Iron(0) Particles: Catalytic Hydrogenations and Spectroscopic Studies

Welther, Alice; Bauer, Matthias; Mayer, Michael; Wangelin, Axel Jacobi von

doi:10.1002/cctc.201100400

Cited by 58 publications

(34 citation statements)

References 53 publications

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“…80 Similarly, solutions of Fe(III) salts including FeCl 3 and Fe(acac) 3 , in THF solution at room temperature are reduced to Fe(0) nanoparticles upon treatment with various Grignard reagents (3.0 equiv), including EtMgBr and PhMgBr. 81 …”

Section: Discussionmentioning

confidence: 99%

Iron-Catalyzed Cross-Coupling of Unactivated Secondary Alkyl Thio Ethers and Sulfones with Aryl Grignard Reagents

2013

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The first systematic investigation of unactivated aliphatic sulfur compounds as electrophiles in transition metal-catalyzed cross-coupling are described. Initial studies focused on discerning the structural and electronic features of the organosulfur substrate which enable the challenging oxidative addition to the C(sp3)–S bond. Through extensive optimization efforts, an Fe(acac)3-catalyzed cross-coupling of unactivated alkyl aryl thio ethers with aryl Grignard reagents was realized, in which a nitrogen “directing group” on the S-aryl moiety of the thio ether served a critical role in facilitating the oxidative addition step. In addition, alkyl phenyl sulfones were found to be effective electrophiles in the Fe(acac)3-catalyzed cross-coupling with aryl Grignard reagents. For the latter class of electrophile, a thorough assessment of the various reaction parameters revealed a dramatic enhancement in reaction efficiency with an excess of TMEDA (8.0 equiv). The optimized reaction protocol was used to evaluate the scope of the method with respect to both the organomagnesium nucleophile and sulfone electrophile.

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Section: Discussionmentioning

confidence: 99%

Iron-Catalyzed Cross-Coupling of Unactivated Secondary Alkyl Thio Ethers and Sulfones with Aryl Grignard Reagents

2013

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“…[9] We envisioned capitalizing on the presence of the labile arene ligands in potassium bis(anthracene)cobaltate 1 and ferrate 2 which render these complexes synthetic precursors quasi-"naked" anionic metal species (Scheme 2). [16] Cobaltate 1 exhibited far higher activity than the related ferrate 2. [12] We tested this catalyst concept for the first time in hydrogenations.…”

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Heteroatom‐Free Arene‐Cobalt and Arene‐Iron Catalysts for Hydrogenations

et al. 2014

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75 years after the discovery of hydroformylation, cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. We have evaluated arene metalates in which the low-valent metal species is--conceptually different from heteroatom-based ligands--stabilized by π coordination to hydrocarbons. Potassium bis(anthracene)cobaltate 1 and -ferrate 2 can be viewed as synthetic precursors of quasi-"naked" anionic metal species; their aggregation is effectively impeded by (labile) coordination to the various π acceptors present in the hydrogenation reactions of unsaturated molecules (alkenes, arenes, carbonyl compounds). Kinetic studies, NMR spectroscopy, and poisoning studies of alkene hydrogenations support the formation of a homogeneous catalyst derived from 1 which is stabilized by the coordination of alkenes. This catalyst concept complements the use of complexes with heteroatom donor ligands for reductive processes.

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“…This is because the larger multiplicity of high spin d 6 Fe II -and d 5 Fe III -XAS, 42 compared with other 3d transition metals, hampers the interpretation and assignment of the spectra, along with peak broadening arising from the fluxional behavior of molecules in the solution. Recently, pioneering research on homogeneous iron catalysis has been conducted by Bauer and co-workers, 43,44 including Fe-catalyzed KTC-type cross-coupling reactions. 45 Formation of monovalent iron species by the reaction of [Fe(acac) 3 ] with over three molar equivalents of PhMgCl in THF/NMP was confirmed.…”

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confidence: 99%

Investigation of Organoiron Catalysis in Kumada–Tamao–Corriu-Type Cross-Coupling Reaction Assisted by Solution-Phase X-ray Absorption Spectroscopy

Takaya

Nakajima

Nakagawa

et al. 2015

Bulletin of the Chemical Society of Japan

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Solution-phase synchrotron X-ray absorption spectroscopy (XAS) is a powerful tool for structural and mechanistic investigations of paramagnetic organoiron intermediates in solution-phase reactions. For paramagnetic organotransition metal intermediates, difficulties are often encountered with conventional NMR-and EPR-based analyses. By using solution-phase XAS, we succeeded in identifying the organoiron species formed in the reaction of iron bisphosphine with mesitylmagnesium bromide, MesMgBr, and 1-bromodecane in a [FeX 2 (SciOPP)]-catalyzed KumadaTamaoCorriu (KTC)-type cross-coupling reaction. X-ray absorption near-edge structure (XANES) spectra showed that the resulting aryliron species possessed a divalent oxidation state. Extended X-ray absorption fine structure (EXAFS) demonstrated that the solution-phase molecular geometries of these species are in satisfactory agreement with the crystallographic geometries of [Fe The renaissance of iron-catalyzed cross-coupling reactions in the last decade 15 has been triggered by their unprecedented nonclassical reactivities and selectivities in comparison with conventional Pd and Ni catalysts.6 Recent worldwide interest in practical research applications, based on the utilization of abundant earth elements and the practical advantages of iron catalysts, including low cost, low toxicity, high availability, and easy separation of metal residues, have also demanded a much greater focus on iron-catalyzed cross-coupling reactions.

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Iron(0) Particles: Catalytic Hydrogenations and Spectroscopic Studies

Cited by 58 publications

References 53 publications

Iron-Catalyzed Cross-Coupling of Unactivated Secondary Alkyl Thio Ethers and Sulfones with Aryl Grignard Reagents

Iron-Catalyzed Cross-Coupling of Unactivated Secondary Alkyl Thio Ethers and Sulfones with Aryl Grignard Reagents

Heteroatom‐Free Arene‐Cobalt and Arene‐Iron Catalysts for Hydrogenations

Investigation of Organoiron Catalysis in Kumada–Tamao–Corriu-Type Cross-Coupling Reaction Assisted by Solution-Phase X-ray Absorption Spectroscopy

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