New mixed ligand Co(II), Ni(II), Cu(II) and Zn(II) complexes of di- (dea) and triethanolamine (tea) with thiocyanate were synthesized and characterized by elemental analyses, magnetic moments, UV-Vis and IR spectra. All the metal complexes of tea, and the Ni(II) and Zn(II) complexes of dea are mononuclear, while the Co(II) and Cu(II) complexes of dea are dimeric. The crystal structure of the bis(mu -diethanolaminato) bis(iso thiocyanato)dicopper(II) complex were determined by single crystal X-ray diffraction. The centrosymmetric binuclear complex contains two strongly distorted square-pyramidally coordinated copper ions bound together by two alkoxo bridges. The bridging oxygen is a deprotonated oxygen of the ethanolic group of dea. The dea ligand also coordinates to the Cu(II) ions through its nitrogen, while the other ethanolic group does not involve in coordination. The thiocyanate anion coordinates to the Cu(II) ion with its nitrogen. Thermal reactivity of the complexes was studied using DTA and TG. Degradation of the amine ligands in the complexes occurs in the first stages of decomposition and the thiocyanate anions decompose at higher temperatures to give corresponding metal oxides. (C) 2001 Elsevier Science B.V. All rights reserved.