Cyclooctadiene rhodium chloride dimer
Encyclopedia
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
..
in hot, deoxygenated aqueous ethanol
in the presence of sodium carbonate
:
[RhCl(COD)]2 is the principal source of the versatile electrophile
"[Rh(COD)]+."
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.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
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
Homogeneous catalysis
In chemistry, homogeneous catalysis is a sequence of reactions that involve a catalyst in the same phase as the reactants. Most commonly, a homogeneous catalyst is codissolved in a solvent with the reactants.-Acid catalysis:...
..
Preparation and reactions
The synthesis of [RhCl(COD)]2 involves treatment of hydrated rhodium trichloride with 1,5-cyclooctadiene1,5-Cyclooctadiene
1,5-Cyclooctadiene is the organic compound with the chemical formula C8H12. Generally abbreviated COD, this diene is a useful precursor to other organic compounds and serves as a ligand in organometallic chemistry.- Synthesis :...
in hot, deoxygenated aqueous ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
in the presence of sodium carbonate
Sodium carbonate
Sodium carbonate , Na2CO3 is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. Sodium carbonate is domestically well-known for its everyday use as a water softener. It can be extracted from the...
:
- 2 RhCl3.3(H2O) + 2 COD + 2 CH3CH2OH + 2 Na2CO3 → [RhCl(COD)]2 + 2 CH3CHOAcetaldehydeAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
+ 8 H2O + 2 CO2 + 4 NaCl
[RhCl(COD)]2 is the principal source of the versatile electrophile
Electrophile
In general electrophiles are positively charged species that are attracted to an electron rich centre. In chemistry, an electrophile is a reagent attracted to electrons that participates in a chemical reaction by accepting an electron pair in order to bond to a nucleophile...
"[Rh(COD)]+."
- [RhCl(COD)]2 + n L → [LnRh(COD)]+Cl- (where L = PR3, alkene, etc. and n = 2 or 3)
In this way, chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
phosphines such as chiraphos
Chiraphos
Chiraphos is a chiral diphosphine employed as a ligand in organometallic chemistry. This bidentate ligand chelates metals via the two phosphine groups. Its name is derived from its description — being both chiral and a phosphine...
, DIPAMP
DIPAMP
DIPAMP is an organophosphorus compound that is used as a ligand in homogeneous catalysis. It is a white solid that dissolves in organic solvents. Work on this compound by W. S. Knowles was recognized with the Nobel Prize in Chemistry. DIPAMP was the basis for of the first practical asymmetric...
, and DIOP
Diop
Diop is a surname, and may refer to:* Aïda Diop* Birago Diop* Boubacar Boris Diop* Cheikh Anta Diop* DeSagana Diop* Djibril Diop Mambéty Senegalese film director, brother of Wasis Diop* Mamadou Diop* Mustapha Papa Diop...
have been attached to Rh. The resulting chiral catalysts are capable of asymmetrically hydrogenating certain prochiral
Prochiral
In stereochemistry, prochiral molecules are those that can be converted from achiral to chiral in a single step.If two identical substituents are attached to a sp3-hybridized atom, the descriptors pro-R and pro-S are used to distinguish between the two...
alkenes.