Trirhenium nonachloride is a compound with the formula ReCl₃, sometimes also written Re₃Cl₉. It is a dark red hygroscopic solid that is insoluble in ordinary solvents. The compound is important in the history of

inorganic chemistry Inorganic chemistry deals with synthesis and behavior of inorganic and organometallic compounds. This field covers chemical compounds that are not carbon-based, which are the subjects of organic chemistry. The distinction between the two disci ...

as an early example of a cluster compound with metal-metal bonds. It is used as a starting material for synthesis of other rhenium complexes.

Structure and physical properties

As shown by

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

trirhenium nonachloride consists of Re₃Cl₁₂ subunits that share three chloride

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with adjacent clusters. The interconnected network of clusters forms sheets. Around each Re center are seven ligands, four bridging chlorides, one terminal chloride, and two Re-Re bonds.Colton, R. Chemistry of rhenium and technetium. 965. ReCl3 showing full coordination sphere around Cl's

ReCl3 showing full coordination sphere around Cl's

The heat of oxidation is evaluated according to the equation: :1/3 Re₃Cl₉ + 4 OH⁻ + 2 OCl⁻ → ReO₄⁻ + 2 H₂O + 5Cl⁻ The enthalpy for this process is 190.7 ± 0.2 kcal/mol.

Preparation and reactions

The compound was discovered in 1932, although these workers did not determine its structure, which is unusual for metal chlorides. Trirhenium nonachloride is efficiently prepared by thermal decomposition of rhenium pentachloride or hexachlororhenic(IV) acid: :3 ReCl₅ → Re₃Cl₉ + 3 Cl₂ If the sample is vacuum sublimed at 500 °C, the resulting material is comparatively unreactive, but the partially hydrated material can be more useful synthetically. Other synthetic methods include treating rhenium with sulfuryl chloride. This process is sometimes conducted with the addition of aluminium chloride. It is also obtained by heating Re₂(O₂CCH₃)₄Cl₂ under HCl: :3/2 Re₂(O₂CCH₃)₄Cl₂ + 6 HCl → Re₃Cl₉ + 6 HO₂CCH₃ Reaction of the tri- and pentachlorides gives rhenium tetrachloride: :3 ReCl₅ + Re₃Cl₉ → 6 ReCl₄

References

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