Names | |
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IUPAC name Copper hydride | |
Other names Copper(I) hydride Cuprous hydride Hydridocopper(I) Cuprane poly[cuprane(1)] | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
ECHA InfoCard | 100.229.864 |
EC Number |
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PubChem CID | |
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) | TWA 1 mg/m3 (as Cu) [2] |
REL (Recommended) | 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). |
Copper hydride is an 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]
In 1844, the French chemist Adolphe Wurtz synthesised copper hydride for the first time. [6] He reduced an aqueous solution of copper(II) sulfate with hypophosphorous acid (H3PO2). In 2011, Panitat Hasin and Yiying Wu were the first to synthesise a metal hydride (copper hydride) using the technique of sonication. [7] Copper hydride has the distinction of being the first metal hydride discovered. In 2013, it was established by Donnerer et al. that, at least up to fifty gigapascals, copper hydride cannot be synthesised by pressure alone. However, they were successful in synthesising several copper-hydrogen alloys under pressure. [5]
In copper hydride, elements adopt the Wurtzite crystal structure [8] [9] (polymeric), being connected by covalent bonds. [1]
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]
CuH generally behaves as a source of H–. For instance, Wurtz reported the double displacement reaction of CuH with hydrochloric acid: [12]
When not cooled below −5 °C (23 °F), copper hydride decomposes, to produce hydrogen gas and a mixture containing elemental copper:
Solid copper hydride is the irreversible autopolymerisation product of the molecular form, and the molecular form cannot be isolated in concentration.
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]
The reactions produce a red-colored precipitate of CuH, which is generally impure and slowly decomposes to liberate hydrogen, even at 0 °C. [14]
This slow decomposition also takes place underwater, [16] however there are reports of the material becoming pyrophoric if dried. [17]
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.
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:
Hydrogen(•) is obtained in situ from the homolytic sonication of water. Reductive sonication produces molecular copper hydride as an intermediate. [7]
Phosphine- and NHC-copper hydride species have been developed as reagents in organic synthesis, albeit of limited use. [19] Most widely used is [(Ph3P)CuH]6 (Stryker's reagent) for the reduction of α,β-unsaturated carbonyl compounds. [20] H2 (at least 80 psi) and hydrosilanes can be used as the terminal reductant, allowing a catalytic amount of [(Ph3P)CuH]6 to be used for conjugate reduction reactions. [21] [22]
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]
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.
Molecular copper hydride can be formed by reducing copper iodide with lithium aluminium hydride in ether and pyridine. [31] 4CuI + LiAlH4→ CuH + LiI + AlI3 This was discovered by E Wiberg and W Henle in 1952. [32] The solution of this CuH in the pyridine is typically dark red to dark orange. [31] A precipitate is formed if ether is added to this solution. [31] This will redissolve in pyridine. Impurities of the reaction products remain in the product. [31] In this study, it was found that the solidified diatomic substance is distinct from the Wurtzite structure. The Wurtzite substance was insoluble and was decomposed by lithium iodide, but not the solidified diatomic species. Moreover, while the Wurtzite substance's decomposition is strongly base catalysed, whereas the solidified diatomic species is not strongly affected at all. Dilts distinguishes between the two copper hydrides as the 'insoluble-' and 'soluble copper hydrides'. The soluble hydride is susceptible to pyrolysis under vacuum and proceeds to completion under 100 °C.
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]
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 19 Piscium. [37] [38]
In vapour experiments, it was found that copper hydride is produced from the elements upon exposure to 310 nanometre radiation. [4]
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.
Wilkinson's catalyst (chloridotris(triphenylphosphene)rhodium(I)) is a coordination complex of rhodium with the formula [RhCl(PPh3)3], where 'Ph' denotes a phenyl group. It is a red-brown colored solid that is soluble in hydrocarbon solvents such as benzene, and more so in tetrahydrofuran or chlorinated solvents such as dichloromethane. The compound is widely used as a catalyst for hydrogenation of alkenes. It is named after chemist and Nobel laureate Sir Geoffrey Wilkinson, who first popularized its use.
The Wacker process or the Hoechst-Wacker process refers to the oxidation of ethylene to acetaldehyde in the presence of palladium(II) chloride and copper(II) chloride as the catalyst. This chemical reaction was one of the first homogeneous catalysis with organopalladium chemistry applied on an industrial scale.
The Corey–House synthesis (also called the Corey–Posner–Whitesides–House reaction and other permutations) is an organic reaction that involves the reaction of a lithium diorganylcuprate () with an organic halide or pseudohalide () to form a new alkane, as well as an ill-defined organocopper species and lithium (pseudo)halide as byproducts.
The Ullmann reaction or Ullmann coupling, named after Fritz Ullmann, couples two aryl or alkyl groups with the help of copper. The reaction was first reported by Ullmann and his student Bielecki in 1901. It has been later shown that palladium and nickel can also be effectively used.
Basketane is a polycyclic alkane with the chemical formula C10H12. The name is taken from its structural similarity to a basket shape. Basketane was first synthesized in 1966, independently by Masamune and Dauben and Whalen. A patent application published in 1988 used basketane, which is a hydrocarbon, as a source material in doping thin diamond layers because of the molecule's high vapor pressure, carbon ring structure, and fewer hydrogen-to-carbon bond ratio.
Metal carbon dioxide complexes are coordination complexes that contain carbon dioxide ligands. Aside from the fundamental interest in the coordination chemistry of simple molecules, studies in this field are motivated by the possibility that transition metals might catalyze useful transformations of CO2. This research is relevant both to organic synthesis and to the production of "solar fuels" that would avoid the use of petroleum-based fuels.
