Rhenium(IV) chloride

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.^[1]

Rhenium(IV) chloride

Unit cell of Rhenium(IV) chloride.
Names
Other names rhenium tetrachloride
Identifiers
CAS Number	13569-71-6
3D model (JSmol)	Interactive image
ChemSpider	75414
ECHA InfoCard	100.033.612
PubChem CID	18469522 PubChem has incorrect charge balance
CompTox Dashboard (EPA)	DTXSID7065540
InChI InChI=1S/4Cl.Re Key: YPYBYMCXDNTAKJ-UHFFFAOYSA-N
SMILES [Cl-].[Cl-].[Cl-].[Cl-].[Re+4]
Properties
Chemical formula	Cl4Re
Molar mass	328.01 g·mol−1
Appearance	black solid
Density	4.5 g·cm−3 (β)
Structure[1]
Crystal structure	Primitive monoclinic
Space group	P2/c, No. 13
Lattice constant	a = 636.2 pm, b = 627.3 pm, c = 1216.5 pm α = 90°, β = 93.15°, γ = 90°[1]
Formula units (Z)	4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[2]

${\displaystyle \mathrm {2\ ReCl_{5}+SbCl_{3}\longrightarrow 2\ ReCl_{4}+SbCl_{5}} }$

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

${\displaystyle \mathrm {2\ ReCl_{5}+C_{2}Cl_{4}\longrightarrow 2\ ReCl_{4}+C_{2}Cl_{6}} }$

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.^[1]