A Terminally Bound Niobium Methylidyne

Kurogi, Takashi; Carroll, Patrick J.; Mindiola, Daniel J.

doi:10.1021/jacs.6b00830

Cited by 43 publications

(33 citation statements)

References 64 publications

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“…Forc omparable P, N,Pn iobium methylidene complexes L n Nb = CH 2 ,r esonances at d = 11.4 and 12.2 ppm are found. [25] Thec orresponding signal for the carbon atom is extremely shifted to lower fields at d = 277.2 ppm, which can be observed in the DEPT135 NMR spectrum. This value is comparable to other d 0 early transition-metal carbene complexes.…”

Section: Methodsmentioning

confidence: 93%

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

et al. 2018

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Transition-metal carbene complexes and their reactivities are a key topic of chemistry. They are an integral part of researches in catalysis, organic synthesis, coordination chemistry, and numerous other areas. In this context, we report the synthesis of a low-valent bis(η :η -(di-p-tolyl)-pentafulvene)niobium chloride. Owing to the π-η :σ-η coordination mode of the pentafulvenes and the resulting high nucleophilic character of the exocyclic carbon atom of the ligand, the bis(η :η -pentafulvene)niobium complex is able to achieve the umpolung of a coordinated vinyl unit and the resulting formation of the first η :η cyclic niobium Schrock carbene complex. This new synthetic route is, in comparison to classical α-hydrogen elimination reactions or thermolysis of diazo compounds, completely unprecedented. The reactivity of the cyclic carbene function and the remaining fulvene ligand is demonstrated by double N-H bond activation of primary amines to niobium imido complexes.

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Section: Methodsmentioning

confidence: 93%

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

et al. 2018

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“…A single resonance between 3.5 and 6.5 ppm is observed in the 1 H NMR spectrum, a doublet of triplets centered at 5.06 ppm ( 1 J(C,H) = 147.8 Hz, 3 J(P,H) = 3.1 Hz), with a relative integration of one. This suggests both a terminal methylidyne 20,24,[45][46][47][48][49][50][51] and a five-coordinate pseudo-square pyramidal structure, as in 4, without metal-arene interactions (vide infra; Scheme 3). The 31 P{ 1 H} and 13 C{ 1 H} NMR data further corroborate the proposed assignment of 4, with a doublet of doublets at dP 40.21 ppm ( 2 J(C,P) = 18.6 and 10.2 Hz) and a characteristic methylidyne resonance at dC 281.19 ppm, respectively.…”

Section: Carbide Protonation Hydride Transfer and Methylidene/co Comentioning

confidence: 99%

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

et al. 2019

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The mechanism originally proposed by Fischer and Tropsch for carbon monoxide (CO) hydrogenative catenation involves CC coupling from a carbide-derived surface methylidene. A single molecular system capable of capturing these complex chemical steps is hitherto unknown. Herein, we demonstrate the sequential addition of proton and hydride to a terminal Mo carbide derived from CO. The resulting anionic methylidene couples with CO (1 atm.) at low-temperature (-78 °C) to release ethenone. Importantly, the synchronized delivery of two reducing equivalents and an electrophile, in the form of a hydride (H-= 2e-+ H +), promotes alkylidene formation from the carbyne precursor and enables coupling chemistry, under conditions milder than those previously described with strong one-electron reductants and electrophiles. Thermodynamic measurements bracket the hydricity and acidity requirements for promoting methylidene formation from carbide as energetically viable upon formal heterolysis of H2. Methylidene formation prior to CC coupling proves critical for organic product release, as evidenced by direct carbide carbonylation experiments. Spectroscopic studies, a monosilylated model system, and Quantum Mechanics computations provide insight into the mechanistic details of this reaction sequence, which serves as a rare model of the initial stages of the Fischer Tropsch synthesis.

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“…A particularly notable signal in the 1 H NMR spectrum is that for the proton of the Nb=CH carbene function, which is found at δ =11.03 ppm. For comparable P,N,P niobium methylidene complexes L n Nb=CH 2 , resonances at δ =11.4 and 12.2 ppm are found . The corresponding signal for the carbon atom is extremely shifted to lower fields at δ =277.2 ppm, which can be observed in the DEPT135 NMR spectrum.…”

Section: Methodsmentioning

confidence: 80%

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

et al. 2018

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Transition-metal carbene complexes and their reactivities are akey topic of chemistry.They are an integral part of researches in catalysis,organic synthesis,coordination chemistry,a nd numerous other areas.I nt his context, we report the synthesis of al ow-valent bis(h 5 :h 1 -(di-p-tolyl)-pentafulvene)niobium chloride.O wing to the p-h 5 :s-h 1 coordination mode of the pentafulvenes and the resulting high nucleophilic character of the exocyclic carbon atom of the ligand, the bis(h 5 :h 1 -pentafulvene)niobium complex is able to achieve the umpolung of ac oordinated vinyl unit and the resulting formation of the first h 5 :h 1 cyclic niobium Schrock carbene complex. This new synthetic route is,incomparison to classical a-hydrogen elimination reactions or thermolysis of diazo compounds,c ompletely unprecedented. The reactivity of the cyclic carbene function and the remaining fulvene ligand is demonstrated by double NÀHb ond activation of primary amines to niobium imido complexes.

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A Terminally Bound Niobium Methylidyne

Cited by 43 publications

References 64 publications

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

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A Terminally Bound Niobium Methylidyne

Cited by 43 publications

References 64 publications

Bis(η5:η1‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

Bis(η5:η1‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

CO Coupling Chemistry of a Terminal Mo Carbide: Sequential Addition of Proton, Hydride, and CO Releases Ethenone

Bis(η5:η1‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

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Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives

Bis(η⁵:η¹‐pentafulvene)niobium(V) Complexes: Efficient Synthons for Niobium Carbene and Imido Derivatives