New mixed-ligands complexes with empirical formulae: M(2,4′-bpy)2L2�H2O (M(II)Zn, Cd), Zn(2-bpy)3L2�4H2O, Cd(2-bpy)2L2�3H2O, M(phen)L2�2H2O (where M(II)=Mn, Ni, Zn, Cd; 2,4′-bpy=2,4′-bipyridine, 2-bpy=2,2′-bipyridine, phen=1,10-phenanthroline, L=HCOO−) were prepared in pure solid state. They were characterized by chemical, thermal and X-ray powder diffraction analysis, IR
spectroscopy, molar conductance in MeOH, DMF and DMSO. Examinations of OCO− absorption bands suggest versatile coordination behaviour of obtained complexes. The 2,4′-bpy acts as monodentate ligand; 2-bpy and phen as chelating ligands. Thermal studies were performed in static air atmosphere. When the temperature raised the dehydration
processes started. The final decomposition products, namely MO (Ni, Zn, Cd) and Mn3O4, were identified by X-ray diffraction.