Rhenium pentachloride explained

Rhenium pentachloride is an inorganic compound with the formula . This red-brown solid is paramagnetic.^[1]

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 ligands, i.e. they connect to two Re atoms. The Re-Re distance is 3.74 Å.^[2] The motif is similar to that seen for tantalum pentachloride.

This compound was first prepared in 1933,^[3] a few years after the discovery of rhenium. The preparation involves chlorination of rhenium at temperatures up to 900 °C.^[4] 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.^[5] Rhenium heptafluoride is known but not the heptachloride.^[6]

Uses and reactions

It degrades in air to a brown liquid.^[7]

Although rhenium pentachloride has no commercial applications, it is of historic significance as one of the early catalysts for olefin metathesis.^[8] 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

1. 10.1021/ja00534a001 . Bridged and Unbridged M₂L₁₀ Complexes . 1980 . Shaik . Sason . Hoffmann . Roald . Fisel . C. Richard . Summerville . Richard H. . Journal of the American Chemical Society . 102 . 14 . 4555–4572 .
2. 10.1107/S0567740868003316 . The crystal structure of ReCl₅ . 1968 . Mucker, K. F. . Acta Crystallographica Section B . 24 . 874 . Smith . G. S. . Johnson . Q. . 6. 1968AcCrB..24..874M .
3. Geilmann, Wilhelm . Wrigge, Friedrich W. . Biltz, Wilhelm. . Rheniumpentachlorid . German . . 1933 . 214 . 244 . 10.1002/zaac.19332140304 . 3.
4. 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. .
5. Farhad . Tamadon . Konrad . Seppelt . The Elusive Halides VCl₅, MoCl₆, and ReCl₆ . . 2013 . 52 . 2 . 767–769 . 10.1002/anie.201207552 . 23172658 .
6. 10.1021/ic9605736 . Stabilization of High Oxidation States in Transition Metals. 2. WCl₆ Oxidizes [WF₆]^-, but Would PtCl₆ Oxidize [PtF₆]^-? An Electrochemical and Computational Study of 5d Transition Metal Halides: [MF₆] ^z versus [MCl₆] ^z (M = Ta to Pt; z = 0, 1−, 2−) . 1998 . MacGregor . Stuart A. . Moock . Klaus H. . Inorganic Chemistry . 37 . 13 . 3284–3292 .
7. 10.1039/J19700001617 . Some reactions of rhenium(V) chloride . 1970 . Edwards, D. A. . Journal of the Chemical Society A . 1617 . Ward . R. T..
8. Ring-opening polymerization of endo and exo-dicyclopentadiene and their 7,8-dihydro derivatives, Hamilton, J.G.; Ivin, K.J.; Rooney, J.J. Journal of Molecular Catalysis 1986, 36, 115.