Abstract Copper(II) complexes with pentadentate ligands derived from the reaction of 1,5-diamino-3-pentanol and ethyl oxalate or nitrobiuret (abbreviated as H5oxdpl and H5bidpl, respectively) and 1,3-diamino-2-propanol and ethyl oxalate or nitrobiuret (abbreviated as H5-oxdrl and H5bidrl, respectively) were prepared and characterized by elemental analyses, infrared and electronic spectra and magnetic susceptibilities. In the case of H5oxdpl, H5bidpl and H5bidrl, binuclear copper(II) complexes, K2[Cu2(oxdpl) (OH)]·H2O, K2[Cu2 (bidpl) (OH)] ·3H2O and K3 [Cu2 (bidrl) (CO3)] ·3H2O, were formed. The two copper ions in these complexes were assumed to be bridged by an alkoxo oxygen of the ligand and an additional bridging ion X− (X− = OH− or CO3 2-). However, the reaction of H5oxdrl with Cu2+ afforded a mononuclear copper(II) complex, K2[Cu(Hacdrl)] (H3acdrl = N,N′-dioxalo-2-hydroxy-1,3-propanediamine).