The First Planar-Chiral Stable Carbene and Its Metal Complexes

Bolm, Carsten; Kesselgruber, Martin; Raabe, Gerhard

doi:10.1021/om010679v

Cited by 102 publications

(46 citation statements)

References 32 publications

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“…[208] The fourth group of chiral N-heterocyclic carbenes or imidazolium precursors are the planar-chiral derivatives. The first representative of this group 119 was presented by Bolm et al [209] Shortly thereafter, Togni et al described the C 2 -symmetrical ferrocenyl carbene 120. [210] Similar compounds [211] or derivatives with phosphine substituents [212] at the ferrocenyl moiety are also known.…”

Section: Methodsmentioning

confidence: 99%

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

2008

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The chemistry of heterocyclic carbenes has experienced a rapid development over the last years. In addition to the imidazolin-2-ylidenes, a large number of cyclic diaminocarbenes with different ring sizes have been described. Aside from diaminocarbenes, P-heterocyclic carbenes, and derivatives with only one, or even no heteroatom within the carbene ring are known. New methods for the synthesis of complexes with N-heterocyclic carbene ligands such as the oxidative addition or the metal atom template controlled cyclization of beta-functionalized isocyanides have been developed recently. This review summarizes the new developments regarding the synthesis of N-heterocyclic carbenes and their metal complexes.

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Section: Methodsmentioning

confidence: 99%

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

2008

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“…The concept of steric tuning was further refined by Glorius and co-workers, who prepared a range of pentacyclic NHC precursors (46)(47)(48)(49)(50)(51) bearing conformationally flexible cyclic rings in proximity to the Pd center (Scheme 15). [83,84] These NHCs proved to be slightly less s donating than the monocyclic imidazolium derivatives as a result of the electron-withdrawing effect of the oxygen atoms at the distal carbon atoms of the imidazolium ring.…”

Section: Improving the Catalytic Activity Of Nhc Ligandsmentioning

confidence: 99%

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

2007

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Palladium-catalyzed C-C and C-N bond-forming reactions are among the most versatile and powerful synthetic methods. For the last 15 years, N-heterocyclic carbenes (NHCs) have enjoyed increasing popularity as ligands in Pd-mediated cross-coupling and related transformations because of their superior performance compared to the more traditional tertiary phosphanes. The strong sigma-electron-donating ability of NHCs renders oxidative insertion even in challenging substrates facile, while their steric bulk and particular topology is responsible for fast reductive elimination. The strong Pd-NHC bonds contribute to the high stability of the active species, even at low ligand/Pd ratios and high temperatures. With a number of commercially available, stable, user-friendly, and powerful NHC-Pd precatalysts, the goal of a universal cross-coupling catalyst is within reach. This Review discusses the basics of Pd-NHC chemistry to understand the peculiarities of these catalysts and then gives a critical discussion on their application in C-C and C-N cross-coupling as well as carbopalladation reactions.

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“…Indeed, ferrocenyl-substituted NHCs are a class of ligands that has been little developed and has a great potential in both asymmetric and non-asymmetric catalysis. [2,14] We thus prepared new ferrocenylphosphane ligand precursors bearing a benzimidazolium moiety and the corresponding rhodium(I) complexes. Although benzimidazolium salts with a ferrocenyl substituent are already known, [15] we report here the first example of a ferrocenylphosphane bearing a benzimidazolium unit.…”

Section: Introductionmentioning

confidence: 99%

Rhodium(I) Complexes of New Ferrocenyl Benzimidazol‐2‐ylidene Ligands: The Importance of the Chelating Effect for Ketone Hydrosilylation Catalysis

et al. 2009

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N‐[(1‐Phosphanylferrocen‐1′‐yl)methyl]‐N′‐[(2,4,6‐trimethylphenyl)methyl]‐5,6‐di‐X‐benzimidazolium tetrafluoroborate salts (X = H, 5a and Me, 5b), precursors of new phosphane‐benzimidazol‐2‐ylidene bifunctional ligands, and related ferrocenyl 5,6‐di‐X‐benzimidazol‐2‐ylidene iodide salts (X = H, 6a and Me, 6b), precursors of monodentate benzimidazol‐2‐ylidene ligands, have been prepared for the first time. Cationic rhodium(I) complexes 7a and 7b and neutral rhodium(I) complexes 8a and 8b have been obtained in good yields and have been fully characterised. Cationic rhodium(I) complexes 10a and 10b were prepared from 8a and 8b, for comparison with complexes 7, but not isolated. All complexes showed good activities for the catalytic hydrosilylation of acetophenone derivatives. The activities are much greater than for related imidazol‐2‐ylidene systems, and the cationic complexes are more active than the neutral complexes; the highest activity is observed for the more soluble complex 7b. The use of bidentate ligands proved to be essential for obtaining good selectivities of the desired alcohol.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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The First Planar-Chiral Stable Carbene and Its Metal Complexes

Cited by 102 publications

References 32 publications

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

Rhodium(I) Complexes of New Ferrocenyl Benzimidazol‐2‐ylidene Ligands: The Importance of the Chelating Effect for Ketone Hydrosilylation Catalysis

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