Synthesis and Reactivity of a Cobalt-Supported Singlet Nitrene.

The synthesis, characterization, and reactivity of a series of cobalt terminal imido complexes supported by an -anchored tripodal tris(carbene) chelate is described, including a Co-supported singlet nitrene. Reaction of the Co precursor [(TIMMN)Co](PF) (TIMMN = -[2-(3-mesityl-idazolin-2-ylidene)-ethyl]amie) with -methoxyphenyl azide yields a Co imide [(TIMMN)Co(NAnisole)](PF) (). Treatment of with 1 equiv of [FeCp](PF) at -35 °C affords a formal Co imido complex [(TIMMN)Co(NAnisole)](PF) (), which features a bent Co-N(imido)-C(Anisole) linkage. Subsequent one-electron oxidation of with 1 equiv of AgPF provides access to the tricationic cobalt imido complex [(TIMMN)Co(NAnisole)](PF) (). 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 Co imido complex exhibits a doublet ground state with considerable imidyl character as a result of covalent Co-NAnisole bonding. At room temperature, readily converts to a Co amine complex involving intramolecular C-H bond amination. Electronically, tricationic complex can be understood as a singlet nitrene bound to Co with significant Co imidyl radical character. Verifying the pronounced electrophilicity, nucleophiles such as HO and BuNH add to ─analogous to the parent free nitrene─in the position of the aromatic substituent, thus, clearly corroborating singlet nitrene-type reactivity.