The hydrous title complex [systematic name: (1,1-dimethylbiguanide-κ2N2,N4)(2-oxidobenzoato-κ2O,O′)copper(II) trihydrate], [Cu(C7H4O3)(C4H11N5)]·3H2O, was synthesized electrolytically from an ethanolic solution of metformin hydrochloride, acetylsalicylic acid, Pepto-Bismol and a copper sacrificial anode. Diffraction data were collected at 0.56 Å resolution, allowing the accurate determination of H-atom positions in the neutral metformin ligand. Both imine groups in metformin have very similar N=C bond lengths, 1.2978 (17) and 1.3033 (17) Å, and the salicylate dianion behaves as a chelating ligand. The coordination sphere of the copper(II) cation deviates marginally from a square-planar arrangement. In the crystal, short Cu...Cu separations of 3.5476 (3) Å are observed, along with classical hydrogen-bonding interactions.
