Grubbs' catalyst
Encyclopedia
Grubbs' Catalyst is a transition metal carbene complex
named after Robert H. Grubbs
, the chemist who first synthesized it. There are two generations of the catalyst, as shown on the right. In contrast to other olefin metathesis
catalysts, Grubbs' Catalysts tolerate other functional groups in the alkene
and are compatible with a wide range of solvents. For these reasons, Grubbs' Catalysts are extraordinarily versatile.
to achieve olefin cross-metathesis (see below), ring-opening metathesis polymerization (ROMP), acyclic diene metathesis polymerization (ADMET), and ring-closing metathesis
. It is easily synthesized from RuCl2(PPh3)3, phenyldiazomethane, and tricyclohexylphosphine
in a one-pot synthesis
. Grubbs' Catalyst is a relatively stable compound in air, which makes handling very easy. The IUPAC name of the 1st Generation Catalyst is benzylidene-bis(tricyclohexylphosphine)dichlororuthenium.
Olefin metathesis
is a reaction between two molecules containing double bonds. The groups bonded to the carbon atoms of the double bond are exchanged between molecules, to produce two new molecules containing double bonds with swapped groups. Whether a cis isomer or trans isomer is formed in this type of reaction is determined by the orientation the molecules assume when they coordinate to the catalyst, as well as the sterics of the substituent
s on the double bond of the newly forming molecule. Other catalysts are effective for this reaction, notably those developed by Richard R. Schrock
(Schrock carbene).
and air, thus is easier to handle in the lab. A catalyst based on an unsaturated N-heterocyclic carbene (1,3-bis(2,4,6-trimethylphenyl)dihydroimidazole) was reported in March 1999 by Nolan's group. Grubbs' group reported a catalyst based on a saturated N-heterocyclic carbene (1,3-bis(2,4,6-trimethylphenyl)imidazolidine) later the same year (August 1999). One phosphine ligand
is replaced with an N-heterocyclic carbene (NHC) and in this case ruthenium is coordinated to two carbene groups. The IUPAC name of the Second Generation Catalyst is benzylidene[1,3- bis(2,4,6-trimethylphenyl)-2- imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium. Both generations of the catalyst are commercially available.
-Grubbs Catalyst, one of the phosphine
ligands is replaced by an isopropyloxy group attached to the benzene ring. Its second generation has the other phosphine ligand replaced by NHC.
In one study a water soluble Grubbs catalyst is prepared by attaching a polyethylene glycol
chain to the imidazoline
group. The imidazolinium salt is deprotonated by potassium hexamethyldisilazide (KHMDS) in situ to give the N-heterocyclic carbene, which displaces one phosphine ligand to give the modified ruthenium complex:
This catalyst is used in the ring-closing metathesis
reaction in water of a diene carrying an ammonium salt group making it water-soluble as well.
is a necessarily very strong material, but over time microcracks in the structure can form. A new material, with potential application in the construction of spaceship hulls, contains Grubbs' Catalyst, as well as capsules of dicyclopentadiene
, which can undergo ring opening metathesis polymerisation
. When a crack in the hull forms, the capsules are ruptured and come into contact with Grubbs' Catalyst, which polymerizes
dicyclopentadiene and seals the crack.
On October 5, 2005, Robert H. Grubbs
, Richard R. Schrock
and Yves Chauvin
won the Nobel Prize in Chemistry
in recognition of their contributions to the development of this widely used process.
Transition metal carbene complex
A transition metal carbene complex is a organometallic compound featuring a divalent organic ligand. The divalent organic ligand coordinated to the metal center is called a carbene. Carbene complexes for almost all transition metals have been reported. Many methods for synthesizing them and...
named after Robert H. Grubbs
Robert H. Grubbs
Robert Howard Grubbs is an American chemist and Nobel laureate.As he noted in his official Nobel Prize autobiography, "In some places, my birthplace is listed as Calvert City and in others Possum Trot [NB: both in Marshall County]...
