Pincer Complexes of Palladium- and Nickel-Containing 3-Butyl-1-(1,10-phenanthrolin-2-yl)imidazolylidene as Efficient Aqueous Sonogashira and Kumada Coupling Reactions

Palladium and nickel complexes, [Pd(L)Cl](PF 6 ) ( 1 ), [Ni(L)Cl](PF 6 ) ( 2 ), and [Ni(L) 2 ](PF 6 ) 2 ( 3 ), containing 3-butyl-1-(1,10-phenanthrolin-2-yl)imidazolylidene (L) have been synthesized and fully characterized by NMR and ESI-MS spectroscopy and X-ray diffraction analysis. The unsymmetrical NNC pincer complexes 1 and 2 are square planar with a chloride trans to the internal nitrogen atom of phenanthroline. Complex 3 is a paramagnetic octahedral complex with its central metal surrounded by two pincer ligands. A catalytic study shows that palladium compound 1 is highly active in copper-free Sonogashira cross-coupling reactions of aryl iodides at room temperature and aryl bromides at 80 °C in neat water. The nickel complex 2 exhibits good activity in the Kumada cross-coupling reaction of aryl chloride at room temperature.