References
- ^ .
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0150". National Institute for Occupational Safety and Health (NIOSH).
- PMID 27454444.
- ^ PMID 11840988.
- ^ PMID 23574244. Archived from the originalon 24 June 2013. Retrieved 20 June 2013.
- ^ Wurtz, A. (1844) "Sur l'hydrure de cuivre" (On copper hydride), Comptes rendus, 18 : 702–704.
- ^ PMID 22179137.
- .
- .
- PMID 26634717.
- PMID 25671787.
- ISBN 978-0-262-26429-7.
- ISBN 978-0-08-037941-8.
- ^ .
- ISBN 978-0-323-16129-9.
- .
- .
- ^ PMID 28379275.
- ISSN 0002-7863.
- ISSN 0002-7863.
- ISSN 1364-548X. Archived from the original(PDF) on 2022-05-14. Retrieved 2019-12-19.
- .
- ISSN 0002-7863.
- PMID 12862472.
- PMID 15108129.
- PMID 19591178.
- PMID 24038866.
- PMID 24106781.
- PMID 24896663.
- ^ ISSN 0002-7863.
- .
- ISSN 0260-1826. Archived from the original(PDF) on 2015-04-02. Retrieved 2013-02-23.
- ISSN 0022-2852.
- S2CID 93779370.
- S2CID 43929297.
- doi:10.1086/190375.
- ISSN 0022-2852. Archived from the original(PDF) on 2005-03-10. Retrieved 2013-02-20.