KW - N-heterocyclic carbene catalysis

A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been synthesized from [3-methyl-1-(2′- phthalimidoethyl)imidazolium] hexafluorophosphate ([NHCMe,PhtH] PF6) by transmetalation and isolated in 67 % yield. The title complex has been applied as catalyst in the Suzuki-Miyaura cross-coupling reaction under benign aqueous conditions. The catalyst is active without any observable initiation period. High average turnover frequencies (TOFs) of up to 55000 h-1 have been reached with catalyst concentrations as low as 0.01 mol-%. A cationic phthalimido-functionalized N-heterocyclic carbene (NHC) palladium(II) complex has been prepared in high yield. The complex was activated instantly, without an initiation period, in the Suzuki-Miyaura cross-coupling reaction under benign aqueous aerobic conditions. Turnover frequencies (TOFs) up to 55000 h-1, were achieved with 0.01 mol-% of the complex.

The first acyclic persistent carbene was reported in 1996, ..

T1 - Enantioselective N-heterocyclic carbene catalyzed annulation reactions with imidazolidinones

metal carbene dimerization has been used in the synthesis of ..

We are fascinated by the diversity of effects that ligands can have to instigate new properties in transition metal complexes and we are therefore strongly interested in designing and developing new ligands that impart specific properties to the metal center. One of these ligands are triazolylidenes, a mesoionic carbene that we discovered in 2008. This ligand offers various opportunities for catalysis, including strong electron donor properties, a high synthetic flexibility that allows for a wide variety of functional and chelating groups to be incorporated, and a high polarity, which imparts solubility in water and other polar media. We have obtained evidence in a variety of catalytic reactions like nickel-catalysed hydrosilylation, ruthenium-catalyzed alcohol dehydrogenation, or iridium-catalyzed water oxidation, that the triazolylidene ligand scaffold is controlling the reactivity of the coordinated metal center. Because of the synthetic versatility and the easy accessibility of the ligand, tailoring of the ligand properties is straightforward and we have disclosed improved catalytic activity by ligand tuning. More recently, we have discovered a straightforward approach to functionalize the ligand on the complex as opposed to the more traditional approach of preparing a functional ligand and only then install the metal center. This approach gives rapid access to a large diversity of functionalized ligands in a very last step, and to ligand scaffolds that are not accessible by traditional routes.

the formulae L n MCRR' are often described as carbene ..

De introductie van een stikstof fragment op de vleugeltip van het NHC ligand, voor de supramoleculaire koppelingsstrategie van de katalysator en FS, slaagde niet.

T1 - Synthesis, characterization and reactivity of N-heterocyclic carbene gold(III) complexes

N-Heterocyclic carbenes (NHCs) were ..

AB - N-Heterocyclic carbenes (NHCs) are valuable ligands in transition metal catalysis, due to their unique electronic properties. However, only a few routes toward unsymmetrically substituted, saturated NHCs are known. We have successfully applied the multicomponent synthesis of 2H-2-imidazolines for the preparation of a range of diversely substituted imidazolidin-2-ylidene complexes under mild conditions. In the desired NHC precursors the substituents at N-1, N-3, C-4, and C-5 were varied easily and independently by choosing the appropriate amine, aldehyde, isocyanide, or halide as starting material. Subsequent formation of the imidazolium salts followed by deprotonation with KO

Chiral N -Heterocyclic Carbenes - Organic chemistry

T1 - Synthesis and characterization of a cationic phthalimido-functionalized N-heterocyclic carbene complex of palladium(II) and its catalytic activity

N-Heterocyclic Carbene (NHC) Compounds | Sigma-Aldrich

N2 - The imidazolium cation 1,3,7,9-tetramethylxanthinium methyl sulfate (1a) is obtained by the reaction of caffeine with dimethyl sulfate. The anion exchange of la gives 1,3,7,9-tetramethylxanthinium hexafluorophosphate (1b). Ligand 1a reacts with Ag 2O in water to yield an N-heterocyclic carbene (NHC) silver(I) complex (2a). Similarly, ligand 1b reacts with Ag 2O in DMSO to yield NHC silver(I) complex 2b in high yield. A carbene transfer reaction of 2b with [Rh(COD)Cl]2 gives NHC Rh(I) complex 3. All compounds were characterized by 1H NMR, 13C NMR, and mass spectrometry. The solid-state structures of 1b, 2b, and 3 were determined by X-ray crystallography.

Transition metal carbene complex - Wikipedia

N2 - N-Heterocyclic carbenes (NHCs) are valuable ligands in transition metal catalysis, due to their unique electronic properties. However, only a few routes toward unsymmetrically substituted, saturated NHCs are known. We have successfully applied the multicomponent synthesis of 2H-2-imidazolines for the preparation of a range of diversely substituted imidazolidin-2-ylidene complexes under mild conditions. In the desired NHC precursors the substituents at N-1, N-3, C-4, and C-5 were varied easily and independently by choosing the appropriate amine, aldehyde, isocyanide, or halide as starting material. Subsequent formation of the imidazolium salts followed by deprotonation with KO