Synthesis and characterization of mononuclear oxime-based palladacycles incorporating phosphorus ylides: application as a catalyst in Suzuki cross coupling reactions and their biological activities

Abstract

The synthesis of mononuclear oxime-based palladacycles of the type [Pd{C,N-C6H4{C(Me)=NOH}-2}(Ph2PCH2CH2PPh2C(H)C(O)C6H4X)]ClO4(X = Cl (1), Br (2), NO2 (3), OCH3 (4)) is reported from the reactions of [Pd{C,N-C6H4{C(Me)=NOH}-2}(μ-Cl)]2 with phosphorus ylides in dichloromethane under reflux. The obtained compounds were characterized by FT-IR, NMR (1H, 13C{H} and 31P{H}) spectroscopic methods and elemental analysis. Splitting of the chloride bridge formed four new mononuclear oxime-based palladacycles incorporating bidentate phosphorus ylides (1-4). These palladacycles were applied for Suzuki-Miyaura cross-coupling reactions under aerobic conditions in EtOH/H2O solvent. Upon optimizing the reaction conditions, complex 3 was highly efficient to catalyze the cross-coupling of aryl halides with phenylboronic acids at a 0.44 mol % palladium loading. Also, the cytotoxic effects of 1-4 were evaluated by an MTT assay in three human carcinoma cell lines: HT29, A549, and 1321N1. The results indicate that these compounds had toxic effects and 4 has greater toxic activity with respect to the other complexes in all three cell lines. Thus, these compounds can be considered as efficient catalysts in cross-coupling reactions and as a cytotoxic agent.