Rhenium(IV) chloride explained

Rhenium(IV) chloride is the inorganic compound with the formula ReCl₄. This black solid is of interest as a binary phase but otherwise is of little practical value. A second polymorph of ReCl₄ is also known.

Preparation

ReCl₄ can be prepared by comproportionation of rhenium(V) chloride and rhenium(III) chloride. It can also be produced by reduction of rhenium(V) chloride with antimony trichloride.^[1]

2 ReCl _{5} +SbCl _{3} \longrightarrow2 ReCl _{4} +SbCl _{5}

Tetrachloroethylene at 120 °C is also effective as a reductant:

2 ReCl _{5} +C _{2Cl} _{4} \longrightarrow2 ReCl _{4} +C _{2Cl} _{6}

Structure

X-ray crystallography reveals a polymeric structure. The Re–Re bonding distance is 2.728 Å. Re centers are octahedral, being surrounded by six chloride ligands. Pairs of octahedra share faces. The Re₂Cl₉ subunits are linked by bridging chloride ligands. The structural motif - corner-shared bioctahedra - is unusual in the binary metal halides.

References

1. Book: Erwin Riedel . Christoph Janiak . Anorganische Chemie . Walter de Gruyter . 978-311022567-9 . 2011.