To avoid pure trial and error, I need some examples of experiments already done with (possibly ammoniacal) aqueous solutions, particles/precipitates of copper (both oxidation states) salts, and acetylene gas.

Since sensitively dependent reactions are often misreported, be sure to provide enough experimental details. No need to interpret anything, just pieces of information are OK.

  • $\begingroup$ I assume most of chemists do not proverbially irritate a venomous snake by a bare foot, unless they have to. $\endgroup$
    – Poutnik
    Apr 1 at 16:04
  • $\begingroup$ @Poutnik Then we need to hope that a non-chemist finds his way to here after celebrating fools' day. $\endgroup$
    – Paul Kolk
    Apr 1 at 18:46
  • 1
    $\begingroup$ @Poutnik Well, most, but there are guys dedicated to making compounds with more nitro groups than C atoms :p $\endgroup$
    – Mithoron
    Apr 1 at 22:14
  • 1
    $\begingroup$ Like C(NO2)4... $\endgroup$
    – Poutnik
    Apr 2 at 4:30
  • $\begingroup$ @user144960 According to Wikipedia it is not a tetra nitrite C(-O-NO)4, but true tetranitromethane C(-NO2)4. // "azidoazide azide" C2N14 is not bad too.... $\endgroup$
    – Poutnik
    Apr 3 at 9:17

1 Answer 1


The OP, Paul Kolk wants examples of synthetic procedures for both copper(i) and Copper(II) acetylides without interpreting anything. Paul Kolk also wants to draw more attention to following part when he opens the bounty:

Detailed descriptions of experiments with the mentioned substances are expected. Cases, where no copper acetylide forms, are still useful to know.

That prompt me to give a try because effects on particle size as mentioned on the title may not be critical in the answer. That's encouraging since I cannot find anything with particle size influence on yield of this reaction in the literature. Actually, since use of ammonia $(\ce{NH3})$ makes almost all $\ce{Cu(I)}$ (cuprous) and $\ce{Cu(II)}$ (cupric) salts soluble in aqueous solution. Also, consider this reaction with $\ce{CuCl}$: $$\ce{H-C#C-H + 2CuCl -> Cu-C#C-Cu + 2HCl}$$ It is way faster than we think and precipitates $\ce{Cu-C#C-Cu}$ (cuprous acetylide or dicopper acetylide) as a red colored solid. When you try to make this compound, you should be very careful because copper(I) acetylide is highly explosive at dry condition!

The most common synthesis of $\ce{Cu-C#C-Cu}$ is the reaction of copper(I) halide (chloride, bromide, or iodide) and acetylene $(\ce{H-C#C-H})$ in ammoniacal solution in presence of hydroxyl amine $(\ce{NH2OH})$, the method of which was frequently used by Cataldo and coworkers in recent years during their work on polyynes.

In general, as the synthesis described by Cataldo and Casari in 2007 (Ref.1), copper(I) iodide $(\ce{CuI}, \pu{6.6 g})$ was dissolved in 30% aqueous ammonia $(\pu{100 mL})$ and distilled water $(\pu{200 mL})$ in presence of hydroxylamine hydrochloride $(\ce{NH2OH.HCl}, \pu{5.6 g})$. A slow stream of acetylene was bubbled in the solution, which was kept in a large Drechsel bottle (for this reaction, acetylene was generated in a separated flask from $\ce{CaC2}$ and water). A reddish-brown precipitate of dicopper acetylide $(\ce{Cu-C#C-Cu})$ was obtained quantitatively and was collected by filtration under reduced pressure to avoid complete drying of the collected precipitate.

A very recent publication (Ref.2) has described the similar procedure with additional details where copper source is $\ce{CuCl}$:

In a glovebox $\pu{2.50 g}$ copper(I) chloride is weighed in a Schlenk tube and $\pu{50 mL}$ of a 25 wt.% ammonia solution are added. The Schleck tube is purged with nitrogen via a septum for $\pu{8 min}$ before switching to acetylene. Immediately a red to brown solid precipitates. After $\pu{2 h}$ reaction time, the Schlenk tube is purged with nitrogen again to remove the remaining acetylene. The precipitate is washed with water and methanol.

The Ref.2 also prepared some of $\ce{Cu-C#C-Cu}$ trapped in solid materials, e.g., Silica $(\ce{SiO2})$. The only difference between the preparation of pure copper(I) acetylide to supported one is the addition of solid materials to the $\pu{50 mL}$ ammonia solution during above procedure. For example, during the preparation of silica supported copper(I) acetylide, calculated amount of silica is added to the $\pu{50 mL}$ ammonia solution and completed the procedure.

It is noteworthy that Bruhm et al. have being able to achieve a Raman spectrum of freshly prepared $\ce{Cu-C#C-Cu}$ (aqueous suspension), in which they interpret the peak at $\pu{1710 cm-1}$ corresponds to the $\ce{C#C}$ bond. This is surprisingly shifted because usual $\ce{C#C}$-bonds are rather expected at $\pu{2100 cm-1}$.

They have also achieved the crystal diffraction structure of crystalline $\ce{Cu-C#C-Cu}$, which is in agreement with well with the pattern published by Judai et al. (Ref.3):

General structure of Cu acetylides

In this general structure of coper acetylides, $\ce{R=Cu, H,}$ or any organic group, e.g., $\ce{Ph}$.

It is encouraged to read a brief review of published old work on copper acetylides (Ref.4). It is also some useful information of new references on the review on Ref.5.


  1. Franco Cataldo and Carlo S. Casari, "Synthesis, Structure and Thermal Properties of Copper and Silver Polyynides and Acetylides." Journal of Inorganic and Organometallic Polymers and Materials 2007, 17, 641–651 (DOI: https://doi.org/10.1007/s10904-007-9150-3).
  2. Tobias Bruhm, Andrea Abram, Johannes Häusler, Oliver Thomys, and Klaus Köhler, "Walter Reppe Revival – Identification and Genesis of Copper Acetylides $\ce{Cu2C2}$ as Active Species in Ethynylation Reactions." Chemistry: A European Journal 2021, 27(68), 16834-16839 (DOI: https://doi.org/10.1002/chem.202101932).
  3. T. K. Judai, J. Nishijo, and N. Nishi, "Self-Assembly of Copper Acetylide Molecules into Extremely Thin Nanowires and Nanocables." Advanced Materials 2006, 18(21), 2842-2846 (DOI: https://doi.org/10.1002/adma.200600771).
  4. V. F. Brameld, M. T. Clark, and A. P. Seyfang, "Copper acetylides." Journal of the Society of Chemical Industry 1947, 66(10), 346-353 (DOI: https://doi.org/10.1002/jctb.5000661007).
  5. Manoj B. Gawande, Anandarup Goswami, François-Xavier Felpin, Tewodros Asefa, Xiaoxi Huang, Rafael Silva, Xiaoxin Zou, Radek Zboril, and Rajender S. Varma, "Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis." Chemical Reviews 2016, 116(6), 3722−3811 (DOI: https://doi.org/10.1021/acs.chemrev.5b00482).

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