The Cation H
 13
 O
 6
 +
 : A Short, Symmetric Hydrogen Bond

Bell, Robert A.; Christoph, Gary G.; Fronczek, Frank R.; Marsh, Richard E.

doi:10.1126/science.190.4210.151

Cited by 88 publications

(66 citation statements)

References 9 publications

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“…For the crystal state, only one example of a type VIII cation is known. It is found in the strictly symmetric Cl − anion environment of a cage compound [(C 9 H 18 ) 3 (NH 2 ) 2 Cl] + Cl − crystallized from HCl solution 61. In the solutions of the present study, the IR data on H(H 2 O) 6 + retain the characteristics of the H 7 O 3 + core, indicating formulation as the H 7 O 3 + ·3H 2 O ion, structure V .…”

Section: Resultssupporting

confidence: 48%

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The Nature of the Hydrated Proton H_(aq)⁺ in Organic Solvents

et al. 2008

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Section: Resultssupporting

confidence: 48%

“…By comparison, the central O⋯O distance in H 5 O 2 + ·4H 2 O should be ca. 2.39(2) Å as in crystal state 61. This distance is typical for L−H + −L proton disolvates with strong L bases, such as diethylether 54,63.…”

Section: Resultsmentioning

confidence: 88%

The Nature of the Hydrated Proton H_(aq)⁺ in Organic Solvents

et al. 2008

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“…One early structure, trapped in a cryptand, has four solvating water molecules, making a H 13 O 6 + ion that is best formulated as H 5 O 2 + ·4H 2 O. 56 In most solid state structures, however, H-bonds to the counterion replace most or all of the solvent molecules. For example, [H 5 O 2 + ·C 6 H 6 ][CHB 11 Cl 11 − ] has one O-H⋯π interaction with benzene and three O-H⋯Cl interactions with the carborane anion.…”

Section: Nature Of H(h2o)n+ In Organic Solventsmentioning

confidence: 99%

Myths about the Proton. The Nature of H⁺ in Condensed Media

2013

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CONSPECTUS Recent research has taught us that most protonated species are decidedly not well represented by a simple proton addition. What is the actual nature of the hydrogen ion (the “proton”) when H+, HA, H2A+ etc. are written in formulae, chemical equations and acid catalyzed reactions? In condensed media, H+ must be solvated and is nearly always di-coordinate – as illustrated by isolable bisdiethyletherate salts having H(OEt2)2+ cations and weakly coordinating anions. Even carbocations such as protonated alkenes have significant C-H---anion hydrogen bonding that gives the active protons two-coordinate character. Hydrogen bonding is everywhere, particularly when acids are involved. In contrast to the normal, asymmetric O-H---O hydrogen bonding found in water, ice and proteins, short, strong, low-barrier (SSLB) H-bonding commonly appears when strong acids are present. Unusually low frequency IR νOHO bands are a good indicator of SSLB H-bonds and curiously, bands associated with group vibrations near H+ in low-barrier H-bonding often disappear from the IR spectrum. Writing H3O+ (the Eigen ion), as often appears in textbooks, might seem more realistic than H+ for an ionized acid in water. However, this, too, is an unrealistic description of H(aq)+. The dihydrated H+ in the H5O2+ cation (the Zundel ion) gets somewhat closer but still fails to rationalize all the experimental and computational data on H(aq)+. Researchers do not understand the broad swath of IR absorption from H(aq)+, known as the “continuous broad absorption” (cba). Theory has not reproduced the cba, but it appears to be the signature of delocalized protons whose motion is faster than the IR timescale. What does this mean for reaction mechanisms involving H(aq)+? For the past decade, the carborane acid H(CHB11Cl11) has been the strongest known Brøsted acid. (It is now surpassed by the fluorinated analogue H(CHB11F11).) Carborane acids are strong enough to protonate alkanes at room temperature, giving H2 and carbocations. They protonate chloroalkanes to give dialkylchloronium ions, which decay to carbocations. By partially protonating an oxonium cation, they get as close to the fabled H4O2+ ion as can be achieved outside of a computer.

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“…The engulfing of the chloride anion inside the katapinand cavity was confirmed years later by the X-ray analysis of the structure of Cl − included in the [9.9.9] bicyclic katapinad [55]. However, while investigations on crown ethers rapidly evolved and many of these compounds were prepared and their chemistry widely explored, studies on anion coordination chemistry remained at the initial stage.…”

Section: Introductionmentioning

confidence: 96%