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Tretiakov S, Lutz M, Titus CJ, de Groot F, Nehrkorn J, Lohmiller T, Holldack K, Schnegg A, Tarrago MFX, Zhang P, Ye S, Aleshin D, Pavlov A, Novikov V, Moret ME. Homoleptic Fe(III) and Fe(IV) Complexes of a Dianionic C 3-Symmetric Scorpionate. Inorg Chem 2023. [PMID: 37369076 DOI: 10.1021/acs.inorgchem.3c00871] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/29/2023]
Abstract
High-valent iron species have been implicated as key intermediates in catalytic oxidation reactions, both in biological and synthetic systems. Many heteroleptic Fe(IV) complexes have now been prepared and characterized, especially using strongly π-donating oxo, imido, or nitrido ligands. On the other hand, homoleptic examples are scarce. Herein, we investigate the redox chemistry of iron complexes of the dianonic tris-skatylmethylphosphonium (TSMP2-) scorpionate ligand. One-electron oxidation of the tetrahedral, bis-ligated [(TSMP)2FeII]2- leads to the octahedral [(TSMP)2FeIII]-. The latter undergoes thermal spin-cross-over both in the solid state and solution, which we characterize using superconducting quantum inference device (SQUID), Evans method, and paramagnetic nuclear magnetic resonance spectroscopy. Furthermore, [(TSMP)2FeIII]- can be reversibly oxidized to the stable high-valent [(TSMP)2FeIV]0 complex. We use a variety of electrochemical, spectroscopic, and computational techniques as well as SQUID magnetometry to establish a triplet (S = 1) ground state with a metal-centered oxidation and little spin delocalization on the ligand. The complex also has a fairly isotropic g-tensor (giso = 1.97) combined with a positive zero-field splitting (ZFS) parameter D (+19.1 cm-1) and very low rhombicity, in agreement with quantum chemical calculations. This thorough spectroscopic characterization contributes to a general understanding of octahedral Fe(IV) complexes.
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Affiliation(s)
- Serhii Tretiakov
- Organic Chemistry & Catalysis, Institute for Sustainable and Circular Chemistry, Utrecht University, 3584 CG Utrecht, The Netherlands
| | - Martin Lutz
- Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Faculty of Science, Utrecht University, 3584 CG Utrecht, The Netherlands
| | - Charles James Titus
- Department of Physics, Stanford University, Stanford, California 94305, United States
| | - Frank de Groot
- Materials Chemistry & Catalysis, Debye Institute for Materials Science, Utrecht University, 3584 CG Utrecht, The Netherlands
| | - Joscha Nehrkorn
- Max-Planck-Institute for Chemical Energy Conversion, EPR Research Group, 45470 Mülheim/Ruhr, Germany
| | - Thomas Lohmiller
- Department Spins in Energy Conversion and Quantum Information Science, Helmholtz Zentrum Berlin für Materialien und Energie GmbH, EPR4 Energy Joint Lab, 12489 Berlin, Germany
| | - Karsten Holldack
- Department of Optics and Beamlines, Helmholtz Zentrum Berlin für Materialien und Energie GmbH, 12489 Berlin, Germany
| | - Alexander Schnegg
- Max-Planck-Institute for Chemical Energy Conversion, EPR Research Group, 45470 Mülheim/Ruhr, Germany
| | | | - Peng Zhang
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China
- University of Chinese Academy of Sciences, Beijing 10049, China
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China
| | - Dmitry Aleshin
- A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Street 28, Moscow 119991, Russia
| | - Alexander Pavlov
- A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Street 28, Moscow 119991, Russia
- Moscow Institute of Physics and Technology, Institutskiy per., 9, Dolgoprudny, Moscow 119991, Russia
| | - Valentin Novikov
- Moscow Institute of Physics and Technology, Institutskiy per., 9, Dolgoprudny, Moscow 119991, Russia
| | - Marc-Etienne Moret
- Organic Chemistry & Catalysis, Institute for Sustainable and Circular Chemistry, Utrecht University, 3584 CG Utrecht, The Netherlands
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Tretiakov S, Witteman L, Lutz M, Moret M. Strain‐Modulated Reactivity: An Acidic Silane. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202015960] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Serhii Tretiakov
- Utrecht University Organic Chemistry & Catalysis Institution Debye Institute for Nanomaterials Science Faculty of Science 3584 CG Utrecht The Netherlands
| | - Léon Witteman
- Utrecht University Organic Chemistry & Catalysis Institution Debye Institute for Nanomaterials Science Faculty of Science 3584 CG Utrecht The Netherlands
| | - Martin Lutz
- Utrecht University Structural Biochemistry Bijvoet Centre for Biomolecular Research Faculty of Science 3584 CH Utrecht The Netherlands
| | - Marc‐Etienne Moret
- Utrecht University Organic Chemistry & Catalysis Institution Debye Institute for Nanomaterials Science Faculty of Science 3584 CG Utrecht The Netherlands
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Tretiakov S, Witteman L, Lutz M, Moret ME. Strain-Modulated Reactivity: An Acidic Silane. Angew Chem Int Ed Engl 2021; 60:9618-9626. [PMID: 33476423 PMCID: PMC8252520 DOI: 10.1002/anie.202015960] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/12/2021] [Indexed: 11/17/2022]
Abstract
Compounds of main‐group elements such as silicon are attractive candidates for green and inexpensive catalysts. For them to compete with state‐of‐the‐art transition‐metal complexes, new reactivity modes must be unlocked and controlled, which can be achieved through strain. Using a tris(2‐skatyl)methylphosphonium ([TSMPH3]+) scaffold, we prepared the strained cationic silane [TSMPSiH]+. In stark contrast with the generally hydridic Si−H bond character, it is acidic with an experimental pKaDMSO within 4.7–8.1, lower than in phenol, benzoic acid, and the few hydrosilanes with reported pKa values. We show that ring strain significantly contributes to this unusual acidity along with inductive and electrostatic effects. The conjugate base, TSMPSi, activates a THF molecule in the presence of CH‐acids to generate a highly fluxional alkoxysilane via trace amounts of [TSMPSiH]+ functioning as a strain‐release Lewis acid. This reaction involves a formal oxidation‐state change from SiII to SiIV, presenting intriguing similarities with transition‐metal‐mediated processes.
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Affiliation(s)
- Serhii Tretiakov
- Utrecht University, Organic Chemistry & Catalysis, Institution Debye Institute for Nanomaterials Science, Faculty of Science, 3584 CG, Utrecht, The Netherlands
| | - Léon Witteman
- Utrecht University, Organic Chemistry & Catalysis, Institution Debye Institute for Nanomaterials Science, Faculty of Science, 3584 CG, Utrecht, The Netherlands
| | - Martin Lutz
- Utrecht University, Structural Biochemistry, Bijvoet Centre for Biomolecular Research, Faculty of Science, 3584 CH, Utrecht, The Netherlands
| | - Marc-Etienne Moret
- Utrecht University, Organic Chemistry & Catalysis, Institution Debye Institute for Nanomaterials Science, Faculty of Science, 3584 CG, Utrecht, The Netherlands
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