Ligand effects in palladium-catalyzed Suzuki and Heck coupling reactions

A range of sterically hindered diimine ligands and their palladium (II) complexes were synthesized. These compounds were fully characterized by elemental analysis, H-1 and C-13-NMR spectroscopy. The use of the palladium complexes as catalysts for Suzuki and Heck coupling has been studied in an attempt to demonstrate the effect of side groups on catalytic activity. It was clearly seen that the location of side -CH3 groups which bound to benzene ring had little effect on catalytic activity. Interestingly when we changed these -CH3 groups with -Cl groups the activity of the complexes increased. On the other hand, side groups which bound to imine nitrogen also had a large effect on catalytic activity. Copyright (C) 2008 John Wiley & Sons, Ltd.