The paper descrives the synthesis of N-derivatives of (R)-1, 2-diaminopropane and the results of investigations on the electrical conductivity, magnetic susceptibility and absorption spectra of their compelexes with copper. As distict from α-amino acid complexes, where the insertion of N-alkyl substituents results in their structure being changed from distorted octahedral to four-coordinate square-planar, diamine comlexes invariably preseve their distorted octahedral structure with the introduction of up to two substituents in the ligand molecule, and in the case of more overloaded ligands binuclear complexes ar formed. Even in solvents with poor coordinative capacity no four-coordinate structures could be detected, which has been explained by the coordination of anions in the axial positions of the positively charged complexes.