A Structurally Analogous Series of Mn(II), Fe(II), and Co(II) Complexes Which Exhibit Three Distinct Reactivities with Dioxygen

The synthesis and characterization of a series of nonheme Fe(II), Mn(II), and Co(II) complexes, MII(BNPAPh2O)(Cl) (M = Fe, Mn, Co), are reported. These complexes were characterized using single-crystal X-ray crystallography, 1H NMR spectroscopy, and ATR-FTIR spectroscopy to establish their structural and electronic properties. Their reactivity with dioxygen revealed distinct metal-dependent pathways. The Mn(II) complex undergoes ligand-based C-N bond cleavage, forming a pentanuclear cluster, whereas the Fe(II) complex reacts with O2 to generate a well-defined FeIII(BNPAPh2O)(OH)(Cl) species, relevant to the rebound intermediate in nonheme iron halogenases. In contrast, the Co(II) complex exhibits no detectable reactivity toward O2. These differences illuminate the intrinsic metal-dependent factors that govern O2 activation and underscore the central role of metal identity in tuning reactivity and selectivity in bioinorganic oxidation chemistry.