Synthesis and Characterization of <i>N</i>-Heterocyclic Carbene Phospha-Palladacycles and Their Properties in Heck Catalysis^†

Palladacycles are among the most active catalyst systems for the Mizoroki−Heck reaction to date. We present N-heterocyclic carbene (NHC) substituted phospha-palladacycles as a new class of catalysts. This new type of palladacycles combines the advantageous stability of phospha-palladacycles with the steric demand and high σ-donor strength of N-heterocyclic carbenes. In this work NHC-substituted phospha-palladacycles are tested in Heck catalysis. The activity of these catalysts allows the coupling of even aryl chlorides in good yields.