σ-Bond Metathesis: A 30-Year Retrospective

Waterman, Rory

doi:10.1021/om400760k

Cited by 264 publications

(231 citation statements)

References 146 publications

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“…The latter implies a 2 + 2 addition, which is a symmetry forbidden reaction, 11 because of the inter-crossing of the σ and σ* levels along the pathway and the high energy costs to invert the population. On the other hand, the concept of σ bond metathesis 49 has been raised for some organometallic compounds of d 0 elements, with interchanging some coordination bonds associated with the alternative formation/ cleavage of metal-element bonds, while the inverse behaviour applies to the associated element-element bonds. Possibly, some relation with eqn (3) may be established because of the electronic equivalence between the P atoms and d 0 metals, but the point has not been further pursued.…”

Section: Cracking In Step V Of the Open Chain 10mentioning

confidence: 99%

The atomic level mechanism of white phosphorous demolition by di-iodine

et al. 2018

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A detailed mechanism of the I 2 -induced transformation of white phosphorus into PI 3 emerges from a DFT analysis. This multi-step process implies that at any stage one P-P and two I-I bonds cleavages, associated with the formation of two P-I bonds plus an in situ generated brand new I 2 molecule.Significant electron transfer between the atoms is observed at any step, but the reactions are better defined as concerted rather than redox. Along the steepest descent to the product, no significant barrier is encountered except for the very first P 4 activation, which costs +14.6 kcal mol −1 . At the atomic level, one first I 2 molecule, a typical mild oxidant, is first involved in a linear halogen bonding interaction (XB) with one P donor, while its terminal I atom is engaged in an additional XB adduct with a second I 2 .Significant electron transfer through the combined diatomics allows the external I atom of the dangling I 3 grouping to convey electrons into the σ* level of one P-P bond with its consequent cleavage. This implies at some point the appearance of a six-membered ring, which alternatively switches its bonding and no-bonding interactions. The final transformation of the P 2 I 4 diphosphine into two PI 3 phosphines is enlightening also for the specific role of the I substituents. In fact, it is proved that an organo-diphosphine analogue hardly undergoes the separation of two phosphines, as reported in the literature. This is attributable to the particularly high donor power of the carbo-substituted P atoms, which prevents the concertedness of the reaction but favors charge separation in an unreactive ion pair.

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Section: Cracking In Step V Of the Open Chain 10mentioning

confidence: 99%

The atomic level mechanism of white phosphorous demolition by di-iodine

et al. 2018

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“…Anal. Calcd for C 17 Kinetics of the Reaction between 1 and Furan. In a Youngtype 5 mm NMR tube in the glovebox, 1 (40 mg, 0.13 mmol) was dissolved in 0.5 mL of cyclohexane-d 12 containing adamantane (16 mg, 0.12 mmol) as an internal standard.…”

Section: ■ Introductionmentioning

confidence: 99%

β-H Abstraction/1,3-CH Bond Addition as a Mechanism for the Activation of CH Bonds at Early Transition Metal Centers

Romero

Dinoi

et al. 2014

Organometallics

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This article describes the generalization of an overlooked mechanism for CH bond activation at early transition metal centers, namely 1,3-CH bond addition at an η 2 -alkene intermediate. The X-ray-characterized [Cp 2 Zr(c-C 3 H 5 ) 2 ] eliminates cyclopropane by a β-H abstraction reaction to generate the transientA rapidly cleaves the CH bond of furan and thiophene to give the furyl and thienyl complexes [Cp 2 Zr(c-C 3 H 5 )(2-C 4 H 3 X)] (X = O, S), respectively. Benzene is less cleanly activated. Mechanistic investigations including kinetic studies, isotope labeling, and DFT computation of the reaction profile all confirm that rapid stereospecific 1,3-CH bond addition across the Zr(η 2 -alkene) bond of A follows the rate-determining β-H abstraction reaction. DFT computations also suggest that an α-CC agostic rotamer of [Cp 2 Zr(c-C 3 H 5 ) 2 ] assists the β-H abstraction of cyclopropane. The nature of the α-CC agostic interaction is discussed in the light of an NBO analysis.

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“…[54] Mit späten Übergangsmetallen und Hauptgruppenelementen in polaren Medien wird eine elektrophile Aktivierung beobachtet. [61,63,64] Das entsprechende Zwischenprodukt wird mithilfe von nukleophilen Reagentien in stabile Verbindungen umgewandelt.…”

Section: C-h-bindungsaktivierung In Der Homogenen Katalyseunclassified

Die direkte katalytische Oxidation von Methan zu Methanol – eine kritische Beurteilung

2017

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Es gibt vielzählige direkte, selektive Ansätze, um Methan partiell zu oxidieren, jedoch ist noch keiner von ihnen zur industriellen Reife gelangt. In diesem Zusammenhang ist die Oxidation von Methan zu Methanol eine schwierige, aber lohnende Aufgabe, da sie eine wirkungsvolle Methode ist, um das Abfackeln von Erdgas, das als Nebenprodukt in der Erdölindustrie anfällt, zu unterbinden, und zugleich die Möglichkeit bietet, Methan zu valorisieren. Dieser Aufsatz berücksichtigt die Synthese von Methanol und seinen Derivaten ausgehend von Methan durch homogen‐ und heterogenkatalytische Methoden. Er zeigt die starken Einschränkungen der direkten katalytischen Synthese von Methanol aus Methan auf und unterstreicht dabei die enorme Überlegenheit von Systemen, die Methanolderivate produzieren oder sich durch Besonderheiten wie die Verwendung von Mehrkomponenten‐Katalysatoren zur Methanolstabilisierung auszeichnen. Für die zukünftige Forschung erweist sich die Stabilisierung von Methanol in der homogenen und heterogenen Katalyse als unentbehrlich.

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σ-Bond Metathesis: A 30-Year Retrospective

Cited by 264 publications

References 146 publications

The atomic level mechanism of white phosphorous demolition by di-iodine

The atomic level mechanism of white phosphorous demolition by di-iodine

β-H Abstraction/1,3-CH Bond Addition as a Mechanism for the Activation of CH Bonds at Early Transition Metal Centers

Die direkte katalytische Oxidation von Methan zu Methanol – eine kritische Beurteilung

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