Chlorobis(ethylene)rhodium dimer

Chlorobis(ethylene)rhodium dimer

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Identifiers
CAS Number	12081-16-2
Properties
Chemical formula	C8H16Cl2Rh2
Molar mass	388.93
Appearance	red solid
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Chlorobis(ethylene)rhodium dimer is an organorhodium compound with the formula Rh₂Cl₂(C₂H₄)₄. It is a red-orange solid that is soluble in nonpolar organic solvents. The molecule consists of two bridging chloride ligands and four ethylene ligands. The ethylene ligands are labile and readily displaced even by other alkenes. A variety of homogeneous catalysts have been prepared from this complex.

The complex is prepared by treating an aqueous methanolic solution of hydrated rhodium trichloride with ethylene at room temperature. Rh(III) is reduced with oxidation of ethylene to acetaldehyde:

2 RhCl₃(H₂O)₃ + 6 C₂H₄ → Rh₂Cl₂(C₂H₄)₄ + 2 CH₃CHO + 4 HCl + 4 H₂O

Reflecting the lability of its ligands, the complex does not tolerate recrystallization.

The complex reacts slowly with water to give acetaldehyde. With HCl, it gives RhCl₂(C₂H₂)₂⁻. The complex catalyzes the dimerization of ethylene to 1-butene.