Synthesis, structure and catalytic activity of a bimacrocylic NHC palladium allyl complex

Winkelmann, Ole; Näther, Christian; Lüning, Ulrich

doi:10.1016/j.jorganchem.2008.05.034

Cited by 17 publications

(10 citation statements)

References 33 publications

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“…7 Indeed, the carbenes derived from imidazole stabilized the palladium complexes due to their pronounced donor properties, being more stable toward deactivating degradation reactions. Thus, the MizorokiHeck reaction employing bromo-and chloroarenes has been satisfactorily catalyzed by the monoNHC Pd(II) complex 1, 8 bis(NHC) Pd(II) complexes 222, 7,911 the tetraNHC Pd(II) complex 23, 12 and Pd(0) complexes 24 and 25 (Chart 1). 7,13 Complexes 26 adopted a pseudo-square-planar geometry where the NHC ligands were in a cis-configuration.…”

Section: ç Mizoroki-heck Reactionmentioning

confidence: 99%

Heterocyclic Carbene–Metal-catalyzed Csp2–Csp2 and Csp–Csp2 Couplings Using Nonmetallic Substrates

Yus¹,

Pastor²

2013

Chemistry Letters

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The use of carbene ligands for transition-metal complexes has been developed in the last decades, being of special interest those carbenes derived from a nitrogen-containing heterocyclic system. An interesting variety of carbenemetal complexes has been tested in the MizorokiHeck reaction. In comparison, few examples can be found for the MatsudaHeck version of this coupling reaction. Additionally, the Sonogashira coupling has been also catalyzed with different carbenemetal catalysts. Ç IntroductionN-Heterocyclic carbenes (NHCs) have emerged in the last years as a new family of ligands with interesting electronic and structural properties.1 The combination of their strong ·-donor and poor ³-acceptor abilities results in good coordination stability and versatility. Consequently, the use of NHC ligands based on imidazolium ions and related heterocycles has appeared as an alternative to phosphanes in the design of new organometallic catalysts.2 One of the main advantages of employing NHC-based catalysts compared with phosphanebased ones is that they are far less prone to oxidation, allowing their prolonged use, and reuse. Although NHCs were presented as simple tertiary phophane mimics, they have been recognized as much more over the past decade. Therefore, NHC ligands have become an interesting alternative to other types of ligands in different cross-coupling catalytic reactions mediated by transition metals.3 Moreover, the easy introduction of chiral elements in the corresponding precursors have made chiral NHCs promising chiral ligands in metal-based asymmetric catalysis. 4 The comparison between phosphane and NHC ligands, from a mechanistic point of view, has been studied, clear differences being found.5 First, the possibility of carbene ligand dissociation is greatly reduced due to its stronger donor ability; and second, the reactivity of the NHCmetal complex is higher probably caused by the lack of back-donation from the metal to the carbene ligand. Jutand and co-workers studied the reactivity of monocarbene and bis(carbene) Pd(0) complexes toward the oxidative addition of aryl halides, concluding that the electronic and steric properties of the carbene ligand are important factors in this step of the catalytic process. 6 Among the carboncarbon coupling reactions, the activation of a CH from an alkene (MizorokiHeck reaction) or an alkyne (Sonogashira reaction) are of special interest. This highlight review describes the progress on the topic of NHC ligands for transition-metal-catalyzed coupling reactions, employing nonmetallic reagents. Thus, both different NHC precursors and NHCmetal complexes with catalytic activity in the Mizoroki Heck, MatsudaHeck, and Sonogashira reactions are compiled. Ç Mizoroki-Heck ReactionIn 1995, Herrmann and co-workers introduced the use of bis(NHC)Pd complexes as catalysts with long-term stability in the MizorokiHeck reaction.7 Indeed, the carbenes derived from imidazole stabilized the palladium complexes due to their pronounced donor properties, being more stable toward...

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Section: ç Mizoroki-heck Reactionmentioning

confidence: 99%

Heterocyclic Carbene–Metal-catalyzed Csp2–Csp2 and Csp–Csp2 Couplings Using Nonmetallic Substrates

Yus¹,

Pastor²

2013

Chemistry Letters

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“…The calixarene macrocycle is too small to accommodate the carboxylate or to let an alkene approach the carbenoid. 66 Also with concave NHC, many complexes can easily be prepared, 37,62 and some of them have been applied to catalyses. By this sterical shielding of the calixarene, the carboxylate and the residues of the alkene are oriented next to each other, and thus the predominant formation of the endo -product is observed.…”

Section: Metal Catalysismentioning

confidence: 99%

“…This results in an orientation in which both, the alkene and the carboxylate residue of the carbene moiety, have to be squeezed in the gap between the 1,10 -phenanthroline and part of calixarene rim. 62 Copper complexes may be used for cyclopropanations, too, but yet with smaller selectivities than 1,10 -phenanthrolines exhibit. 64b The last decade has shown the increasing importance of N -heterocyclic carbenes as ligands for transition metals.…”

Section: Metal Catalysismentioning

confidence: 99%

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Concave Reagents

Lüning¹

2010

Molecular Encapsulation

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“…Many other metal-NHC complexes have been obtained by using appropriate transfer reagents Ag(I)-NHC complexes. For example, Pd, Ru, Ni, Rh and Ir NHC complexes successfully have been transferred by using this method [22][23][24][25][26]. In the commonly used method in the synthesis of Ag(I)-NHC complexes, a silver base has been used as agent of deprotonation.…”

Section: Introductionmentioning

confidence: 99%

2-Methyl-1,4-Benzodioxan Substituted Ag(I)-N-Heterocyclic Carbene Complexes and Ru(II)-N-Heterocyclic Carbene Complexes: Synthesis, Crystal Structure and Transfer Hydrogenation of Aromatic Ketones

Â¹,

Gök²

2015

Organic Chem Curr Res

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Synthesis, structure and catalytic activity of a bimacrocylic NHC palladium allyl complex

Cited by 17 publications

References 33 publications

Heterocyclic Carbene–Metal-catalyzed Csp2–Csp2 and Csp–Csp2 Couplings Using Nonmetallic Substrates

Heterocyclic Carbene–Metal-catalyzed Csp2–Csp2 and Csp–Csp2 Couplings Using Nonmetallic Substrates

Concave Reagents

2-Methyl-1,4-Benzodioxan Substituted Ag(I)-N-Heterocyclic Carbene Complexes and Ru(II)-N-Heterocyclic Carbene Complexes: Synthesis, Crystal Structure and Transfer Hydrogenation of Aromatic Ketones

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