- Copper-Catalyzed Aziridination with Redox-Active Ligands: Molecular Spin Catalysis
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Small-molecule catalysts as mimics of biological systems illustrate the chemists’ attempts at emulating the tantalizing abilities displayed by nature's metalloenzymes. Among these innate behaviors, spin multistate reactivity is used by biological systems as it offers thermodynamic leverage towards challenging chemical reactivity but this concept is difficult to translate into the realm of synthetic organometallic catalysis. Here, we report a rare example of molecular spin catalysis involving multistate reactivity in a small-molecule biomimetic copper catalyst applied to aziridination. This behavior is supported by spin state flexibility enabled by the redox-active ligand.
- Ren, Yufeng,Cheaib, Khaled,Jacquet, Jérémy,Vezin, Hervé,Fensterbank, Louis,Orio, Maylis,Blanchard, Sébastien,Desage-El Murr, Marine
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supporting information
p. 5086 - 5090
(2018/02/21)
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- C?N Bond Formation from a Masked High-Valent Copper Complex Stabilized by Redox Non-Innocent Ligands
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The reactivity of a stable copper(II) complex bearing fully oxidized iminobenzoquinone redox ligands towards nucleophiles is described. In sharp contrast with its genuine low-valent counterpart bearing reduced ligands, this complex performs high-yielding C?N bond formations. Mechanistic studies suggest that this behavior could stem from a mechanism akin to reductive elimination occurring at the metal center but facilitated by the ligand: it is proposed that a masked high oxidation state of the metal can be stabilized as a lower copper(II) oxidation state by the redox ligands without forfeiting its ability to behave as a high-valent copper(III) center. These observations are substantiated by a combination of advanced EPR spectroscopy techniques with DFT studies. This work sheds light on the potential of redox ligands as promoters of unusual reactivities at metal centers and illustrates the concept of masked high-valent metallic species.
- Jacquet, Jérémy,Chaumont, Pauline,Gontard, Geoffrey,Orio, Maylis,Vezin, Hervé,Blanchard, Sébastien,Desage-El Murr, Marine,Fensterbank, Louis
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supporting information
p. 10712 - 10716
(2016/09/03)
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- Dinuclear and mononuclear manganese(IV)-radical complexes and their catalytic catecholase activity
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Seven o-aminophenol ligands based on aniline and m-phenylenediamine, which act as mono- and di-nucleating non-innocent ligands, respectively, together with their seven Mn(IV)-complexes, 1-7 are described. One of them, 1, is dinuclear and 2-7 are mononuclear, in which the ligands are coordinated in their oxidized o-iminobenzosemiquinone radical forms. The crystal structures of 1 and 3 were determined by X-ray diffraction and the electronic structures were established by various physical methods including EPR and variable-temperature (2-290 K) susceptibility measurements. Electrochemical measurements (CV and SQW) indicate primarily ligand-centered redox processes. The Mn(IV)-radical complexes, 1-7, catalyze the oxidation of 3,5-di-tert-butylcatechol with molecular oxygen as the sole oxidant to afford 3,5-di-tert-butylquinone quantitatively under mild conditions to mimic the function of the copper-containing enzyme catechol oxidase. An "on-off" mechanism of the radicals without redox participation of the metal center is proposed for the catalytic oxidation process. Complex 1 is found to be a good catalyst for oxidative C-C coupling of hindered phenols to diphenoquinones.
- Mukherjee, Soumen,Weyhermueller, Thomas,Bothe, Eberhard,Wieghardt, Karl,Chaudhuri, Phalguni
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p. 3842 - 3853
(2007/10/03)
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