期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 60, 期 30, 页码 16480-16486出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.202103170
关键词
cobalt; density functional theory calculations; EPR spectroscopy; N-heterocyclic carbenes; terminal imides
资金
- German Federal Ministry of Education and Research (BMBF) [03SF0502]
- FAU
- Alexander-von-Humboldt foundation
- Fonds der Chemischen Industrie
- German-American Fulbright Commission
- Projekt DEAL
The synthesis of high-valent cobalt(IV) imido complex [(TIMMNmes)Co-IV(NAd)](OTf)(2) (4) via reaction with 1-adamantylazide is discussed. Despite a short half-life at room temperature, compound 4 can be isolated at low temperatures in pure form. Experimental and computational analysis confirm the molecular and electronic structure of 4, suggesting high covalency and substantial triplet nitrene character.
The reaction of the cobalt(I) complex [(TIMMNmes)Co-I](BPh4) (2) (TIMMNmes=tris-[2-(3-mesitylimidazolin-2-ylidene)methyl]amine) with 1-adamantylazide yields the cobalt(III) imido complex [(TIMMNmes)Co-III(NAd)](BPh4) (3) with concomitant release of dinitrogen. The N-anchor in diamagnetic 3 features an unusual, planar tertiary amine, which results from repulsive electrostatic interaction with the filled d(z(2))-orbital of the cobalt ion and negative hyperconjugation with the neighboring methylene groups. One-electron oxidation of 3 with [FeCp2](OTf) provides access to the rare, high-valent cobalt(IV) imido complex [(TIMMNmes)Co-IV(NAd)](OTf)(2) (4). Despite a half-life of less than 1 h at room temperature, 4 could be isolated at low temperatures in analytically pure form. Single-crystal X-ray diffractometry and EPR spectroscopy corroborate the molecular structure and the d(5) low-spin, S=1/2 , electron configuration. A computational analysis of 4 suggests high covalency within the Co-IV=NAd bond with non-negligible spin density located at the imido moiety, which translates into substantial triplet nitrene character.
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