Hydrogen‐bonded supramolecule of N,N′‐bis(4‐pyridylmethyl)oxalamide and a zigzag chain structure of catena‐poly[[[dichloridocobalt(II)]‐μ‐N,N′‐bis(4‐pyridylmethyl)oxalamide‐κ2N4:N4′] hemihydrate]

N,N′‐Bis(4‐pyridylmethyl)oxalamide, C₁₄H₁₄N₄O₂, exists as a dimer which is extended into a two‐dimensional network with other dimers through pyridine–amide hydrogen bonds. The crystal structure of the title coordination polymer, {CoCl₂(C₁₄H₁₄N₄O₂)]·0.5H₂O}_n, features a one‐dimensional zigzag chain, in which the cobalt ion sits at a twofold symmetry position and adopts a tetrahedral geometry, and the bridging ligand lies on an inversion center and connects to Co^II ions in a bis‐monodentate mode. Furthermore, two interwoven chains create a cavity of ca 8.6 × 8.6 Å, which produces a three‐dimensional channel. Water molecules are held in the channel by hydrogen bonds.