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Lewis Acid/Base Interaction Matrix Database

Type 1 Lewis Acid/Base Complexation Chemistry

2 Complexes

Type 1 complexes, typified by hydrogen H2, are covalently bonded. The bonding is frontier molecular orbital (FMO) controlled. Hydrogen, H2, has a 1σ2 MO structure, ie they have two electrons in their 1σ molecular orbital.

Find out more about the bonding diatomic species elsewhere in this webbook, here.

Charge: Complexes can be neutral, H2, or positively charged [H3]+.

Protons complex with hydride ions to form molecular hydrogen, H2, a uniquely simple and much studied diatomic molecule.

The H+  +  H   →  H2  reaction is not reversible: H2 does not act as a proton donor (although at high temperature, when exposed to high energy UV radiation or when absorbed onto a metallic surface, H2 can homolytically dissociate: radical cleavage).

As protons and hydride ions do not exist as independent species, they require "delivery" by donor complexes, ie reagents. Protons, H+ ions, are supplied by Brønsted acids and hydride ions by hydride donor complexes.

For example, hydrogen chloride an H+ donor reacts with sodium hydride an H donor to give diatomic hydrogen and sodium chloride:

   HCl + NaH    →  H2 + NaCl

[H3]+, the product of H+ and H2, is the simplest possible triatomic molecular ion – it has only two electrons – and is of considerable theoretical interest.

The [H3]+ molecular ion occupies an important position in theoretical models of interstellar chemistry as the [H3]+ forms in hydrogen-rich interstellar gas clouds. The [H3]+ ion can protonate carbon, oxygen and other atoms, thereby initiating the interstellar synthesis of nearly 100 molecules including: hydroxyl radicals (HO•), carbon monoxide, ethanol, linear polyacetylenes and cyclopropenylidene.

(In this author's opinion the [H3]+ ion should be called the 'hydronium ion', and [OH3]+ should be the 'oxonium ion'.)

Congeneric Series: Few series.
Type 1 Lewis acid/base complex (generic)

more here
Duteronium ion

more here
Helonium ion

more here

more here
Hydrogen deuteride

more here
Hydronium ion, [H3]+

more here
Interactions and reactions classified as:
      1 +1 1
      1 +1 1
      1 +1 1
      1 +1 1

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Poster Nucleophiles & Bases

© Mark R. Leach 1999 –

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