LCC-CNRS, Université de Toulouse, CNRS, Toulouse, France.
Univ. Grenoble Alpes, CEA, CNRS, INAC, SyMMES, F-38000 Grenoble, France.
Dalton Trans. 2021 Oct 19;50(40):14264-14272. doi: 10.1039/d1dt02182f.
Oxidation of the half-sandwich Mn complexes Cp(CO)Mn(NHC) bearing dialkyl-, arylalkyl- and diarylsubstituted N-heterocyclic carbene ligands (NHC = IMe, IMeMes, IMes) affords the corresponding stable Mn radical cations Cp(CO)Mn(NHC) isolated in 92-95% yield. Systematic X-ray diffraction studies of the series of Mn and Mn NHC complexes revealed the expected characteristic structural changes upon oxidation, namely the elongation of the Mn-CO and Mn-NHC bonds as well as the diminution of the OC-Mn-CO angle. ESR spectra of Cp(CO)Mn(IMes) in frozen solution (CHCl/toluene 1 : 1, 70 K) allowed the identification of two conformers for this complex and their structural assignment using DFT calculations. The stability of these NHC complexes in both metal oxidation states, moderate oxidation potentials and the ease of detection of Mn species by a variety of spectroscopic techniques (UV-Vis, IR, paramagnetic H NMR, and ESR) make these compounds promising objects for applications as redox-active organometallic fragments.
半三明治型 Mn 配合物 Cp(CO)Mn(NHC)（其中 NHC 为 IMe、IMeMes 和 IMes）的氧化作用，可生成相应的、稳定的 Mn 自由基阳离子 Cp(CO)Mn(NHC)，产率为 92-95%。对一系列 Mn 和 Mn-NHC 配合物的系统 X 射线衍射研究表明，氧化过程中存在预期的特征结构变化，即 Mn-CO 和 Mn-NHC 键的伸长以及 OC-Mn-CO 角的减小。在冷冻溶液（CHCl/甲苯 1:1，70 K）中，ESR 光谱可用于鉴定该配合物的两种构象，并使用 DFT 计算对其结构进行了归属。这些 NHC 配合物在两种金属氧化态下的稳定性、中等氧化电位以及通过各种光谱技术（UV-Vis、IR、顺磁 H NMR 和 ESR）易于检测 Mn 物种，使这些化合物成为作为氧化还原活性有机金属片段的应用的有前途的对象。