In chemistry, a boranylium ion is an inorganic cation with the chemical formula BR+
2, where R represents a non-specific substituent. Being electron-deficient, boranylium ions form adducts with Lewis bases. Boranylium ions have historical names that depend on the number of coordinated ligands:
Borane, also known as borine, is an unstable and highly reactive molecule with the chemical formula BH
3. The preparation of borane carbonyl, BH3(CO), played an important role in exploring the chemistry of boranes, as it indicated the likely existence of the borane molecule. However, the molecular species BH3 is a very strong Lewis acid. Consequently, it is highly reactive and can only be observed directly as a continuously produced, transitory, product in a flow system or from the reaction of laser ablated atomic boron with hydrogen. It normally dimerizes to diborane in the absence of other chemicals.
Diborane(2), also known as diborene, is an inorganic compound with the formula B2H2. The number 2 in diborane(2) indicates the number of hydrogen atoms bonded to the boron complex. There are other forms of diborane with different numbers of hydrogen atoms, including diborane(4) and diborane(6).
The Krische allylation involves the enantioselective iridium-catalyzed addition of an allyl group to an aldehyde or an alcohol, resulting in the formation of a secondary homoallylic alcohol. The mechanism of the Krische allylation involves primary alcohol dehydrogenation or, when using aldehyde reactants, hydrogen transfer from 2-propanol. Unlike other allylation methods, the Krische allylation avoids the use of preformed allyl metal reagents and enables the direct conversion of primary alcohols to secondary homoallylic alcohols.
In organic chemistry, the Fujiwara–Moritani reaction is a type of cross coupling reaction where an aromatic C-H bond is directly coupled to an olefinic C-H bond, generating a new C-C bond. This reaction is performed in the presence of a transition metal, typically palladium. The reaction was discovered by Yuzo Fujiwara and Ichiro Moritani in 1967. An external oxidant is required to this reaction to be run catalytically. Thus, this reaction can be classified as a C-H activation reaction, an oxidative Heck reaction, and a C-H olefination. Surprisingly, the Fujiwara–Moritani reaction was discovered before the Heck reaction.
The Mukaiyama hydration is an organic reaction involving formal addition of an equivalent of water across an olefin by the action of catalytic bis(acetylacetonato)cobalt(II) complex, phenylsilane and atmospheric oxygen to produce an alcohol with Markovnikov selectivity.
In organic chemistry, the Murai reaction is an organic reaction that uses C-H activation to create a new C-C bond between a terminal or strained internal alkene and an aromatic compound using a ruthenium catalyst. The reaction, named after Shinji Murai, was first reported in 1993. While not the first example of C-H activation, the Murai reaction is notable for its high efficiency and scope. Previous examples of such hydroarylations required more forcing conditions and narrow scope.
A lanthanocene is a type of metallocene compound that contains an element from the lanthanide series. The most common lanthanocene complexes contain two cyclopentadienyl anions and an X type ligand, usually hydride or alkyl ligand.
The Stahl oxidation is a copper-catalyzed aerobic oxidation of primary and secondary alcohols to aldehydes and ketones. Known for its high selectivity and mild reaction conditions, the Stahl oxidation offers several advantages over classical alcohol oxidations.
The inorganic imides are compounds containing an ion composed of nitrogen bonded to hydrogen with formula HN2−. Organic imides have the NH group, and two single or one double covalent bond to other atoms. The imides are related to the inorganic amides (H2N−), the nitrides (N3−) and the nitridohydrides (N3−•H−).
Metal-ligand cooperativity (MLC) is a mode of reactivity in which a metal and ligand of a complex are both involved in the bond breaking or bond formation of a substrate during the course of a reaction. This ligand is an actor ligand rather than a spectator, and the reaction is generally only deemed to contain MLC if the actor ligand is doing more than leaving to provide an open coordination site. MLC is also referred to as "metal-ligand bifunctional catalysis." Note that MLC is not to be confused with cooperative binding.
The nitro-Mannich reaction is the nucleophilic addition of a nitroalkane to an imine, resulting in the formation of a beta-nitroamine. With the reaction involving the addition of an acidic carbon nucleophile to a carbon-heteroatom double bond, the nitro-Mannich reaction is related to some of the most fundamental carbon-carbon bond forming reactions in organic chemistry, including the aldol reaction, Henry reaction and Mannich reaction.
A hydrocupration is a chemical reaction whereby a ligated copper hydride species, reacts with a carbon-carbon or carbon-oxygen pi-system; this insertion is typically thought to occur via a four-membered ring transition state, producing a new copper-carbon or copper-oxygen sigma-bond and a stable (generally) carbon-hydrogen sigma-bond. In the latter instance (copper-oxygen), protonation (protodemetalation) is typical – the former (copper-carbon) has broad utility. The generated copper-carbon bond (organocuprate) has been employed in various nucleophilic additions to polar conjugated and non-conjugated systems and has also been used to forge new carbon-heteroatom bonds.
Tantalocene trihydride, or bis(η5-cyclopentadienyl)trihydridotantalum, is an organotanalum compound in the family of bent metallocenes consisting of two cyclopentadienyl rings and three hydrides coordinated to a tantalum center. Its formula is TaCp2H3, and it is a white crystalline compound that is sensitive to air. It is the first example of a molecular trihydride of a transition metal.