Synthetic Advances for Mechanistic Insights: Metal–Oxygen Intermediates with a Macrocyclic Pyridinophane System

Jeong, Donghyun; Kim, Kyungmin; Lee, Yujeong; Cho, Jaeheung

doi:10.1021/acs.accounts.3c00582

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“…The analogs of R 1 ,R 2 -DAP ligands ( N,N′ -di-R 1 -2,11-diaza[3.3](2,6)- p -R 2 -pyridinophane) have been widely utilized for modifying N -substituents on the R 1 group for steric effects and the R 2 group for the electronic effects on the metal center (Scheme ). − Recently, we reported the generation and characterization of a series of (hydro)peroxocobalt(III) complexes, [Co III (R 2 -TBDAP)(O 2 )] + and [Co III (R 2 -TBDAP)(O 2 H)] 2+ (R 2 = Cl, OCH 3 ), with controlled the electronic effect on the R 2 group of the tetraazamacrocylic ligand . The electronic effect resulting from modified ligands was investigated by comparing the electrochemical features of peroxocobalt(III) complexes and the reactivities in oxygen atom transfer reactions with thioanisole by hydroperoxocobalt(III) complexes .…”

Section: Introductionmentioning

confidence: 99%

Controlling Reactivity through Spin Manipulation: Steric Bulkiness of Peroxocobalt(III) Complexes

Kim,

Lee,

Tripodi

et al. 2024

J. Am. Chem. Soc.

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The intrinsic relationship between spin states and reactivity in peroxocobalt(III) complexes was investigated, specifically focusing on the influence of steric modulation on supporting ligands. Together with the previously reported [Co III (TBDAP)(O 2 )] + (2 Tb ), which exhibits spin crossover characteristics, two peroxocobalt(III) complexes, [Co III (MDAP)-(O 2 )] + (2 Me ) and [Co III (ADDAP)(O 2 )] + (2 Ad ), bearing pyridinophane ligands with distinct N-substituents such as methyl and adamantyl groups, were synthesized and characterized. By manipulating the steric bulkiness of the N-substituents, control of spin states in peroxocobalt(III) complexes was demonstrated through various physicochemical analyses. Notably, 2 Ad oxidized the nitriles to generate hydroximatocobalt(III) complexes, while 2 Me displayed an inability for such oxidation reactions. Furthermore, both 2 Ad and 2 Tb exhibited similarities in spectroscopic and geometric features, demonstrating spin crossover behavior between S = 0 and S = 1. The steric bulkiness of the adamantyl and tertbutyl group on the axial amines was attributed to inducing a weak ligand field on the cobalt(III) center. Thus, 2 Ad and 2 Tb are an S = 1 state under the reaction conditions. In contrast, the less bulky methyl group on the amines of 2 Me resulted in an S = 0 state. The redox potential of the peroxocobalt(III) complexes was also influenced by the ligand field arising from the steric bulkiness of the Nsubstituents in the order of 2 Me (−0.01 V) < 2 Tb (0.29 V) = 2 Ad (0.29 V). Theoretical calculations using DFT supported the experimental observations, providing insights into the electronic structure and emphasizing the importance of the spin state of peroxocobalt(III) complexes in nitrile activation.

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Section: Introductionmentioning

confidence: 99%

Controlling Reactivity through Spin Manipulation: Steric Bulkiness of Peroxocobalt(III) Complexes

Kim,

Lee,

Tripodi

et al. 2024

J. Am. Chem. Soc.

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Synthetic Advances for Mechanistic Insights: Metal–Oxygen Intermediates with a Macrocyclic Pyridinophane System

Abstract: We reported the first study on dioxygenase-like nitrile activation by a mononuclear cobalt(III)−peroxo intermediate. The resultant cobalt-(III)−hydroximate complexes were confirmed by X-ray crystallography and various spectroscopic techniques.

Cited by 1 publication

References 56 publications

Controlling Reactivity through Spin Manipulation: Steric Bulkiness of Peroxocobalt(III) Complexes

Controlling Reactivity through Spin Manipulation: Steric Bulkiness of Peroxocobalt(III) Complexes

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