Acidity of Several Anilinium Derivatives in Pure Tetrahydrofuran

Garrido, Gemma; Rosés, Martı́; Ràfols, Clara; Bosch, Elisabeth

doi:10.1007/s10953-008-9262-6

Cited by 20 publications

(12 citation statements)

References 31 publications

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“…pK a MeCN (HB + /B) = 1.13pK  THF (HB + /B) + 3.2 (14) A comparison of pK a values for cationic nitrogen-based acids in several other solvents is available. 50 For neutral acids the correlation is different as mentioned above (Equation 15). [7][8] Equation 15…”

Section: Equation 14mentioning

confidence: 99%

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

2016

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Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.

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Section: Equation 14mentioning

confidence: 99%

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

2016

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“…23 This observation is consistent with the notion that protonation of P 3 B FeN 2 – is slowed under the present conditions, likely as a result of the insolubility of the triflate salt [Ph 2 NH 2 ][OTf] and its attenuated acidity relative to HBAr F 4 . 17,18,33 Clearly, differences in the rates of key elementary steps under the new conditions described here may lead to new mechanistic scenarios for N 2 -to-NH 3 conversion.…”

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confidence: 94%

“…Summary of conditions used for catalytic N 2 -to-NH 3 conversion by P 3 B Fe + highlighting the estimated enthalpic driving force (ΔΔ H f ). − …”

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confidence: 99%

Catalytic N₂-to-NH₃ Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET

et al. 2017

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We have recently reported on several Fe catalysts for N2-to-NH3 conversion that operate at low temperature (−78 °C) and atmospheric pressure while relying on a very strong reductant (KC8) and acid ([H(OEt2)2][BArF4]). Here we show that our original catalyst system, P3BFe, achieves both significantly improved efficiency for NH3 formation (up to 72% for e– delivery) and a comparatively high turnover number for a synthetic molecular Fe catalyst (84 equiv of NH3 per Fe site), when employing a significantly weaker combination of reductant (Cp*2Co) and acid ([Ph2NH2][OTf] or [PhNH3][OTf]). Relative to the previously reported catalysis, freeze-quench Mössbauer spectroscopy under turnover conditions suggests a change in the rate of key elementary steps; formation of a previously characterized off-path borohydrido–hydrido resting state is also suppressed. Theoretical and experimental studies are presented that highlight the possibility of protonated metallocenes as discrete PCET reagents under the present (and related) catalytic conditions, offering a plausible rationale for the increased efficiency at reduced driving force of this Fe catalyst system.

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“…The calculated values of pK a compared with experimental values (Garrido et al 2008) are summarized in Table 1. For the most of the studied substituted anilinium ions, the deviations are within 1 pK a unit.…”

Section: Resultsmentioning

confidence: 99%

The DFT calculations of pK_a values of the cationic acids of aniline and pyridine derivatives in common solvents

Poliak

2014

Acta Chimica Slovaca

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Abstract:The theoretical pK a values of the derivatives of anilinium and pyridinium ions in 7 solvents are presented. For this purpose, the usage of isodesmic reaction scheme using the DFT/B3LYP approach with IEFPCM solvation was evaluated. We have shown that the suitable selection of reference species has the primary influence on the resulting data. For the studied anilinium ion derivatives the nonsubstituted anilinium ion seems to be a satisfactory reference system. The calculated values are in good accordance with the available experimental data with the RMS error of 1.00 and 0.99 pK a units in water and THF, respectively. The highest error in predicted pK a value is less than 2.0 pK a units in all cases. The chemical accuracy of the applied treatment is limited in the case of nitroaniline ions and the maximal therotetical uncertainty for derivatives of the pyridinium ion is within 2.1 pK a units. Our theoretical results enable us to predict the values of pK a for the solvents, where the experimental data are not completely available. Also the influence of the chemical structure on the accuracy of the applied method was discussed.

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Acidity of Several Anilinium Derivatives in Pure Tetrahydrofuran

Cited by 20 publications

References 31 publications

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

Catalytic N₂-to-NH₃ Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET

The DFT calculations of pK_a values of the cationic acids of aniline and pyridine derivatives in common solvents

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Acidity of Several Anilinium Derivatives in Pure Tetrahydrofuran

Cited by 20 publications

References 31 publications

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

Catalytic N2-to-NH3 Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET

The DFT calculations of pKa values of the cationic acids of aniline and pyridine derivatives in common solvents

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Catalytic N₂-to-NH₃ Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET

The DFT calculations of pK_a values of the cationic acids of aniline and pyridine derivatives in common solvents