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Tuning the Reactivity of Chromium(III)-Superoxo Species by Coordinating Axial Ligands

Title
Tuning the Reactivity of Chromium(III)-Superoxo Species by Coordinating Axial Ligands
Authors
Goo, Yi ReMaity, Annada C.Cho, Kyung-BinLee, Yong-MinSeo, Mi SookPark, Young JunCho, JaeheungNam, Wonwoo
Ewha Authors
남원우이용민서미숙
SCOPUS Author ID
남원우scopus; 이용민scopusscopus; 서미숙scopusscopus
Issue Date
2015
Journal Title
INORGANIC CHEMISTRY
ISSN
0020-1669JCR Link1520-510XJCR Link
Citation
vol. 54, no. 21, pp. 10513 - 10520
Publisher
AMER CHEMICAL SOC
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
Metal-superoxo species have attracted much attention recently as key intermediates in enzymatic and biomimetic oxidation reactions. The effect(s) of axial ligands on the chemical properties of metal-superoxo complexes has never been explored previously. In this study, we synthesized and characterized chromium(III)-superoxo complexes bearing TMC derivatives with pendant pyridine and imidazole donors, such as [Cr-III(O-2)-(TMC-Py)](2+) (1, TMC-Py = 4,8,11-trimethyl-1-(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane) and [Cr-III(O-2)(TMC-Im)](2+) (2, TMC-Im = 4,8,11-trimethyl-1-(2-methylimidazolmethyl)-1,4,8,11-tetraazacyclotetradecane). The reactivity of chromium(III)-superoxo complexes binding different axial ligands, such as 1, 2, and [Cr-III(O-2)(TMC)(Cl)](+) (3, TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), was then investigated in CH bond activation and oxygen atom transfer reactions. Kinetic studies revealed that the reactivity of the Cr(III)-superoxo complexes depends on the axial ligands, showing the reactivity order of 1 > 2 > 3 in those electrophilic oxidation reactions. It was also shown that there is a good correlation between the reactivity of the chromium(III)-superoxo complexes and their redox potentials, in which the redox potentials of the chromium(III)-superoxo complexes are in the order 1 > 2 > 3. DFT calculations reproduced the reactivity order between 1 and 3 in both C-H bond activation and oxygen atom transfer reactions, and the latter reaction is described using orbital interactions. The calculations are also in agreement with the experimentally obtained redox potentials. The present results provide the first example showing that the reactivity of metal-superoxo species can be tuned by the electron-donating ability of axial ligands bound trans to the metal-superoxo moiety.
DOI
10.1021/acs.inorgchem.5b02068
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자연과학대학 > 화학·나노과학전공 > Journal papers
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