Hetero-Bimetallic Complexes Based on an Anthyridine Ligand Preparation and Catalytic Activity

Complexation of anthyridine-based ligand L with [(eta(6)-cymene)RuCl2](2), [Cp*RhCl2](2), and [Cp*IrCl2](2) yielded a mononuclear complex: [(N,N-L)Ru(eta(6)-cymene)Cl]Cl (1), [(N,N-L)Rh(Cp*)Cl]Cl (2), and [(N,N-L)Ir(Cp*)Cl]Cl (3), respectively [L = 5-phenyl-2,8-di-2-pyridinylanthyridine]. Upon treatment with (CH3CN)PdCl2, complexes 1-3 underwent o-metalation to yield heterobimetallic complexes Ru-Pd, Rh-Pd, and Ir-Pd, respectively. Complexes were all characterized by spectroscopic method, and some are further confirmed by X-ray crystallography. Complex Ru-Pd exhibits catalytic activities for the tandem reactions of Suzuki-Miyaura coupling/transfer hydrogenation of p-bromoacetophenone with phenylboronic acid in isopropanol, whereas Ir-Pd shows a moderate activity. However, complex Rh-Pd does not behave the same way. Furthermore, catalytic activity of these heterobimetallic complexes toward debromination/transfer hydrogenation of p-bromoacetophenonewas also investigated. The catalytic pathways of these processes were studied and discussed. This study reveals the base used in the reactions plays an important role in the reaction pathway.