ChemInform Abstract: TETRAKIS(ETHYLENE)IRONDILITHIUM AND BIS(μ4‐1,5‐CYCLOOCTADIENE)IRONDILITHIUM

Jonas, Klaus; Schieferstein, Ludwig; Krueger, C.; Tsay, Yi‐Hung

doi:10.1002/chin.197944295

Cited by 2 publications

(11 citation statements)

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“…36 Complex 30 can be obtained on large scale as an airsensitive crystalline material on treatment of ferrocene with lithium under an ethene atmosphere. 37 Because the central iron atom displays a formal oxidation state of -2 and is bound to four kinetically labile olefin ligands, it constitutes a highly nucleophilic and accessible reactive site.…”

Section: Preparative Aspectsmentioning

confidence: 99%

“…Specifically, it was shown that the ferrate complex [Fe(C 2 H 4 ) 4 ][Li(tmeda)] 2 ( 30 ) induces reactions of aromatic Grignard reagents with a variety of alkyl, allyl, and propargyl halides, even in the presence of esters, ketones, nitriles, isocyanates, or tert -amines (Table ) . Complex 30 can be obtained on large scale as an air-sensitive crystalline material on treatment of ferrocene with lithium under an ethene atmosphere . Because the central iron atom displays a formal oxidation state of −2 and is bound to four kinetically labile olefin ligands, it constitutes a highly nucleophilic and accessible reactive site.…”

Section: Preparative Aspectsmentioning

confidence: 99%

“…Furthermore, the reactivity of the in situ catalyst can be emulated with structurally well defined ferrate complexes such as 30 , 37 , or 38 (Figure ). , Their iron centers exhibit formal oxidation states of −2 or 0 and feature fairly covalent bonds to the escorting lithium atoms. Because the kinetically labile ethylene ligands ensure a rather “bare” character of the central metal, such complexes show all structural characteristics one might expect for [Fe(MgCl) 2 ] n .…”

Section: Mechanistic Aspectsmentioning

confidence: 99%

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The Promise and Challenge of Iron-Catalyzed Cross Coupling

2008

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Transition metal catalysts, particularly those derived from the group VIII-X metals, display remarkable efficiency for the formation of carbon-carbon and carbon-heteroatom bonds through the reactions of suitable nucleophiles with organic electrophilic partners. Within this subset of the periodic table, palladium and nickel complexes offer the broadest utility, while additionally providing the deepest mechanistic insight into thus-termed "cross-coupling reactions". The mammoth effort devoted to palladium and nickel catalysts over the past 30 years has somewhat obscured reports of alternative metal complexes in this arena. As cross-coupling reactions have evolved into a critical support for modern synthetic chemistry, the search for alternative catalysts has been taken up with renewed vigor.When the current generation of synthetic chemists reflects back to the origins of cross coupling for inspiration, the well-documented effect of iron salts on the reactivity of Grignard reagents with organic electrophiles surfaces as a fertile ground for alternative catalyst development. Iron possesses the practical benefits more befitting an alkali or alkaline earth metal, while displaying the unique reactivity of a d-block element. Therefore the search for broadly applicable iron catalysts for cross coupling is an increasingly important goal in modern synthetic organic chemistry.This Account describes the evolution of iron-catalyzed cross coupling from its inception in the work of Kochi to the present. Specific emphasis is placed on reactivity and synthetic applications, with selected examples from acyl-, alkenyl-, aryl-, and alkyl halide/pseudohalide cross coupling included. The typical reaction partners are Grignard reagents, though organomanganese, -copper, and -zinc derivatives have also been used in certain cases. Such iron-catalyzed processes occur very rapidly even at low temperature and therefore are distinguished by broad functional group compatibility. Furthermore, recent advances in carbon-heteroatom bond formation and studies relevant to the general reactivity of in situ generated and structurally defined "low-valent" iron catalysts are presented.The preparative aspects of iron-catalyzed cross coupling are encouraging, but the inclination to classify these processes within the characteristic reaction manifold is premature, as mechanistic studies have evolved at a comparatively slow pace. A typical protocol for cross coupling employs an Fe(+2) or Fe(+3) precatalyst, which is reduced in situ by the organometallic nucleophile. The nature of the resulting active component(s) is still best described, more than 30 years later, in Kochi's original terms as a "reduced form of soluble iron". Despite huge gaps in our current knowledge, three distinct mechanisms have been formulated, largely based on empirical evidence: a "canonical" cross-coupling process, a manifold wherein alkylation of an organoiron intermediate replaces transmetalation as a key step, and finally a proposal reliant on the formation of nucleophilic ate comp...

