Copper(I) Iodide | CAS 7681-65-4 | ≥99%

Copper(I) iodide (cuprous iodide, CuI) is a widely used soft Cu(I) source in synthesis and a well-studied p-type semiconductor. It adopts the zincblende (γ) structure at room temperature, converting to wurtzite (β) and rock-salt (α) phases on heating. Essentially insoluble in water, it dissolves in concentrated iodide solutions through iodocuprate formation and is soluble in ammonia and selected donor solvents such as acetonitrile. Commercial material is commonly supplied as white to off-white powder; slight cream or tan colouration can arise from trace iodine impurities.

Applications in synthesis

• Sonogashira co-catalysis: a classical Cu(I) co-catalyst alongside palladium in the coupling of aryl, heteroaryl and vinyl halides with terminal alkynes; Cu(I) forms a copper acetylide that transmetalates to palladium, accelerating the coupling under amine bases.
• Ullmann-type C–N, C–O and C–S coupling: a Cu(I) source for ligand-accelerated coupling chemistry — including diamine-, amino-acid- and 1,3-diketone-supported variants — used for arylation of amines, amides, phenols, azoles and related heteroatom nucleophiles.
• Azide–alkyne cycloaddition (CuAAC): Cu(I) source for copper-catalysed click reactions between organic azides and terminal alkynes, giving 1,4-disubstituted 1,2,3-triazoles through copper-acetylide chemistry.
• Aromatic Finkelstein reaction: catalyst for halide exchange that converts aryl, heteroaryl and vinyl bromides into the corresponding iodides, typically with sodium iodide and a diamine ligand in dioxane.
• Organocuprate generation: precursor to Gilman-type cuprates (R2CuLi) and related organocopper reagents for conjugate (1,4-) addition and substitution chemistry.

Beyond synthesis

• Coordination chemistry and luminescent clusters: a soft Cu(I) building block for complexes with N-heterocyclic carbene, phosphine and pyridyl ligands, and for [Cu4I4] cubane and stair-step clusters whose Cu–Cu interactions give temperature-dependent (thermochromic) photoluminescence.
• p-Type semiconductor and transparent conductor: γ-CuI is a wide-direct-bandgap p-type semiconductor (~3.1 eV) with high hole mobility, studied as a hole-transport layer in thin-film photovoltaics and in transparent electronics.