Steric Stabilization of Nucleophilic Carbenes

Denk, Michael; Thadani, Avinash N.; Hatano, Ken; Lough, Alan J.

doi:10.1002/anie.199726071

Cited by 172 publications

(133 citation statements)

References 43 publications

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“…(5 mL). After evaporation of Et 2 O, multinuclear NMR spectroscopy indicates the quantitative formation of dimer 3d, [23] along with two equivalents of triphenylphosphine.…”

Section: Reduction Of C-triphenylphosphonio-imidazolidinium Salt 1dmentioning

confidence: 99%

New Synthetic Routes to C‐Amino Phosphorus Ylides and their Subsequent Fragmentation into Carbenes and Phosphines

Conejero¹,

Song²,

Martín³

et al. 2006

Chemistry An Asian Journal

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Phosphonio-substituted aldiminium, iminium and imidazolidinium salts are readily prepared in excellent yields by addition of phosphines to Alder's dimer, or by treatment of the corresponding chloro iminium salt with the in situ generated phosphine/trimethylsilyl triflate adduct. A two-electron reduction, using either potassium metal or tetrakis(dimethylamino)ethylene, leads to the corresponding C-amino phosphorus ylides. When basic phosphine fragments are used, the ylides can be isolated; otherwise they spontaneously undergo a fragmentation into carbene and phosphine. Although the reduction/fragmentation sequence occurs under mild conditions, this method is limited to the preparation of transient carbenes, due to the non-availability of sterically hindered dications, and consequently of phosphorus ylides bearing bulky carbon substituents. To overcome this difficulty, a second novel route to phosphorus ylides has been developed: The addition, at low temperature, of 2,4-di-tert-butyl-ortho-quinone to readily available C-amino phosphaalkenes. Provided the phosphorus atom bears either an amino or tert-butyl group, a [4+1]-cycloaddition occurs, and the resulting ylides spontaneously undergo a fragmentation into a dioxaphospholane and a spectroscopically observed carbene.

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“…(5 mL). After evaporation of Et 2 O, multinuclear NMR spectroscopy indicates the quantitative formation of dimer 3d, [23] along with two equivalents of triphenylphosphine.…”

Section: Reduction Of C-triphenylphosphonio-imidazolidinium Salt 1dmentioning

confidence: 99%

New Synthetic Routes to C‐Amino Phosphorus Ylides and their Subsequent Fragmentation into Carbenes and Phosphines

Conejero¹,

Song²,

Martín³

et al. 2006

Chemistry An Asian Journal

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“…Interestingly, our preliminary screening led us to choose NHCs with different stabilities towards dimerization; the dimer from the carbene in 2 is unknown, whereas the dimer from the carbene in 1 is a volatile olefin. 15 Some Cu(I) precursors are well known to undergo disproportionation reactions to Cu(0) and Cu(II), which has been exploited in the CVD of copper metal films. 16 This process relies on the clean purging from the deposition zone of the Cu(II) product along with any stabilizing Lewis base employed in the Cu(I) precursor.…”

Section: Introductionmentioning

confidence: 99%

Deposition of Copper by Plasma-Enhanced Atomic Layer Deposition Using a Novel N-Heterocyclic Carbene Precursor

et al. 2013

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Access to the full text of the published version may require a subscription. Rights AbstractTwo novel N-heterocyclic carbene (NHC)-containing copper(I) amides are reported as atomic layer deposition (ALD) precursors. 1,3-diisopropyl-imidazolin-2-ylidene copper hexamethyldisilazide (1) and 4,5-dimethyl-1,3-diisopropyl-imidazol-2-ylidene copper hexamethyldisilazide (2) were synthesized and structurally characterized. The thermal behaviour of both compounds was studied by thermogravimetric analysis (TGA), and they were both found to be reasonably volatile compounds. Compound 1 had no residual mass in the TGA and showed long-term stability at temperatures as high as 130 °C, while 2 had a residual mass of 7.4 %. Copper metal with good resistivity was deposited using 1 by plasma-enhanced atomic layer deposition. The precursor demonstrated self-limiting behaviour indicative of ALD, and gave a growth rate of 0.2 Å/cycle. Compound 2 was unsuccessful as an ALD precursor under similar conditions. Density functional theory calculations showed that both compounds adsorb dissociatively onto a growing copper film as long as there is some atomic roughness, via cleavage of the Cu-carbene bond.

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“…A substituição dos NHC's pelas fosfinas estericamente impedidas BuPAd 2 , o-biph-PCy 2 e PtBu 3 levou à formação do produto em conversão e rendimentos bastante superiores (entradas [12][13][14].…”

Section: Reações De Acoplamentos Cruzadosunclassified

“…12 Esta diferença de reatividade tem sido atribuída a vários fatores, como a relativa aromaticidade dos carbenos do tipo A (insaturados) e a menor diferença de energia do estado singleto para o estado tripleto excitado para os carbenos do tipo B (aproximadamente 80 kcal/mol para os imidazolidenos e aproximadamente 70 kcal/mol para os imidazolinilidenos). 13 Existe portanto uma relação proporcional entre a energia de ativação para a formação do dímero (E a ) e a diferença de energia entre os estados singleto e tripleto (∆E S-T ), ou seja, a E a para a dimerização fica maior à medida que ∆E S-T aumenta.…”

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Catalisadores contendo carbenos n-heterocíclicos como ligantes: propriedades, sínteses, aplicações e comparação com outros ligantes

Pastre¹,

Correia²

2008

Quím. Nova

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Steric Stabilization of Nucleophilic Carbenes

Cited by 172 publications

References 43 publications

New Synthetic Routes to C‐Amino Phosphorus Ylides and their Subsequent Fragmentation into Carbenes and Phosphines

New Synthetic Routes to C‐Amino Phosphorus Ylides and their Subsequent Fragmentation into Carbenes and Phosphines

Deposition of Copper by Plasma-Enhanced Atomic Layer Deposition Using a Novel N-Heterocyclic Carbene Precursor

Catalisadores contendo carbenos n-heterocíclicos como ligantes: propriedades, sínteses, aplicações e comparação com outros ligantes

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