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Section: Preparative Aspectsmentioning

confidence: 99%

Section: Preparative Aspectsmentioning

confidence: 99%

Section: Mechanistic Aspectsmentioning

confidence: 99%

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The Promise and Challenge of Iron-Catalyzed Cross Coupling

2008

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“…592 The valency of complexes 964−966 was described using an adapted Feltham−Enemark notation, 489 given that assigning individual oxidation states for both metals can be complicated by the presence of an intermetal covalent bond. Therefore, 964, 965, and 966 were assigned electronic configurations of {FeSn} 8 , {FeSn} 9 It remained unclear, after analysis by 57 Fe Mossbauer spectroscopy, whether the electron configuration of 967 should be described as an {FeSn} 10 unit engaged in πbackbonding with a silyldiazenium(1+) ligand or as an {FeSn} 8 unit acting as π-donor to a diazenido(2−) ligand. Quantum chemical calculations (DFT) indicated a strong correlation between the charge on the Sn center (atom trans to the N 2 unit) and both the polarization of the N 2 unit and the charge on the distal N atom.…”

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confidence: 99%

“…% by the sequential reaction of 723 with HOTf and Cp* 2 Co in supercooled 2-MeTHF. Therefore, simultaneous use of the two reductants, KC8 and Cp* 2 Co, can drive the catalytic N 2 fixation in this system. However, the dianionic complex 723 is only accessible by treatment with the stronger reductant KC 8 , since Cp* 2 Co alone is only sufficiently strong to produce [(P 3 B…”

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confidence: 99%

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

Landaeta,

Horsley Downie,

Wolf

2024

Chem. Rev.

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This review surveys the synthesis and reactivity of low-oxidation state metalate anions of the d-block elements, with an emphasis on contributions reported between 2006 and 2022. Although the field has a long and rich history, the chemistry of transition metalate anions has been greatly enhanced in the last 15 years by the application of advanced concepts in complex synthesis and ligand design. In recent years, the potential of highly reactive metalate complexes in the fields of small molecule activation and homogeneous catalysis has become increasingly evident. Consequently, exciting applications in small molecule activation have been developed, including in catalytic transformations. This article intends to guide the reader through the fascinating world of low-valent transition metalates. The first part of the review describes the synthesis and reactivity of d-block metalates stabilized by an assortment of ligand frameworks, including carbonyls, isocyanides, alkenes and polyarenes, phosphines and phosphorus heterocycles, amides, and redox-active nitrogen-based ligands. Thereby, the reader will be familiarized with the impact of different ligand types on the physical and chemical properties of metalates. In addition, ion-pairing interactions and metal−metal bonding may have a dramatic influence on metalate structures and reactivities. The complex ramifications of these effects are examined in a separate section. The second part of the review is devoted to the reactivity of the metalates toward small inorganic molecules such as H 2 , N 2 , CO, CO 2 , P 4 and related species. It is shown that the use of highly electron-rich and reactive metalates in small molecule activation translates into impressive catalytic properties in the hydrogenation of organic molecules and the reduction of N 2 , CO, and CO 2 . The results discussed in this review illustrate that the potential of transition metalate anions is increasingly being tapped for challenging catalytic processes with relevance to organic synthesis and energy conversion. Therefore, it is hoped that this review will serve as a useful resource to inspire further developments in this dynamic research field.

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ChemInform Abstract: TETRAKIS(ETHYLENE)IRONDILITHIUM AND BIS(μ4‐1,5‐CYCLOOCTADIENE)IRONDILITHIUM

Abstract: Ferrocen (I) reagiert bei Raumtemp. und wenig erhöhtem Ethylendruck (5 at ) mit Li‐Sand zu dem Komplex (II).

Cited by 2 publications

References 2 publications

The Promise and Challenge of Iron-Catalyzed Cross Coupling

The Promise and Challenge of Iron-Catalyzed Cross Coupling

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

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