Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Egerlandstraße 1, 91058 Erlangen, Germany.
Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany.
J Am Chem Soc. 2023 Jun 28;145(25):13650-13662. doi: 10.1021/jacs.3c01478. Epub 2023 Jun 13.
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 (TIMMN = -[2-(3-mesityl-idazolin-2-ylidene)-ethyl]amie) with -methoxyphenyl azide yields a Co imide (TIMMN)Co(NAnisole) (). Treatment of with 1 equiv of FeCp at -35 °C affords a formal Co imido complex (TIMMN)Co(NAnisole) (), 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) (). 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.
描述了一系列钴末端亚氨基配合物的合成、表征和反应性，这些配合物由锚定的三足三（碳烯）螯合物支撑，包括一个钴支持的单线态氮烯。钴前体(TIMMN)Co（TIMMN= -[2-(3-均三甲苯基-咪唑啉-2-亚基）-乙基]胺）与 -甲氧基苯叠氮反应生成钴亚胺(TIMMN)Co(NAnisole)（）。在-35°C下，用 1 当量的FeCp处理，得到一个形式上的钴亚氨基配合物(TIMMN)Co(NAnisole)（），其特征为弯曲的 Co-N(亚氨基)-C(Anisole)键。随后，用 1 当量的 AgPF 对进行单电子氧化，可得到三价钴亚氨基配合物(TIMMN)Co(NAnisole)（）。所有配合物均进行了充分的表征，包括单晶 X 射线衍射（SC-XRD）分析、红外（IR）振动、紫外/可见（UV/vis）电子吸收、多核 NMR、X 波段电子顺磁共振（EPR）、电子核双共振（ENDOR）和高能分辨荧光探测 X 射线吸收光谱（HERFD XAS）。量子化学计算提供了对所有化合物电子结构的额外见解。二价钴亚氨基配合物 表现出双重态基态，由于与 Co-NAnisole 的共价键合，具有相当大的亚氨基特征。在室温下， 容易转化为涉及分子内 C-H 键氨化的钴胺配合物。在电子方面，三价配合物 可以被理解为与 Co 键合的单线态氮烯，具有显著的 Co 亚氨基自由基特征。验证了其明显的亲电性，亲核试剂如 HO 和 BuNH 与芳香取代基的 -位加成，类似于母体游离氮烯，因此，清楚地证实了单线态氮烯型反应性。
