The nature of Pd–carbene and Pd–halogen bonds in (bisNHC)PdX₂ type catalysts: insights from density functional theory

Abstract

Pd–carbene and Pd–halogen play a key role in the catalytic activity of (bisNHC)PdX2 complexes and they can be fine-tuned with proper substitution in the carbene moiety and choosing a weakly coordinating halide ion.

Pd‐PEPPSI‐IPent‐SiO2: A Supported Catalyst for Challenging Negishi Coupling Reactions in Flow

“…[11] Forthe most difficult and selective cross-couplings, the ligandsa rchitecture has become necessarily larger and more complex, [2][3][4][5][6] which had in turn made attempts to alter the preparation of such ligands to contain alinker, to affix the ligand to as urface,c onsiderably more difficult. TheP d À Cb ond is much stronger than the Pd À P bond, [14] meaning that carbenes are more likely to remain affixed to the metal throughout catalysis.C onversely,p hosphines readily come on and off the metal, and thus explains why excess ligand is often used in catalysis applications to avoid the metal blacking out. TheP d À Cb ond is much stronger than the Pd À P bond, [14] meaning that carbenes are more likely to remain affixed to the metal throughout catalysis.C onversely,p hosphines readily come on and off the metal, and thus explains why excess ligand is often used in catalysis applications to avoid the metal blacking out.…”

“…[11a, 12, 13] Also, there is concern over metal ligation, that is,whether the metal is loaded on the ligand prior to binding of the complex to the surface,w hich may cause the metal to become dislodged, or after ligand attachment, which is now ah eterogeneous reaction. TheP d À Cb ond is much stronger than the Pd À P bond, [14] meaning that carbenes are more likely to remain affixed to the metal throughout catalysis.C onversely,p hosphines readily come on and off the metal, and thus explains why excess ligand is often used in catalysis applications to avoid the metal blacking out. This ready complexation/ decomplexation would be as ignificant disadvantage for flow chemistry as the metal will be swept down and eventually completely out of the catalyst bed.…”

In situ XAS study of the local structure and oxidation state evolution of palladium in a reduced graphene oxide supported Pd(ii) carbene complex during an undirected C–H acetoxylation reaction

“…In this system the only strong electron-pair donor to Pd in 1@rGO is the NHC ligand and the Pd-NHC bond is very stable with a calculated bond energy of 45-50 kcal mol −1 . 36 Therefore, it is expected to remain bound to Pd during the reaction. Furthermore, the 1@rGO catalyst showed good recyclability and could be reused up to four runs with only slight decrease in the activity which attests to the stable Pd-C(NHC) bond.…”

Pd‐PEPPSI‐IPent‐SiO2: A Supported Catalyst for Challenging Negishi Coupling Reactions in Flow

“…Also, there is concern over metal ligation, that is, whether the metal is loaded on the ligand prior to binding of the complex to the surface, which may cause the metal to become dislodged, or after ligand attachment, which is now a heterogeneous reaction. The Pd−C bond is much stronger than the Pd−P bond, meaning that carbenes are more likely to remain affixed to the metal throughout catalysis. Conversely, phosphines readily come on and off the metal, and thus explains why excess ligand is often used in catalysis applications to avoid the metal blacking out.…”