The mixed- valence trinuclear cobalt complexes Co(III)- Co(II)- Co(III) with schiff bases derivatives of β – alanine a α – aminoacids (glycine, leycine, aminobutyrik acid) have been synthezed and the IR, -elektronic spectras and maqnetic moments of this comlexes analysed. The comparison of obtained parameters for the complexes with similar parameters mixed – valence cobalt complexes with known X- ray structure, made it possibly to carry out identification of their structures. In the complexes with Schiff bases of β – alanine derivatives the central Co(II) ion are co-ordinates by two oxygen atoms of the bidentate carboxylate group and four water molecules. The terminal Co(III) ions come out as monoanionic monodentate liqands. In the case of α-amineacids derivatives, Co(II) ion is coordinated by six water molecules and bound up with terminal monoanionic Co(III) comlexes by hydrogen bonds.