Mechanisms of Photoredox Catalysis Featuring Nickel–Bipyridine Complexes

ACS Catalysis, Journal Year: 2024, Volume and Issue: 14(11), P. 9055 - 9076

Published: May 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.

Language: Английский

---

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

ACS Catalysis, Journal Year: 2025, Volume and Issue: unknown, P. 4665 - 4680

Published: March 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.

Language: Английский

---

Leveraging the Redox Promiscuity of Nickel To Catalyze C–N Coupling Reactions

The Journal of Organic Chemistry, Journal Year: 2024, Volume and Issue: unknown

Published: Jan. 17, 2024

This perspective details advances made in the field of Ni-catalyzed C–N bond formation. The use this Earth abundant metal to decorate amines, amides, lactams, and heterocycles enables direct access a variety biologically active industrially relevant compounds sustainable manner. Herein, different strategies that leverage propensity Ni facilitate both one- two-electron processes will be surveyed. first part Perspective focuses on couplings at room temperature by accessing oxidized Ni(III) intermediates. In context, photochemical, electrochemical, chemically mediated analyzed. A special emphasis has been put providing comprehensive explanation mechanistic avenues have proposed these chemistries; either Ni(I/III) self-sustained cycles or Ni(0/II/III) photochemically pathways. second ligand designs also enable reactivity via Ni(0/II) mechanism. Finally, we discuss our thoughts possible future directions field.

Language: Английский

---

Ultrafast Photophysics of Ni(I)–Bipyridine Halide Complexes: Spanning the Marcus Normal and Inverted Regimes

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(22), P. 15506 - 15514

Published: May 22, 2024

Owing to their light-harvesting properties, nickel–bipyridine (bpy) complexes have found wide use in metallaphotoredox cross-coupling reactions. Key these transformations are Ni(I)–bpy halide intermediates that absorb a significant fraction of light at relevant reaction irradiation wavelengths. Herein, we report ultrafast transient absorption (TA) spectroscopy on library eight complexes, the first such characterization any Ni(I) species. The TA data reveal formation and decay Ni(I)-to-bpy metal-to-ligand charge transfer (MLCT) excited states (10–30 ps) whose relaxation dynamics well described by vibronic Marcus theory, spanning normal inverted regions as result simple changes bpy substituents. While lifetimes relatively long for MLCT first-row transition metal duration precludes excited-state bimolecular reactivity photoredox We also present one-step method generate an isolable, solid-state species, which decouples light-initiated from dark, thermal cycles catalysis.

Language: Английский

---

Mechanistic Evidence of a Ni(0/II/III) Cycle for Nickel Photoredox Amide Arylation

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(43)

Published: Sept. 9, 2023

This work demonstrates the dominance of a Ni(0/II/III) cycle for Ni-photoredox amide arylation, which contrasts with other C-heteroatom couplings that operate via Ni(I/III) self-sustained cycles. The kinetic data gathered when using different Ni precatalysts supports an initial Ni(0)-mediated oxidative addition into aryl bromide. Using NiCl2 as precatalyst resulted in observable induction period, was found to arise from photochemical activation event generate Ni(0) and be prolonged by unproductive comproportionation between Ni(II) situ generated active species. Ligand exchange after yields amido complex, identified catalyst resting state reaction. Stoichiometric experiments showed oxidation this intermediate required yield functionalized products. presented rate-limiting photochemically-mediated Ni(II/III) enable C-N reductive elimination. An alternative manifold discarded based on EPR measurements. mechanistic insights uncovered herein will inform community how subtle changes reaction conditions may impact pathway, have enabled us include chlorides coupling partners reduce loading 20-fold without any reactivity loss.

