Hydride Affinities of Substituted Alkenes: Their Prediction by Density Functional Calculations and Rationalisation by Triadic Formula

Vianello, Robert; Peran, Nena; Maksić, Zvonimir B.

doi:10.1002/ejoc.200600640

Cited by 10 publications

(7 citation statements)

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“…It was found that the allenes should belong to a group of strong hydride ion acceptors, and their hydride affinities were much larger than those of the conjugated or isolated dienes . The computational and experimental data on some of the hydride affinities are readily available, − which is fortunate as they could serve as a good probe of the electrophilicities of compounds, for the identification of their reducing agents or as the measure for the relative stabilities of the carbocations …”

Section: Introductionmentioning

confidence: 99%

Carbon Atom as an Extremely Strong Nucleophilic and Electrophilic Center: Dendritic Allenes Are Powerful Organic Proton and Hydride Sponges

Radić

Maksić

2019

J. Org. Chem.

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Gas-phase proton affinities (PAs) and hydride affinities (HAs) of organic bases possessing an allene moiety and substituted with methyl, dimethylamino, cyano, and vinyl substituents were examined with the B3LYP/6-311+G(2df,p)//B3LYP/6-31G(d) model. It was shown that a number of superbases and hyperbases can be obtained, as well as the potent hydride sponges. Methyl or dimethylamino substituents increased the proton affinity of the parent molecule, and the cyano substituents increased its hydride affinity. When the vinyl substituents are placed on allene, both the hydride and the proton affinities increased. A disubstituted allene with two dimethylamino groups is the smallest studied superbase, whereas the allene tetrasubstituted with four vinyl groups gives the smallest superbase possessing only alkene substituents. By introducing the vinyl group as a repeating subunit, one can obtain dendritic structures with the investigated substituents determining its properties. By changing the dimethylamino with the cyano group, a dendrimeric molecule can change from a hyperbase with a proton affinity of 324.6 kcal mol–1 to a very strong hydride ion acceptor with a hydride affinity of 205.4 kcal mol–1, while possessing the same proton or hydride ion attachment site.

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Section: Introductionmentioning

confidence: 99%

Carbon Atom as an Extremely Strong Nucleophilic and Electrophilic Center: Dendritic Allenes Are Powerful Organic Proton and Hydride Sponges

Radić

Maksić

2019

J. Org. Chem.

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“…However, the proton-accepting ability is markedly reduced moving from PMe 3 to P(C 6 F 5 ) 3 and PH 3 . Like proton affinity, hydride affinity (HA) is a measure of a molecule's ability to bind a hydride, but relatively few investigations have been focused on HA [98][99][100][101][102][103][104][105]. As a very simple base (electron donor) with only two electrons, the hydride ion can form the simplest example of donor-acceptor interaction with electron-acceptor.…”

Section: Resultsmentioning

confidence: 99%

Steric and electronic effects on the heterolytic H₂‐splitting by phosphine‐boranes R₃B/PR′₃(R = C₆F₅, Ph; R′ = C₆H₂Me₃,tBu, Ph, C₆F₅, Me, H): A computational study

Gao

2010

Int J of Quantum Chemistry

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The steric and electronic effects exerted by the substituents R/R 0 on the heterolytic H 2 -splitting by phosphine-boranes R 3 B/PR 0 3 [R ¼ C 6 F 5 (1), Ph (2); R 0 ¼ C 6 H 2 Me 3 (a), tBu (b), Ph (c), C 6 F 5 (d), Me (e), H (f)] have been studied by performing quantum mechanical density functional theory and RI-MP2 calculations. Energy decomposition analyses based on the block-localized wavefunction method show that the nature of the interaction between R 3 B and PR 0 3 is strongly dependent on the BAP distance. With short BAP distances ($2.1 Å ), the strength of Lewis pairs results from the balance among various energy terms, and both strong and weak dative bonds can be found in this group. However, at long BAP distances (>4.0 Å ), the correlation and dispersion energy (DE corr ) dominates. In other words, the van der Waals (vdW) interaction rules these weakly bound complexes. No ion-pair structures of 1f and 2c-2f can be located as they instantly converge to vdW complexes R 3 BÁÁÁH 2 ÁÁÁPR 0 3 . We thus propose a model, which predicts that when the sum (E hp ) of the hydride affinity (HA) of BR 3 and the proton affinity (PA) of PR 0 3 is higher than 340.0 kcal/mol, the ion-pair [R 3 BH À ][HPR 0þ 3 ] can be observed, whereas with E hp below this value, the ion pair would instantly undergo the combination of proton and hydride with the release of H 2 . The overall reaction energies (1a-1e and 2a-2b) can be best described by a fitting equation with HA(BR 3 ), PA(PR 0 3 ), and the binding energy DE b (BR 3 /PR 0 3 ) as predictor variables:(BR 3 /PR 0 3 ) þ 245.3 kcal/mol. The fitting equation provides quantitative insights into the steric and electronic effects on the thermodynamic aspects of the heterolytic H 2 -splitting reactions. The electronic effects are reflected by HA(BR 3 ) and PA(PR 0 3 ), and DE b can be significantly influenced by the steric overcrowding.a Structural parameters are based on the optimal geometries at the B3LYP/6-31G(d,p) level; the basis sets used for calculations are cc-pVDZ. b Calculated at the RI-MP2/cc-pVDZ level. a 1HHa refers to the ion-pair complex obtained from Lewis pair 1a and so on. b DE zpe;cp b refers to binding energy after ZPE and 50% BSSE corrections.

