TMEDA in Iron‐Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic “ate” Complex Formation

Bedford, Robin B.; Brenner, Peter; Carter, Emma; Cogswell, Paul M.; Haddow, Mairi F.; Harvey, Jeremy N.; Murphy, D. M.; Nunn, Joshua; Woodall, Christopher H.

doi:10.1002/anie.201308395

Cited by 143 publications

(221 citation statements)

References 31 publications

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“…A previous report showed similar effects of co-solvent on iron speciation in which ligation of tetramethylethylenediamine (TMEDA) to magnesium cations in homoleptic triaryl-ferrate complexes was observed. [9] …”

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confidence: 99%

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The N‐Methylpyrrolidone (NMP) Effect in Iron‐Catalyzed Cross‐Coupling with Simple Ferric Salts and MeMgBr

et al. 2018

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The use of N-methylpyrrolidone (NMP) as a co-solvent in ferric salt catalyzed cross-coupling reactions is crucial for achieving the highly selective, preparative scale formation of cross-coupled product in reactions utilizing alkyl Grignard reagents. Despite the critical importance of NMP, the molecular level effect of NMP on in situ formed and reactive iron species that enables effective catalysis remains undefined. Herein, we report the isolation and characterization of a novel trimethyliron(II) ferrate species, [Mg(NMP) ][FeMe ] (1), which forms as the major iron species in situ in reactions of Fe(acac) and MeMgBr under catalytically relevant conditions where NMP is employed as a co-solvent. Importantly, combined GC analysis and Fe Mössbauer spectroscopic studies identified 1 as a highly reactive iron species for the selective formation generating cross-coupled product. These studies demonstrate that NMP does not directly interact with iron as a ligand in catalysis but, alternatively, interacts with the magnesium cations to preferentially stabilize the formation of 1 over [Fe Me ] cluster generation, which occurs in the absence of NMP.

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confidence: 99%

“…Both Bedford and Fürstner have independently reported the isolation of triaryl-ferrate complexes which are reactive with electrophile, but unlike 1 lack high selectivity in producing cross-coupled product. [9,12] …”

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The N‐Methylpyrrolidone (NMP) Effect in Iron‐Catalyzed Cross‐Coupling with Simple Ferric Salts and MeMgBr

et al. 2018

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“…25,[27][28][29][30] In the current case, the coupling of 1-bromo-5-hexene (17) with PhMgCl in the presence of 1 was employed for this purpose (Scheme 4). Activation of 17 first gives the alkyl radical (18) [18]. However, r 1 depends upon the reaction pathway.…”

mentioning

confidence: 99%

“…On the other hand, in the bimetallic oxidative addition and escape-rebound pathways, the combination of an alkyl radical with an iron ion is an intermolecular reaction and is 1 st order on the catalyst. Therefore, r 1 = k 1 [cat] [18], and the ratio of 19/20 is 1 st order on catalyst loading. Figure 4 shows that the ratio of 19/20 is linearly dependent on the loading of catalyst (1) in the coupling of 17…”

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Iron Pincer Complexes as Catalysts and Intermediates in Alkyl–Aryl Kumada Coupling Reactions

et al. 2014

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Abstract. Iron-catalyzed alkyl-aryl Kumada coupling has developed into an efficient synthetic method, yet its mechanism remains vague. Here, we apply a bisoxazolinylphenylamido pincer ligand (Bopa) to stabilize the catalytically active Fe center, resulting in isolation and characterization of well-defined iron complexes whose catalytic roles are probed and confirmed. Reactivity studies of the iron complexes identifies an Fe(II) "ate" complex, [Fe(Bopa-Ph)(Ph) 2 ] -, as the active species for the oxidative addition of alkyl halide. Experiments using radicalprobe substrates and DFT computations reveal a bimetallic and radical mechanism for the oxidative addition. The kinetics of the coupling of an alkyl iodide with PhMgCl indicates that formation of the "ate" complex, rather than oxidative addition, is the turnover determining step. This work provides insights in iron-catalyzed cross coupling reactions of alkyl halides.3

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“…Confirmation of this assignment was provided by an identical EPR spectrum recorded upon reaction of FeX 2 or FeX 3 with ArMgX (X = Cl, Br), in which no phosphine ligand was present (Fig. 2e) [43].…”

Section: Iron (I) Catalyzed Cross-couplingmentioning

confidence: 92%

The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

Carter

Murphy

2015

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TMEDA in Iron‐Catalyzed Kumada Coupling: Amine Adduct versus Homoleptic “ate” Complex Formation

Cited by 143 publications

References 31 publications

The N‐Methylpyrrolidone (NMP) Effect in Iron‐Catalyzed Cross‐Coupling with Simple Ferric Salts and MeMgBr

The N‐Methylpyrrolidone (NMP) Effect in Iron‐Catalyzed Cross‐Coupling with Simple Ferric Salts and MeMgBr

Iron Pincer Complexes as Catalysts and Intermediates in Alkyl–Aryl Kumada Coupling Reactions

The Role of Low Valent Transition Metal Complexes in Homogeneous Catalysis: An EPR Investigation

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