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 other
proton donor. With a van der Waals radius of 1.2 Å, hydrogen atoms do not usually approach other hydrogen atoms closer than 2.4 Å. Close approaches near 1.8 Å, are, however, characteristic of dihydrogen bonding.
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Boron hydrides
An early example of this phenomenon is credited to Brown and Heseltine.
Interest in dihydrogen bonding was reignited upon the crystallographic characterization of the molecule ammonia borane. In this molecule, like the one studied by Brown and Hazeltine, the hydrogen atoms on nitrogen have a partial positive charge, denoted Hδ+, and the hydrogen atoms on boron have a partial negative charge, often denoted Hδ−.
Coordination chemistry
Protonation of transition metal hydride complexes is generally thought to occur via dihydrogen bonding.[Natalia V. Belkova, Elena S. Shubina, and Lina M. Epstein "Diverse World of Unconventional Hydrogen Bonds" Acc. Chem. Res., 2005, 38, 624–631. ] This kind of H−H interaction is distinct from the H−H bonding interaction in transition metal complexes having dihydrogen bound to a metal.
In neutral compounds
So-called hydrogen–hydrogen bond interactions have been proposed to occur between two neutral non-bonding hydrogen atoms from atoms in molecules theory, while similar interactions have been shown to exist experimentally.[Bakhmutov, Vladimir. I. Dihydrogen bonds: Principles, Experiments and Applications; John Wiley & Sons, Inc.: Hoboken, NJ, 2008. .]
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