Theoretical and experimental investigation of the electron affinities of allene and propyne

Ciommer, Bernhard; Nguyen, K.M.; Schwarz, Helmut; Frenking, G.; Kwiatkowski, Georg; Illenberger, Eugen

doi:10.1016/0009-2614(84)80198-0

Cited by 14 publications

(8 citation statements)

References 18 publications

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“…23 Interestingly, the reduction potential of methylallene has never been measured, even though a value of −2.1 V is estimated for the two-electron reduction of tetraphenylallene. 20 A more relevant quantity is the electron affinity of allene, which is −1.9 ± 0.1 V. 24 These approximate values suggest that electron transfer from (Me 5 C 5 ) 2 Yb to methylallene is not a preposterous idea. Thus, the key element in the electron-transfer cycle is the difference between the estimated electron affinities of methylallene and dimethylacetylene.…”

Section: ð2þmentioning

confidence: 99%

“…20 A more relevant quantity could be the electron affinity of allene, which is -1.9±0.1V. 24 These approximate values suggest that electron transfer from (Me 5 C 5 ) 2 Yb to methylallene is not a preposterous idea. Thus, the key element in the electron-transfer cycle is the difference between the estimated electron affinities of methylallene and dimethylacetylene.…”

Section: Introductionmentioning

confidence: 99%

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Can a pentamethylcyclopentadienyl ligand act as a proton-relay in f-element chemistry? Insights from a joint experimental/theoretical study

et al. 2015

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Isomerisation of buta-1,2-diene to but-2-yne by (Me(5)C(5))(2)Yb is a thermodynamically favourable reaction, with the Δ(r)G° estimated from experimental data at 298 K to be -3.0 kcal mol(-1). It proceeds in hydrocarbon solvents with a pseudo first-order rate constant of 6.4 × 10(-6) s(-1) and 7.4 × 10(-5) s(-1) in C(6)D(12) and C(6)D(6), respectively, at 20 °C. This 1,3-hydrogen shift is formally forbidden by symmetry and has to occur by an alternative pathway. The proposed mechanism for buta-1,2-diene to but-2-yne isomerisation by (Me(5)C(5))(2)Yb involves coordination of methylallene (buta-1,2-diene) to (Me(5)C(5))(2)Yb, and deprotonation of methylallene by one of the Me(5)C(5) ligands followed by protonation of the terminal methylallenyl carbon to yield the known coordination compound (Me(5)C(5))(2)Yb(η(2)-MeC[triple bond, length as m-dash]CMe). Computationally, this mechanism is not initiated by a single electron transfer step, and the ytterbium retains its oxidation state (II) throughout the reactivity. Experimentally, the influence of the metal centre is discussed by comparison with the reaction of (Me(5)C(5))(2)Ca towards buta-1,2-diene, and (Me(5)C(5))(2)Yb with ethylene. The mechanism by which the Me(5)C(5) acts as a proton-relay within the coordination sphere of a metal also rationalises the reactivity of (i) (Me(5)C(5))(2)Eu(OEt(2)) with phenylacetylene, (ii) (Me(5)C(5))(2)Yb(OEt(2)) with phenylphosphine and (iii) (Me(5)C(5))(2)U(NPh)(2) with H(2) to yield (Me(5)C(5))(2)U(HNPh)(2). In the latter case, the computed mechanism is the heterolytic activation of H(2) by (Me(5)C(5))(2)U(NPh)(2) to yield (Me(5)C(5))(2)U(H)(HNPh)(NPh), followed by a hydrogen transfer from uranium back to the imido nitrogen atom using one Me(5)C(5) ligand as a proton-relay. The overall mechanism by which hydrogen shifts using a pentamethylcyclopentadienyl ligand as a proton-relay is named Carambole in reference to carom billiards.

