Synthesis and Reactivity of a Cobalt-Supported Singlet Nitrene

Mao W, Zhang Z, Fehn D, Jannuzzi SA, Heinemann FW, Scheurer A, van Gastel M, DeBeer S, Munz D, Meyer K (2023)

Publication Type: Journal article

Publication year: 2023


Book Volume: 145

Pages Range: 13650-13662

Journal Issue: 25

DOI: 10.1021/jacs.3c01478


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 CoI precursor [(TIMMNmes)CoI](PF6) (TIMMNmes = tris-[2-(3-mesityl-imidazolin-2-ylidene)-methyl]amine) with p-methoxyphenyl azide yields a CoIII imide [(TIMMNmes)CoIII(NAnisole)](PF6) (1). Treatment of 1 with 1 equiv of [FeCp2](PF6) at −35 °C affords a formal CoIV imido complex [(TIMMNmes)Co(NAnisole)](PF6)2 (2), which features a bent Co-N(imido)-C(Anisole) linkage. Subsequent one-electron oxidation of 2 with 1 equiv of AgPF6 provides 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 CoIV imido complex 2 exhibits a doublet ground state with considerable imidyl character as a result of covalent Co-NAnisole bonding. At room temperature, 2 readily converts to a CoII amine complex involving intramolecular C-H bond amination. Electronically, tricationic complex 3 can be understood as a singlet nitrene bound to CoIII with significant CoIV imidyl radical character. Verifying the pronounced electrophilicity, nucleophiles such as H2O and tBuNH2 add to 3─analogous to the parent free nitrene─in the para position of the aromatic substituent, thus, clearly corroborating singlet nitrene-type reactivity.

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Mao, W., Zhang, Z., Fehn, D., Jannuzzi, S.A., Heinemann, F.W., Scheurer, A.,... Meyer, K. (2023). Synthesis and Reactivity of a Cobalt-Supported Singlet Nitrene. Journal of the American Chemical Society, 145(25), 13650-13662.


Mao, Weiqing, et al. "Synthesis and Reactivity of a Cobalt-Supported Singlet Nitrene." Journal of the American Chemical Society 145.25 (2023): 13650-13662.

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