Synthesis, characterization and investigation of the cataltic activities of dimeric palladium N-heterocycic carbene complexes

Recently, N-heterocyclic carbenes have become a sought-after ligand in coordination chemistry and organic conversion reactions. The inherently strong σ-donor ability of NHCs enhances the exceptional bonding of carbenes to metal centers and the stability of the metal-carbene bond. In addition, both electron transfer from the carbene p-orbital by π-backlinking and electron transfer from the carbene p-orbital to the metal as a π-donor create synergistic effects on metal-ligand bonding. Due to the strong -donor and weak -acceptor properties of N-hetrocyclic carbenes, it creates a steric volume with a higher electron density at or around the metal center than phosphine ligands. Thanks to these unique properties of NHCs, M-NHC complexes exhibit very good catalytic performance with high stability in catalytic reactions. The synthesis of organic compounds by organic transformation reactions in the presence of different metal complexes is very important for industry and academia. In recent years C-H activation reactions are very important in the synthesis of substituted heteroarenes or organic molecules used in many fields especially in pharmaceutical chemistry. The synthesis of directly targeted substituted heterocyclic compounds without the formation of organometallic reagents is a very economical and environmentally friendly synthetic procedure due to the catalyst used and the mild reaction conditions. Since the use of Pd-NHC complexes in this field is increasing day by day, the development of new generation Pd-NHC complexes in this field is very important for academia and industry. For these reasons, within the scope of this thesis, the catalytic activities of synthesized Pd-NHC complexes were investigated for 2-isobutylthiazole with aryl bromides in direct C-H activation. The results of this thesis can be listed under tree general headings; 1) Benzimidazole-based symmetric and asymmetric NHC precursors (2a-f) were synthesized and their structural characterizations were made by different spectroscopic methods. 2) Dimeric-bridged palladium complexes (4a-f) of benzimidazole-based symmetric and asymmetric NHC precursors were synthesized and their structures were elucidated by appropriate spectroscopic methods. 3) The catalytic activities of the synthesized dimeric-bridged Pd-NHC complexes (4a-f) were investigated for 2-isobutylthiazole with aryl bromides in C-H activation reactions.