Metal Complexes of N‐Heterocyclic Carbenes—A New Structural Principle for Catalysts in Homogeneous Catalysis

Herrmann, Wolfgang A.; Elison, Martina; Fischer, Jakob; Köcher, Christian; Artus, Georg R. J.

doi:10.1002/anie.199523711

Cited by 1,057 publications

(634 citation statements)

References 21 publications

Supporting

Mentioning

603

Contrasting

Unclassified

Order By: Relevance

“…In complexes 2 and 3, the metal is in a distorted square-planar environment (sum of bond angles around Pd 360.37° and around Ni 361.17°). The carbene-palladium bond distance (2.019 Å) is in the typical range for C-Pd single bonds, and very similar to that observed for related N-heterocyclic carbene palladium complexes (1.95 -2.07 Å) [11]. The nickel-carbene bond length of 1.841 Å is slightly shorter than observed for nickel(II) complexes bearing Cl and NHC ligands cis to one another [12].…”

Section: Resultssupporting

confidence: 80%

A Stable (Amino)(phosphino)carbene as Bidentate Ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

et al. 2006

View full text Add to dashboard Cite

Two original complexes featuring an (amino)(phosphino)carbene η 2 -bonded to the metal have been obtained in 60 and 80 % yields, by addition of the corresponding stable carbene to PdCl 2 (cod) and NiCl 2 (PPh 3 ) 2 , respectively. Both complexes have been fully characterized including X-ray diffraction studies. The catalytic activity of the palladium complex has been evaluated for aryl amination reactions.

show abstract

Section: Resultssupporting

confidence: 80%

A Stable (Amino)(phosphino)carbene as Bidentate Ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

et al. 2006

View full text Add to dashboard Cite

show abstract

Section: ç Mizoroki-heck Reactionmentioning

confidence: 99%

“…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.14 The comparison of the catalytic activity between 26 complexes did not allow to conclude any universal trend, but complex 4 exhibited higher activity than complex 5 what may be attributed to ·-and ³-contributions of the substituents in the corresponding NHCligand. Interestingly, the palladium(0) complex 25, which has been prepared by Beller's research group and employed in the MatsudaHeck reaction (vide infra), 15 catalyzed also the reaction between aryl iodides and enones yielding the MizorokiHeck…”

mentioning

confidence: 99%

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

Yus¹,

Pastor²

2013

Chemistry Letters

View full text Add to dashboard Cite

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...

show abstract

“…76 The group reported the synthesis of complexes 27 and 28 (70 and 40% yield, respectively) by reaction of Pd(OAc) 2 with the adequate iodides, the dimethylimidazolium and the diimidazolium 26 (Scheme 16). The authors studied the efficiency of both complexes in Heck-Mizoroki coupling reactions using a series of aryl halides and butyl acrylate and verified that the conversion of 4-chloronitrobenzene and 4-chlorobenzaldehyde proceed quantitatively in the presence of complex 27 only with the addition of IL tbab (Scheme 17).…”

Section: Heck-mizoroki Reaction In Ils Catalyzed By N-heterocyclic Camentioning

confidence: 99%

Revisiting Heck–Mizoroki reactions in ionic liquids

Santos¹,

Barata²,

Faustino³

et al. 2013

RSC Adv.

View full text Add to dashboard Cite

show abstract

Metal Complexes of N‐Heterocyclic Carbenes—A New Structural Principle for Catalysts in Homogeneous Catalysis

Cited by 1,057 publications

References 21 publications

A Stable (Amino)(phosphino)carbene as Bidentate Ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

A Stable (Amino)(phosphino)carbene as Bidentate Ligand for Palladium and Nickel Complexes: Synthesis, Structure, and Catalytic Activity.

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

Revisiting Heck–Mizoroki reactions in ionic liquids

Contact Info

Product

Resources

About