Syntheses and Characterization of new Pd-C,N,N-Pincer complexes and their application in Suzuki-Coupling reactions

The discovery of Herrmann in 1995, that also palladacycles can be applied in carbon-carbon coupling reactions of aryl halides, stimulated the research of this easily available and fairly stable group of compounds.[1] We synthesised a series of both, neutral and cationic Pd-C,N,N pincer complexes, which stem from the known ligand (6-phenyl-2-((2,6-diisopropylphenyl)imino)pyridine).[2] The palladium compounds 1 through 5 were characterised by multinuclear 1D and 2D NMR spectroscopy, IR spectroscopy and elemental analysis. For compounds 1 and 2 also the solid state structures were determined by means of single crystal X-ray structure analyses. Since no example exists for the application of Pd-C,N,N pincer complexes in Suzuki coupling reactions, we tested compounds 1 through 5 in the coupling of 4-bromo- and 4-chloroacetophenone with phenylboronic acid in refluxing 1, 4-dioxane. REFERENCES [1] Herrmann, W., A., Brossmer, C., Oefele, K., Reisinger, C., P., Priermeier, T., Beller, M., Fischer, H. Angew. Chem. Int. Ed. Engl., 1995, 34, 1844. [2] Bianchini, C., Mantovani, G., Meli, A., Migliacci, F. Organometallics, 2003, 22, 2545.