Palladium(0) pre-catalysts with heteroditopic NHC-amine ligands by transmetallation from their silver(I) complexes

Abstract

The synthesis of an air-stable series of Pd0 complexes with dissymmetric bidentate N-heterocyclic carbene-amine ligands has been performed. The key step is an unprecedented carbene transfer from Ag1 to obtain electron-rich zero-valent palladium precatalysts. The coordination behavior of the ligands was determined with X-ray crystallography. Surprising results were obtained in the catalysis of transfer semi-hydrogenation, where the addition of base appeared not to be necessary to obtain the desired product stereoselectively. © 2009 John Wiley & Sons, Ltd.