Cyclopalladated complexes containing tridentate thiosemicarbazone ligands of biological significance: Synthesis, structure and antimalarial activity
摘要:
The C-H activation reaction of two aryl-derived thiosemicarbazones with K-2[PdCl4] affords tetranuclear cyclopalladated complexes (3 and 4) where the thiosemicarbazone ligand acts as a tridentate donor [C,N,S] coordinated to palladium via the ortho-carbon of the aryl ring, imine nitrogen and thiolato sulfur. The palladiumesulfur bridging coordination bonds give rise to a Pd4S4 core. These Pd-S-bridging bonds were cleaved with a variety of mono-and bis-phosphines to give a series of mono, di and tetranuclear organopalladium complexes (5-12) where the phosphorus atom coordinates to palladium trans to the imine nitrogen. All of the complexes were fully characterized using various analytical and spectroscopic techniques. These palladium complexes along with their free ligands were evaluated as bioorganometallic antimalarial agents against two Plasmodium falciparum strains, 3D7 (chloroquine sensitive) and K1 (chloroquine and pyrimethamine resistant). Some of the complexes were found to be moderate inhibitors of parasite growth and were more active than the corresponding free ligand. (C) 2010 Elsevier B. V. All rights reserved.
Cyclometallated Pd(II) thiosemicarbazone complexes: new catalyst precursors for Suzuki-coupling reactions
摘要:
Four tridentate [C,N,S] thiosemicarbazone Pd(II) complexes were applied as catalyst precursors for the Suzuki-Miyaura coupling of a variety of aryl halides and aryl boronic acids. After screening various catalytic conditions, it was found that one dinuclear complex IV containing the bis(diphenylphosphino) ferrocene spacer was able to efficiently catalyze these reactions with yields up to 99% irrespective of the type of aryl substituent on the substrate. (C) 2012 Elsevier Ltd. All rights reserved.