Lewis Acid/Base Interaction Matrix Database


Type 21 Lewis Acid/Base Complexation Chemistry
Heavy Metal Hydrides

              V2+      +   2H           VH2
              Re7+    +   9H           [ReH9]

Bonding:

  • Metallic or interstitial hydrides are formed by many d-block and f-block elements when heated with hydrogen under pressure. The hydrides tend to be non-stoichiometric and they may be of variable composition.
  • There is a hydride gap where elements do not form hydrides. This roughly maps to the siderophile elements.
  • Intermediate hydrides have properties between metallic and covalent.

Metallic properties and non-stoichiometric compositions are common. The bonded hydrogen may be mobile. In various models the hydrogen may be present as H+ with the lost electrons going to the metal’s d-orbitals. In other models the hydrogen is assumed to have acquired electrons from the metallic conduction band and so be present as H.

Note that even though a metal may not form a hydride, it can still form a hydride complex ion, for example rhenium:

              Re7+    +   9H           [ReH9]

Charge: Complexes may be negatively charged or they may be neutral.
Chemistry:

Hydride and hydrogen donors. Transition metal hydrides, MHn, can sometimes be formed by ‘dissolving’ hydrogen gas into a bulk metal to from a metal/hydride phase. This phase is the active ‘hydrogenating agent’ employed during catalytic hydrogenation. Palladium metal is able to absorb 900 times its own volume of hydrogen gas.

Transition metal/hydride coordination complexes can be formed by nucleophilic displacement of a halogen (or other nucleofugal ligand) by hydride ions supplied by LiAlH4 or NaBH4:

Metallic hydrides materials are usually dark powders or brittle solids. The bonding mechanism is important because heavy metal hydrides are being actively considered as hydrogen storage materials for hydrogen powered automobiles.

Congeneric Series: Few series.
Type 21 Lewis acid/base complex (generic)
Chlorohydrobis(triethylphosphine) platinium(II)

more here
Iron titanium hydride

more here
Lanthanum nickel hydride

more here
Magnesium nickel hydride

more here
Palladium hydride

more here
Rhenium nonahydride ion

more here
Scandium(II) hydride

more here
Tetracarbonylhydrocobalt(I)

more here
Tricarbonylhydrocobalt(I)

more here


Interactions and reactions classified as:
Type 21 Lewis Acid/Base Complexation Chemistry
       +
      2 +1 2
      1 +9 1
      1 +1 +2 +1 1
      1 +6 1
      1 +4 1
      1 +4 1



Poster
Nucleophiles & Bases

© Mark R. Leach 1999-


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