Stable Cyclometallated Palladium Complexes of Arylamides: Synthesis, Redox and Anticancer Activities

Air‐stable cyclometalated palladium(II) complexes with benzamide ligands were synthesized in high yields and characterized by X‐ray diffraction analysis, CVA, 1H NMR, 13C NMR spectroscopy, MALDI‐MS, and ESI‐MS. The electrochemical oxidation of the complexes is reversible in the presence of a quinoline substituent in the ligand and gives Pd (III) species that do not undergo reductive elimination and are detectable by ESR spectroscopy. The complexes showed high cytotoxicity against cervical cancer (M‐HeLa) and duodenal adenocarcinoma (HuTu 80), a human mammary ductal adenocarcinoma line (MCF‐7) and a human lung carcinoma cell line (A549). The possibility of generating reactive oxygen species in solution (such as OH−radicals), which can be responsible for the antitumor activity of the studied complexes, using the ESR method was shown. Synthesis and characterization of the palladacycles with arylamides ligands are described. The complexes are easily oxidized; some are reversible into Pd(II)/Pd(III) derivatives resistant to reductive elimination. In light, palladacycles generate OH‐radicals from water. High antitumor activity has been established, in some cases 7–12 times higher than cisplatin.