2-Phosphinoimidazole ligands have found application in various Pd-catalyzed transformations, including in Suzuki-Miyaura cross couplings. We recently discovered that palladium N-H N-heterocyclic carbene (NHC) complexes can be generated via non-oxidative insertion of a Pd(II) salt into the C-P bond of the 2-phosphinoimidazole ligand. In this report, we show that an equilibrium exists between the palladium P-N complex and the N-H NHC complex with 2-(dialkylphosphino)-imidazole ligands. We also demonstrate that P-dialkylphosphinoimidazole ligands enable excellent reactivity in Suzuki cross couplings with aryl chlorides. Our studies suggest that the N-H NHC form of the catalyst may be essential for the observed high reactivity of these complexes.

Palladium N-H N-heterocyclic carbene complexes and their reactivity in Suzuki-Miyaura reactions of aryl chlorides

ACS Spring 2022

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