%0 Generic %A Zaragoza, Jan Paulo T. %A Siegler, Maxime A. %A Goldberg, David P. %D 2018 %T A Reactive Manganese(IV)–Hydroxide Complex: A Missing Intermediate in Hydrogen Atom Transfer by High-Valent Metal-Oxo Porphyrinoid Compounds %U https://acs.figshare.com/articles/dataset/A_Reactive_Manganese_IV_Hydroxide_Complex_A_Missing_Intermediate_in_Hydrogen_Atom_Transfer_by_High-Valent_Metal-Oxo_Porphyrinoid_Compounds/5985073 %R 10.1021/jacs.8b00350.s007 %2 https://acs.figshare.com/ndownloader/files/10740883 %K High-Valent Metal-Oxo Porphyrinoid Compounds High-valent metal-hydroxide species %K metal-mediated O 2 activation %K OH %K Mn IV %K Hydrogen Atom Transfer %K XRD %K complexes Mn V %K higher-valent Mn V %K Marcus plot correlations %K k 2 %K range k 2 %K H atom abstractor %K H atom transfer %K DTBP %K III %K O 2 production %K II %K isotope effect measurements %X High-valent metal-hydroxide species are invoked as critical intermediates in both catalytic, metal-mediated O2 activation (e.g., by Fe porphyrin in Cytochrome P450) and O2 production (e.g., by the Mn cluster in Photosystem II). However, well-characterized mononuclear MIV(OH) complexes remain a rarity. Herein we describe the synthesis of MnIV(OH)­(ttppc) (3) (ttppc = tris­(2,4,6-triphenylphenyl) corrole), which has been characterized by X-ray diffraction (XRD). The large steric encumbrance of the ttppc ligand allowed for isolation of 3. The complexes MnV(O)­(ttppc) (4) and MnIII(H2O)­(ttppc) (1·H2O) were also synthesized and structurally characterized, providing a series of Mn complexes related only by the transfer of hydrogen atoms. Both 3 and 4 abstract an H atom from the O–H bond of 2,4-di-tert-butylphenol (2,4-DTBP) to give a radical coupling product in good yield (3 = 90(2)%, 4 = 91(5)%). Complex 3 reacts with 2,4-DTBP with a rate constant of k2 = 2.73(12) × 104 M–1 s–1, which is ∼3 orders of magnitude larger than 4 (k2 = 17.4(1) M–1 s–1). Reaction of 3 with a series of para-substituted 2,6-di-tert-butylphenol derivatives (4-X-2,6-DTBP; X = OMe, Me, tBu, H) gives rate constants in the range k2 = 510(10)–36(1.4) M–1 s–1 and led to Hammett and Marcus plot correlations. Together with kinetic isotope effect measurements, it is concluded that O–H cleavage occurs by a concerted H atom transfer (HAT) mechanism and that the MnIV(OH) complex is a much more powerful H atom abstractor than the higher-valent MnV(O) complex, or even some FeIV(O) complexes. %I ACS Publications