[(Triethyl­ene­tetra­mine)copper(II)]-μ-cyanido-κ²N:C-[bis(cyanido-κC)copper(I)]

The title compound, [Cu₂(CN)₃(C₆H₁₈N₄)] or [Cu(trien)(CN)Cu(CN)₂], where trien is triethyl­ene­tetra­mine, is a mixed-valence complex crystallizing as discrete mol­ecules, with Cu^I and Cu^II ions linked by a bridging cyanide group. The Cu^II ion is in a square-pyramidal coordination environment, with the N atoms of the tetra­dentate trien ligand occupying the basal positions and Cu—N bond lengths in the range 2.028 (4)–2.047 (4) Å. An N-bonded cyanide group is in the apical position, with a slightly longer Cu—N bond length of 2.127 (4) Å. The Cu^I ion exhibits a trigonal–planar coordination geometry, bonded to the C atoms of the bridging cyanide group and two terminal cyanide groups with Cu—C bond lengths in the range 1.925 (4)–1.948 (5) Å. In the crystal, hydrogen bonding involving the tertiary N—H groups of the trien ligand and N atoms of symmetry-related terminal cyanide groups links mol­ecules into a ribbon extending in the b-axis direction.