Preparation and Characterization of a Formally NiIV-Oxo Complex with a Triplet Ground State and Application in Oxidation Reactions
- 등재 SCIE, SCOPUS
- 발행기관 American Chemical Society
- 발행년도 2022
- 총서유형 Journal
- URI http://www.dcollection.net/handler/ewha/000000203318
- 본문언어 영어
- Published As https://doi.org/10.1021/jacs.2c10196
- PubMed https://pubmed.ncbi.nlm.nih.gov/36454200
초록/요약
High-valent first-row transition-metal-oxo complexes are important intermediates in biologically and chemically relevant oxidative transformations of organic molecules and in the water splitting reaction in (artificial) photosynthesis. While high-valent Fe- A nd Mn-oxo complexes have been characterized in detail, much less is known about their analogues with late transition metals. In this study, we present the synthesis and detailed characterization of a unique mononuclear terminal Ni-O complex. This compound, [Ni(TAML)(O)(OH)]3-, is characterized by an intense charge-transfer (CT) band around 730 nm and has an St= 1 ground state, as determined by magnetic circular dichroism spectroscopy. From extended X-ray absorption fine structure (EXAFS), the Ni-O bond distance is 1.84 Å. Ni K edge XAS data indicate that the complex contains a Ni(III) center, which results from an unusually large degree of Ni-O π-bond inversion, with one hole located on the oxo ligand. The complex is therefore best described as a low-spin Ni(III) complex (S = 1/2) with a bound oxyl (O-) ligand (S = 1/2), where the spins of Ni and oxyl are ferromagnetically coupled, giving rise to the observed St= 1 ground state. This bonding description is roughly equivalent to the presence of a Ni-O single (σ) bond. Reactivity studies show that [Ni(TAML)(O)(OH)]3-is a strong oxidant capable of oxidizing thioanisole and styrene derivatives with large negative ρ values in the Hammett plot, indicating its electrophilic nature. The intermediate also shows high reactivity in C-H bond activation of hydrocarbons with a kinetic isotope effect of 7.0(3) in xanthene oxidation. © 2022 American Chemical Society. All rights reserved.
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