Tandem CH Activation/Arylation Catalyzed by Low‐Valent Iron Complexes with Bisiminopyridine Ligands

Salanouve, Elise; Bouzemame, Ghania; Blanchard, Sébastien; Derat, Étienne; Murr, Marine Desage‐El; Fensterbank, Louis

doi:10.1002/chem.201304459

Cited by 28 publications

(11 citation statements)

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“…An example includes C-H activation/arylation, by the group of Fensterbank, applying iron complexes bearing a bisiminopyridine ligand [57]. Several other examples have been described using this concept [23], but in most cases these were not investigated with EPR spectroscopy.…”

Section: Application Of Epr For Redox Active Ligandsmentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

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In the context of homogeneous catalysis, openshell systems are often quite challenging to characterize. Nuclear magnetic resonance (NMR) spectroscopy is the most frequently applied tool to characterize organometallic compounds, but NMR spectra are usually broad, difficult to interpret and often futile for the study of paramagnetic compounds. As such, electron paramagnetic resonance (EPR) has proven itself as a useful spectroscopic technique to characterize paramagnetic complexes and reactive intermediates. EPR spectroscopy is a particularly useful tool to investigate their electronic structures, which is fundamental to understand their reactivity. This paper describes some selected examples of studies where EPR spectroscopy has been useful for the characterization of open-shell organometallic complexes. The paper concentrates in particular on systems where EPR spectroscopy has proven useful to understand catalytic reaction mechanisms involving paramagnetic organometallic catalysts. The expediency of EPR spectroscopy in the study of organometallic chemistry and homogenous catalysis is contextualized in the introductory Sect. 1. Section 2 of the review focusses on examples of C-C and C-N bond formation reactions, with an emphasis on catalytic reactions where ligand/substrate non-innocence plays an important role. Both carbon and nitrogen centered radicals have been shown to play an important role in these reactions. A few selected examples of catalytic alcohol oxidation proceeding via related N-centered ligand radicals are included in this section as well. Section 3 covers examples of the use of EPR spectroscopy to study important commercial ethylene oligomerization and polymerization processes. In Sect. 4 the use of EPR spectroscopy to understand the mechanisms of Atom Transfer Radical Polymerization is discussed. While this review focusses predominantly on the application of EPR spectroscopy in mechanistic studies of C-C and C-N bond formation reactions mediated by organometallic catalysts, a few selected examples describing the application of EPR spectroscopy in other catalytic reactions such as water splitting, photo-catalysis, photo-redox-catalysis and related reactions in which metal initiated (free) radical formation plays a role are included as well. EPR spectroscopic investigation in this area of research are dominated by EPR spectroscopic studies in isotropic solution, including spin trapping experiments. These reactions are highlighted in Sect. 5. EPR spectroscopic studies have proven useful to discern the correct oxidation states of the active catalysts and also to determine the effective concentrations of the active species. EPR is definitely a spectroscopic technique that is indispensable in understanding the reactivity of paramagnetic complexes and in conjunction with other advanced techniques such as X-ray absorption spectroscopy and pulsed laser polymerization it will continue to be a very practical tool.

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Section: Application Of Epr For Redox Active Ligandsmentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

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“…Desage‐El Murr, Fensterbank, and co‐workers described an efficient way to form C−C bonds through a C−H activation/C−C coupling tandem reaction, catalyzed by iron complex 18 with a bisiminopyridine ligand (Scheme ) . Csp 2 −Csp 2 bond formation was achieved between benzene and aryl bromides, in the presence of KHMDS.…”

Section: Csp2−csp2 Couplingmentioning

confidence: 94%

Metal‐Promoted Coupling Reactions Implying Ligand‐Based Redox Changes

2016

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Coupling reactions are staples in the synthetic world and their efficiency relies on well‐defined, mostly bis‐electronic, elementary catalytic steps. An area of great interest currently lies in the taming of radical species and their efficient introduction in catalytic cycles. Among these species bearing radical character, redox‐active ligands hold much potential and can be used to sustain synthetically relevant couplings by introducing ligand‐based electronic contribution. This minireview aims at presenting the current state of this promising field.

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“…They have been successfully used in various synthetic endeavours such as polymerization, cycloisomerization, cycloaddition, hydrosilylation and hydroboration . We were interested to evaluate the potential utility of an iron complex bearing a bisiminopyridine ligand (Scheme ) in a C−H activation/arylation reaction . The selected benchmark reaction involves para‐methoxy‐aryl bromide and benzene, acting both as solvent and unactivated C−H partner (Scheme ).…”

Section: C−h Activation With Iron Complexes Bearing Redox‐active (Nonmentioning

confidence: 99%

Iron and Single Electron Transfer: All is in the Ligand

Murr

Fensterbank

Ollivier

2017

Israel Journal of Chemistry

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This account describes some advances we have made in the field of iron catalysis. Two types of reactivity have been uncovered. Based on the use of an iron(II) precatalyst in the presence of NaBH 4 , the first one consists in a SET which can be useful for the reductive dehalogenation of iodide and bromide derivatives. Switching to the noninnocent bis-iminopyridine ligands promotes a previously undescribed Csp 2 ÀH activation reaction leading to biaryl derivatives. First clues into the intricate nature of the mechanism were obtained and suggested that the redoxactive bis-iminopyridine ligand acts as an electron reservoir. The resulting buildup of electron density triggers the CÀH bond breaking. All these findings are discussed in light of the existing literature and perspectives are given.

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Tandem CH Activation/Arylation Catalyzed by Low‐Valent Iron Complexes with Bisiminopyridine Ligands

Cited by 28 publications

References 82 publications

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

Metal‐Promoted Coupling Reactions Implying Ligand‐Based Redox Changes

Iron and Single Electron Transfer: All is in the Ligand

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