Chromium(v)-oxo and chromium(iii)-superoxo complexes bearing a macrocyclic TMC ligand in hydrogen atom abstraction reactions

Cho, Jaeheung; Woo, JongRoul; Han, Jung Eun; Kubo, Minoru; Ogura, Takashi; Nam, Wonwoo

doi:10.1039/c1sc00386k

Cited by 62 publications

(67 citation statements)

References 57 publications

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“…This value is smaller than the KIE values obtained for most metal-oxo mediated HAT reactions (3 – 25). 13,14,24 It is nearly the same as the KIE reported for the PCET reaction of guanidine with Ru(bpy) 3 3+ , 19 as well as those of 4-substituted phenols and dicopper-dioxygen complexes. 15 Interestingly, 2,4-di- tert -butylphenol exhibited a significantly larger KIE of 4.72 (Figure 1B), which is in the typical range for a HAT process.…”

supporting

confidence: 79%

“…A HAT mechanism has been established for the phenol oxidation mediated by the terminal Mn V -oxo (TBP8Cz)Mn V O ( 1 ) (TBP8Cz = octakis(para-tert-butylphenyl)corrolazinato 3- ) 13 and Cr III -superoxo, [Cr III (TMC)(O 2 )(Cl)] + (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) complexes. 14 In contrast, the reactions of phenols with two distinct homodinuclear dicopper-dioxygen complexes having bis (μ-oxo)dicopper(III) and (μ-η 2 :η 2 -peroxo)dicopper(II) cores exhibit a PCET mechanism. 15 Metal mediated oxidation of phenols by a PT-ET mechanism is unknown in the literature, although this mechanism has been previously invoked for the oxidation of phenols by organic radicals.…”

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confidence: 99%

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Mechanism of phenol oxidation by heterodinuclear Ni Cu bis(μ-oxo) complexes involving nucleophilic oxo groups

et al. 2014

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confidence: 79%

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confidence: 99%

Mechanism of phenol oxidation by heterodinuclear Ni Cu bis(μ-oxo) complexes involving nucleophilic oxo groups

et al. 2014

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“…4c). In high-valent metal-oxo and metal-superoxo complexes, a linear relationship such as this has been cited in support of an H-atom abstraction mechanism in phenol O-H bond oxidations 29–31 .…”

Section: Resultsmentioning

confidence: 91%

Crystallographic and spectroscopic characterization and reactivities of a mononuclear non-haem iron(III)-superoxo complex

et al. 2014

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Mononuclear nonheme iron(III)-superoxo species (FeIII-O2−•) have been implicated as key intermediates in the catalytic cycles of dioxygen activation by nonheme iron enzymes. Although nonheme iron(III)-superoxo species have been trapped and characterized spectroscopically in enzymatic and biomimetic reactions, no structural information has yet been obtained. Here we report for the first time the isolation, spectroscopic characterization, and crystal structure of a mononuclear side-on (η2) iron(III)-superoxo complex with a tetraamido macrocyclic ligand (TAML), [FeIII (TAML) (O2)]2− (1). The nonheme iron(III)-superoxo species undergoes both electrophilic and nucleophilic oxidation reactions as well as O2-transfer between metal complexes. In the O2-transfer reaction, 1 transfers the bound O2 unit to a manganese(III) analogue, resulting in the formation of a manganese(IV)-peroxo complex, [MnIV(TAML)(O2)]2− (2); 2 is characterized structurally and spectroscopically as a mononuclear side-on (η2) manganese(IV)-peroxo complex. The difference in the redox distribution between the metal ions and O2 in 1 and 2 is rationalized using density functional theory calculations.

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“…[4] A variety of metal–TMC complexes with oxo, superoxo, peroxo, and hydroperoxo ligands have been synthesized and spectroscopically and/or structurally characterized. [2h, 5–10] In particular, the first high-resolution crystal structures of mononuclear nonheme iron(IV)–oxo and iron(III)–peroxo complexes, such as [Fe IV (14-TMC)(O)] 2+ and [Fe III (14-TMC)(O 2 )] + , were successfully obtained by using the 14-TMC macrocyclic ligand. [7a, 10a] It was also shown that the iron(III)–peroxo complex [Fe III (14-TMC)(O 2 )] + was cleanly converted to the corresponding iron(III)–hydroperoxo complex, [Fe III (14-TMC)(OOH)] 2+ , upon protonation; this was followed by clean conversion of the iron(III)–hydroperoxo complex to an iron(IV)–oxo complex, [Fe IV (14-TMC)(O)] 2+ , through homolytic O–O bond cleavage.…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization, and Reactivity of Cobalt(III)–Oxygen Complexes Bearing a Macrocyclic N‐Tetramethylated Cyclam Ligand

Kim

Cho

Lee

et al. 2013

Chemistry A European J

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Mononuclear metal–dioxygen species are key intermediates that are frequently observed in the catalytic cycles of dioxygen activation by metal-loenzymes and their biomimetic compounds. In this work, a side-on cobalt-(III)–peroxo complex bearing a macro-cyclic N-tetramethylated cyclam (TMC) ligand, [CoIII(15-TMC)(O2)]+, was synthesized and characterized with various spectroscopic methods. Upon protonation, this cobalt(III)–peroxo complex was cleanly converted into an end-on cobalt(III)–hydroperoxo complex, [CoIII(15-TMC)(OOH)]2+. The cobalt(III)–hydroperoxo complex was further converted to [CoIII(15-TMC-CH2-O)]2+ by hydroxylation of a methyl group of the 15-TMC ligand. Kinetic studies and 18O-labeling experiments proposed that the aliphatic hydroxylation occurred via a CoIV–oxo (or CoIII–oxyl) species, which was formed by O–O bond homolysis of the cobalt(III)–hydroperoxo complex. In conclusion, we have shown the synthesis, structural and spectroscopic characterization, and reactivities of mono-nuclear cobalt complexes with peroxo, hydroperoxo, and oxo ligands.

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Chromium(v)-oxo and chromium(iii)-superoxo complexes bearing a macrocyclic TMC ligand in hydrogen atom abstraction reactions

Cited by 62 publications

References 57 publications

Mechanism of phenol oxidation by heterodinuclear Ni Cu bis(μ-oxo) complexes involving nucleophilic oxo groups

Mechanism of phenol oxidation by heterodinuclear Ni Cu bis(μ-oxo) complexes involving nucleophilic oxo groups

Crystallographic and spectroscopic characterization and reactivities of a mononuclear non-haem iron(III)-superoxo complex

Synthesis, Characterization, and Reactivity of Cobalt(III)–Oxygen Complexes Bearing a Macrocyclic N‐Tetramethylated Cyclam Ligand

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