Generation and Coordinating Properties of a Carbene Bearing a Phosphorus Ylide: An Intensely Electron‐Donating Ligand

Nakafuji, Shin-ya; Kobayashi, Junji; Kawashima, Takayuki

doi:10.1002/anie.200704746

Cited by 104 publications

(72 citation statements)

References 42 publications

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“…However, the change in π‐acidity is not very significant despite the presence of the electron‐withdrawing boron centre. Based on the calculated E σ values, ylide stabilized carbenes ( 5 – 13 ) are found to have significantly enhanced electron‐donation ability compared to non‐ylidic ones, which is in agreement with earlier findings –,. It is evident from Table that installation of the benzene ring in the backbone of ring skeleton ( 14 ) stabilizes both σ‐donor and π‐acceptor orbitals implying a decrease and an increase in σ‐donation and π‐acceptance ability, respectively, compared to the parent carbene 1 .…”

Section: Resultssupporting

confidence: 91%

“…This prompted us to undertake a theoretical study to investigate the possible changes in the electronic and ligand properties of CAAC upon varying the skeletal groups or changing the substituents attached to the carbenic centre (Scheme ). Our choice of the ylide group as the ring substituents was prompted by experimental reports of not only stabilization of the singlet state but also better electron‐donation ability of ylide stabilized carbenes –,. On the other hand, boron and silicon have the ability to withdraw electron density from the amino or ylide groups via p π –p π or p π –σ* Si‐C conjugation, respectively, thereby effecting both the nucleophilicity and electrophilicity of the carbene centre.…”

Section: Introductionmentioning

confidence: 99%

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Electronic and Ligand Properties of Skeletally Substituted Cyclic (Alkyl)(Amino)Carbenes (CAACs) and Their Reactivity towards Small Molecule Activation: A Theoretical Study

Bharadwaz

Chetia

Phukan

2017

Chemistry A European J

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Quantum chemical calculations have been carried out to understand the ligand properties of skeletally modified cyclic alkyl amino carbenes. The stability of these carbenes has been assessed from an evaluation of their singlet-triplet and stabilization energy values. Ylide substituted carbenes are found to be more stable than non-ylidic ones in their optimized singlet state. Nucleophilicity and electrophilicity indices values were evaluated in order to further investigate the reactivity of these carbenes. The calculated values of proton affinities and the degree of gallium pyramidalization in the carbene-GaCl adducts correlate well with the σ-basicity of these carbenes. The reactivity of non-ylidic carbenes toward the activation of both H and NH are calculated to be more favourable compared to that of parent CAAC. On the other hand, ylide anchored carbenes are found to be unsuccessful toward the activation of both H and NH .

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Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Electronic and Ligand Properties of Skeletally Substituted Cyclic (Alkyl)(Amino)Carbenes (CAACs) and Their Reactivity towards Small Molecule Activation: A Theoretical Study

Bharadwaz

Chetia

Phukan

2017

Chemistry A European J

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“…The anticipated free carbene readily coordinates to a suitable Pd 2+ or Rh + complex to form the complexes 212 and 213, respectively. 146 Employing such methods, complexes that contain AYCs stabilized by an internal sulfonium-ylide 214 or composed of a pyrazolderived heterocycle 215 have also been prepared. 147 The observed CO frequencies in the IR spectra of 213b (average ν CO ) 2012 cm ), and 215 (average ν CO ) 2009 cm -1 ) indicate a remarkably high electron-donating ability of these carbene ligands (cf.…”

Section: (Amino)(ylide)carbenesmentioning

confidence: 99%

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

et al. 2009

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theme are found via the replacement or displacement of one N atom, thus providing carbenes derived from pyrazolium, isothiazolium, and even quinolinium salts that contain a stabilizing heteroatom in a remote position (G-J in Figure 1). Recently, carbenes such as K, which are comprised of only one heteroatom and lack delocalization through the heterocycle, have been discovered as versatile ligands, thus constituting another important class of carbenes with low heteroatom stabilization. Both the synthesis of the organometallic complexes of these ligands as well as the (catalytic) properties of the coordinated metal centers generally show distinct differences, compared to the more classical NHC complexes, such as C2-metallated imidazolylidenes. This review intends to describe such differences and highlights the chemical peculiarities of these types of N-heterocyclic carbene complexes. It introduces, in a qualitative manner, the synthetic routes that have been established for the preparation of such complexes, covering the literature from the very beginning of activities in this area up to 2008. While specialized reviews on some aspects of the present topic have recently appeared, 7 a comprehensive overview of the subject has not been available thus far. Rather than just being descriptive, the present account is mainly directed toward the impact of these still unusual metal-carbene bonding modes on the electronic properties and on the new catalytic applications that have been realized by employing such new carbene complexes. As a consequence of our focus on complexes with less-stabilized heterocyclic ligands, systems comprising acyclic carbenes have not been included, and the interested reader is, instead, referred to the pioneering and

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“…This distance does not differ from typical Pd-C bond lengths in normal carbene palladium complexes, and it is slightly shorter than the average palladium-carbon distance in cyclic (alkyl)(amino)carbenes or (amino)(ylide)carbenes (average 2.03(1) Å) [32,35]. An interesting comparison is offered by a series of N-methyl-pyridinium-derived palladium salts comprising the metal bound to C2, to C3, or to C4 (cf.…”

Section: Pd-c Carbene Bond Length Analysismentioning

confidence: 99%

Abnormal NHC Palladium Complexes: Synthesis, Structure, and Reactivity

Poulain¹,

Iglesias²,

Albrecht

2011

COC

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Developments in palladium chemistry have been spurred predominantly by the outstanding application potential of this metal in catalysis. The quest for new ligands in order to modulate the catalytic activity and selectivity of the palladium center has been greatly stimulated by the discovery of N-heterocyclic carbenes as formally neutral, strongly donating, and covalently binding ligands. Abnormal variations of N-heterocyclic carbenes, even though known (yet not recognized) for 30 years, have received very little attention until recently. In parts this may have been due to the fact that the free abnormal carbene ligand is much less stable than the normal carbene analogues. In the last decade, significant progress has been made in abnormal carbene palladium chemistry and reliable synthetic routes as well as promising catalytic applications have been developed. As a consequence, these type of complexes have gradually transformed from laboratory curiosities to unique formally neutral ligands with exceptional donor ability. Here, the advances in abnormal carbene palladium chemistry are summarized. In an attempt to stimulate the entry of newcomers in this fascinating field of research, elementary aspects of synthesis are discussed as well as progress in characterization of the complexes. Most recent (catalytic) applications may highlight the potential of this rapidly growing area of palladium chemistry.

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Generation and Coordinating Properties of a Carbene Bearing a Phosphorus Ylide: An Intensely Electron‐Donating Ligand

Cited by 104 publications

References 42 publications

Electronic and Ligand Properties of Skeletally Substituted Cyclic (Alkyl)(Amino)Carbenes (CAACs) and Their Reactivity towards Small Molecule Activation: A Theoretical Study

Electronic and Ligand Properties of Skeletally Substituted Cyclic (Alkyl)(Amino)Carbenes (CAACs) and Their Reactivity towards Small Molecule Activation: A Theoretical Study

Beyond ConventionalN-Heterocyclic Carbenes: Abnormal, Remote, and Other Classes of NHC Ligands with Reduced Heteroatom Stabilization

Abnormal NHC Palladium Complexes: Synthesis, Structure, and Reactivity

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