Rhenium heptafluoride

Rhenium heptafluoride is the compound with the formula ReF₇. It is a yellow low melting solid and is the only thermally stable metal heptafluoride. It has a distorted pentagonal bipyramidal structure similar to IF₇, which was confirmed by neutron diffraction at 1.5 K. The structure is non-rigid, as evidenced by electron diffraction studies.

Rhenium heptafluoride can be prepared from the elements at 400 °C:

2 Re + 7 F₂ → 2 ReF₇

It also can be produced by the explosion of rhenium metal under sulfur hexafluoride.

It hydrolyzes under a base to form perrhenic acid and hydrogen fluoride:

ReF₇ + 4H₂O → HReO₄ + 7HF

With fluoride donors such as CsF, the ReF⁻
₈ anion is formed, which has a square antiprismatic structure. With antimony pentafluoride, SbF₅, a fluoride acceptor, the ReF⁺
₆ cation is formed.