Evaluating a Dispersion of Sodium in Sodium Chloride for the Synthesis of Low‐Valent Nickel Complexes**

Humphrey, Elliot L. B. Johnson; Kennedy, Alan R.; Sproules, Stephen; Nelson, David J.

doi:10.1002/ejic.202101006

Cited by 8 publications

(12 citation statements)

References 61 publications

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“…The observed g iso value is 2.211, which is also consistent with the prior reports. 19,25,63,64 Overall, both EPR spectra are consistent with monomeric d 9 Ni I complexes, as observed by SCXRD.…”

Section: Implications Of Bulky Monophosphine Speciation At Ni I In Cr...supporting

confidence: 83%

“…Thorough investigation of a chemical process that may occur upon freezing has not been conducted, as spin relaxation for 18 is sufficiently long to observe a room-temperature spectrum. The observed g iso value is 2.211, which is also consistent with the prior reports. ,,, Overall, both EPR spectra are consistent with monomeric d 9 Ni I complexes, as observed by SCXRD.…”

Section: Resultsmentioning

confidence: 99%

“…The spectrum of a frozen toluene solution contained 17 features, no resolved hyperfine splitting, and an observed value of g avg = 2.261, which is similar to the previous reports of well-defined monomeric (bpy/phen)Ni I (halide) complexes (g avg = 2.19−2.24). 19,25,63,64 For 18, a color change from dark green to red was observed upon freezing in both 2-MeTHF and toluene, and the spectra exhibited abnormal line shape (see Supporting Information). Thorough investigation of a chemical process that may occur upon freezing has not been conducted, as spin relaxation for 18 is sufficiently long to observe a room-temperature spectrum.…”

Section: Implications Of Bulky Monophosphine Speciation At Ni I In Cr...mentioning

confidence: 99%

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Synthesis of Nickel(I)–Bromide Complexes via Oxidation and Ligand Displacement: Evaluation of Ligand Effects on Speciation and Reactivity

Newman-Stonebraker,

Raab,

Roshandel

et al. 2023

J. Am. Chem. Soc.

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Nickel's +1 oxidation state has received much interest due to its varied and often enigmatic behavior in increasingly popular catalytic methods. In part, the lack of understanding about Ni I results from common synthetic strategies limiting the breadth of complexes that are accessible for mechanistic study and catalyst design. We report an oxidative approach using tribromide salts that allows for the generation of a well-defined precursor, [Ni I (COD)Br] 2 , as well as several new Ni I complexes. Included among them are complexes bearing bulky monophosphines, for which structure−speciation relationships are established and catalytic reactivity in a Suzuki−Miyaura coupling (SMC) is investigated. Notably, these routes also allow for the synthesis of well-defined monomeric t-Bu bpy-bound Ni I complexes, which has not previously been achieved. These complexes, which react with aryl halides, can enable previously challenging mechanistic investigations and present new opportunities for catalysis and synthesis.

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Section: Implications Of Bulky Monophosphine Speciation At Ni I In Cr...supporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Implications Of Bulky Monophosphine Speciation At Ni I In Cr...mentioning

confidence: 99%

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Synthesis of Nickel(I)–Bromide Complexes via Oxidation and Ligand Displacement: Evaluation of Ligand Effects on Speciation and Reactivity

Newman-Stonebraker,

Raab,

Roshandel

et al. 2023

J. Am. Chem. Soc.

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“…Single-crystal X-ray crystallography analysis confirmed a trigonal planar geometry, similar to the previously reported analogous complex ( Me bpy)NiCl 4. 27 The bond angles of N1−Ni−Cl and N2−Ni−Cl were determined to be 136.99(13) and 139.58(13)°, respectively, indicating a symmetrical structure. However, the dihedral angel of N1−Ni− N2−Cl was measured to be 170.8°, revealing a slight deviation from perfect trigonal planar geometry.…”

Section: ■ Resultsmentioning

confidence: 98%

“…In contrast, the three-coordinate ( Me bpy)NiCl 4 ( Me bpy = 6,6′-dimethyl-2,2′bpy) exhibits a nickel-centered radical, with Me bpy being nonredox-active. 27 In other examples, the formation of oligomers can alter the geometry of the complexes and impact the assignment of the electronic structure. 13,28 Phen-ligated nickel complexes also display variations in redox activity.…”

Section: ■ Introductionmentioning

confidence: 99%

Ligand Redox Activity of Organonickel Radical Complexes Governed by the Geometry

Dawson,

Lin,

Neary

et al. 2023

J. Am. Chem. Soc.

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Nickel-catalyzed cross-coupling reactions often employ bidentate πacceptor N-ligands to facilitate radical pathways. This report presents the synthesis and characterization of a series of organonickel radical complexes supported by bidentate N-ligands, including bpy, phen, and pyrox, which are commonly proposed and observed intermediates in catalytic reactions. Through a comparison of relevant analogues, we have established an empirical rule governing the electronic structures of these nickel radical complexes. The N-ligands exhibit redox activity in four-coordinate, square-planar nickel radical complexes, leading to the observation of ligand-centered radicals. In contrast, these ligands do not display redox activity when supporting three-coordinate, trigonal planar nickel radical complexes, which are better described as nickel-centered radicals. This trend holds true irrespective of the nature of the actor ligands. These results provide insights into the beneficial effect of coordinating salt additives and solvents in stabilizing nickel radical intermediates during catalytic reactions by modulating the redox activity of the ligands. Understanding the electronic structures of these active intermediates can contribute to the development and optimization of nickel catalysts for cross-coupling reactions.

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Werner Salt as Nickel and Ammonia Source for Photochemical Synthesis of Primary Aryl Amines

Song,

et al. 2023

Angewandte Chemie

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Cheap, stable and easy‐to‐handle Werner ammine salts have been known for more than a century; but they have been rarely used in organic synthesis. Herein, we report that the Werner hexammine complex [Ni(NH₃)₆]Cl₂ can be used as both a nitrogen and a catalytic nickel source that allow for the efficient amination of aryl chlorides in the presence of a catalytic amount of bipyridine ligand under the irradiation of 390‐395 nm light without the need of any additional catalysts. More than 80 aryl chlorides, including more than 20 drug molecules, were aminated, demonstrating the practicality and generality of this method in synthetic chemistry. A slow NH3 release mechanism is in operation, obviating the problem of catalyst poisoning. Still interestingly, we show that the Werner salt can be easily recovered and reused, solving the problem of easy deactivation and difficult recovery of transition metal nickel catalysts. The protocol thus provides an efficient new strategy for the synthesis of primary aryl amines.

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Evaluating a Dispersion of Sodium in Sodium Chloride for the Synthesis of Low‐Valent Nickel Complexes**

Cited by 8 publications

References 61 publications

Synthesis of Nickel(I)–Bromide Complexes via Oxidation and Ligand Displacement: Evaluation of Ligand Effects on Speciation and Reactivity

Synthesis of Nickel(I)–Bromide Complexes via Oxidation and Ligand Displacement: Evaluation of Ligand Effects on Speciation and Reactivity

Ligand Redox Activity of Organonickel Radical Complexes Governed by the Geometry

Werner Salt as Nickel and Ammonia Source for Photochemical Synthesis of Primary Aryl Amines

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