Cyclooctadiene rhodium chloride dimer is the

organorhodium compound Organorhodium chemistry is the chemistry of organometallic compounds containing a rhodium- carbon chemical bond, and the study of rhodium and rhodium compounds as catalysts in organic reactions. Stable organorhodium compounds and transient organor ...

with the formula Rh₂Cl₂(C₈H₁₂)₂, commonly abbreviated hCl(COD)sub>2 or Rh₂Cl₂(COD)₂. This yellow-orange, air-stable compound is a widely used precursor to homogeneous catalysts.Giordano, G.; Crabtree, R. H. “Di-μ-chloro-bis(η⁴-1,5-cyclooctadiene)dirhodium(I)” Inorganic Syntheses, 1990, volume 28, pages 88-90.

Preparation and reactions

The synthesis of hCl(COD)sub>2 involves heating a solution of hydrated

rhodium trichloride Rhodium(III) chloride refers to inorganic compounds with the formula RhCl3(H2O)''n'', where ''n'' varies from 0 to 3. These are diamagnetic solids featuring octahedral Rh(III) centres. Depending on the value of ''n'', the material is either a den ...

with

1,5-cyclooctadiene Cycloocta-1,5-diene is a cyclic hydrocarbon with the chemical formula , specifically . There are three configurational isomers with this structure, that differ by the arrangement of the four C–C single bonds adjacent to the double bonds. Each ...

in aqueous

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

in the presence of

sodium carbonate Sodium carbonate, , (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions ...

: :2 RhCl₃·3H₂O + 2 COD + 2 CH₃CH₂OH + 2 Na₂CO₃ → hCl(COD)sub>2 + 2 CH₃CHO + 8 H₂O + 2 CO₂ + 4 NaCl hCl(COD)sub>2 is principally used as a source of the

electrophile In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carrie ...

" h(COD)sup>+." : hCl(COD)sub>2 + L → Rh(COD)sup>+Cl⁻ (where L = PR₃, alkene, etc. and = 2 or 3) In this way,

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from i ...

phosphines Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula , classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting ...

can be attached to Rh. The resulting chiral complexes are capable of

asymmetric hydrogenation Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from othe ...

. A related but still more reactive complex is

chlorobis(cyclooctene)rhodium dimer Chlorobis(cyclooctene)rhodium dimer is an organorhodium compound with the formula Rh2Cl2(C8H14)4, where C8H14 is ''cis''- cyclooctene. Sometimes abbreviated Rh2Cl2(coe)4, it is a red-brown, air-sensitive solid that is a precursor to many other or ...

. The dimer reacts with a variety of Lewis bases (L) to form adducts with the stoichiometry RhCl(L)(COD).

Structure

The molecule consists of a pair of square planar Rh centers bound to a

and two chloride ligands that are

shared Shared may refer to: * Sharing * Shared ancestry or Common descent * Shared care * Shared-cost service * Shared decision-making in medicine * Shared delusion (disambiguation), Shared delusion, various meanings * Shared government * Shared intellig ...

between the Rh centers. The Rh₂Cl₂ core is also approximately planar,"Di-μ-chloro-bis cis,cis-η4-1,5-cyclooctadiene)rhodium(I) a redetermination" De Ridder, Kirk J. A. Acta Crystallographica, Section C: Crystal Structure Communications 1994, C50, 1569-72. in contrast to the highly bent structure of

cyclooctadiene iridium chloride dimer Cyclooctadiene iridium chloride dimer is an organoiridium compound with the formula r(μ2-Cl)(COD)sub>2, where COD is the diene 1,5-cyclooctadiene (C8H12). It is an orange-red solid that is soluble in organic solvents. The complex is used as a p ...

where the dihedral angle is 86°.

References

External links

* {{Rhodium compounds Organorhodium compounds Homogeneous catalysis Cyclooctadiene complexes Dimers (chemistry) Chloro complexes Rhodium(I) compounds