498 °C (anhydrous)
100 °C (dehydration of dihydrate)
993 °C (anhydrous, decomp)
is the chemical compound with the formula CuCl2
. This is a light brown solid, which slowly absorbs moisture to form a blue-green dihydrate. The copper(II) chlorides are some of the most common copper(II) compounds, after copper sulfate.
adopts a distorted cadmium iodide structure. In this motif, the copper centers are octahedral. Most copper(II) compounds exhibit distortions from idealized octahedral geometry due to the Jahn-Teller effect, which in this case describes the localization of one d-electron into a molecular orbital that is strongly antibonding with respect to a pair of chloride ligands. In CuCl2
O, the copper again adopts a highly distorted octahedral geometry, the Cu(II) centers being surrounded by two water ligands and four chloride ligands, which bridge asymmetrically to other Cu centers.
Copper(II) chloride is paramagnetic. Of historical interest, CuCl2
O was used in the first electron paramagnetic resonance measurements by Yevgeny Zavoisky in 1944.
Aqueous solution prepared from copper(II) chloride contain a range of copper(II) complexes depending on concentration, temperature, and the presence of additional chloride ions. These species include blue color of [Cu(H2
]2+ and yellow or red color of the halide complexes of the formula [CuCl2+x
Copper(II) hydroxide precipitates upon treating copper(II) chloride solutions with base:
Partial hydrolysis gives copper oxychloride, Cu2
, a popular fungicide.
is a mild oxidant. It decomposes to CuCl and 2
Cl at 1000 °C:
reacts with several metals to produce copper metal or copper(I) chloride with oxidation of the other metal. To convert copper(II) chloride to copper(I) derivatives, it can be convenient to reduce an aqueous solution with sulfur dioxide as the reductant:
reacts with HCl or other chloride sources to form complex ions: the red CuCl3
−, and the yellow CuCl4
Some of these complexes can be crystallized from aqueous solution, and they adopt a wide variety of structures.
Copper(II) chloride also forms a variety of coordination complexes with ligands such as pyridine and triphenylphosphine oxide:
However "soft" ligands such as phosphines (e.g., triphenylphosphine), iodide, and cyanide as well as some tertiary amines induce reduction to give copper(I) complexes.
Copper(II) chloride is prepared commercially by the action of chlorination of copper:
It can also be generated by treatment of the hydroxide, oxide, or copper(II) carbonate with hydrochloric acid. Electrolysis of aqueous sodium chloride with copper electrodes produces (among other things) a blue-green foam that can be collected and converted to the hydrate.
Copper(II) chloride can also be prepared by mixing dilute hydrochloric acid with copper(II) sulfate.
may be prepared directly by union of the elements, copper and chlorine.
may be purified by crystallization from hot dilute hydrochloric acid, by cooling in a 2
Copper(II) chloride occurs naturally as the very rare mineral tolbachite and the dihydrate . Both are found near fumaroles. More common are mixed oxyhydroxide-chlorides like atacamite Cu2
Cl, arising among Cu ore beds oxidation zones in arid climate (also known from some altered slags).
A major industrial application for copper(II) chloride is as a co-catalyst with palladium(II) chloride in the Wacker process. In this process, ethene (ethylene) is converted to ethanal (acetaldehyde) using water and air. During the reaction, 2
PdCl is reduced to Pd, and the CuCl2
serves to re-oxidize this back to PdCl2
. Air can then oxidize the resultant CuCl back to CuCl2
, completing the cycle.
The overall process is:
Copper(II) chloride is used as a catalyst in a variety of processes that produce chlorine by oxychlorination. The Deacon process takes place at about 400 to 450 °C in the presence of a copper chloride:
Copper(II) chloride catalyzes the chlorination in the production of vinyl chloride and dichloroethane.
Copper(II) chloride is used in the Copper–chlorine cycle in which it splits steam into a copper oxygen compound and hydrogen chloride, and is later recovered in the cycle from the electrolysis of copper(I) chloride.
Copper(II) chloride has some highly specialized applications in the synthesis of organic compounds. It effects chlorination of aromatic hydrocarbons- this is often performed in the presence of aluminium oxide. It is able to chlorinate the alpha position of carbonyl compounds:
This reaction is performed in a polar solvent such as dimethylformamide (DMF), often in the presence of lithium chloride, which accelerates the reaction.
, in the presence of oxygen, can also oxidize phenols. The major product can be directed to give either a quinone or a coupled product from oxidative dimerization. The latter process provides a high-yield route to 1,1-binaphthol:
Such compounds are intermediates in the synthesis of BINAP and its derivatives
Copper(II) chloride dihydrate promotes the hydrolysis of acetonides, i.e., for deprotection to regenerate diols or aminoalcohols, as in this example (where TBDPS = -butyldiphenylsilyltert
also catalyses the free radical addition of sulfonyl chlorides to alkenes; the alpha-chlorosulfone may then undergo elimination with base to give a vinyl sulfone product.]
Copper(II) chloride is also used in pyrotechnics as a blue/green coloring agent. In a flame test, copper chlorides, like all copper compounds, emit green-blue.
In humidity indicator cards (HICs), cobalt-free brown to azure (copper(II) chloride base) HICs can be found on the market. In 1998, the European Community (EC) classified items containing cobalt(II) chloride of 0.01 to 1% w/w as T (Toxic), with the corresponding R phrase of R49 (may cause cancer if inhaled). As a consequence, new cobalt-free humidity indicator cards have been developed that contain copper.
It is toxic and only concentrations below 5 ppm are allowed in drinking water by the US Environmental Protection Agency.