Palladium(II) Complexes Containing Both the Chelating β-Diketonato and σ-Pyridyl Ligands. Catalyzed Coordination-site Exchange Reactions

A novel type of palladium(II) complexes, [Pd(β-dik)(pyridyl)(PPh3)] and [Pd(β-dik)(pyridyl)]2 containing a chelating acetylacetonate, trifluoroacetylacetonate, or hexafluoroacetylacetonate anion and 2-, 3-, or 4-pyridyl radical as the coexisting ligands were prepared and characterized by elemental analysis and molecular weight determination as well as 1H and 13C NMR spectroscopy. [Pd(acac)(C5H3(6-Cl)N–C2)(PPh3)] is stereochemically rigid in solution but undergoes the coordination-site exchange reaction catalyzed by nitrogen and phosphorus bases and donor solvents. Similar reaction of [Pd(acac)(C5H4N–C2)(PPh3)] is catalyzed by triphenylphosphine liberated by the dinuclear-complex formation reaction (autocatalysis). Intact molecules of [Pd(acac)(C5H4N–C3 and –C4) (PPh3)] catalyze mutually their own coordination-site exchange (self-catalysis).