Cyclometalated 2‑Phenylimidazole Palladium Carbene Complexes in the Catalytic Suzuki–Miyaura Cross-Coupling Reaction

• Published in: Organometallics Vol. 33; no. 15; pp. 3966 - 3976
• Main Authors: Micksch, Maik, Tenne, Mario, Strassner, Thomas
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.08.2014
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om5004336

We present the syntheses of 12 cyclometalated palladium C∧N 2-phenylimidazole carbene complexes with different N-1 groups as well as different substituents at the C-2 phenyl group of the cyclometalating imidazole. We investigated the influence of these substituents by comparing the catalytic performance of the complexes in the Suzuki–Miyaura cross-coupling reaction of aryl chlorides. We can show a strong dependence between the steric demand of the N-1 substituent of the cyclometalating imidazole and the catalytic activity in the cross-coupling reaction. The most active complex shows a wide substrate scope, where several aryl as well as benzyl chlorides could be coupled with different boronic acids in excellent yields using very low catalyst concentrations of 0.05 mol %.