Homo‐ and Heterobimetallic Complexes Bearing NHC Ligands: Applications in α‐Arylation of Amide, Suzuki–Miyaura Coupling Reactions, and Tandem Catalysis

Abstract

A heterobimetallic IrIII/PdII complex from a dicarbene donor ligand featuring cyclometalated IrIII and PEPPSI type PdII is presented along with a homodinuclear PEPPSI type PdII complex starting from the same bis‐imidazolium salt. All the PdII complexes are active precatalyst in both α‐arylation and Suzuki–Miyaura coupling reactions. The heterobimetallic IrIII/PdII complex shows much higher yields in tandem C–C coupling/transfer hydrogenation reactions compared to the equimolar mixture of their mononuclear PdII and IrIII counterparts.

Heterobimetallic Carbene Complexes Bearing Cyclometalated IrIII/RhIII and Mixed NHCPy/PPh3 Coordinated PdII Centers: Structures and Tandem Catalysis

“…The reaction of PEPPSI type complexes [3] or [6] [14] with 1.1 equiv. of PPh 3 in acetonitrile resulted in the formation of heterobimetallic complexes [7] or [8] (Scheme 2).…”

“…The corresponding mononuclear cyclometalated Rh III complex [10] and the mononuclear palladium(II) complexes cis-/ trans- [12] have also been synthesized using the similar procedure described in the stepwise synthesis of heterobimetallic complex [7], starting from imidazolium salt 9 [19] (Scheme 3) and the earlier reported mononuclear PEPPSI type complex [11], [14] respectively.…”

“…We have recently demonstrated the synthesis and catalytic tandem reactions of heterobimetallic complex bearing cyclometalated Ir III and PEPPSI type Pd II centers, using the aforementioned synthetic strategy. [14] Here, we present a series of heterobimetallic M III À Pd II (M = Ir, Rh) complexes from a dicarbene donor ligand featuring cyclometalated M III (M = Ir, Rh) and mixed NHC^Py/PPh 3 coordinated Pd II centers along with their tandem catalytic applications and structural diversities. The design of the heterobimetallic complexes was based on the observations that the cyclometalated complexes bearing M III (M = Rh, Ir) are potent catalysts for the transfer hydrogenation reaction for a wide range of organic substrates [15] and Pd II complexes featuring mixed NHC^Py/PPh 3 donor ligands have received wide applicability as catalysts for a wide range of organic transformations.…”

Palladium(0) Nanoparticles Immobilized onto Silica/Starch Composite: Sustainable Catalyst for Hydrogenations and Suzuki Coupling

“…Catalytic cross-coupling reaction of organotin [55][56][57][58], zinc [59],copper [60], boron [61], or magnesium compounds [62][63][64] constitute the most generally applicable strategy for the synthesis of biaryls. Over the past decades, it has continuously been improved and reached an impressive level of performance [65][66][67][68].…”

Possible Synthetic Approaches for Heterobimetallic Complexes by Using nNHC/tzNHC Heteroditopic Carbene Ligands

“…Heterobimetallic catalysis is thus an emerging research area [18], whose development is, however, slowed down by a non-trivial synthetic problem, namely a straightforward and rational synthesis of heterobimetallic complexes. The synthesis and catalytic application of heterobimetallic complexes bearing NHC donors have been reviewed five years ago by Peris and Hahn [18] and more recent examples have been reported by the same authors [19,20,21,22], as well as by other ones [23,24]. Although successful synthetic approaches are present in the literature, the majority of them is not general and works only in specific conditions.…”