scholarly journals Oxidative Addition of Aryl Halides to a Ni(I)-Bipyridine Complex

2022 ◽  
Author(s):  
Stephen Ting ◽  
Wendy Williams ◽  
Abigail Doyle
Keyword(s):  
Oxidative Addition ◽  
Aryl Halides ◽  
Solution Phase ◽  
Nickel Catalysis ◽  
Mechanistic Studies ◽  
Redox Equilibrium ◽  
Aryl Bromides ◽  
First Time

The oxidative addition of aryl halides to bipyridine- or phenanthroline-ligated nickel(I) is a commonly proposed step in nickel catalysis. However, there is a scarcity of complexes of this type that both are well-defined and undergo oxidative addition with aryl halides, hampering organometallic studies of this process. We report the synthesis of a well-defined Ni(I) complex, [(CO2Etbpy)NiCl]4 (1). Its solution-phase speciation is characterized by a significant population of monomer and a redox equilibrium that can be perturbed by π-acceptors and σ-donors. 1 reacts readily with aryl bromides, and mechanistic studies are consistent with a mechanism proceeding through an initial Ni(I) → Ni(III) oxidative addition. Such a process was demonstrated stoichiometrically for the first time, affording a structurally characterized Ni(III) aryl complex.

scholarly journals Overcoming Limitations in Dual Photoredox/Nickel catalyzed C–N Cross-Couplings due to Catalyst Deactivation

2019 ◽  
Author(s):  
Sebastian Gisbertz ◽  
Susanne Reischauer ◽  
Bartholomäus Pieber
Keyword(s):  
Carbon Nitride ◽  
Catalyst Deactivation ◽  
Aryl Halides ◽  
Attractive Alternative ◽  
Nickel Catalysis ◽  
Broad Absorption ◽  
Aryl Bromides ◽  
Nitride Semiconductor ◽  
Palladium Catalyzed ◽  
High Concentrations

Dual photoreodox/nickel catalyzed C–N cross-couplings are an attractive alternative to the palladium catalyzed Buchwald-Hartwig reaction, but are limited to aryl halides containing electron-withdrawing groups. We show that the formation of catalytically inactive nickel-black is responsible for this limitation. Deposition of nickel-black further deactivates heterogeneous photocatalysts restricting their recyclability. We demonstrate that catalyst deactivation can be avoided by the combination of nickel catalysis and a carbon nitride semiconductor. The broad absorption range of the organic, heterogeneous photocatalyst enables a wavelength dependent reactivity control to prevent nickel-black formation. A second approach is to run the reactions at high concentrations to increase the formation of nickel-amine complexes that reduce nickel-black formation. This allows reproducible, selective C–N cross-couplings of electron-rich aryl bromides.<br>

scholarly journals The catalytic mechanism of the Suzuki-Miyaura reaction

2021 ◽  
Author(s):  
Juliet macharia ◽  
Chetan Joshi ◽  
Joseph Izzo ◽  
Victor Wambua ◽  
Sungjin Kim ◽  
...  
Keyword(s):  
Catalytic Mechanism ◽  
Palladium Complex ◽  
Isotope Effects ◽  
Oxidative Addition ◽  
Kinetic Isotope Effects ◽  
Boronic Acids ◽  
Aryl Halides ◽  
Kinetic Isotope ◽  
Aryl Bromides ◽  
Insight Into

Abstract: Experimental and theoretical 13C kinetic isotope effects are utilized to obtain atomistic insight into the catalytic mechanism of the Pd(PPh3)4 catalyzed Suzuki-Miyaura reaction of aryl halides and aryl boronic acids. Under catalytic conditions, we establish that oxidative addition of aryl bromides occurs to a 12-electron monoligated palladium complex (Pd(PPh3)). For aryl iodides, the first irreversible step in the catalytic cycle precedes oxidative addition and is shown to be binding of the iodoarene to Pd(PPh3). Our results suggest that the commonly proposed oxidative addition to the 14-electron Pd(PPh3)2 complex can occur only in the presence of excess added ligand or under stoichiometric conditions. The transmetalation step, under catalytic conditions, is shown to proceed via a tetracoordinate boronate (8B4) intermediate with a Pd-O-B linkage.

