A Novel N-heterocyclic Carbene Palladium Complexes Synthesis And Application

Ever since Ardengo and his coworkers isolated the first free stable N-heterocyclic carbene (NHC) in 1991, study of N-heterocyclic carbene metal complexes have attracted much attention as one of the most promising fields in organometallics. NHC-metal complexes derived from imidazolium or benzimidazolium salts have been increasingly used in organic catalysis, and exihibited superior versatility and more environmental firendly than the widely used phosphine complexes.Several novel functionalized benzimidazolium salts, three new NHC-Pd complexes have synthesized, and characterized their structure by H1-NMR, C13-NMR and X-Ray Diffraction. We have studied the crystal structure of these NHC-Pd complexes, and investigated the application of these NHC-Pd as catalysts in carbon-carbon coupling reactions and carbon-nitrogen coupling reactions. Finally we discovered that:(1) A combination of NHC-Pd complex 108 and potassium phosphate with water/methanol (5:1) as solvent proved to be an effective catalytic system for the coupling of aryl bronic acid with aryl bromides, but not for that of aryl chlorides. (2) A combination of NHC-Pd complex 109, TBAB and potassium phosphate, with water as solvent proved to be an excellent catalytic system for the coupling of aryl bronic acid with aryl bromides and some activiated aryl chlorides. (3) A combination of NHC-Pd complex 108, and K2CO3, with dioxane as solvent proved to be an excellent catalytic system for the coupling of aryl bromides with styrene. Suzuki Cross Coupling Heck Coupling...