Chemistry of monoorganopalladium complexes relevant to catalysis

Neutral and cationic organopalladium complexes have been prepared as models for active intermediates involved in palladium-catalyzed reactions. Comparison of the reactivities of the neutral and cationic complexes revealed the much higher reactivities of the latter toward β-elimination and olefin or CO insertion. Generation of the solvent-coordinated hemilabile site on the cationic organopalladium complexes was indicated as a dominant factor in enhancing the reactivities. Utilizing the reactivity of an acylpalladium complex toward hydrogen, a novel, selective, and environmentally benign hydrogenation process catalyzed by palladium complexes to give various aldehydes has been developed.