T h e w o r k p r e s e n t e d i n t h i s t h e s i s d e a l s wi th the preparation and characterization of some new Pd(II) ,PtII, Rh(III) , Ir(III) , V(IV) and U(VI) metal complexes using substituted phosphine ligands. The ligands used were : O- Diphenylphosphine benzoic acid (HL) , o- Diphenylphosphineoxids benzoic acid (HLO) and o- Di phenyl phosphinesulfide benzoic acid (HLS). The prepared complexes were characterized using infrared, uv. -vis. ¹H-nmr and elemental analysis , and from these measurements , the structures of the complexes were detected. Characterizations of these complexes was discussed using information's obtained from investigation of their physical properties. Conductivity measurements in CHCl and DMF showed that, all the complexes were neutral (non-ionic) The results obtained from infrared spectra pointed out that, in the case of complexes with the (HL) ligand , the ligand coordinated through phosphorous atom and one of the oxygen atoms of the carboxylate group. But in the complexes of (HLO) and (HLS), the ligands coordinate through oxygen and sulfur atoms of the P=0 and P=S groups respectively,in addition to one of the oxygen atoms of carboxylate group. On the other hand, in U(VI) complexes the l igands coordinated through the two oxygen atoms of thecarboxylate group. From the spectral measurements monomer structures were assumed for Rh(CII), Ir(III) V(IV) and U(VI) complexes, while dimeric structures were proposed for Pd(II) and Pt(II) complexes.