Synthesis, Characterization, and Catalytic Activity of <i>N</i>-Heterocyclic Carbene (NHC) Palladacycle Complexes

Ms, Viciu; Ra, Kelly; Stevens, E. D.; Naud, Frédéric; Studer, Martin; Nolan, Steven P.

doi:10.1021/ol034264c

Cited by 299 publications

(131 citation statements)

References 29 publications

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“…[153] Novel mixed Pd catalysts bearing both a heterocyclic carbene and a phosphane as ligands have been used in the Suzuki coupling with aryl chlorides, [154] whereas new carbene-containing palladacycles have found use in the amination of aryl chlorides, [155] in both cases without reaching high TON.…”

Section: ð8þmentioning

confidence: 99%

High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

2004

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This review discusses the problems associated with developing high-turnover catalysts for the cross-coupling and Heck reactions. New developments in the area, principally constituted by palladacycles and coordinatively unsaturated Pd catalysts featuring bulky phosphanes of high donicity, are reviewed from a mechanistic and synthetic standpoint, and compared with more traditional catalysts obtained from conventional mono-and polydentate Nand P-based ligands, as well as Pd catalysts without strong ligands, such as Pd colloids or heterogeneous catalysts. Carbene ligands are also briefly presented. Whereas a single, most promising approach to highturnover Pd catalysis cannot presently be defined, it is clear that the new "PdL 1 " catalysts (where L 1 is a monodentate bulky P ligand of high donicity) represent the latest, most important development in Pd research, certainly from the standpoint of scope and probably also from the standpoint of efficiency. High turnovers with these catalysts have been described and their use will certainly increase in the next few years. The review ends with a brief discussion containing practical considerations on how to choose a high TON catalyst for a given Heck or cross-coupling reaction of interest.

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Section: ð8þmentioning

confidence: 99%

High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

2004

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“…Finally, the NHC ligands enhance the elimination of the final product from the palladium center as a result of their bulky nature. [6,11,23,29,42,43] The above described versatility, stability and unique catalytic properties of NHC-containing transition metal catalysts make them interesting candidates for supported catalysis. Over the past five years, NHCs have been grafted onto different supports ranging from mesoporous silica to soluble polyA C H T U N G T R E N N U N G (styrene)s. [44][45][46][47][48][49][50][51][52][53] While often successful, metal leaching and low metal loadings remain a major shortcoming for most supported catalysts.…”

Section: Introductionmentioning

confidence: 99%

Poly(norbornene)‐Supported N‐Heterocyclic Carbenes as Ligands in Catalysis

Sommer

Weck

2006

Adv Synth Catal

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In this contribution, we present the synthesis of norbornene-supported N-heterocyclic (NHC) carbenes. These functionalized norbornenes were polymerized via ring-opening metathesis polymerization in a controlled fashion either before or after metalation with a variety of palladium and ruthenium precursors resulting in the formation of polymersupported NHC-based metal catalysts. The activities of the palladium-based catalysts in the SuzukiMiyaura, Sonogashira and Heck coupling reactions were studied in detail. In all cases, the polymeric catalysts demonstrated the same activity as their small molecule analogues. Furthermore, we carried out preliminary investigations into the stability of these catalysts using poisoning studies. A clear dependence of the stability of the polymer-supported catalysts on their palladium precursor was observed with palladium acetate-based polymeric NHC catalysts being the most stable. Finally, we have studied the reactivity of our supported NHC ruthenium complexes as catalysts for ring-closing metathesis. Again, in all cases good conversions were observed with comparable activities to other supported NHC-ruthenium catalysts. Lastly, we were able to remove the ruthenium catalysts from the solution quantitatively demonstrating the possibility of metal removal.

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“…On the other hand, the simple dimeric N-containing palladacycle derived from the chloropalladation of N,N-dimethyl-1-phenylpropargylamine promotes the coupling of aryl iodides and activated aryl bromides (substituted with electron-withdrawing groups) with acrylates and styrene at room temperature. [4] Moreover, it was recently reported that adducts resulting from the association of dimeric nitrogen-containing palladacycles with carbenes [5] or secondary and tertiary phosphines [6] (Figure 1) generate highly active catalyst precursors for C À C and C À N couplings. These catalyst precursors combine the stability induced by the palladated unit with the steric and electronic properties associated with phosphorus and carbene ligands.…”

Section: Introductionmentioning

confidence: 99%

On the Use of Non‐Symmetrical Mixed PCN and SCN Pincer Palladacycles as Catalyst Precursors for the Heck Reaction

et al. 2004

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OPPh 2 and t-BuSCH 2 CH 2 C ¼ C(o-NC 5 H 4 ), respectively. The molecular structures of 1 and 3 have been ascertained by means of X-ray diffraction analysis. The catalytic properties of these mixed donor group pincer-type palladacycles have been evaluated in the arylation of olefins (Heck reaction). The pincer palladacycle 1 is highly active for the coupling of aryl iodides and aryl bromides with n-butyl acrylate. In contrast it is only moderately active for the coupling of aryl chlorides substituted with electron-withdrawing groups and inactive for the coupling of electron neutral and electron deactivated aryl chlorides.

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Synthesis, Characterization, and Catalytic Activity of N-Heterocyclic Carbene (NHC) Palladacycle Complexes

Cited by 299 publications

References 29 publications

High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

High‐Turnover Palladium Catalysts in Cross‐Coupling and Heck Chemistry: A Critical Overview

Poly(norbornene)‐Supported N‐Heterocyclic Carbenes as Ligands in Catalysis

On the Use of Non‐Symmetrical Mixed PCN and SCN Pincer Palladacycles as Catalyst Precursors for the Heck Reaction

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