Banerjee Saikat, Rasheed Waqas, Fan Ruixi, Draksharapu Apparao, Oloo Williamson N, Guo Yisong, Que Lawrence
Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA.
Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Chemistry. 2019 Jul 22;25(41):9608-9613. doi: 10.1002/chem.201902048. Epub 2019 Jun 27.
The [Fe (O)(Me NTB)] (Me NTB=tris[(1-methyl-benzimidazol-2-yl)methyl]amine) complex 1 has been shown by Mössbauer spectroscopy to have an S=1 ground state at 4 K, but is proposed to become an S=2 trigonal-bipyramidal species at higher temperatures based on a DFT model to rationalize its very high C-H bond-cleavage reactivity. In this work, H NMR spectroscopy was used to determine that 1 does not have C -symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme Fe =O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 Fe =O complexes can be as reactive as their S=2 counterparts. This result emphasizes the need to identify factors besides the ground spin state of the Fe =O center to rationalize nonheme oxoiron(IV) reactivity.
[Fe (O)(Me NTB)]（Me NTB = 三[(1 - 甲基 - 苯并咪唑 - 2 - 基)甲基]胺）配合物1经穆斯堡尔光谱表明在4 K时具有S = 1基态，但基于密度泛函理论（DFT）模型推测在较高温度下会变成S = 2的三角双锥物种，以解释其非常高的C - H键裂解反应活性。在这项工作中，利用核磁共振氢谱确定1在溶液中不具有C₂对称性且不是S = 2物种。我们的结果表明，1在非血红素Fe =O配合物中是独特的，在193 K时保持其S = 1自旋态和高反应活性，这证明S = 1的Fe =O配合物可以与其S = 2的对应物一样具有反应活性。这一结果强调了除了Fe =O中心的基态自旋态之外，还需要确定其他因素来解释非血红素氧合铁（IV）的反应活性。
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