Aryl–Fluoride Bond-Forming Reductive Elimination from Nickel(IV) Centers

Meucci, Elizabeth A.; Ariafard, Alireza; Canty, Allan J.; Kampf, Jeff W.; Sanford, Melanie S.

doi:10.1021/jacs.9b06896

Cited by 46 publications

(33 citation statements)

References 73 publications

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“… 1 Nickel couplings are hence believed to go through higher-valent intermediates, 2 , 3 accessed by stoichiometric redox modulators, such that the RE is more favorable. 4 , 5 …”

Section: Introductionmentioning

confidence: 99%

Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carboxylate O-Arylations

et al. 2020

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Dual photocatalysis and nickel catalysis can effect cross-coupling under mild conditions, but little is known about the in situ kinetics of this class of reactions. We report a comprehensive kinetic examination of a model carboxylate O -arylation, comparing a state-of-the-art homogeneous photocatalyst (Ir(ppy) 3 ) with a competitive heterogeneous photocatalyst (graphitic carbon nitride). Experimental conditions were adjusted such that the nickel catalytic cycle is saturated with excited photocatalyst. This approach was designed to remove the role of the photocatalyst, by which only the intrinsic behaviors of the nickel catalytic cycles are observed. The two reactions did not display identical kinetics. Ir(ppy) 3 deactivates the nickel catalytic cycle and creates more dehalogenated side product. Kinetic data for the reaction using Ir(ppy) 3 supports a turnover-limiting reductive elimination. Graphitic carbon nitride gave higher selectivity, even at high photocatalyst-to-nickel ratios. The heterogeneous reaction also showed a rate dependence on aryl halide, indicating that oxidative addition plays a role in rate determination. The results argue against the current mechanistic hypothesis, which states that the photocatalyst is only involved to trigger reductive elimination.

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“… 1 Nickel couplings are hence believed to go through higher-valent intermediates, 2 , 3 accessed by stoichiometric redox modulators, such that the RE is more favorable. 4 , 5 …”

Section: Introductionmentioning

confidence: 99%

Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carboxylate O-Arylations

et al. 2020

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“…1 Nickel couplings are hence believed to go through highervalent intermediates, [2][3] accessed by stoichiometric redox modulators, such that the RE is more favorable. [4][5] The combination of photocatalysis with nickel catalysis has provided an elegant pathway by which nickel can turn over without adding excessive reductants or harsh conditions. [6][7] Iridium polypyridyl complexes were found to act as photocatalysts (PCs) to effect C-N, C-O, and C-C couplings using nickel(II) precatalysts.…”

Section: Introductionmentioning

confidence: 99%

Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carboxylate O-Arylations

Malik¹,

Madani²,

Pieber³

et al. 2020

Preprint

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In this study we use in situ infrared tracking to describe the kinetics of dual photo- and nickel-catalyzed carboxylate O-arylations. We examined both a state-of-the-art homogeneous (Ir(ppy)<sub>3</sub>) and heterogeneous (graphitic carbon nitride) photocatalyst, comparing their kinetics to each other, and to the existing mechanistic proposal. We argue against the current hypothesis, specifically that the photocatalyst is only involved to trigger a rate-limiting reductive elimination.<br>

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“…Aromatic fluorination enabled by Ni III -F intermediates. Adapted from reference[102].A Ni IV -F compound which enables aromatic fluorination has been recently reported (Scheme 25)[103]. The Ni II complex 97 bearing the potentially tridentate tris(pyrazolyl)borate ligand (Tp) was reacted with selectfluor to afford the diamagnetic aryl-Ni IV -F species 98 in ca.…”

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confidence: 99%

High-Valent NiIII and NiIV Species Relevant to C–C and C–Heteroatom Cross-Coupling Reactions: State of the Art

Nebra

2020

Molecules

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Ni catalysis constitutes an active research arena with notable applications in diverse fields. By analogy with its parent element palladium, Ni catalysts provide an appealing entry to build molecular complexity via cross-coupling reactions. While Pd catalysts typically involve a M0/MII redox scenario, in the case of Ni congeners the mechanistic elucidation becomes more challenging due to their innate properties (like enhanced reactivity, propensity to undergo single electron transformations vs. 2e− redox sequences or weaker M–Ligand interaction). In recent years, mechanistic studies have demonstrated the participation of high-valent NiIII and NiIV species in a plethora of cross-coupling events, thus accessing novel synthetic schemes and unprecedented transformations. This comprehensive review collects the main contributions effected within this topic, and focuses on the key role of isolated and/or spectroscopically identified NiIII and NiIV complexes. Amongst other transformations, the resulting NiIII and NiIV compounds have efficiently accomplished: i) C–C and C–heteroatom bond formation; ii) C–H bond functionalization; and iii) N–N and C–N cyclizative couplings to forge heterocycles.

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Aryl–Fluoride Bond-Forming Reductive Elimination from Nickel(IV) Centers

Cited by 46 publications

References 73 publications

Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carboxylate O-Arylations

Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carboxylate O-Arylations

Evidence for Photocatalyst Involvement in Oxidative Additions of Nickel-Catalyzed Carboxylate O-Arylations

High-Valent NiIII and NiIV Species Relevant to C–C and C–Heteroatom Cross-Coupling Reactions: State of the Art

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