Elucidating the Mechanism of Excited-State Bond Homolysis in Nickel–Bipyridine Photoredox Catalysts

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(14), С. 6516 - 6531

Опубликована: Март 30, 2022

Ni 2,2'-bipyridine (bpy) complexes are commonly employed photoredox catalysts of bond-forming reactions in organic chemistry. However, the mechanisms by which they operate still under investigation. One potential mode catalysis is via entry into Ni(I)/Ni(III) cycles, can be made possible light-induced, excited-state Ni(II)-C bond homolysis. Here, we report experimental and computational analyses a library Ni(II)-bpy aryl halide complexes, Ni(Rbpy)(R'Ph)Cl (R = MeO, t-Bu, H, MeOOC; R' CH3, OMe, F, CF3), to illuminate mechanism At given excitation wavelengths, photochemical homolysis rate constants span 2 orders magnitude across these structures correlate linearly with Hammett parameters both bpy ligands, reflecting structural control over key metal-to-ligand charge-transfer (MLCT) ligand-to-metal (LMCT) energy surfaces (PESs). Temperature- wavelength-dependent investigations reveal moderate barriers (ΔH‡ ∼ 4 kcal mol-1) minimum threshold (∼55 mol-1, 525 nm), respectively. Correlations electronic structure calculations further support repulsive triplet PESs featuring critical aryl-to-Ni LMCT lead rupture. Structural provides rational approach utilize photonic leverage processes synthetic

Язык: Английский

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Nickel Meets Aryl Thianthrenium Salts: Ni(I)-Catalyzed Halogenation of Arenes

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(18), С. 9988 - 9993

Опубликована: Май 1, 2023

Herein, a regioselective, late-stage two-step arene halogenation method is reported. We propose how unusual Ni(I)/(III) catalysis enabled by combination of aryl thianthrenium and Ni redox properties that hitherto unachieved with other (pseudo)halides. The catalyst accessed in situ from inexpensive NiCl2·6(H2O) zinc without the need supporting ligands.

Язык: Английский

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Interrogating the Mechanistic Features of Ni(I)-Mediated Aryl Iodide Oxidative Addition Using Electroanalytical and Statistical Modeling Techniques

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(15), С. 8689 - 8699

Опубликована: Апрель 4, 2023

While the oxidative addition of Ni(I) to aryl iodides has been commonly proposed in catalytic methods, an in-depth mechanistic understanding this fundamental process is still lacking. Herein, we describe a detailed study using electroanalytical and statistical modeling techniques. Electroanalytical techniques allowed rapid measurement rates for diverse set iodide substrates four classes catalytically relevant complexes (Ni(MeBPy), Ni(MePhen), Ni(Terpy), Ni(BPP)). With >200 experimental rate measurements, were able identify essential electronic steric factors impacting through multivariate linear regression models. This led classification mechanisms, either three-center concerted or halogen-atom abstraction pathway based on ligand type. A global heat map predicted was created shown applicable better reaction outcome case Ni-catalyzed coupling reaction.

Язык: Английский

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General cross-coupling reactions with adaptive dynamic homogeneous catalysis

Nature, Год журнала: 2023, Номер unknown

Опубликована: Июнь 14, 2023

Язык: Английский

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Mechanisms of Photoredox Catalysis Featuring Nickel–Bipyridine Complexes

ACS Catalysis, Год журнала: 2024, Номер 14(11), С. 9055 - 9076

Опубликована: Май 29, 2024

Metallaphotoredox catalysis can unlock useful pathways for transforming organic reactants into desirable products, largely due to the conversion of photon energy chemical potential drive redox and bond transformation processes. Despite importance these processes cross-coupling reactions other transformations, their mechanistic details are only superficially understood. In this review, we have provided a detailed summary various photoredox mechanisms that been proposed date Ni-bipyridine (bpy) complexes, focusing separately on photosensitized direct excitation reaction By highlighting multiple key findings, depict how mechanisms, which ultimately define substrate scope, themselves defined by ground- excited-state geometric electronic structures Ni-based intermediates. We further identify knowledge gaps motivate future studies development synergistic research approaches spanning physical, organic, inorganic chemistry communities.

