Lewis Acid/Base Interaction Matrix Database

s-HOMO Lewis Bases

Hydride Ion, Hydrogen & Helium

H  D  T
H2  D2  T2

Search for s-HOMO Lewis bases species in The Chemical Thesaurus

FMO Topology: s-HOMO Lewis bases have spherical 1s or ovoid (peanut) 1s HOMOs which are devoid of the closed electron shells which hinder complexation (due to closed-shell/closed-shell repulsion) seen in all other Lewis base types.
Charge: Negative (H, hydride) or neutral (H2, hydrogen).
HSAB: Intrinsically soft. The softest and most polarisable of all species.

Nearly all of the elements are able to form hydride compounds:

When s-HOMO Lewis bases interact with Lewis acids to form a complex they are deemed to reduce the Lewis acid: s-HOMO Lewis bases are reducing agents.

The hydride ion is a strong proton abstracting base and nucleophile. H2 is only very weakly basic such that H2, D2, T2, HD, HT and DT hardly seem to be basic at all, yet as they can be protonated to [H3]+ (in the gas phase) they must be Lewis bases.

H and H2 form metallic complexes.

Helium can be protonated under gas phase conditions to [HHe]+ so it is a Lewis base, an s-HOMO Lews base.

Congeneric Series:

H  D  T
H2  D2  T2

s-HOMO Lewis base (generic)
Deuteride ion

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Hydride ion

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Hydrogen deuteride

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Triteride ion

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Nucleophiles & Bases

© Mark R. Leach 1999-

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