Synthesis of PNNP-type diiminodiphosphine ligands and paladium(II) complexes, investigation of catalytic activities in suzuki C-C coupling reactions

In this thesis, three different tetradentate ligands (L1-3) with diiminodiphosphine derivative PNNP donor atoms and cationic palladium(II) metal complexes (K1-3) were synthesized by reaction of these ligands with Pd(COD)Cl2. In addition, bimetallic neutral palladium(II) metal complexes (K4-5) have been successfully synthesized as a result of the reactions of L1 ligand with Pd(COD)Cl2 and Pd(COD)ClMe compounds. Structure analyses of all compounds were characterized by analytical methods such as FTIR, HRMS, X-ray diffraction and NMR (1H, 13C, 31P ve 19F). The catalytic activities of the obtained Pd(II) complexes were investigated in Suzuki C-C coupling reactions. First of all, optimization studies were carried out on the model reaction between 4-bromotoluene and phenylboronic acid in the presence of K1 catalyst by trying different solvent, base and temperature combinations, and the reaction condition with the highest conversion yield determined as ethanol, K2CO3 and 80°C, respectively. Afterwards, the effect of the catalyst amount on the reaction was investigated, and the substrate effect with activated and deactivated aryl bromide derivatives was investigated in detail. Catalytic efficiency results were interpreted by correlating the synthesized complexes with the steric volume around palladium, and it was determined that complexes with higher steric hindrance gave better results in Suzuki C-C coupling reactions. When all the results are evaluated; it was determined that the most effective catalyst was K5 bimetallic palladium(II) metal complex and all the synthesized catalysts showed high conversion in Suzuki C-C coupling reactions with low temperature and low palladium content.