Synthesis of unsymmetrical N-heterocyclic carbene complexes and their catalytic properties

N-heterocyclic carbenes (NHCs) are considered alternatives to phosphine ligand in metal complexes due to strong ?-donor but poor ?-acceptor abilities, low toxicity and their stability to air and moisture. Because of these properties of transition metal carbene complexes used as catalyst in many organic reaction. N-heterocyclic metal carbene complexes are effective catalysts in many useful transformations, such as C-C and C-N coupling reactions, transfer hydrogenation, olefin metathesis, hydrosilylation, hydroformylation e.t.c. In this study, a series of unsymmetrical N,N?-disubstituted imidazolium salts were synthesized as N-heterocyclic carbene precursors. These compounds were used to synthesize of N-heterocyclic metal (Pd, Ru) complexes. These complexes are classified into three groups, which are donor-functionalized NHC-Pd (6a,b) complexes, NHC ligated palladacyclic complexes (7a-c) and NHC-Ru complexes (8a-c). Due to hemilabil behavior, this study focused on the synthesis of NHC-metal complexes. Catalytic properties of synthesized complexes were investigated in Suzuki-Miyaura cross-coupling reaction and transfer hydrogenation of acetophenone. These new compounds were characterized by analytical method, elemental analysis, 1H- and 13C-NMR spectroscopy. In addition, 6a numbered structures of the compound has also been characterized by X-ray diffraction.