Iron(II) hydride

However, as the name is compositional in nature, it does not distinguish between compounds of the same stoichiometry, such as molecular species, which exhibit distinct chemical properties.

Dihydridoiron, also systematically named ferrane(2), is a related inorganic compound with the chemical formula FeH2 (also written [FeH2]).

Aqueous solutions of adducts of weak-field Lewis bases are however, unstable due to hydrolysis of the dihydridoiron and hydridoiron(1+) groups: It should be expected that iron dihydride clusters and iron(II) hydride have similar acid-base properties, although reaction rates and equilibrium constants are different.

Since it is a polymeric solid, a monocrystalline sample is not expected to undergo state transitions, such as melting and dissolution, as this would require the rearrangement of molecular bonds and consequently, change its chemical identity.

Colloidal crystalline samples, wherein intermolecular forces are relevant, are expected to undergo state transitions.

[4] At least up to −173 °C (−279 °F), iron(II) hydride is predicted to have a body-centred tetragonal crystalline structure with the I4/mmm space group.

[2] A few of dihydridoiron's electronic states lie relatively close to each other, giving rise to varying degrees of radical chemistry.

Furthermore, Crystal field theory predicts that the low transition energies correspond to a colourless compound.

It occurs as a brittle component within the solid matrix, with a physical makeup that depends on its formation conditions and subsequent heat treatment.

As it decomposes over time, the alloy will slowly become softer and more ductile, and may start to suffer from hydrogen embrittlement.

As dihydridoiron is an electron-deficient molecule, it spontaneously autopolymerises in its pure form, or converts to an adduct upon treatment with a Lewis base.

Upon treatment of adducts of weak-field Lewis bases with a dilute standard acid, it converts to an hydridoiron(1+) salt and elemental hydrogen.