New Types of N-Heterocyclic Ligands and the Catalytic Activity of Their Transition Metal Complexes

Nitrogen donor-containing compounds have been shown great potentials as ligands to construct highly active non-phosphine organometallic catalysts because nitrogen donor-containing organometallic complexes usually exhibit good stability to oxygen and moisture, and are usually more reactive than transition metal complexes of phosphine ligands. Pyridyl-supported N-heterocyclic ligands such as pyridylbispyrazolyl (pseudo N3) ligands,1,2 pyrazolylpyridylN-heterocyclic carbene (NNC) ligands,3 pyridyl-supported oxazolinylN-heterocyclic carbene (NNC) ligands and other mixed nitrogen donor (NNN) ligands are explored in our laboratories. Chiral fragments are also introduced into the ligands to prepare catalysts for asymmetrical organic reactions. The molecular structures of the ligands and their transition metal complexes are measured by X-ray crystallographic studies. Highly active catalysts for transfer hydrogenation of ketones and Suzuki-Miyaura reactions have been developed.