The work in this thesis include the preparation and characterization of a series of Vanadium (IV) in the term of (VO+2) ion, Chromium(III) and Zinc complexes with five (O,O),(N,N), (O,N) donor ligands, these ligands include:mandilic acid (L1),0-phenylen di amine (L2),benzilic acid (L3),pyruvic acid (L4) and N-N' bis(salicylidene)ethylene di amine(L5), later was prepared ( L5) from the reaction of ethylene diamine with salicylaldehyde.The characterization of all the complexes resulting from the reaction in both basic medium ,in case of( L1,L3 and L4), and neutral medium in case of( L2and L5),was carried out using different techniques,which include vibrational (FT-IR) and electronic (UV-Vis) spectroscopy,metal analysis, molar conductance and magnetic susceptibility measurements. Metal analysis and molar conductance measurements indicate 1:2 metal to ligand ratio for all the complexes in the solid state, except those of (L5) where it was 1:1.Molar conductance values indicate nutral nature for the six complexes of( L3 and L5),while the three complexes of the neutral ligand (L2) were ionic.The complexes of (L1 and L4) were neutral except those of Chromium (III)ion which were ionic.The infrared absorption spectral study suggested that, the ligands were ionic bidentate,except those of (L2) which were neutral bidentate . The spectra also indicate the absence of inorganic anionic group in these complexes, except that of Cr (III) with (L5and L3) in which achloride ion was coordinated to the metal. Also it was found that the Vanadyl ion (VO+2) retains its identity during complexation reaction.The magnetic susceptibility values performed at room temperature indicate that all the complexes of VO+2and Cr+3 were paramagnetic and mono nuclear. From the results of the above techniques and those of electronic study, it was suggested that vanadium complexes were square pyramidal, and those of chromium were octahedral, while those of zinc were tetrahedral.