Synthesis, decom­position studies and crystal structure of a three-dimensional CuCN network structure with protonated N-methyl­ethano­lamine as the guest cation

The com­pound poly[2-hy­droxy-N-methyl­ethan-1-aminium [μ(3)-cyanido-κ(3) C:C:N-di-μ-cyanido-κ(4) C:N-dicuprate(I)]], {(C(3)H(10)NO)[Cu(2)(CN)(3)]}(n) or [meoenH]Cu(2)(CN)(3), crystallizes in the tetra­gonal space group P4(3). The structure consists of a three-dimensional (3D) anionic Cu(I)CN network with noncoordinated protonated N-methyl­ethano­lamine cations providing charge neutrality. Pairs of cuprophilic Cu atoms are bridged by the C atoms of μ(3)-cyanide ligands, which link these units into a 4(3) spiral along the c axis. The spirals are linked together into a 3D anionic network by the two other cyanide groups. The cationic moieties are linked into their own 4(3) spiral via N—H⋯O and O—H⋯O hydrogen bonds, and the cations inter­act with the 3D network via an unusual pair of N—H⋯N hydrogen bonds to one of the μ(2)-cyanide groups. Thermogravimetric analysis indicates an initial loss of the base cation and one cyanide as HCN at temperatures in the range 130–250 °C to form CuCN. We show how loss of a specific cyanide group from the 3D CuCN structure could form the linear CuCN structure. Further heating leaves a residue of elemental copper, isolated as the oxide.