Synthesis and characterization of triphenylphosphine adducts of ferrocene-based palladacycles and their performance in the Suzuki and Sonogashira reactions with bromo- and chloroarenes.

A new triphenylphosphine adduct of cyclopalladated ferrocenylpyridazine containing a chloride anion, 2a, has been synthesized from the reaction of the chloride-bridged palladacyclic dimer 1a with triphenylphosphine. The corresponding adducts 3a,b containing iodide anion have been readily prepared through anion exchange reactions of 2a,b with NaI in acetone. These complexes were characterized by elemental analysis, IR and 1H-NMR. Additionally, their crystal structures have been determined by X-ray diffraction and intermolecular C-H···X (Cl, Br, I) bonds were found in the crystals. The use of these palladacycles as catalysts for the Suzuki and Sonogashira reactions was examined. The complexes 2a,b exhibited higher catalytic activity than the corresponding 3a,b in the Suzuki reaction. However, the order of activity of adducts with varying halogen anions is 3a~3b > 2a~>2b in the Sonogashira reaction.