Carbene Stability

Gronert, Scott; Keeffe, James R.; O’Ferrall, Rory A. More

doi:10.1002/9781118730379.ch1

Cited by 8 publications

(12 citation statements)

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“…In a recent paper Gronert and coworkers discussed the strategies for assessing the stability of various classes of carbenes and the relevant experimental and computational procedures which were used [33]. The carbene stabilization energy (CSE) and the singlet-triplet gaps (DE ST ) were even reported.…”

Section: Nhc Stabilitymentioning

confidence: 99%

“…The authors emphasized that assessing the carbene stability is a richly rewarding but could be a frustrating endeavor. In fact, a precise description of stability in practical application is problematic as appropriate, universal reference state cannot always be defined [33]. Accordingly, any definition of stable carbene is subjective.…”

Section: Nhc Stabilitymentioning

confidence: 99%

“…[36] The stronger tendency to dimerize of saturated NHCs, compared with unsaturated ones, was correlated to electronic effects [37,38]. used [33]. The carbene stabilization energy (CSE) and the singlet-triplet gaps (DEST) were even reported.…”

Section: Nhc Stabilitymentioning

confidence: 99%

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Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

2016

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In the last twenty years, N-heterocyclic carbenes (NHCs) have acquired considerable popularity as ligands for transition metals, organocatalysts and in metal-free polymer synthesis. NHCs are generally derived from azolium based salts NHCH+X− by deprotonation or reduction (chemical or electrochemical) of NHCH+. The extensive knowledge of the physicochemical properties of NHCH+/NHC system could help to select the conditions (scaffold of NHC, nature of the counter-ion X−, solvent, etc.) to enhance the catalytic power of NHC in a synthesis. The electrochemical behavior of NHCH+/NHC system, in the absence and in the presence of solvent, was extensively discussed. The cathodic reduction of NHCH+ to NHC and the anodic oxidation of NHC, and the related effect of the scaffold, solvent, and electrodic material were emphasized. The electrochemical investigations allow acquiring further knowledge as regards the stability of NHC, the acidic and nucleophilic properties of NHCH+/NHC system, the reactivity of NHC versus carbon dioxide and the effect of the hydrogen bond on the catalytic efficiency of NHC. The question of the spontaneous or induced formation of NHC from particular ionic liquids was reconsidered via voltammetric analysis. The results suggested by the classical and the electrochemical methodologies were compared and discussed.

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Section: Nhc Stabilitymentioning

confidence: 99%

Section: Nhc Stabilitymentioning

confidence: 99%

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Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

2016

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“…Rory More O'Ferrall was recently interested in electronic structural effects on the stabilities of carbenes, and in particular, the comparison of such effects between singlet carbenes and their conjugate acid carbenium ions. [1,30,[34][35][36] Singlet carbenes (but not triplet carbenes) with attached EWGs share many structural features with their conjugate acid carbenium ions as can be seen from the structures shown in Figs. 5 and 6.…”

Section: Comparisons With Singlet Ewg-carbenesmentioning

confidence: 99%

“…Structural characteristics for a set of EWG-carbenes are described in Table 3, all calculated at the G3MP2 level. A carbene stabilization enthalpy, CSE, [30,36] analogous to CSE+, is defined there, and values are included in the table. Note that carbene CSE values are calculated via their heats of hydrogenation, a reaction that produces the same product as hydride ion addition to the corresponding carbocations.…”

Section: Comparisons With Singlet Ewg-carbenesmentioning

confidence: 99%

Calculated stabilities and structures for carbocations and singlet carbenes bearing electron‐withdrawing groups

Gronert

Keeffe

2013

J of Physical Organic Chem

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Carbocations and carbenes, as electron-deficient species, require electron donation from the remainder of the molecule to the carbon center by whatever means available. Classical interactions include resonance, polar and polarizability effects, but neighboring group participation of several sorts can also serve as stabilizing factors. Simple carbocations with directly attached electron-withdrawing groups (EWGs), that is, EWG-CH 2 + ions, comprise one group by which these interactions may be probed. This article provides computational evidence at the MP2/6-311 + G** level for variable but significant stabilizing interactions between the carbocation center and common EWGs, many via bridging (partial or symmetrical), neighboring group participation, homoconjugation or π interactions. Bridging from atoms possessing nonbonding electron pairs is a common motif. Removal of bridging by application of geometric constraints nullifies bridging stabilization, but does not eliminate the possibility of other stabilizing interactions, for example polar, polarizability and π donation from the EWG. The potential for π donation from strong EWGs has not been widely appreciated in the past. A carbocation stabilization enthalpy, CSE+, is defined as the enthalpy of the isodesmic reaction CH 3 + + R-H → CH 4 + R + . Comparisons are made with singlet carbenes bearing EWGs for which many structural features are similar.

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Silicon‐Derived Singlet Nucleophilic Carbene Reagents in Organic Synthesis

Priebbenow

2020

Adv Synth Catal

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Carbene Stability

Cited by 8 publications

References 98 publications

Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

Advances in the Knowledge of N-Heterocyclic Carbenes Properties. The Backing of the Electrochemical Investigation

Calculated stabilities and structures for carbocations and singlet carbenes bearing electron‐withdrawing groups

Silicon‐Derived Singlet Nucleophilic Carbene Reagents in Organic Synthesis

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