Synthesis of cytotoxic iron‐containing macrocycles through unexpected C(sp2)−C(sp2) bonds formation

In previous reports, it has been demonstrated that cyclometalated iron(II/III) complexes can be prepared by reacting iron(0) precursors and mercurated or brominated derivatives. However, in this report, the reaction between [Fe3(CO)12] 6-phenyl-2,2'-bipyridine 2,6-diphenyl-pyridine pincer derivatives led to compounds which C(sp2)−C(sp2) bonds have formed two ligands. A 16-electron iron(II) complex (1Cl) bearing a tetradentate ligand originating from dimerization of was isolated, while protonated 14-membered macrocycle with [FeBr4]- as counterion (2) obtained 2,6-diphenyl-pyridine. Studies X-ray diffraction crystallography, NMR, UV−vis cyclic voltammetry confirmed structures. Additionally, cytotoxicity new toward gastric cancer cell lines evaluated, established presence center crucial for an elevated activity.