Dihydrogen bond: Difference between revisions

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In [[chemistry]], a '''dihydrogen bond''' is a kind of [[hydrogen bond]], an interaction between a [[metal hydride]] bond and an OH or NH group or another [[proton]] donor. The first example of this phenomenon is credited to Brown and Heseltine.<ref>Brown,{{Cite M. P.; Heseltine, R. W. "Co-ordinated BH3 as a proton acceptor group in hydrogen bonding" Chemical Communications 1968, page 1551-2. DOI: 10.1039/C19680001551</ref> They observed intense absorptions in the [[IR spectroscopy|IR band]]s at 3300 and 3210&nbsp;cm<sup>-1</sup> for a solution of (CH<sub>3</sub>)<sub>2</sub>NHBH<sub>3</sub>. The higher energy band is assigned to a normal N-H vibration whereas the lower energy band is assigned to the same bond, which is interacting with the B-H. Upon dilution of the solution, the 3300&nbsp;cm<sup>-1</sup> band increased in intensity and the 3210&nbsp;cm<sup>-1</sup> band decreased, indicative of intermolecular association.journal
| issue = 23
| pages = 1551-1552
| last = Brown
| first = M. P.
| coauthors = R. W. Heseltine
| title = Co-ordinated BH3 as a proton acceptor group in hydrogen bonding
| journal = Chemical Communications (London)
| accessdate = 2009-04-29
| date = 1968
| url = http://dx.doi.org/10.1039/C19680001551
}}</ref> They observed intense absorptions in the [[IR spectroscopy|IR band]]s at 3300 and 3210&nbsp;cm<sup>-1</sup> for a solution of (CH<sub>3</sub>)<sub>2</sub>NHBH<sub>3</sub>. The higher energy band is assigned to a normal N-H vibration whereas the lower energy band is assigned to the same bond, which is interacting with the B-H. Upon dilution of the solution, the 3300&nbsp;cm<sup>-1</sup> band increased in intensity and the 3210&nbsp;cm<sup>-1</sup> band decreased, indicative of intermolecular association.
 
Interest in dihydrogen bonding was reignited upon the crystallographic characterization of the molecule [[ammonia borane|H<sub>3</sub>NBH<sub>3</sub>]]. In this molecule, like the one studied by Brown and Hazeltine, the hydrogen atoms on nitrogen have a partial positive charge, denoted H<sup>δ+</sup>, and the hydrogen atoms on boron have a partial negative charge, often denoted H<sup>δ-</sup>.<ref>A{{Cite New Intermolecular Interaction: Unconventional Hydrogen Bonds with Element-Hydride Bonds as Proton Acceptor" Crabtree, R. H.; Siegbahn, P. E. M.; Eisenstein, O.; Rheingold, A. L.; Koetzle, T. F. ''Acc. Chem. Res.'' '''1996''', ''29(7)'', 348 - 354.</ref> In other words, the amine is a protic acid and the borane end is hydridic. The resulting B-H<sup>...</sup>H-N attractions stabilize the molecule as a solid. In contrast, the related substance ethane, H<sub>3</sub>CCH<sub>3</sub>, is a gas with a boiling point 285 °C lower. Because two hydrogen atoms are involved, this is termed a dihydrogen bond.journal
| doi = 10.1021/ar950150s
| volume = 29
| issue = 7
| pages = 348-354
| last = Crabtree
| first = Robert H.
| coauthors = Per E. M. Siegbahn, Odile Eisenstein, Arnold L. Rheingold, Thomas F. Koetzle
| title = A New Intermolecular Interaction: Unconventional Hydrogen Bonds with Element−Hydride Bonds as Proton Acceptor
| journal = Accounts of Chemical Research
| accessdate = 2009-04-29
| date = 1996-01-01
| url = http://dx.doi.org/10.1021/ar950150s
}}</ref> In other words, the amine is a protic acid and the borane end is hydridic. The resulting B-H<sup>...</sup>H-N attractions stabilize the molecule as a solid. In contrast, the related substance ethane, H<sub>3</sub>CCH<sub>3</sub>, is a gas with a boiling point 285 °C lower. Because two hydrogen atoms are involved, this is termed a dihydrogen bond.
 
Formation of a dihydrogen bond is assumed to precede formation of H<sub>2</sub> from the reaction of a hydride and a protic acid. A very short dihydrogen bond is observed in NaBH<sub>4</sub><sup>'''.'''</sup>2H<sub>2</sub>O with H---H contacts of 1.79, 1.86, and 1.94 Å. <ref>Custelcean,{{Cite R.; Jackson, J. E. "Dihydrogen Bonding: Structures, Energetics, and Dynamics" Chemical Reviews 2001, volume 101, page 1963-1980.</ref>journal
| doi = 10.1021/cr000021b
| volume = 101
| issue = 7
| pages = 1963-1980
| last = Custelcean
| first = Radu
| coauthors = James E. Jackson
| title = Dihydrogen Bonding: Structures, Energetics, and Dynamics
| journal = Chemical Reviews
| accessdate = 2009-04-28
| date = 2001-07-01
| url = http://dx.doi.org/10.1021/cr000021b
}}</ref>
 
This kind of H---H interaction is distinct from the H---H bonding interaction in [[transition metal]] complexes having dihydrogen bound to a metal.<ref>Kubas,{{Cite G. J., "Metal Dihydrogen and &sigma;-Bond Complexes", Kluwer Academic/Plenum Publishers: New York, 2001.</ref> Another so-called [[hydrogen hydrogen bond]] is postulated to exist in certain compounds between two neutral non-bonding hydrogen atoms.book
| edition = 1
| publisher = Springer
| isbn = 0306464659
| last = Kubas
| first = Gregory J.
| title = Metal Dihydrogen and -Bond Complexes - Structure, Theory, and Reactivity
| date = 2001-08-31
}}</ref> Another so-called [[hydrogen hydrogen bond]] is postulated to exist in certain compounds between two neutral non-bonding hydrogen atoms.
 
==References==