Ring‐Size‐Modulated Reactivity of Putative Dicobalt‐Bridging Nitrides: C−H Activation versus Phosphinimide Formation

Cui, Peng; Wang, Qiuran; McCollom, Samuel P.; Manor, Brian C.; Carroll, Patrick J.; Tomson, Neil C.

doi:10.1002/anie.201708966

Cited by 41 publications

(37 citation statements)

References 51 publications

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“…It has come to light in recent years that the lifetime of CoO complexes can be extended through the coordination of redox-inactive Lewis acids to the oxo moiety. , These compounds are still short-lived, but under this cooperative model, the second metal can alleviate charge density that would otherwise occupy antibonding orbitals, thereby extending lifetimes. Notably, Tomson and co-workers have capitalized upon this strategy utilizing macrocyclic pyridyl–diimine ligands to generate the putative dinuclear cobalt nitride [( n PDI 2 )Co 2 (μ-N)(PMe 3 ) 2 ] 3+ . This nitride is not observed, but its formation is indicated through the isolation of phosphinimide and intramolecular C–H amination products formed as the result of passing Co–N–Co formation.…”

Section: Introductionmentioning

confidence: 73%

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H₂

et al. 2020

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Room temperature photolysis of the bis(azide)cobaltate(II) complex [Na(THF)x] [( ket guan)Co(N3)2] ( ket guan = [( t Bu2CN)C(NDipp)2] -, Dipp = 2,6-diisopropylphenyl) (3a) in THF cleanly forms the binuclear cobalt nitride [Na(THF)4{[( ket guan)Co(N3)]2(μ-N)}]n (1). Compound 1 represents the first example of an isolable, bimetallic cobalt nitride complex, and it has been fully characterized by spectroscopic, magnetic, and computational analyses. Density functional theory supports a Co III =N=Co III canonical form with significant π-bonding between the cobalt centers and the nitride atom. Unlike other Group 9 bridging nitride complexes, no radical character is detected at the bridging N-atom of 1. Indeed, 1 is unreactive towards weak C-H donors and even co-crystallizes with a molecule of cyclohexadiene (CHD) in its crystallographic unit cell to give 1•CHD as a room temperature stable product. Notably, addition of pyridine to 1 or photolyzed solutions of [( ket guan)Co(N3)(py)]2 (4a) leads to destabilization via activation of the nitride unit, resulting in the mixed-valent Co(II)/(III) bridged imido species [( ket guan)Co]2(μ-NH)(μ-N3) (5) formed from intermolecular hydrogen atom abstraction (HAA) of strong C-H bonds (BDE ~ 100 kcal/mol). Kinetic rate analysis of the formation of 5 in the presence of C6H12 or C6D12 gives a KIE = 2.5±0.1, supportive of a HAA formation pathway. The reactivity of our system was further probed by photolyzing C6D6/py-d5 solutions of 4a under an H2 atmosphere (150 psi), which leads to the exclusive formation of the bis(imido) [( ket guan)Co(μ-NH)]2 (6) as a result of dihydrogen activation. These results provide unique insights into the chemistry and electronic structure of late 3d-metal nitrides while providing entryway into C-H activation pathways.

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Section: Introductionmentioning

confidence: 73%

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H₂

et al. 2020

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“…Initially prepared as modular terpyridine mimics, pyridine(diimines) (PDIs) have emerged as a privileged ligand class in homogeneous catalysis, particularly with Earth-abundant transition metals . Following independent reports from Brookhart, Bennett, and Gibson describing high-activity PDI iron(II) and cobalt(II) dihalide catalyst/methylaluminoxane (MAO) activator combinations for ethylene polymerization, PDI ligands have since been applied in the cycloaddition and hydrofunctionalization of olefins, carbonyl hydrosilylation, and C–H functionalization as well as small-molecule activation including N 2 , NH 3 , O 2 , and CO 2 …”

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confidence: 99%

Pyridine(diimine) Chelate Hydrogenation in a Molybdenum Nitrido Ethylene Complex

Bezdek

Chirik

2019

Organometallics

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Addition of H2 gas to the aryl-substituted pyridine(diimine) molybdenum nitride ( iPrPDI)Mo(N)(C2H4) ([1-(N)(η 2 -C 2 H 4 )]; iPrPDI = 2,6-(2,6-iPr2-C6H3NCMe)2C5H3N) in the presence of the rhodium hydride precatalyst (η5-C5Me5)(py-Ph)Rh(H) ([Rh–H]; py-Ph = 2-phenylpyridine) resulted in partial hydrogenation of the central pyridine of the iPrPDI chelate to yield ( iPrTHPDI)Mo(N)(C2H4) ([2-(N)(η 2 -C 2 H 4 )]; iPrTHPDI = 2,6-(2,6-iPr2-C6H3NCMe)2C5H6N). The product, [2-(N)(η 2 -C 2 H 4 )], was structurally and spectroscopically characterized, and its electronic structure was examined by density functional theory (DFT). The stepwise addition of H atoms from [Rh–H] to [1-(N)(η 2 -C 2 H 4 )] was computed to be thermodynamically viable by DFT.

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“…We recently described the putative formation of a pair of transient bridging nitrides between two cobalt ions . The isolation of products that result from intramolecular hydrogen atom abstraction, P=N bond formation, and N‐atom insertion into an aliphatic C−H bond provided compelling evidence for the formation of highly electrophilic Co 2 ( μ ‐N) cores.…”

Section: Methodsmentioning

confidence: 99%

N−H Bond Formation at a Diiron Bridging Nitride

et al. 2020

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Despite their connection to ammonia synthesis, little is known about the ability of iron‐bound, bridging nitrides to form N−H bonds. Herein we report a linear diiron bridging nitride complex supported by a redox‐active macrocycle. The unique ability of the ligand scaffold to adapt to the geometric preference of the bridging species was found to facilitate the formation of N−H bonds via proton‐coupled electron transfer to generate a μ‐amide product. The structurally analogous μ‐silyl‐ and μ‐borylamide complexes were shown to form from the net insertion of the nitride into the E−H bonds (E=B, Si). Protonation of the parent bridging amide produced ammonia in high yield, and treatment of the nitride with PhSH was found to liberate NH3 in high yield through a reaction that engages the redox‐activity of the ligand during PCET.

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Ring‐Size‐Modulated Reactivity of Putative Dicobalt‐Bridging Nitrides: C−H Activation versus Phosphinimide Formation

Cited by 41 publications

References 51 publications

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H₂

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H₂

Pyridine(diimine) Chelate Hydrogenation in a Molybdenum Nitrido Ethylene Complex

N−H Bond Formation at a Diiron Bridging Nitride

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Ring‐Size‐Modulated Reactivity of Putative Dicobalt‐Bridging Nitrides: C−H Activation versus Phosphinimide Formation

Cited by 41 publications

References 51 publications

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H2

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H2

Pyridine(diimine) Chelate Hydrogenation in a Molybdenum Nitrido Ethylene Complex

N−H Bond Formation at a Diiron Bridging Nitride

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Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H₂

Isolation of a Bimetallic Cobalt(III) Nitride and Examination of Its Hydrogen Atom Abstraction Chemistry and Reactivity toward H₂