The Role of NHC Ligands in Oxidation Catalysis

Palladium nanoparticles capped by thermoresponsive N‐heterocyclic carbene: Two different approaches for a comparative study

“…[ 1–4 ] Among the ligands, N‐heterocyclic carbene (NHC) ligands are considered particularly attractive because of their versatility in chemical structures, tolerance against moisture, air, and ease of synthesis. [ 5,6 ] Additionally, by being a strong σ donor and weak π acceptor, it formed a strong ligand–metal bond that enhanced the stability and reactivity of transition metal catalysts in organometallic transformations. [ 7–9 ] Furthermore, owing to its strong σ donating and weak accepting ability than the commercial phosphine ligands, it enhances the crucial steps of coupling reactions such as oxidation addition and reductive elimination, which, in turn, increases the efficiency of such catalysts towards cross‐coupling reactions.…”

Hydrogen‐transfer reduction of α,β‐unsaturated carbonyl compounds catalyzed by naphthyridine‐functionalized N‐heterocyclic carbene complexes

“…[2] Compared to coupling reactions, Pd-NHC-catalyzed hydrogen-transfer reductions are less explored. [10] We studied the selective reduction of C═C in α,β-unsaturated carbonyl compounds catalyzed by 5-7 using formate as the hydrogen-transfer agent.…”

“…With the optimized conditions in hand, the reduction of a variety of α,β-unsaturated carbonyl compounds catalyzed by 5 was investigated ( Table 6). Most of the α,β-unsaturated carbonyl compounds are found to undergo C═C bond reduction selectively to afford the corresponding saturated carbonyl compounds in good to excellent yields ( Table 6, entries [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. For α,β-unsaturated ester, carboxylic acid and amide, the reduction proceeds smoothly to give the corresponding products ( Table 6, entries 3-6 and 18).…”

Maßgeschneiderte Aryl‐Alkyl‐substituierte ionische Flüssigkeiten (TAAILs) – die nächste Generation ionischer Flüssigkeiten

“…[5] Die gegenwärtig wichtigste Klasse der ILs sind Imidazoliumsalze, die generell sp 3 [6] Wir untersuchen Imidazolium-basierte Verbindungen als Vorstufen zur Synthese von NHC-Metallkomplexen; [7] NHCs (N-heterocyclische Carbene) sind eine sehr interessante Klasse von Liganden in der homogenen Katalyse. [8] Sie sind in der Regel stabiler als die Phosphinliganden und wurden bisher als s-Donorliganden mit vernachlässigbarem p-Anteil beschrieben. Jedoch fanden wir bei substituierten aromatischen Systemen einen großen Substituenteneffekt auf die NMR-Verschiebungen des Imidazoliumkerns und begannen, den Einfluss von elektronenziehenden und -schiebenden Substituenten zu untersuchen.…”