Язык: Английский

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C–heteroatom coupling with electron-rich aryls enabled by nickel catalysis and light

Nature Catalysis, Год журнала: 2024, Номер 7(6), С. 733 - 741

Опубликована: Май 7, 2024

Abstract Nickel photoredox catalysis has resulted in a rich development of transition-metal-catalysed transformations for carbon–heteroatom bond formation. By harnessing light energy, the transition metal can attain oxidation states that are difficult to achieve through thermal chemistry catalytic manifold. For example, nickel reactions have been reported both synthesis anilines and aryl ethers from aryl(pseudo)halides. However, oxidative addition simple systems is often sluggish absence special, electron-rich ligands, leading catalyst decomposition. Electron-rich electrophiles therefore currently fall outside scope many field. Here we provide conceptual solution this problem demonstrate nickel-catalysed C–heteroatom bond-forming arylthianthrenium salts, including amination, oxygenation, sulfuration halogenation. Because redox properties salts primarily dictated by thianthrenium, highly donors be unlocked using NiCl 2 under irradiation form desired C‒heteroatom bonds.

Язык: Английский

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Nickel-mediated aerobic C(sp2)–nucleophile coupling reactions for late-stage diversification of aryl electrophiles

Nature Synthesis, Год журнала: 2025, Номер unknown

Опубликована: Янв. 16, 2025

Язык: Английский

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Catalysis in the Excited State: Bringing Innate Transition Metal Photochemistry into Play

ACS Catalysis, Год журнала: 2025, Номер unknown, С. 4665 - 4680

Опубликована: Март 5, 2025

Transition metal catalysis is an indispensable tool for organic synthesis that has been harnessed, modulated, and perfected many decades by careful selection of centers ligands, giving rise to synthetic methods with unparalleled efficiency chemoselectivity. Recent developments have demonstrated how light irradiation can also be recruited as a powerful dramatically alter the outcome catalytic reactions, providing access innovative pathways remarkable potential. In this context, adoption photochemical conditions mainstream strategy drive reactions unveiled exciting opportunities exploit rich excited-state framework transition metals applications. This Perspective examines advances in application complexes standalone photocatalysts, exploiting innate reactivity their excited states beyond common use photoredox catalysts. An account relevant examples dissected provide discussion on electronic reorganization, orbitals involved, associated different types states. analysis aims practitioners fundamental principles guiding strategies understand, design, apply light-activation homogeneous synthesis.

Язык: Английский

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Nickel-Coordinated Carbon Nitride as a Metallaphotoredox Platform for the Cross-Coupling of Aryl Halides with Alcohols

ACS Catalysis, Год журнала: 2020, Номер 10(24), С. 15178 - 15185

Опубликована: Дек. 9, 2020

Light-driven dual catalysis that combines photosensitizers and transition-metal complexes has become a powerful approach for diverse cross-coupling reactions. Heterogeneous photocatalysts recently have gained growing attention to build such catalytic system controllable reaction kinetics enhanced activity. Incorporating metal catalyst into the framework of photocatalyst could endow unique metallaphotoredox platforms. Herein, we assemble carbon nitride nickel (C3N4–Ni) via direct coordination Ni2+ C3N4 nitrogen, visible-light-driven carbon–oxygen cross-coupling. By operating with an imidazole auxiliary ligand, C3N4–Ni efficiently catalyzed etherification variety aryl bromides alcohols or hydroxylation water, exhibiting turnover numbers >500. Ni maintained as isolated single site without aggregation after photoreaction recovered demonstrate sustained activity additional loading. Our work signifies potential uniting in well-designed sensitizer–metal architecture complex organic transformations.

Язык: Английский

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The Application of Pulse Radiolysis to the Study of Ni(I) Intermediates in Ni-Catalyzed Cross-Coupling Reactions

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(25), С. 9332 - 9337

Опубликована: Июнь 15, 2021

Here we report the use of pulse radiolysis and spectroelectrochemistry to generate low-valent nickel intermediates relevant synthetically important Ni-catalyzed cross-coupling reactions interrogate their reactivities toward comproportionation oxidative addition processes. Pulse provided a direct means singly reduced [(dtbbpy)NiBr], enabling identification rapid Ni(0)/Ni(II) process taking place under electrolysis conditions. This approach also permitted measurement Ni(I) rates with electronically differentiated aryl iodide electrophiles (kOA = 1.3 × 104–2.4 105 M–1 s–1), an elementary organometallic step often proposed in nickel-catalyzed reactions. Together, these results hold implications for number

Язык: Английский

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