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 P 4 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.