Oxidative Addition of Imidazolium Salts to Ni<sup>0</sup> and Pd<sup>0</sup>: Synthesis and Structural Characterization of Unusually Stable Metal–Hydride Complexes

Clément, Nicolas D.; Cavell, Kingsley J.; Jones, Cameron; Elsevier, Cornelis J.

doi:10.1002/ange.200353409

Cited by 56 publications

(26 citation statements)

References 30 publications

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“…The aim of this section is [95][96][97][98] The strength of the PdÀNHC bonds renders ligand exchange (Schemes 20-25) an excellent general route to Pd-NHC complexes starting from the preformed carbene and Pd II or Pd 0 complexes with alkenes, [99] phosphanes, [91] nitrogen ligands, [45] or bridging chloride [37,100] or acetate ligands. [101] Pure [102] Another approach is to use an azolium salt precursor in the presence of a base to form in situ the NHC, which is captured by Pd (Schemes 16 and 27-29).…”

Section: General Synthetic Methods For Pd-nhc Complexesmentioning

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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Section: General Synthetic Methods For Pd-nhc Complexesmentioning

confidence: 99%

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

2007

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“…[95][96][97][98] Der Ligandenaustausch, angetrieben durch die starke Pd-NHC-Bindung, bietet eine ausgezeichnete Möglichkeit, Pd-NHC-Komplexe ausgehend von Pd II -oder Pd 0 -Komplexen mit Alkenen, [99] Phosphanen, [91] Stickstoffdonorliganden [45] oder verbrückenden Chlorid- [37,100] oder Acetationen herzustellen (Schema 20-25).…”

Section: Allgemeine Synthesemethoden Für Pd-nhc-komplexeunclassified

“…Werden hingegen Salze von schwach koordinierenden Anionen wie BF 4 À oder PF 6 À in Acetonitril verwendet, entstehen die kationischen Palladium-AcetonitrilKomplexe, die in Form ihrer BF 4 -oder PF 6 -Salze isoliert werden (Schema 30). [98,104] Schließlich inserieren Pd 0 -Spezies oxidativ in C-H-, [95] C-Cl- [107] und C-S-Bindungen [108] (Schema [32][33][34] …”

Section: Allgemeine Synthesemethoden Für Pd-nhc-komplexeunclassified

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

2007

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Palladiumkatalysierte C‐C‐ und C‐N‐Kupplungen zählen zu den vielseitigsten und leistungsfähigsten Syntheseverfahren. Seit 15 Jahren erfreuen sich die N‐heterocyclischen Carbene (NHCs) wachsender Beliebtheit als Liganden für palladiumvermittelte Kreuzkupplungen und ähnliche Methoden. Sie sind in vielerlei Hinsicht den üblichen tertiären Phosphanen überlegen. Weil NHCs stark σ‐elektronenschiebend sind, können sie auch anspruchsvolle Substrate zu oxidativen Insertionen bewegen. Andererseits führen ihre Sperrigkeit und ihre besondere Topologie zu einer raschen reduktiven Eliminierung. Schließlich tragen die starken Pd‐NHC‐Bindungen zur hohen Stabilität der aktiven Spezies bei – auch bei niedrigen Ligand/Pd‐Verhältnissen und hohen Temperaturen. Wenn erst stabile, anwenderfreundliche und leistungsstarke NHC‐Pd‐Präkatalysatoren kommerziell verfügbar sind, liegt das Ziel eines universellen Kreuzkupplungskatalysators in greifbarer Nähe. Dieser Aufsatz beschreibt zunächst die chemischen Grundlagen zu den NHC‐Pd‐Komplexen, um ihre Besonderheiten kennenzulernen. Anschließend folgt eine umfassende Diskussion zur Anwendung dieser Katalysatoren in C‐C‐ und C‐N‐Kreuzkupplungen sowie in der Carbopalladierung.

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“…The reductive elimination of neopentane from 141 [261] yields a highly reactive Pt 0 compound as an intermediate, which at 80 8C oxidatively adds dimethylimidazolium iodide to give the hydrido complex 142 (Scheme 73). [260] This method is only applicable for sterically less-demanding N,N'-substituted imidazolium salts [262] to electron-rich and coordinatively unsaturated complexes of the type [M 0 (NHC) 2 ] (M = Ni, Pd) which were generated in situ. [263] The oxidative addition to nickel(0) proceeds at ambient temperature, whereas the palladium complex 143 b forms at 55 8C.…”

Section: Angewandte Chemiementioning

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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Oxidative Addition of Imidazolium Salts to Ni⁰ and Pd⁰: Synthesis and Structural Characterization of Unusually Stable Metal–Hydride Complexes

Cited by 56 publications

References 30 publications

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

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

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

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Oxidative Addition of Imidazolium Salts to Ni0 and Pd0: Synthesis and Structural Characterization of Unusually Stable Metal–Hydride Complexes

Cited by 56 publications

References 30 publications

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

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

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

Heterocyclic Carbenes: Synthesis and Coordination Chemistry

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Oxidative Addition of Imidazolium Salts to Ni⁰ and Pd⁰: Synthesis and Structural Characterization of Unusually Stable Metal–Hydride Complexes