The new ligands have been prepared in this work (potassium 2- carbomethoxy amino 5-5trithiocarbonate 1,3,4-thiadiazole ) (LI) was prepared from 2-carbomethoxy amino-5-mercapto 1,3,4-thiadiazole with CS2 in alkali media , while the second ligand was prepared from 2-N(4-N,N-dimethylamino benzyliden)-5-mercapto 1,3,4-thiadiazole with CS2 and in alkali media to obtain potassium 2-N( 4-N,N-dimethylaminobenzyliden )4-trithiocarbonate 1,3,4- thiadiazole ( LII).The products were isolated and characterized by appropriate physical measurement , vibrational and electronic spectroscopy . The new ligands have been used to prepare a number of new complexes with the selected metal ions Cd(II), Cu(II) , Ni(II) , Co(II) , Fe(III) , and Mn(II) . These complexes were studied and characterized using FT,IR, UV-Vis. spectra, molar conductivity, magnetic susceptibility , melting point , and atomic absorption measurement. We concluded that the [Cu2L2Cl2(H2O)2]. 3C2H5OH, [Ni L2 Cl2].2H2O, [Fe2L2(OH) 2 Cl4] .4H2O and [Mn L2 (H2O)2] . 2H2O have octahedral geometry while [Cd L2]. 3C2H5OH and [Co L H2O Cl ].3H2O have tetrahedral geometry for the complexes of LI. While octahedral geometry for the complexes of LII for the [Cu L2 (H2O)4 Cl2].2H2O , [Mn L2 (H2O) (OAc)].3 H2O [Ni L2 (H2O)2 Cl2].C2H5OH , [Fe2 L4 (OH) 2].5H2O and [Co2L2(H2O)4Cl2]. 2.5 C2H5OH ,But [Cd L2]. 4C2H5OH have tetrahedral geometry Different bonding and structural behavior were revealed through the study of the coordination chemistry of the metal complexes of the new ligands. The nature of bonding between the metal ion and the donor atom of the ligands were demonstrated through the calculated Racah parameter and the other ligand field parameters,which were calculated using the suitable Tanaba-sugano diagram. The antibacterial activity for the ligands and their metal complexes were studied against two selected microorganisms pseudomonas earuginsa and staphylococcus aureus using ( 10mM ) and ( 5mM ) concentration in nutrient agar medium . The results were showed a great enhancement of activity of some complexes relative to that of their respective ligands , these were attributed to the synergetic effect between the metal ion and the ligand , in addition to the difference in the structural varieties .