, the chemist who first synthesized it. There are two generations of the catalyst, as shown on the right. In contrast to other olefin metathesis
Olefin metathesis
Olefin metathesis or transalkylidenation is an organic reaction that entails redistribution of alkylene fragments by the scission of carbon - carbon double bonds in olefins . Its advantages include the creation of fewer sideproducts and hazardous wastes. Yves Chauvin, Robert H. Grubbs, and Richard R...
catalysts, Grubbs' Catalysts tolerate other functional groups in the alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
and are compatible with a wide range of solvents. For these reasons, Grubbs' Catalysts are extraordinarily versatile.
First generation catalyst
The First Generation Catalyst is often used in organic synthesisOrganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
to achieve olefin cross-metathesis (see below), ring-opening metathesis polymerization (ROMP), acyclic diene metathesis polymerization (ADMET), and ring-closing metathesis
Ring-closing metathesis
Ring-closing metathesis or RCM is a variation on olefin metathesis that allows the closing of previously hard to make rings...
. It is easily synthesized from RuCl2(PPh3)3, phenyldiazomethane, and tricyclohexylphosphine
Tricyclohexylphosphine
Tricyclohexylphosphine is the tertiary phosphine with the formula P3. Commonly used as a ligand in organometallic chemistry, it is often abbreviated to PCy3, where Cy stands for cyclohexyl...
in a one-pot synthesis
One-pot synthesis
In chemistry a one-pot synthesis is a strategy to improve the efficiency of a chemical reaction whereby a reactant is subjected to successive chemical reactions in just one reactor...
. Grubbs' Catalyst is a relatively stable compound in air, which makes handling very easy. The IUPAC name of the 1st Generation Catalyst is benzylidene-bis(tricyclohexylphosphine)dichlororuthenium.
Olefin metathesis
Olefin metathesis
Olefin metathesis or transalkylidenation is an organic reaction that entails redistribution of alkylene fragments by the scission of carbon - carbon double bonds in olefins . Its advantages include the creation of fewer sideproducts and hazardous wastes. Yves Chauvin, Robert H. Grubbs, and Richard R...
is a reaction between two molecules containing double bonds. The groups bonded to the carbon atoms of the double bond are exchanged between molecules, to produce two new molecules containing double bonds with swapped groups. Whether a cis isomer or trans isomer is formed in this type of reaction is determined by the orientation the molecules assume when they coordinate to the catalyst, as well as the sterics of the substituent
Substituent
In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon...
s on the double bond of the newly forming molecule. Other catalysts are effective for this reaction, notably those developed by Richard R. Schrock
Richard R. Schrock
Richard Royce Schrock is an American chemist and Nobel laureate recognized for his contributions to the metathesis reaction used in organic chemistry.-Biography:...
(Schrock carbene).
Second generation catalyst
The Second Generation Catalyst has the same uses in organic synthesis as the First Generation Catalyst, but has a higher activity. This catalyst is stable toward moistureMoisture
Humidity is the amount of moisture the air can hold before it rains. Moisture refers to the presence of a liquid, especially water, often in trace amounts...
and air, thus is easier to handle in the lab. A catalyst based on an unsaturated N-heterocyclic carbene (1,3-bis(2,4,6-trimethylphenyl)dihydroimidazole) was reported in March 1999 by Nolan's group. Grubbs' group reported a catalyst based on a saturated N-heterocyclic carbene (1,3-bis(2,4,6-trimethylphenyl)imidazolidine) later the same year (August 1999). One phosphine ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
is replaced with an N-heterocyclic carbene (NHC) and in this case ruthenium is coordinated to two carbene groups. The IUPAC name of the Second Generation Catalyst is benzylidene[1,3- bis(2,4,6-trimethylphenyl)-2- imidazolidinylidene]dichloro(tricyclohexylphosphine)ruthenium. Both generations of the catalyst are commercially available.
