- Copper (II) chloride (CuCl₂) is a widely used inorganic compound composed of copper in the +2 oxidation state and chloride ions.
- In its anhydrous form, it appears as a brownish-yellow or yellowish-brown crystalline solid, while the dihydrate form (CuCl₂·2H₂O) is much more common and exhibits a vivid blue-green to emerald-green color, reflecting its hydrated structure and coordination with water molecules. Copper(II) chloride is highly soluble in water and forms blue-colored aqueous solutions due to the presence of hydrated [Cu(H₂O)₄]²⁺ ions, which are often in dynamic equilibrium with chloride-complexed species.
- CuCl₂ is a paramagnetic compound, owing to its d⁹ electronic configuration, and exhibits characteristic spectral and magnetic properties typical of Cu²⁺ complexes. In solution, it can exist in a range of coordination environments, particularly in the presence of excess chloride ions, where it forms tetrahedral complexes like [CuCl₄]²⁻, giving rise to greenish hues. The compound is also hygroscopic, readily absorbing moisture from the air to form hydrated forms.
- This compound finds extensive application in chemical synthesis, electrochemistry, and metallurgy. In organic chemistry, CuCl₂ serves as an oxidizing agent and a catalyst in various reactions such as chlorination of hydrocarbons, oxidative coupling, and the Wacker oxidation (involving palladium and copper chloride for converting alkenes to ketones). It is also used in the synthesis of coordination compounds and metal-organic frameworks (MOFs).
- Industrially, copper(II) chloride is employed in textile and dye industries, wood preservation, and as a component of etching solutions for printed circuit boards. It is also used in photographic processes, fungicides, and colorants for ceramics and glasses, where it imparts a distinctive greenish-blue coloration.
- CuCl₂ can be synthesized by dissolving copper metal in hydrochloric acid and hydrogen peroxide, or by direct chlorination of copper at elevated temperatures. The hydrated form can be easily prepared by crystallizing from aqueous solution, while the anhydrous form requires careful drying under controlled conditions.
- Despite its usefulness, copper(II) chloride is toxic and should be handled with care. It is corrosive, can cause skin and eye irritation, and is harmful if ingested or inhaled. It is also toxic to aquatic organisms, so environmental exposure must be minimized. Prolonged contact may lead to copper poisoning, characterized by gastrointestinal distress, liver damage, and other systemic effects.
