Carbon–Fluorine Reductive Elimination from Nickel(III) Complexes

Lee, Hee Jun; Ritter, Tobias

doi:10.1002/ange.201701552

Cited by 24 publications

(5 citation statements)

References 48 publications

(35 reference statements)

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“…More recently, Ritter has shown that the stoichiometric reaction of the Ni II model complex A with Selectfluor affords a transient Ni III (aryl)(F) species with proposed structure B (Figure 1A). 17 Recent work from our group has shown that multidentate pyridine-and pyrazole-containing ligands support organometallic Ni III and Ni IV complexes that participate in challenging reductive elimination reactions, including C-(sp 3 )−heteroatom and C(sp 2 )−CF 3 couplings. 18−20 We hypothesized that analogous ligand systems might enable the isolation and reactivity studies of high-valent Ni(σaryl)(F) intermediates.…”

Section: ■ Introductionmentioning

confidence: 99%

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

et al. 2019

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The treatment of pyridine-and pyrazole-ligated Ni II σaryl complexes with Selectfluor results in C(sp 2 )−F bond formation under mild conditions. With appropriate design of supporting ligands, diamagnetic Ni IV σ-aryl fluoride intermediates can be detected spectroscopically and/or isolated during these transformations. These studies demonstrate for the first time that Ni IV σ-aryl fluoride complexes participate in challenging C(sp 2 )−F bond-forming reductive elimination to yield aryl fluoride products.

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Section: ■ Introductionmentioning

confidence: 99%

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

et al. 2019

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“…27 The g-values of the axial signal closely matched those reported for other Ni III species in literature, strongly suggesting the formation of a Ni III -centered radical upon irradiation. [28][29][30][31] In contrast, despite several attempts, we were unable to detect or trap ethyl radicals derived from 1a (see Section 6.6 in Supplementary Information). Furthermore, several representative reactions were conducted in the presence of an excess of butylated hydroxytoluene (BHT), a well-known radical scavenger.…”

Section: Mechanistic Investigationmentioning

confidence: 77%

Rapid and Scalable Photocatalytic C(sp2)–C(sp3) Suzuki−Miyaura Cross-Coupling of Aryl Bromides with Alkyl Boranes

Wan

Capaldo

Djossou

et al. 2023

Preprint

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In recent years, there has been a growing demand for drug design approaches that incorporate a higher number of sp3-hybridized carbons, necessitating the development of innovative cross-coupling strategies to reliably introduce aliphatic fragments. Here, we present a novel and powerful approach for the light-mediated B-alkyl Suzuki−Miyaura cross-coupling between alkyl boranes and aryl bromides. Alkyl boranes can be easily generated via hydroboration from readily available alkenes, exhibiting excellent regioselectivity and enabling the selective transfer of a diverse range of primary alkyl fragments onto the arene ring. This methodology eliminates the need for expensive catalytic systems and sensitive organometallic compounds, operating efficiently at room temperature within just 30 minutes. Interestingly, our mechanistic studies reveal an unexpected mechanistic scenario that operates through transmetalation rather than alkyl radical formation, setting it apart from established metallaphotoredox protocols. Moreover, we demonstrate the advantageous translation of the present protocol to continuous-flow conditions, enhancing scalability, safety, and overall efficiency of the method. This versatile approach offers significant potential for accelerating drug discovery efforts by enabling the introduction of complex aliphatic fragments in a straightforward and reliable manner.

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“…The magnitude of the hyperfine splitting with axial 19 F is consistent with EPR data reported for other Ni(III) complexes with Ni−F bonds. 57 To further test our hypothesis regarding the coordinationinduced valence tautomerism, we performed two experiments: ( S42). In contrast, the room-temperature EPR spectrum for 1[BF 4 ] with pyridine still shows only an isotropic resonance at g ∼ 2 (Figure S37).…”

Section: Synthesis and Characterization Of Ni(ii) Complexesmentioning

confidence: 98%

The Influence of Redox-Innocent Donor Groups in Tetradentate Ligands Derived from o-Phenylenediamine: Electronic Structure Investigations with Nickel

et al. 2019

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The continued development of redox-active ligands requires an understanding as to how ligand modifications and related factors affect the locus of redox activity and spin density in metal complexes. Here we describe the synthesis, characterization, and electronic structure of nickel complexes containing triaryl NNNN (1) and SNNS (2) ligands derived from o-phenylenediamine. The tetradentate ligands in 1 and 2 were investigated and compared to those in metal complexes with compositionally similar ligands to determine how ligand-centered redox properties change when redox-active flanking groups are replaced with redox-innocent NMe 2 or SMe. A derivative of 2 in which the phenylene backbone was replaced with ethylene (3) was also prepared to interrogate the importance of o-phenylenediamine for ligand-centered redox activity. Cyclic voltammograms collected for 1 and 2 revealed two fully reversible ligand-centered redox events. Remarkably, several quasireversible ligand-centered redox waves were also observed for 3 despite the absence of the o-phenylenediamine subunit. Oxidizing 1 and 2 with silver salts containing different counteranions (BF 4 − , OTf − , NTf 2 − ) allowed the electrochemically generated complexes to be analyzed as a function of different oxidation states using single-crystal X-ray diffraction (XRD), EPR spectroscopy, and S K-edge X-ray absorption spectroscopy. The experimental data are corroborated by DFT calculations, and together, they reveal how the location of unpaired spin density and electronic structure in singly and doubly oxidized salts of 1 and 2 varies depending on the coordinating ability of the counteranions and exogenous ligands such as pyridine.

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Carbon–Fluorine Reductive Elimination from Nickel(III) Complexes

Cited by 24 publications

References 48 publications

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

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

Rapid and Scalable Photocatalytic C(sp2)–C(sp3) Suzuki−Miyaura Cross-Coupling of Aryl Bromides with Alkyl Boranes

The Influence of Redox-Innocent Donor Groups in Tetradentate Ligands Derived from o-Phenylenediamine: Electronic Structure Investigations with Nickel

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