The β‐Agostic Structure in (C5Me5)2Sc(CH2CH3): Solid‐State NMR Studies of (C5Me5)2Sc−R (R=Me, Ph, Et)

Culver, Damien B.; Huynh, Winn; Tafazolian, Hosein; Ong, Ta‐Chung; Conley, Matthew P.

doi:10.1002/anie.201805738

Cited by 27 publications

(10 citation statements)

References 34 publications

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“…17 O, 27 Al, 45 Sc). [36][37][38][39] 3. The Spectator Oxo Ligand During Olefin Epoxidation MTO is a prototypical epoxidation catalyst, able to efficiently epoxidise olefins in the presence of hydrogen peroxide (H 2 O 2 ).…”

Section: Methodsmentioning

confidence: 99%

Probing the Electronic Structure of Spectator Oxo Ligands by 17O NMR Spectroscopy

Gordon

Copéret

2020

Chimia

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Spectator oxo ligands are ubiquitous in catalysis, in particular in olefin epoxidation and olefin metathesis. Here we use computationally derived 17O NMR parameters to probe the electronic structure of spectator oxo ligands in these two reactions. We show that 17O NMR parameters allow to distinguish between doubly-bonded and triply-bonded oxo ligands, giving detailed insights into the frontier molecular orbitals involved in the metaloxo bonds along the reaction pathway. On the one hand, our study shows that in olefin epoxidation catalysed by methyltrioxorhenium (MTO), the oxo ligand significantly changes its bonding mode upon formation of the oxygen-transferring Re-oxo-bisperoxo-species, changing its nature from a doubly bonded to a triply bonded oxo ligand. On the other hand, only minor changes in the binding mode are found along the olefin metathesis reaction pathway with Mo- and W-based oxo-alkylidene species, in which the oxo ligand behaves as a triply bonded ligand throughout the reaction. This finding contrasts earlier studies that proposed that the change of binding mode of the oxo ligand was key to metallacyclobutane formation.

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Section: Methodsmentioning

confidence: 99%

Probing the Electronic Structure of Spectator Oxo Ligands by 17O NMR Spectroscopy

Gordon

Copéret

2020

Chimia

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“…The most studied members of the family are metallocenes of the transition metals, the reactivity and properties of which are remarkably diverse, leading to widespread applications in established areas such as olefin polymerization catalysis [1] and polymer chemistry, [2,3] whilst also accounting for new developments in small-molecule activation [4,5] and redox-active materials. [6,7] Metallocenes are also prominent in f-element chemistry owing to their distinct catalytic and stoichiometric reactivity, [8,9] and for their ability to provide platforms for the study of fundamental aspects of chemical bonding in lanthanide and actinide compounds. [10] Recently, metallocenes of certain anisotropic lanthanides have risen to prominence as high-performance single-molecule magnets.…”

Section: Isolation Of a Perfectly Linear Uranium(ii) Metallocenementioning

confidence: 99%

Isolation of a Perfectly Linear Uranium(II) Metallocene

et al. 2020

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Reduction of the uranium(III) metallocene [(η5‐C5iPr5)2UI] (1) with potassium graphite produces the “second‐generation” uranocene [(η5‐C5iPr5)2U] (2), which contains uranium in the formal divalent oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground‐state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f3 6d1. Appreciable covalent contributions to the metal‐ligand bonds were determined from a computational study of 2, including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s‐6d mixing.

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“…In fact, the concept of agostic interaction has been extended to the transition‐metal complexes involved in the activation of B−H and C−C bonds. Besides, many complexes of late transition metals (e.g., Au and Sc) have been confirmed to show agostic interactions. Moreover, a kind of new aromatic‐ring agostic interactions has been recognized recently …”

Section: Introductionmentioning

confidence: 99%

Agostic Interactions in Early Transition‐Metal Complexes: Roles of Hyperconjugation, Dispersion, and Steric Effect

Lin

2019

Chemistry A European J

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The agostic interaction is a ubiquitous phenomenon in catalytic processes and transition‐metal complexes, and hyperconjugation has been well recognized as its origin. Yet, recent studies showed that either short‐range London dispersion or structural constraints could be the driving force, although proper evaluation of the role of hyperconjugation therein is needed. Herein, a simple variant of valence bond theory was employed to study a few exemplary Ti complexes with α‐ or β‐agostic interactions and interpret the agostic effect in terms of the steric effect, hyperconjugation, and dispersion. For the complexes [MeTiCl3(dmpe)] and [MeTiCl3(dhpe)] with α‐agostic interactions, hyperconjugation plays the dominant role with comparable magnitudes in both systems, but dispersion is solely responsible for the stronger agostic interaction in the former compared with the latter. For the complexes [EtTiCl3(dmpe)] and [EtTiCl3(dhpe)] with β‐agostic interactions, however, hyperconjugation and dispersion play comparable roles, and the weaker steric repulsion leads to a stronger agostic effect in the former than in the latter. Thus, the present study clarifies the variable and sensitive roles of steric, hyperconjugative, and dispersion interactions in the agostic interaction.

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The β‐Agostic Structure in (C₅Me₅)₂Sc(CH₂CH₃): Solid‐State NMR Studies of (C₅Me₅)₂Sc−R (R=Me, Ph, Et)

Cited by 27 publications

References 34 publications

Probing the Electronic Structure of Spectator Oxo Ligands by 17O NMR Spectroscopy

Probing the Electronic Structure of Spectator Oxo Ligands by 17O NMR Spectroscopy

Isolation of a Perfectly Linear Uranium(II) Metallocene

Agostic Interactions in Early Transition‐Metal Complexes: Roles of Hyperconjugation, Dispersion, and Steric Effect

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