Different coordination modes of 5,5-diethylbarbiturate in the copper(II) complexes with some aliphatic amines: Synthesis, spectroscopic, thermal and structural studies

The reaction of the 5,5-diethlybarbiturate anion (barb) with copper(II) in the presence of N,N-dimethylethylenediamine (dmen), bis(3-aminopropyl)amine (bapa) and N,N′-bis(3-aminopropyl)ethylenediamine (apen) results in five-coordinate complexes [Cu(barb)2(dmen)]·0.5H2O (1), [Cu(barb)2(bapa)] (2), and [Cu(barb)2(apen)]·2H2O (3). X-ray single crystal diffraction studies show that one is monodentate and the other one is bidentate in 1, and both barb ligands are N-coordinated in 2, whereas in 3, one barb ligand is N-coordinated, while the second barb ligand behaves as a counter-ion.