Efficient Palladium-catalyzed Suzuki–Miyaura reactions using phenolic Schiff base ligands under ambient conditions in aqueous media

Selective Formation of Mononuclear Palladium and Acetonitrile-Bridged Dinuclear Palladium Complexes Containing a Chiral Tridentate Ligand

From the chiral Schiff base tridentate ligand L_Ph, unusual acetonitrile-bridged dinuclear palladium complex 1 and organopalladium complex 1' were synthesized selectively by using acetonitrile and ethanol, respectively. The chiral tridentate Schiff base ligand was bound to the palladium metal center with different chelation modes ([ONO] for 1 and [CNO] for 1'). Complex 1 constitutes the first example of dinuclear metal complexes connected only by a bridging acetonitrile, in which an exceptionally short C≡N bond distance [0.945(12) Å] of bridged acetonitrile was observed. To study the influence of a phenyl group attached to an imine, the phenyl-free ligand L_H was prepared and used. In that case, an acetonitrile bridge was not observed. Theoretical calculation studies supporting the formation of 1 and 1' are favored.

Pronounced effect of pore dimension of silica support on Pd-catalyzed Suzuki coupling reaction under ambient conditions

The pore size of the mesoporous silica support affects the reactivity of heterogeneous palladium catalysts in the Suzuki reaction under ambient conditions, which is leveled at higher temperature.