In the section one of this thesis, the colorful pincer complex CNO synthiszed from reaction between Pd(OAc) 2 and pincer ligand 2-(N,N-Dimethyl-4-aminophenyl) azobenzene carboxylic acid and characterized by NMR, FT-IR spectroscopy and elemental analysis. The structure of pincer complex has been ascertained by single crystal X-ray crystallography and shows a slightly distorted square planar geometry around the metal atom. In addition, the sensitizing property of this complex was investigated. In second section, the phosphorus ylides R 3 PdCHC(O)PhR (R= OMe and Ph) react with the 1,5-cyclooctadiene complex [PdCl 2 (cod)]; cod = C 8 H 12 = 1,5-cyclooctadiene) to give the monomeric cyclooctenyl complexes [PdCl 2 {C 8 H 12 {CH(PPh 3 )C-(O)PhR}}] (R = OMe , Ph ) which synthesized and fully characterized by elemental analysis and spectroscopic studies (IR and multi nuclear NMR). The study of the biological properties of the two complexes has been focused on the binding properties of the complexes with FS DNA and bovine serum albumin (BSA) investigated by UV and fluorescence spectroscopy. In the last section, four new air- and moisture-stable mononuclear CN -type palladacyclic complexes and a cyclooctenyl Pd(II) complex bearing a phosphorous ylide, were used in the Heck and Suzuki–Miyaura coupling reactions under aerobic conditions.