(I) The reaction of bromo-bridged cyclopalladated complex of tri- o -tolylphosphine with aromatic and aliphatic bidentate N-donor ligands (pyrazine, 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethane, 1,3-bis(4-pyridyl)propane, ethylenediamine) were investigated. These reactions lead to the new P,C-palladacycles which were fully characterized by IR, NMR spectroscopies and CHN analysis. Interestingly, the linear organometallic polymer in a zig-zag manner was obtained and structurally determined by X-ray crystallogaraphy in which the pyrazine molecules act as the bridging ligands between Pd (II) centers. Two layers ONIOM (QM:QM) calculations were performed on the organometallic polymer [Pd(P( o -tolyl) 3 )(pyrazine)] n (n=1 to 10) in order to study the stability trend of polymer as a function of size (n). (II) The reaction of binuclear chloro-bridged cyclopalladated complex of phosphorus ylide with bis(diphenylphosphino)ethane (dppe) and bis(diphenylphosphino)propane (d) were reported. The reaction of the precursor complex with diphosphine ligands in a 1:2 molar ratio gives the mononuclear bischelate cyclopalladated complex while the reaction in a 1:1 molar ratio gives the diphosphino-bridged binuclear complexes. It is noteworthy that dppe and d are very strong chelating ligands in square planar complexes and there are few examples of d 8 metal complexes with bridging dppe and d due to their appropriate bite angles. (III) New organometallic structures of Pd (II) complexes were designed using natural amino acids as bio-potential ligands. The bischelate orthopalladated complexes were fully characterized by spectroscopic methods and X-ray crystallograohy analysis. To the best of our knowledge, this is the first (IV) Synthesis and characterizations of orthopalladated complex driving from bis[4-(dimethylamino)phenyl] methaniminium chloride (Auramine-O) is described. A simple route is degsined to prepare a supported CN-palladacycle catalyst based on functionalized TiO 2 as a very suitable inorganic support. The resulting ultra Pd-loaded material was investigated as a catalyst for copper- and amine- free Sonogashira coupling reactions of phenylacetylene with aryl halides which were carried out in the absence of phosphine ligands under air. In the context of green chemistry, heterogeneous catalysis of Sonogashira coupling reactions of phenylacetylene with aryl iodides carried out in ethanol as a green solvent.