Rhenium pentachloride is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the formula . This red-brown solid is

paramagnetic Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, ...

Structure and preparation

Rhenium pentachloride has a bioctahedral structure and can be described as Cl₄Re(μ-Cl)₂ReCl₄. The (μ-Cl)₂ part of this formula indicates that two chloride ligands are

bridging ligand In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually r ...

s, i.e. they connect to two Re atoms. The Re-Re distance is 3.74 Å. The motif is similar to that seen for

tantalum pentachloride Tantalum(V) chloride, also known as tantalum pentachloride, is an inorganic compound with the formula . It takes the form of a white powder, and is commonly used as a starting material in tantalum chemistry. It readily hydrolyzes to form tantalum ...

. This compound was first prepared in 1933, a few years after the discovery of rhenium. The preparation involves chlorination of rhenium at temperatures up to 900 °C.Roger Lincoln, Geoffrey Wilkinson "Rhenium Pentachloride and Volatile Metal Chlorides by Direct Chlorination Using a Vertical-Tube Reactor" Inorganic Syntheses, 1980, Volume 20, Pages 41–43. . The material can be purified by sublimation. ReCl₅ is one of the most oxidized binary chlorides of Re. It does not undergo further chlorination. ReCl₆ has been prepared from

rhenium hexafluoride Rhenium hexafluoride, also rhenium(VI) fluoride, (ReF6) is a compound of rhenium and fluorine and one of the seventeen known binary hexafluorides. Chemistry Rhenium hexafluoride is made by combining rhenium heptafluoride with additional rheniu ...

. Rhenium heptafluoride is known but not the heptachloride.

Uses and reactions

It degrades in air to a brown liquid. Although rhenium pentachloride has no commercial applications, it is of historic significance as one of the early catalysts for

olefin metathesis In organic chemistry, Olefin Metathesis or Alkene Metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the Bond cleavage, scission and regeneration of carbon-carbon double bonds. Because of the ...

. Reduction gives trirhenium nonachloride. Oxygenation affords the Re(VII) oxychloride: :ReCl₅ + 3 Cl₂O → ReO₃Cl + 5 Cl₂ Comproportionation of the penta- and trichloride gives rhenium tetrachloride.

References

{{Chlorides Rhenium compounds Chlorides Metal halides Substances discovered in the 1930s