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“…In addition to high hydrogen binding energies, hydride acceptors tend to have high electron binding energies. Computations suggest that the electron-withdrawing character of -CN and -NO 2 groups produce very stable hydride adducts corresponding to positive electron affinities (2.4 kcal mol -1 and 27.7 kcal mol -1 , respectively) [63]. The nitrogen atoms in the 1,3,5-triazine ring should have a similar effect on the electron affinity by shifting electron density away from the nearby reaction center reducing the Coulombic repulsive forces and increasing the effective nuclear charge.…”

Section: Potential Energy Surface Of 135-triazine Reactionsmentioning

confidence: 99%

Gas Phase Reactions of 1,3,5-Triazine: Proton Transfer, Hydride Transfer, and Anionic σ-Adduct Formation

Garver

Yang

Kato

et al. 2011

J. Am. Soc. Mass Spectrom.

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The gas phase reactivity of 1,3,5-triazine with several oxyanions and carbanions, as well as amide, was evaluated using a flowing afterglow-selected ion flow tube mass spectrometer. Isotopic labeling, H/D exchange, and collision induced dissociation experiments were conducted to facilitate the interpretation of structures and fragmentation processes. A multi-step (→ HCN + HC 2 N 2 − → CN − + 2 HCN) and/or single-step (→ CN − + 2 HCN) ring-opening collision-induced fragmentation process appears to exist for 1,3,5-triazinide. In addition to proton and hydride transfer reactions, the data indicate a competitive nucleophilic aromatic addition pathway (S N Ar) over a wide range of relative gas phase acidities to form strong anionic σ-adducts (Meisenheimer complexes). The significant hydride acceptor properties and stability of the anionic σ-adducts are rationalized by extremely electrophilic carbon centers and symmetric charge delocalization at the electron-withdrawing nitrogen positions. The types of anion-arene binding motifs and their influence on reaction pathways are discussed.

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Hydride Affinities of Substituted Alkenes: Their Prediction by Density Functional Calculations and Rationalisation by Triadic Formula

Cited by 10 publications

References 46 publications

Carbon Atom as an Extremely Strong Nucleophilic and Electrophilic Center: Dendritic Allenes Are Powerful Organic Proton and Hydride Sponges

Carbon Atom as an Extremely Strong Nucleophilic and Electrophilic Center: Dendritic Allenes Are Powerful Organic Proton and Hydride Sponges

Steric and electronic effects on the heterolytic H₂‐splitting by phosphine‐boranes R₃B/PR′₃(R = C₆F₅, Ph; R′ = C₆H₂Me₃,tBu, Ph, C₆F₅, Me, H): A computational study

Gas Phase Reactions of 1,3,5-Triazine: Proton Transfer, Hydride Transfer, and Anionic σ-Adduct Formation

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Hydride Affinities of Substituted Alkenes: Their Prediction by Density Functional Calculations and Rationalisation by Triadic Formula

Cited by 10 publications

References 46 publications

Carbon Atom as an Extremely Strong Nucleophilic and Electrophilic Center: Dendritic Allenes Are Powerful Organic Proton and Hydride Sponges

Carbon Atom as an Extremely Strong Nucleophilic and Electrophilic Center: Dendritic Allenes Are Powerful Organic Proton and Hydride Sponges

Steric and electronic effects on the heterolytic H2‐splitting by phosphine‐boranes R3B/PR′3(R = C6F5, Ph; R′ = C6H2Me3,tBu, Ph, C6F5, Me, H): A computational study

Gas Phase Reactions of 1,3,5-Triazine: Proton Transfer, Hydride Transfer, and Anionic σ-Adduct Formation

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Steric and electronic effects on the heterolytic H₂‐splitting by phosphine‐boranes R₃B/PR′₃(R = C₆F₅, Ph; R′ = C₆H₂Me₃,tBu, Ph, C₆F₅, Me, H): A computational study