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Section: ð2þmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Can a pentamethylcyclopentadienyl ligand act as a proton-relay in f-element chemistry? Insights from a joint experimental/theoretical study

et al. 2015

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“…Also low-energy approximate calculations clearly show a pronounced isomeric effect on the elastic cross section for electron impact on simple hydrocarbons [26][27][28]. A variation of resonance positions for isomers of fluorinated hydrocarbons was noticed in the electron transmission spectra [29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Isomer effects on the total cross section for electron scattering from C₄F₆molecules

Szmytkowski¹,

Kwitnewski²

2003

J. Phys. B: At. Mol. Opt. Phys.

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The absolute total cross section (TCS) for electron scattering from hexafluoro-1,3-butadiene (1,3-C 4 F 6) was obtained in a transmission experiment for electron impact energies from 0.6 to 370 eV. The TCS energy function has two pronounced enhancements separated by a deep minimum located near 2.6 eV: a low-energy hump around 1 eV and a dominant very broad enhancement centred near 30 eV. The 1,3-C 4 F 6 TCS results are compared with the data for hexafluoro-2-butyne (2-C 4 F 6) and the influence of the structural differences on the electron-scattering TCS for isomers of the C 4 F 6 molecule (isomeric effect) is explicitly indicated. The most pronounced role of the molecular geometry on the magnitude and shape of the TCS energy dependence is observed at the lowest energies studied. Above 40 eV the TCSs for both isomers are close to each other. Some conformities of TCSs within a series of perfluorocarbons (C 2 F 4 , 1,3-C 4 F 6 , C 6 F 6) as well as in a series of their hydrocarbon counterparts (C 2 H 4 , 1,3-C 4 H 6 , C 6 H 6) are also pointed out and discussed.

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“…In the present work the measurements were carried out for two C 3 H 4 isomers: allene (1, 2-propadiene) and propyne (methylacetylene). To date, descriptions in the literature of the processes involved in electron collision with allene molecules have been sparse and are limited to low-energy trapped-electron spectra measured by Knoop (1972), the electron impact excitation (Mosher et al 1975) and the electron transmission spectrum (Ciommer et al 1984). More attention has been dedicated to electron scattering from another C 3 H 4 isomer, propyne.…”

Section: Introductionmentioning

confidence: 99%

Total cross sections for electron scattering with some C₃hydrocarbons

Szmytkowski

Kwitnewski

2002

J. Phys. B: At. Mol. Opt. Phys.

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Absolute total cross sections (TCSs) for electron scattering from two C3H4 isomers (allene and propyne) and from propane (C3H8) have been measured in a linear electron-beam transmission experiment for impact energy ranging from 0.5 to 370 eV. Low-energy TCS functions for C3H4 are dominated by prominent structures: a resonant-like enhancement of the cross section for allene peaks at around 2.3 and 3.4 eV for propyne, while very broad enhancement is centred at 9.5–10 and 8.0–8.5 eV for allene and propyne respectively. Some supplementary weak features are also discernible. The general shape of cross sections for both C3H4 isomers is similar except that the cross section enhancements are at different locations. In addition, the TCS for propyne has been compared with cross sections for other open-chain hydrocarbons with three carbon atoms, i.e. propene (C3H6) and propane (C3H8), and the effect of the multiplicity of the C–C bond on the low-energy scattering is demonstrated.

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Theoretical and experimental investigation of the electron affinities of allene and propyne

Cited by 14 publications

References 18 publications

Can a pentamethylcyclopentadienyl ligand act as a proton-relay in f-element chemistry? Insights from a joint experimental/theoretical study

Can a pentamethylcyclopentadienyl ligand act as a proton-relay in f-element chemistry? Insights from a joint experimental/theoretical study

Isomer effects on the total cross section for electron scattering from C₄F₆molecules

Total cross sections for electron scattering with some C₃hydrocarbons

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Theoretical and experimental investigation of the electron affinities of allene and propyne

Cited by 14 publications

References 18 publications

Can a pentamethylcyclopentadienyl ligand act as a proton-relay in f-element chemistry? Insights from a joint experimental/theoretical study

Can a pentamethylcyclopentadienyl ligand act as a proton-relay in f-element chemistry? Insights from a joint experimental/theoretical study

Isomer effects on the total cross section for electron scattering from C4F6molecules

Total cross sections for electron scattering with some C3hydrocarbons

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Product

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Isomer effects on the total cross section for electron scattering from C₄F₆molecules

Total cross sections for electron scattering with some C₃hydrocarbons