INTRODUCTION In the family of heterocyclic compounds, nitrogen containing heterocycles with an oxygen atom and complexes are considered as an important class of compounds in medicinal chemistry because of their interesting diversified biological application 1 . During the past years considerable evidences have also accumulated to demonstrate the efficacy of 1,3,4-oxadiazoles including antibacterial, anti-inflammatory, antimalarial, antitubercular, antihypoglycemic, ORIENTAL JOURNAL OF CHEMISTRY www.orientjchem.org ISSN: 0970-020 X CODEN: OJCHEG 2011, Vol. 27, No. (4): Pg. 1465-1473 Est. 1984 An International Open Free Access, Peer Reviewed Research Journal Preparation Ligand 5-(3-chlorophenyl)-1,3,4-oxadiazole-2-thiol by New Method and Complexation with Transition Metals AHMED S.M. AL-JANABI¹*, G.A. AL-SOUMADAIY² and BUSHRA A. KHEAR-ALLAH³ ¹Department of Biochemistry, College of Veterinary Medicine, University of Tikrit, Tikrit (Iraq). ²Department of Chemistry, College of Science, University of Tikrit, Tikrit (Iraq). ³Department of Chemistry, College of Education, University of Tikrit, Tikrit (Iraq). *Corresponding author: E-mail: a_sh200683@yahoo.com (Received: September 25, 2011; Accepted: October 26, 2011) ABSTRACT A ligand 5-(3-chlorophenyl)-1,3,4-oxadiazol-2-thiol (CPoxSH) synthesized by two methods and its Zn(II), Cd(II), Hg(II), Mn(II), Co(II), and Ni(II) complexes were synthesized. The ligand were prepared by two methods, microwave and classic method, m-chlorobenzol hydrazine(A) was prepared the hydrazinolysis of methyl m-chlorobenzoate(B) with hydrazine hydrate in abs. ethanol. Refluxing of m- chlorobenzol hydrazine(C) in basic medium with carbon disulfide CS 2 to give 5-(3-chlorophenyl)-1,3,4- oxadiazol-2-thiol (D). And complexation with [HgX 2 ] ( X= Cl, Br, SCN)(1:1), and [Hg(OAc) 2 ] (1:2) mole proportion of ligand. Reaction of MCl 2 .xH 2 O [M(II)= Cd, Zn, Mn, Co, Ni] and [M(OAc) 2 .xH 2 O [M = Cd, Zn, Co, Ni] with ligand by (1:2) mole proportion. The preparation ligand and complexes were characterized by element analysis, IR spectral data , 1 H and 13 C-{ 1 H} NMR data. Key words: Oxadiazole, Transition metal, Thione, complexes, microwave, anticancer, antileishmanial, antiviral, anticonvulsant and insecticidal properties 1-4 . In some cases, metal complexes of these ligands shown higher anticancer activity than the free ligand, and some of thes complexes classified as clinical agents for therapy of human leukaemias 5-10 . The use of microwaves in organic synthesis has increased dramatically in the last years, receiving widespread acceptance and becoming an indispensable tool 5 . Microwave technology has become a powerful tool in organic