Cyclooctadiene rhodium chloride dimer

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Cyclooctadiene rhodium chloride dimer
CAS number 12092-47-6 YesY
ChemSpider 21171524 YesY
Jmol-3D images Image 1
Molecular formula C16H24Cl2Rh2
Molar mass 493.0806 g/mol
Melting point 243 °C
Solubility in other solvents dichloromethane
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Cyclooctadiene rhodium chloride dimer is the chemical compound with the formula Rh2Cl2(C8H12)2, commonly abbreviated [RhCl(COD)]2 or Rh2Cl2(COD)2. This yellow-orange, air-stable compound is a widely used precursor to homogeneous catalysts.[1]

Preparation and reactions[edit]

The synthesis of [RhCl(COD)]2 involves treatment of hydrated rhodium trichloride with 1,5-cyclooctadiene in hot, deoxygenated aqueous ethanol in the presence of sodium carbonate:[1]

2 RhCl3.3(H2O) + 2 COD + 2 CH3CH2OH + 2 Na2CO3 → [RhCl(COD)]2 + 2 CH3CHO + 8 H2O + 2 CO2 + 4 NaCl

[RhCl(COD)]2 is the principal source of the versatile electrophile "[Rh(COD)]+."

[RhCl(COD)]2 + n L → [LnRh(COD)]+Cl- (where L = PR3, alkene, etc. and n = 2 or 3)

In this way, chiral phosphines such as chiraphos, DIPAMP, and DIOP have been attached to Rh. The resulting chiral catalysts are capable of asymmetrically hydrogenating certain prochiral alkenes.[2]

See Also[edit]


  1. ^ a b Giordano, G.; Crabtree, R. H. “Di-μ-chloro-bis(η4-1,5-cyclooctadiene)dirhodium(I)” Inorganic Syntheses, 1990, volume 28, pages 88-90. ISBN 0-471-52619-3.
  2. ^ W. S. Knowles (2003). "Asymmetric Hydrogenations (Nobel Lecture 2001)". Advances in Synthesis and Catalysis 345 (1–2): 3. doi:10.1002/adsc.200390028.