Copper(I) hydroxide
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| IUPACName =
| OtherNames = Cuprous hydroxide; Copper monohydroxide
| Section1 = {{Chembox Identifiers
| CASNo = 19650-79-4
| PubChem = 9855444
| SMILES = [OH-].[Cu+]
| InChI=1S/Cu.H2O/h;1H2/q+1;/p-1
| InChIKey = ZMHWUUMELDFBCZ-UHFFFAOYSA-M
| ChemSpiderID = 8031144
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| Section2 = {{Chembox Properties
| Formula = CuOH
| MolarMass = 80.55 g/mol
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| Section3 = {{Chembox Hazards
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Copper(I) hydroxide is the inorganic compound with the chemical formula of CuOH. Little evidence exists for its existence. A similar situation applies to the monohydroxides of gold(I) and silver(I). Solid CuOH has been claimed however as an unstable yellow-red solid.{{cite journal|last1=Soroka|first1=Inna L.|last2=Shchukarev|first2=Andrey|last3=Jonsson|first3=Mats|last4=Tarakina|first4=Nadezda V.|last5=Korzhavyi|first5=Pavel A.|title=Cuprous hydroxide in a solid form: does it exist?|journal=Dalton Transactions|date=2013|volume=42|issue=26|pages=9585–94|doi=10.1039/C3DT50351H|pmid=23673918}} The topic has been the subject of theoretical analysis.{{cite journal|last1=Korzhavyi|first1=P.A.|last2=Soroka|first2=I.|last3=Boman|first3=M.|last4=Johansson|first4=B.|title=Thermodynamics of stable and metastable Cu-OH compounds.|journal=Solid State Phenomena|date=2011|volume=172|pages=973–78|doi=10.4028/www.scientific.net/SSP.172-174.973|s2cid=137644376 }}
Copper(I) hydroxide would also be expected to easily oxidise to copper(II) hydroxide:
:{{chem2|4CuOH + 2 H2O + O2 -> 4Cu(OH)2}}
It would also be expected to rapidly dehydrate:
:{{chem2|2CuOH -> Cu2O + H2O}}
Solid CuOH would be of interest as a possible intermediate in the formation of copper(I) oxide (Cu2O), which has diverse applications, e.g. applications in solar cells.{{cite journal |title=Thin film deposition of Cu2O and Application for Solar Cells|journal=Solar Energy|date=2006|volume=1;80|issue=6|pages=715–22|doi=10.1016/j.solener.2005.10.012}}
Solid CuOH
Theoretical calculations predict that CuOH would be stable. Specifically, the dissociation of Cu(OH)2− leading to CuOH is subject to an energy of 62 ± 3 kcal/mol.{{cite journal|last1=Illas|first1=F.|last2=Rubio|first2=J.|last3=Centellas|first3=F.|last4=Virgili|first4=J.|title=Molecular Structure of Copper (I) Hydroxide and Copper Hydroxide (1-) (Cu (OH)2−). An ab initio Study.|journal=The Journal of Physical Chemistry|date=1984|volume=88|issue=22|pages=5225–28|doi=10.1021/j150666a022}}
:{{chem2|Cu(OH)2- -> CuOH + OH-}}
Without evidence for its existence, CuOH has been invoked as a catalyst in organic synthesis{{cite journal|last1=Luo|first1=K.|last2=Li|first2=W.|last3=Lin|first3=J.|last4=Jin|first4=Y.|title=Tandem Reaction of Heterocyclic Ketene Aminals with Diazoesters: Synthesis of Pyrimidopyrrolidone Derivatives.|journal=Tetrahedron Letters|date=2019|volume=60|issue=41|pages=151136|doi=10.1016/j.tetlet.2019.151136|s2cid=203143147 }}
Gaseous CuOH
Gaseous CuOH has been characterized spectroscopically using intracavity laser spectroscopy,{{cite journal |last1=Harms |first1=J.C. |last2=O'Brien |first2=L.C. |last3=O'Brien |first3=J.J. |date=2019 |title=Rotational Analysis of the [15.1] A "–X~ 1A′ Transition of CuOH and CuOD Observed at High Resolution with Intracavity Laser Spectroscopy. |journal=Journal of Molecular Spectroscopy |volume=362 |pages=8–13 |doi=10.1016/j.jms.2019.05.013|s2cid=191158971 }} single vibronic level emission,{{cite journal |last1=Tao |first1=C. |last2=Mukarakate |first2=C. |last3=Reid |first3=S.A. |date=2007 |title=Single Vibronic Level Emission Spectroscopy and Fluorescence Lifetime of the B~ 1A "→ X~ 1A′ System of CuOH and CuOD. |journal=Chemical Physics Letters |volume=449 |issue=4–6 |pages=282–85 |doi=10.1016/j.cplett.2007.10.084}} and microwave spectroscopic detection.{{cite journal |last1=Whitham |first1=C.J. |last2=Ozeki |first2=H. |last3=Saito |first3=S. |date=1999 |title=Microwave spectroscopic detection of transition metal hydroxides: CuOH and AgOH. |journal=The Journal of Chemical Physics |volume=15;110 |issue=23 |pages=11109–12 |doi=10.1063/1.479051|hdl=10098/1528 |hdl-access=free }}
CuOH is calculated to be bent, with the point group Cs. In this case, the bond distance of the Cu-O bond was 1.818 Å and the bond distance of the O-H bond was 0.960 Å. The bond angle for this geometry was 131.9°. The compound is highly ionic in character, which is why this angle is not exactly 120°. Structural parameters for linear CuOH have also been examined computationally.
Ligand-stabilized Cu(I) hydroxides
Although simple CuOH compounds are fairly elusive or restricted to the gas-phase within spectrometers, some derivatives are well characterized.
Specifically cuprous hydroxides have been prepared using bulky NHC co-ligands.{{cite journal |doi=10.1021/om100733n |title=A Versatile Cuprous Synthon: [Cu(IPr)(OH)] (IPr = 1,3 Bis(diisopropylphenyl)imidazol-2-ylidene) |date=2010 |last1=Fortman |first1=George C. |last2=Slawin |first2=Alexandra M. Z. |last3=Nolan |first3=Steven P. |journal=Organometallics |volume=29 |issue=17 |pages=3966–3972 }} In addition to Cu(IPr)OH, the dimer {{chem2|[Cu(IPr)]2OH]+}} (as its {{chem2|BF4-}} salt){{cite journal |doi=10.1039/C4CC03346A |title=[{Cu(IPr)}2(μ-OH)][BF4]: Synthesis and Halide-Free CuAAC Catalysis |date=2014 |last1=Ibrahim |first1=Houssein |last2=Guillot |first2=Régis |last3=Cisnetti |first3=Federico |last4=Gautier |first4=Arnaud |journal=Chemical Communications |volume=50 |issue=54 |pages=7154–7156 |pmid=24854111 }}) and the aquo complex {{chem2|[Cu(IPr)]OH2]+}} (as its {{chem2|SbF6-}}) have been characterized by X-ray crystallography.{{cite journal |doi=10.1039/D0CP05222A |title=Synthesis and Characterization of N-Heterocyclic Carbene–M⋯OEt2 Complexes (M = Cu, Ag, Au). Analysis of Solvated Auxiliary-Ligand Free [(NHC)M]+ Species |date=2021 |last1=Muñoz-Castro |first1=Alvaro |last2=Wang |first2=Guocang |last3=Ponduru |first3=Tharun Teja |last4=Dias |first4=H. V. Rasika |journal=Physical Chemistry Chemical Physics |volume=23 |issue=2 |pages=1577–1583 |pmid=33406199 }}