The oxomanganese­(IV) complex [(dpaq)­MnIV(O)]+-M n+ (1-M n+ , M n+ = redox-inactive metal ion, H-dpaq = 2-[bis­(pyridin-2-ylmethyl)]­amino-N-quinolin-8-ylacetamide), generated in the reaction of the precursor hydroxomanganese­(III) complex 1 with iodosylbenzene (PhIO) in the presence of redox-inactive metal triflates, has recently been reported. Herein the generation of the same oxomanganese­(IV) species from 1 using various combinations of protic acids and oxidants at 293 K is reported. The reaction of 1 with triflic acid and the one-electron-oxidizing agent [RuIII(bpy)3]3+ leads to the formation of the oxomanganese­(IV) complex. The putative species has been identified as a mononuclear high-spin (S = 3/2) nonheme oxomanganese­(IV) complex (1-O) on the basis of mass spectrometry, Raman spectroscopy, EPR spectroscopy, and DFT studies. The optical absorption spectrum is well reproduced by theoretical calculations on an S = 3/2 ground spin state of the complex. Isotope labeling studies confirm that the oxygen atom in the oxomanganese­(IV) complex originates from the MnIII–OH precursor and not from water. A mechanistic investigation reveals an initial protonation step forming the MnIII–OH2 complex, which then undergoes one-electron oxidation and subsequent deprotonations to form the oxomanganese­(IV) transient, avoiding the requirements of either oxo-transfer agents or redox-inactive metal ions. The MnIV–oxo complex cleaves the C–H bonds of xanthene (k 2 = 5.5 M–1 s–1), 9,10-DHA (k 2 = 3.9 M–1 s–1), 1,4-CHD (k 2 = 0.25 M–1 s–1), and fluorene (k 2 = 0.11 M–1 s–1) at 293 K. The electrophilic character of the nonheme MnIV–oxo complex is demonstrated by a large negative ρ value of 2.5 in the oxidation of para-substituted thioanisoles. The complex emerges as the “most reactive” among the existing MnIV/V–oxo complexes bearing anionic ligands.

The reactivities of Fe(iv) oxido complexes of two pentadentate ligands are related to steric and electronic properties of the ligands.

Abstract. Three iron(II)-(1) using substituted 2-aminophenolates. Single crystal structure of 4 reveals that the mononuclear central iron atom is coordinated by a tetradentate N 3 C ligand and a monoanionic bidentate 4-NO 2 -HAP giving rise to a distorted octahedral coordination arrangement. The six-coordinate iron(II)

The reactivity of a mononuclear high‐spin iron(III)‐alkylperoxo intermediate [FeIII(t‐BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t‐BuLUrea)(H2O)(OTf)](OTf) (1) [t‐BuLUrea=1,1′‐(((pyridin‐2‐ylmethyl)azanediyl)bis(ethane‐2,1‐diyl))bis(3‐(tert‐butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C−H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C−H bonds of aliphatic substrates with high chemo‐ and stereoselectivity in the presence of 2,6‐lutidine. While 2 itself is a sluggish oxidant, 2,6‐lutidine assists the heterolytic O−O bond cleavage of the metal‐bound alkylperoxo, giving rise to a reactive metal‐based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.

The synthesis, characterization and reactivity studies of iron(ii) complexes [Fe(PySH)](OTf), 1-(OTf)2, [Fe(PySH)](ClO), 1-(ClO4)2, and [Fe(PyS)], (2), of a 2-mercaptopyridine (PySH) ligand are discussed. The X-ray crystal structures of both 1-(OTf)2 and 1-(ClO4)2 reveal a distorted tetrahedral geometry at the iron(ii) center with identical constituents. All the pyridine nitrogen atoms are protonated and thiolate ions are coordinated to the iron(ii) center. The structure and function of complex 1-(OTf)2 or 1-(ClO4)2 resembles the active site of rubredoxin. Complex 2 has octahedral geometry at the iron(ii) center forming a 1-D coordination polymer. Complex 1-(OTf)2 exhibits a high positive redox potential (E = 0.23 V vs. Ag/AgCl) which reduces to -0.12 V in the presence of triethylamine under an inert atmosphere. This change of the redox potential is highly reversible in the presence of a weak acid such as p-toluenesulfonic acid, pTsOH. DFT studies show that the complex cation [Fe(PySH)] upon treatment with a base converts to its anionic congener, [Fe(PyS)], via the deprotonation of the pyridinium moiety. The iron(ii) complexes readily react with molecular oxygen to yield the corresponding iron(iii) complex, which rapidly decays to form pyridine disulphide (PyS) and an iron(ii) complex.