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Schlachta TP, Kühn FE. Cyclic iron tetra N-heterocyclic carbenes: synthesis, properties, reactivity, and catalysis. Chem Soc Rev 2023; 52:2238-2277. [PMID: 36852959 DOI: 10.1039/d2cs01064j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
Cyclic iron tetracarbenes are an emerging class of macrocyclic iron N-heterocyclic carbene (NHC) complexes. They can be considered as an organometallic compound class inspired by their heme analogs, however, their electronic properties differ, e.g. due to the very strong σ-donation of the four combined NHCs in equatorial coordination. The ligand framework of iron tetracarbenes can be readily modified, allowing fine-tuning of the structural and electronic properties of the complexes. The properties of iron tetracarbene complexes are discussed quantitatively and correlations are established. The electronic nature of the tetracarbene ligand allows the isolation of uncommon iron(III) and iron(IV) species and reveals a unique reactivity. Iron tetracarbenes are successfully applied in C-H activation, CO2 reduction, aziridination and epoxidation catalysis and mechanisms as well as decomposition pathways are described. This review will help researchers evaluate the structural and electronic properties of their complexes and target their catalyst properties through ligand design.
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Affiliation(s)
- Tim P Schlachta
- Technical University of Munich, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Molecular Catalysis, Lichtenbergstraße 4, 85748 Garching, Germany.
| | - Fritz E Kühn
- Technical University of Munich, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Molecular Catalysis, Lichtenbergstraße 4, 85748 Garching, Germany.
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2
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Organometallic Chemistry within the Structured Environment Provided by the Macrocyclic Cores of Carbaporphyrins and Related Systems. Molecules 2023; 28:molecules28031496. [PMID: 36771158 PMCID: PMC9920839 DOI: 10.3390/molecules28031496] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/27/2023] [Accepted: 01/30/2023] [Indexed: 02/08/2023] Open
Abstract
The unique environment within the core of carbaporphyrinoid systems provides a platform to explore unusual organometallic chemistry. The ability of these structures to form stable organometallic derivatives was first demonstrated for N-confused porphyrins but many other carbaporphyrin-type systems were subsequently shown to exhibit similar or complementary properties. Metalation commonly occurs with catalytically active transition metal cations and the resulting derivatives exhibit widely different physical, chemical and spectroscopic properties and range from strongly aromatic to nonaromatic and antiaromatic species. Metalation may trigger unusual, highly selective, oxidation reactions. Alkyl group migration has been observed within the cavity of metalated carbaporphyrins, and in some cases ring contraction of the carbocyclic subunit takes place. Over the past thirty years, studies in this area have led to multiple synthetic routes to carbaporphyrinoid ligands and remarkable organometallic chemistry has been reported. An overview of this important area is presented.
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Zámbó GG, Mayr J, Sauer MJ, Schlachta TP, Reich RM, Kühn FE. The first macrocyclic abnormally coordinating tetra-1,2,3-triazole-5-ylidene iron complex: a promising candidate for olefin epoxidation. Dalton Trans 2022; 51:13591-13595. [PMID: 36039702 DOI: 10.1039/d2dt02561b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The first macrocyclic and abnormally coordinating, mesoionic N-heterocyclic carbene iron complex has been synthesised and characterised via ESI-MS, EA, SC-XRD, CV, NMR and UV/Vis spectroscopy. 13C-NMR spectroscopy and CV measurements indicate a strong σ-donor ability of the carbene moieties, suggesting an efficient catalytic activity of the iron complex in oxidation reactions. Initial tests in the epoxidation of cis-cyclooctene as a model substrate confirm this assumption.
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Affiliation(s)
- Greta G Zámbó
- Molecular Catalysis, Department of Chemistry and Catalysis Research Centre, Technische Universität München, Lichtenbergstr. 4, 85784 Garching bei München, Germany.
| | - Johannes Mayr
- Molecular Catalysis, Department of Chemistry and Catalysis Research Centre, Technische Universität München, Lichtenbergstr. 4, 85784 Garching bei München, Germany.
| | - Michael J Sauer
- Molecular Catalysis, Department of Chemistry and Catalysis Research Centre, Technische Universität München, Lichtenbergstr. 4, 85784 Garching bei München, Germany.
| | - Tim P Schlachta
- Molecular Catalysis, Department of Chemistry and Catalysis Research Centre, Technische Universität München, Lichtenbergstr. 4, 85784 Garching bei München, Germany.
| | - Robert M Reich
- Molecular Catalysis, Department of Chemistry and Catalysis Research Centre, Technische Universität München, Lichtenbergstr. 4, 85784 Garching bei München, Germany.
| | - Fritz E Kühn
- Molecular Catalysis, Department of Chemistry and Catalysis Research Centre, Technische Universität München, Lichtenbergstr. 4, 85784 Garching bei München, Germany.
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Malan FP. Structural, Electrochemical and Catalytic Elucidation of Cyclooctadiene Ru(II)‐Nitrile Complexes of the Type [RuCl
2
(cod)(NCR)
2
]. ChemistrySelect 2022. [DOI: 10.1002/slct.202201432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Frederick P. Malan
- Department of Chemistry University of Pretoria Lynnwood road, Hatfield Pretoria 0002
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Zámbó GG, Schlagintweit JF, Reich RM, Kühn FE. Organometallic 3d transition metal NHC complexes in oxidation catalysis. Catal Sci Technol 2022. [DOI: 10.1039/d2cy00127f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The development of processes for the selective oxidation of hydrocarbons is a major focus in catalysis research. Making this process simultaneously environmentally friendly is still challenging. 3d transition metals are...
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Schlachta TP, Anneser MR, Schlagintweit JF, Jakob CHG, Hintermeier C, Böth AD, Haslinger S, Reich RM, Kühn FE. Mimicking reactive high-valent diiron- μ2-oxo intermediates of nonheme enzymes by an iron tetracarbene complex. Chem Commun (Camb) 2021; 57:6644-6647. [PMID: 34126626 DOI: 10.1039/d1cc02027g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The first diiron(iii,iv)-μ2-oxo tetracarbene complex is isolated and characterized by SC-XRD, UV/Vis, EPR, Evans' NMR and elemental analysis. CV indicates the presence of a transient high-valent diiron(iv)-μ2-oxo species. Its formation and decay is investigated via UV/Vis kinetics and NMR.
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Affiliation(s)
- Tim P Schlachta
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Markus R Anneser
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Jonas F Schlagintweit
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Christian H G Jakob
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Carolin Hintermeier
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Alexander D Böth
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Stefan Haslinger
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Robert M Reich
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
| | - Fritz E Kühn
- Molecular Catalysis, Catalysis Research Center and Department of Chemistry, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany.
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