Language: Английский

---

Unified Photocatalytic Strategy for the Cross-Coupling of Alcohols with Aryl Halides Enabled by Synergistic Nickel and Iron LMCT Catalysis

ACS Catalysis, Journal Year: 2024, Volume and Issue: 14(17), P. 12757 - 12768

Published: Aug. 9, 2024

The use of alcohol feedstock as a coupling partner in cross-coupling reactions offers an extraordinary potential for the efficient synthesis Csp3-rich complex molecular scaffolds. This prominent strategy relies on generation alkoxy radicals, which can react via various radical pathways to give carbon-centered radicals that be engaged C–C bond formation reactions. However, involving catalytic directly from native alcohols are highly challenging and scope existing methods remains particularly limited. Moreover, unified incorporate broad range with aryl halides is currently unavailable. Herein, we report general photocatalytic platform combines nickel iron ligand-to-metal charge transfer (LMCT) catalysis selective deconstructive Csp3–Csp3 cleavage arylation unactivated alcohols. protocol leverages ability photoinduced LMCT generate diversely substituted alcohols, enabling implementation bond-forming manifolds. These include dehydroxymethylative aliphatic remote cyclic yield alkyl ketones, methylation using tertiary methyl source. methodology practical engaging large variety commercially available under mild conditions, abundant catalysts. Mechanistic studies, including stoichiometric organometallic chemistry voltammetry, provide insights into crucial role ancillary ligand surrounding catalyst stabilizing both low- high-valent intermediates.

Language: Английский

---

Advances in Nickel-Catalyzed O-Arylation of Aliphatic Alcohols and Phenols with (Hetero)aryl Electrophiles

Synthesis, Journal Year: 2023, Volume and Issue: 56(02), P. 229 - 238

Published: July 20, 2023

Abstract Transition-metal catalysis has been consequential in enabling carbon–heteroatom bond-forming reactions. Recent breakthroughs Ni-catalyzed cross-couplings have offered competitive and, some cases, superior reactivity to Pd- or Cu-based processes. Amidst the ongoing renaissance this field, C–O cross-coupling of alcohols and (hetero)aryl (pseudo)halides surfaced as an effective strategy for synthesis ethers. Methodologies achieve such transformations tend rely on one three catalytic approaches: (i) thermal conditions often accompanied by ancillary ligand design tailored Ni catalysis; (ii) synergistic combination photoredox (iii) electrochemically driven catalysis. In instances, these protocols provided access expanded substrate scope, including use inexpensive abundant electrophile coupling partners (e.g., chlorides). This Short Review aims summarize recent progress development O-arylations primary, secondary, tertiary aliphatic alcohols, well phenols, with electrophiles. 1 Introduction 2 Thermally Promoted Cross-Coupling 2.1 Primary Secondary Aliphatic Alcohols 2.2 Tertiary 2.3 Phenols 3 Photochemically 3.1 3.2 4 Electrochemically 4.1 5 Conclusions Outlook

Language: Английский

---

Electrolysis in thin layer: A technique for electroanalytical and electrosynthetic applications

Current Opinion in Electrochemistry, Journal Year: 2024, Volume and Issue: 44, P. 101445 - 101445

Published: Feb. 7, 2024

Language: Английский

---

Mechanistic Insights into the Visible-Light-Driven O–Arylation of Carboxylic Acids Catalyzed by Xanthine-Based Nickel Complexes

Chemical Science, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

Experimental and theoretical investigations were conducted to gain insight into the mechanism of light-driven Ni-catalyzed arylation carboxylates.

Language: Английский

---

Brønsted Acid-Facilitated Thioetherification Cross-Coupling Reactions with Nickel and Visible Light

ACS Catalysis, Journal Year: 2025, Volume and Issue: 15(3), P. 1467 - 1476

Published: Jan. 9, 2025

Transition metal-catalyzed cross-coupling reactions are essential in modern organic synthesis, facilitating the rapid creation of complex molecular structures. Traditionally, these rely heavily on conventional bases, with only a few exceptions reported. Recently, we developed adaptive dynamic homogeneous catalysis (AD-HoC), method that enables C(sp2)–S cross-couplings without needing traditional ligands, or additives. Given growing demand for protocols compatible acidic conditions cross-couplings, revisited AD-HoC to pioneer acid-facilitated transition thioetherification. Our swift synthesis thioethers using nickel and visible light, substoichiometric amount Brønsted acid acting as an enabler. NMR kinetic studies indicate absence acid, system displays induction period characteristic autocatalysis. Introducing simple additive eliminates this significantly accelerates reaction. Moreover, protocol has been successfully scaled gram-level continuous flow technology, achieving productivities over 100 g per hour commercially available lab-scale photoreactor. This highlights method's robustness scalability, making it powerful tool large-scale applications.

Language: Английский

---