| Autor: |
Mao, Weiqing, Zhang, Zihan, Fehn, Dominik, Jannuzzi, Sergio A. V., Heinemann, Frank W., Scheurer, Andreas, van Gastel, Maurice, DeBeer, Serena, Munz, Dominik, Meyer, Karsten |
| Zdroj: |
Journal of the American Chemical Society; June 2023, Vol. 145 Issue: 25 p13650-13662, 13p |
| Abstrakt: |
The synthesis, characterization, and reactivity of a series of cobalt terminal imido complexes supported by an N-anchored tripodal tris(carbene) chelate is described, including a Co-supported singlet nitrene. Reaction of the CoIprecursor [(TIMMNmes)CoI](PF6) (TIMMNmes= tris-[2-(3-mesityl-imidazolin-2-ylidene)-methyl]amine) with p-methoxyphenyl azide yields a CoIIIimide [(TIMMNmes)CoIII(NAnisole)](PF6) (1). Treatment of 1with 1 equiv of [FeCp2](PF6) at −35 °C affords a formal CoIVimido complex [(TIMMNmes)Co(NAnisole)](PF6)2(2), which features a bent Co–N(imido)–C(Anisole) linkage. Subsequent one-electron oxidation of 2with 1 equiv of AgPF6provides access to the tricationic cobalt imido complex [(TIMMNmes)Co(NAnisole)](PF6)3(3). All complexes were fully characterized, including single-crystal X-ray diffraction (SC-XRD) analyses, infrared (IR) vibrational, ultraviolet/visible (UV/vis) electronic absorption, multinuclear NMR, X-band electron paramagnetic resonance (EPR), electron nuclear double resonance (ENDOR), and high-energy-resolution fluorescence-detected X-ray absorption spectroscopy (HERFD XAS). Quantum chemical calculations provide additional insight into the electronic structures of all compounds. The dicationic CoIVimido complex 2exhibits a doublet ground state with considerable imidyl character as a result of covalent Co–NAnisole bonding. At room temperature, 2readily converts to a CoIIamine complex involving intramolecular C–H bond amination. Electronically, tricationic complex 3can be understood as a singlet nitrene bound to CoIIIwith significant CoIVimidyl radical character. Verifying the pronounced electrophilicity, nucleophiles such as H2O and tBuNH2add to 3─analogous to the parent free nitrene─in the paraposition of the aromatic substituent, thus, clearly corroborating singlet nitrene-type reactivity. |
| Databáze: |
Supplemental Index |
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