Hoveyda-Grubbs Catalyst
In the first generation HoveydaAmir H. Hoveyda
For the former Iranian prime minister, see Amir-Abbas Hoveida.Amir H. Hoveyda is professor of chemistry at Boston College in Chestnut Hill, MA, and currently holds the position of department chair. He studies asymmetric catalysis, and is particularly noted for his work on developing catalysts for...
-Grubbs Catalyst, one of the phosphine
Phosphine
Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...
ligands is replaced by an isopropyloxy group attached to the benzene ring. Its second generation has the other phosphine ligand replaced by NHC.
In one study a water soluble Grubbs catalyst is prepared by attaching a polyethylene glycol
Polyethylene glycol
Polyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. It has also been known as polyethylene oxide or polyoxyethylene , depending on its molecular weight, and under the tradename Carbowax.-Available forms:PEG, PEO, or POE refers to an...
chain to the imidazoline
Imidazoline
Imidazoline is a nitrogen-containing heterocycle with formula C3H6N2, derived from imidazole. The ring contains an imine bond, and the carbons at the 4 and 5 positions are singly bonded, rather than doubly bonded for the case of imidazole...
group. The imidazolinium salt is deprotonated by potassium hexamethyldisilazide (KHMDS) in situ to give the N-heterocyclic carbene, which displaces one phosphine ligand to give the modified ruthenium complex:
This catalyst is used in the ring-closing metathesis
Ring-closing metathesis
Ring-closing metathesis or RCM is a variation on olefin metathesis that allows the closing of previously hard to make rings...
reaction in water of a diene carrying an ammonium salt group making it water-soluble as well.
Applications
An interesting application of Grubbs' Catalyst is in the aerospace industry. A spaceship's hullHull (watercraft)
A hull is the watertight body of a ship or boat. Above the hull is the superstructure and/or deckhouse, where present. The line where the hull meets the water surface is called the waterline.The structure of the hull varies depending on the vessel type...
is a necessarily very strong material, but over time microcracks in the structure can form. A new material, with potential application in the construction of spaceship hulls, contains Grubbs' Catalyst, as well as capsules of dicyclopentadiene
Dicyclopentadiene
Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula C10H12. At room temperature, it is a white crystalline solid with a camphor-like odor. Its energy density is 10,975 Wh/l....
, which can undergo ring opening metathesis polymerisation
Ring opening metathesis polymerisation
Ring-opening metathesis polymerization is a type of olefin metathesis chain-growth polymerization that produces industrially important products. The driving force of the reaction is relief of ring strain in cyclic olefins and a wide variety of catalysts have been discovered...
. When a crack in the hull forms, the capsules are ruptured and come into contact with Grubbs' Catalyst, which polymerizes
Polymerization
In polymer chemistry, polymerization is a process of reacting monomer molecules together in a chemical reaction to form three-dimensional networks or polymer chains...
dicyclopentadiene and seals the crack.
On October 5, 2005, Robert H. Grubbs
Robert H. Grubbs
Robert Howard Grubbs is an American chemist and Nobel laureate.As he noted in his official Nobel Prize autobiography, "In some places, my birthplace is listed as Calvert City and in others Possum Trot [NB: both in Marshall County]...
, Richard R. Schrock
Richard R. Schrock
Richard Royce Schrock is an American chemist and Nobel laureate recognized for his contributions to the metathesis reaction used in organic chemistry.-Biography:...
and Yves Chauvin
Yves Chauvin
Yves Chauvin is a French chemist and Nobel Prize laureate. He is honorary research director at the Institut français du pétrole and a member of the French Academy of Science. Chauvin received his degree from the Lyon School of Chemistry, Physics and Electronics in 1954.He was awarded the 2005...
won the Nobel Prize in Chemistry
Nobel Prize in Chemistry
The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...
in recognition of their contributions to the development of this widely used process.