copperI

Copper(I), also called cuprous, denotes the +1 oxidation state of copper in compounds and coordination complexes. The electronic configuration of Cu+ is [Ar]3d10, giving it a closed d shell. As a soft Lewis acid, copper(I) tends to bind to soft ligands and often adopts two-coordinate linear geometries or four-coordinate tetrahedral arrangements in many complexes.

In aqueous solutions copper(I) is relatively unstable because it tends to disproportionate to copper(II) and copper metal: 2 Cu+ → Cu2+ + Cu. Stabilization requires ligands that strongly stabilize Cu+, such as halides, sulfide, cyanide, phosphines, or amines. In such media Cu+ forms various coordination complexes and can participate in redox chemistry and catalysis. The stability of Cu+ thus depends strongly on the surrounding ligands and solvent.

Common copper(I) compounds include cuprous oxide, Cu2O, which is a red solid; copper(I) chloride, CuCl, a white solid; copper(I) sulfide, Cu2S; and copper(I) cyanide, CuCN. These compounds are generally less soluble in water than many copper(II) salts and exhibit diverse structural motifs depending on ligand environment and solid-state packing.

Occurrence and relevance: Cu2O occurs as the mineral cuprite and has historical use as a pigment and in ceramics; CuCl is used in organic synthesis and as a precursor to other copper compounds. Copper(I) centers appear in certain biological systems and in synthetic coordination complexes, where their stabilization and reactivity are explored for catalysis, materials science, and inorganic chemistry research.