Transition-Metal-Catalyzed Hydroxylation Reaction of Aryl Halide for the Synthesis of Phenols

Synlett ◽  
2021 ◽  
Author(s):  
D. Xue ◽  
L. Yang
Keyword(s):  
Transition Metal ◽  
Aryl Halide ◽  
High Reactivity ◽  
Aryl Halides ◽  
Biologically Active ◽  
Nickel Catalysis ◽  
Aryl Chlorides ◽  
Aryl Bromides ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

AbstractPhenols are important components of pharmaceuticals, biologically active natural products, and materials. Here, we briefly discuss recent advances in catalytic hydroxylation reactions for the synthesis of phenols, with particular attention to our recent work. H2O is proved to be an efficient hydroxide reagent in converting (hetero)aryl halides into the corresponding phenols under synergistic organophotoredox and nickel catalysis. Aryl bromides as well as less reactive aryl chlorides show high reactivity in this catalytic system. This methodology can be applied to the efficient synthesis of diverse phenols and allows the hydroxylation of multifunctional pharmaceutically relevant aryl halides.1 Introduction2 Representative Methods for Transition-Metal-Catalyzed Hydroxylation of (Hetero)Aryl Halides3 Organophotoredox/Ni Dual Catalytic Hydroxylation of Aryl Halides with Water4 Summary and Outlook

scholarly journals Overcoming Limitations in Dual Photoredox/Nickel catalyzed C–N Cross-Couplings due to Catalyst Deactivation

2019 ◽  
Author(s):  
Sebastian Gisbertz ◽  
Susanne Reischauer ◽  
Bartholomäus Pieber
Keyword(s):  
Carbon Nitride ◽  
Catalyst Deactivation ◽  
Aryl Halides ◽  
Attractive Alternative ◽  
Nickel Catalysis ◽  
Broad Absorption ◽  
Aryl Bromides ◽  
Nitride Semiconductor ◽  
Palladium Catalyzed ◽  
High Concentrations

Dual photoreodox/nickel catalyzed C–N cross-couplings are an attractive alternative to the palladium catalyzed Buchwald-Hartwig reaction, but are limited to aryl halides containing electron-withdrawing groups. We show that the formation of catalytically inactive nickel-black is responsible for this limitation. Deposition of nickel-black further deactivates heterogeneous photocatalysts restricting their recyclability. We demonstrate that catalyst deactivation can be avoided by the combination of nickel catalysis and a carbon nitride semiconductor. The broad absorption range of the organic, heterogeneous photocatalyst enables a wavelength dependent reactivity control to prevent nickel-black formation. A second approach is to run the reactions at high concentrations to increase the formation of nickel-amine complexes that reduce nickel-black formation. This allows reproducible, selective C–N cross-couplings of electron-rich aryl bromides.<br>

scholarly journals Mechanistic Studies of the Oxidative Addition of Aryl Halides to Ni(0) Centers Bearing Phosphine Ligands

2020 ◽  
Vol 74 (6) ◽  
pp. 495-498
Author(s):  
Pablo Marcelo Pérez-García ◽  
Marc-Etienne Moret
Keyword(s):  
Significant Influence ◽  
Oxidative Addition ◽  
Cross Coupling ◽  
Phosphine Ligands ◽  
Aryl Halides ◽  
Entry Point ◽  
Mechanistic Studies ◽  
Recent Advances ◽  
Mechanistic Understanding ◽  
Catalytic Cycles

The oxidative addition of aryl halides is a common entry point in catalytic cycles for cross-coupling and related reactions. In the case of phosphine-supported nickel(0) fragments, the formation of reactive Ni(ii)–aryl products often competes with the production of Ni(i) species. Here, recent advances in the mechanistic understanding of these reactions are highlighted. In particular, the denticity of the supporting ligand has a significant influence on the outcome of the reaction.

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