Aluminium(I) compounds

In chemistry, aluminium(I) refers to monovalent aluminium (+1 oxidation state) in both ionic and covalent bonds. Along with aluminium(II), it is an extremely unstable form of aluminium.

While late Group 13 elements such as thallium and indium prefer the +1 oxidation state, aluminium(I) is rare. Aluminium does not experience the inert-pair effect, a phenomenon where valence s electrons are poorly shielded from nuclear charge due to the presence of filled d and f orbitals.^[1] As such, aluminium (III) (${\displaystyle {\ce {Al^3+}}}$) is the much more common oxidation state for aluminium.

Aluminium(I) compounds are both prone to disproportionation and difficult to prepare.^[2] At standard conditions, they readily oxidize to the aluminium(III) form.