NMR Reveals That a Highly Reactive Nonheme FeIV=O Complex Retains Its Six-Coordinate Geometry and S=1 State in Solution |
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Authors: | Saikat Banerjee Waqas Rasheed Ruixi Fan Dr. Apparao Draksharapu Dr. Williamson N. Oloo Prof. Dr. Yisong Guo Prof. Dr. Lawrence Que Jr. |
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Affiliation: | 1. Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455 USA;2. Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213 USA |
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Abstract: | The [FeIV(O)(Me3NTB)]2+ (Me3NTB=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, 1H NMR spectroscopy was used to determine that 1 does not have C3-symmetry in solution and is not an S=2 species. Our results show that 1 is unique among nonheme FeIV=O complexes in retaining its S=1 spin state and high reactivity at 193 K, providing evidence that S=1 FeIV=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 FeIV=O center to rationalize nonheme oxoiron(IV) reactivity. |
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Keywords: | DFT calculations NMR spectroscopy nonheme iron oxoiron(IV) complexes two-state reactivity |
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