Peroxocobalt(<scp>iii</scp>) species activates nitriles<i>via</i>a superoxocobalt(<scp>ii</scp>) diradical state

Cho, Dasol; Choi, Seulhui; Cho, Jaeheung; Baik, Mu‐Hyun

doi:10.1039/d0dt00042f

Cited by 9 publications

(24 citation statements)

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“…12e,f Recently, we reported the distinct reactivity of a side-on peroxocobalt(III) complex, [Co III (TBDAP)(O 2 )] + (1), which reacts with nitriles to give hydroximatocobalt(III) complexes, [Co III (TBDAP)(R−C( NO)O)] + (R = Me (3), Et, and Ph). 13,14 In the present work, we report that mononuclear peroxocobalt(III) complex 1…”

Section: ■ Introductionmentioning

confidence: 58%

“…Recently, we reported that the reactive form of 1 capable of activating nitrile substrates consists of a triplet Co(II)-superoxo species, [Co II (TBDAP)(O 2 – )] + , when M n + is not present. As shown in Figure , 1 can bind a nitrile substrate via the transition state 1-TS at 12.3 kcal mol –1 to give intermediate A .…”

Section: Resultsmentioning

confidence: 99%

“…The conversion of 2 to 3 with the addition of triethylamine can be explained in terms of intramolecular electron transfer in deprotonated peroxyimidatocobalt(III) species, T B . Previously, we proposed that the hydroximatocobalt(III) complex 3 forms from a kinetically and thermodynamically approachable oxyl–nitrene diradical intermediate that is formed from the homolytic cleavage of a O–O bond in deprotonated peroxyimidatocobalt(III) species, T B (Scheme a) . The generation of oxyl and nitrene radical species leads to a radical coupling mechanism that gives the expected product 3 after some structural rearrangements.…”

Section: Resultsmentioning

confidence: 99%

“…Previously, we proposed that the hydroximatocobalt(III) complex 3 forms from a kinetically and thermodynamically approachable oxyl− nitrene diradical intermediate that is formed from the homolytic cleavage of a O−O bond in deprotonated peroxyimidatocobalt(III) species, T B (Scheme 4a). 14 The generation of oxyl and nitrene radical species leads to a radical coupling mechanism that gives the expected product 3 after some structural rearrangements. During this process, as the O−O bond is cleaved homolytically, the proximal oxygen radical, as shown in Scheme 4c, is immediately stabilized by ferromagnetic coupling with the triplet cobalt(III) center.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The impact of redox-inactive metal ions on metal–(alkyl)peroxo complexes remains largely underexplored, and the mechanism is poorly understood. Previously, it was observed that the nucleophilic reactivity of metal–(alkyl)peroxo species with aldehydes decreases as the Lewis acidity of redox-inactive metal ions increases. , Recently, we reported the distinct reactivity of a side-on peroxocobalt(III) complex, [Co III (TBDAP)(O 2 )] + ( 1 ), which reacts with nitriles to give hydroximatocobalt(III) complexes, [Co III (TBDAP)(R–C(NO)O)] + (R = Me ( 3 ), Et, and Ph). , In the present work, we report that mononuclear peroxocobalt(III) complex 1 forms different products via nitrile activation reaction with the assistance of redox-inactive Lewis acidic metal ions (M n + ). In the presence of relatively weak Lewis acids, such as Zn 2+ , La 3+ , Lu 3+ , and Y 3+ , 1 reacts with nitriles to produce peroxyimidatocobalt(III) complexes, [Co III (TBDAP)(R–C(NH)O 2 )] 2+ (R = Me ( 2 ) and Ph ( 2 Ph )) (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

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Controlled Regulation of the Nitrile Activation of a Peroxocobalt(III) Complex with Redox-Inactive Lewis Acidic Metals

et al. 2021

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Redox-inactive metal ions play vital roles in biological O2 activation and oxidation reactions of various substrates. Recently, we showed a distinct reactivity of a peroxocobalt(III) complex bearing a tetradentate macrocyclic ligand, [CoIII(TBDAP)(O2)]+ (1) (TBDAP = N,N′-di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane), toward nitriles that afforded a series of hydroximatocobalt(III) complexes, [CoIII(TBDAP)(R–C(NO)O)]+ (R = Me (3), Et, and Ph). In this study, we report the effects of redox-inactive metal ions on nitrile activation of 1. In the presence of redox-inactive metal ions such as Zn2+, La3+, Lu3+, and Y3+, the reaction does not form the hydroximatocobalt(III) complex but instead gives peroxyimidatocobalt(III) complexes, [CoIII(TBDAP)(R–C(NH)O2)]2+ (R = Me (2) and Ph (2 Ph )). These new intermediates were characterized by various physicochemical methods including X-ray diffraction analysis. The rates of the formation of 2 are found to correlate with the Lewis acidity of the additive metal ions. Moreover, complex 2 was readily converted to 3 by the addition of a base. In the presence of Al3+, Sc3+, or H+, 1 is converted to [CoIII(TBDAP)(O2H)(MeCN)]2+ (4), and further reaction with nitriles did not occur. These results reveal that the reactivity of the peroxocobalt(III) complex 1 in nitrile activation can be regulated by the redox-inactive metal ions and their Lewis acidity. DFT calculations show that the redox-inactive metal ions stabilize the peroxo character of end-on Co−η1-O2 intermediate through the charge reorganization from a CoII–superoxo to a CoIII–peroxo intermediate. A complete mechanistic model explaining the role of the Lewis acid is presented.

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Section: ■ Introductionmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%