This dark blue salt is well known as an early example of a compound featuring quadruple bond between its metal centers.

[1] Soviet chemists first reported K2[Re2Cl8] in 1954,[2] but it was not until 1964 that Cotton and Harris characterized the compound as featuring a short Re–Re bond, the first of its kind discovered.

[3][4] The results of this classic study subsequently led to new work into other metals capable of forming metal–metal bonds, such as chromium, molybdenum, tungsten, and technetium.

[5][6][7] A high-yield synthesis of the tetrabutylammonium salt involves treating the perrhenate salt with benzoyl chloride followed by HCl: Octachlorodirhenate(III) is a precursor to other complexes with multiply-bonded rhenium centers as the quadruple bond is quite stable and is often maintained in ligand substitution reactions.

For example, upon treatment with concentrated HBr, the complex forms the analogous anion [Re2Br8]2−, which can easily be converted into other dirhenium species.