Suvnmary. The interaction between Cu2+ and the terdentate ligands N-picolinoyl-ethylenediamine, glycine-2-pyridylmethylamide, Na-(Z-pyridylmethyl)-glycinamide and Na-(Z-pyridylmethyl)-glycine-ethylamide, respectively, has been studied by spectrophotometry and potentiomctry. At high pH values the ionised amide group undergoes complex formation and the resulting chclates have similar structures and stabilities. In slightly acidic solution however, each ligand gives rise to a different species. These facts are explaincd by assuming that the neutral amide group coordinates through its carbonyl oxygen atom. The stability constant and the absorption spectrum of each complex have been calculated by computer programmes.Rontgen-Strukturanalysen zeigen, dass Amide mit Cu2+ und anderen d-MetallIonen zwei Arten von Komplexen bilden, indem entweder der Carbonylsauerstoff sein Elektronenpaar zur Verfugung stellt (I) oder das Stickstoffatorn der deprotonierten Amidgruppe gebunden wird (11) [l]