Chelating Bis(N‐Heterocyclic Carbene) Palladium‐Catalyzed Reactions

Abstract

N-Heterocyclic carbenes (NHCs) have been widely employed in the construction of various metal complexes and applied in the field of catalysis. In this review, a series of palladium complexes comprising chelating bis(NHC) donors (Pd-bis(NHC) complexes) are outlined according to their application in homogeneous catalysis. Examples of metal-organic frameworks containing Pd-bis(NHC) moieties are briefly discussed, in terms of their use in heterogeneous catalysis. The catalytic applications of Pd-bis(NHC) complexes (or moieties in heterogeneous catalysts) are mainly focused on the Mizoroki-Heck, Suzuki-Miyaura, and Sonogashira coupling reactions. Another 14 types of reactions are also summarized beyond these three types of reactions.

Bis-NHC–Ag/Pd(OAc)2 Catalytic System Catalyzed Transfer Hydrogenation Reaction

“…This observation is contrary to recent reports, in which trans-alkenes were found to be a major product through in situ Z→ E isomerization in the Pd-catalyzed semihydrogenation of internal alkynes in aqueous solution [52,53,[56][57][58]. In addition, K2CO3 and K3PO4•H2O were not the best choices as the base, indicating that the basicity of the base might affect the reaction rate (entries 2, 5, and 6) [60]. With Pd(II) sources, 3a was transformed to olefin efficiently, but Recently, numerous studies of Pd-catalyzed transfer hydrogenation using H2O as the hydrogen agent and the solvent have been reported [51][52][53][54][55][56][57][58][59].…”

Molecular complexes and main-chain organometallic polymers based on Janus bis(carbenes) fused to metalloporphyrins

“…[14][15][16][17][18] Many examples of bis(NHCs) acting as chelating ligands can be found in the literature since they have found useful applications in catalysis. 11,[19][20][21] On the contrary, examples of non-chelating bis(NHC)s acting as bridging ligands are relatively scarce. For this purpose, rigid spacers such as -conjugated systems are often used to obtain bis(NHC)s featuring linearly opposed coordination sites.…”

Palladium complexes bearing an N‐heterocyclic carbene–sulfonamide ligand for cooligomerization of ethylene and polar monomers

“…One strategy for developing active catalysts is to replace the phosphine moiety by other stronger σ‐donors such as N‐heterocyclic carbene (NHC) . A variety of bidentate NHC ligands have thus far been investigated in metal‐catalyzed olefin polymerization reactions, including those bearing arenolate, enolate, sulfonate, and pyridine as a counterpart, but few catalysts exhibited activity for olefin/polar monomer copolymerization, presumably due to the short lifetime of the catalysts.…”