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Revision as of 15:30, 21 May 2005 by 62.255.32.14 (talk)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)| Grubbs' Catalyst 1 Generation | |
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| File:Grubbs Catalyst 1st Generation.png | |
| General | |
| Molecular formula | C43H72Cl2P2Ru |
| Molar mass | 822.96 g/mol |
| Appearance | Purple Solid |
| CAS number | |
| Melting point | 153 °C (426 K) |
| Grubbs' Catalyst 2 Generation | |
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| General | |
| Molecular formula | C46H65Cl2N2PRu |
| Molar mass | 848.97 g/mol |
| Appearance | Pinkish-Brown Solid |
| CAS number | |
| Melting point | 143.5-148.5 °C (416.5-421.5 K) |
Grubbs' Catalyst is named after the chemist by whom it was first synthesized, Robert H. Grubbs. 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.
The 1 Generation Catalyst is often used in organic synthesis to achieve olefin cross-metathesis (see below), ring-opening metathesis polymerization (ROMP), 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 1 Generation Catalyst is benzylidene-bis(tricyclohexylphosphine)dichlororuthenium.
Olefin metathesis, shown below, 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 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 substituents on the double bond of the newly forming molecule. Other catalysts are effective for this reaction, notably those developed by Schrock (Schrock carbene).
The 2 Generation Catalyst has the same uses in organic synthesis as the 1 Generation Catalyst, but has a higher activity. This catalyst is also air stable and is easily synthesized from the combination of the 1 Generation Catalyst and alkoxy-protected 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene. The IUPAC name of the 2 Generation Catalyst is benzylidenedichloro(tricyclohexylphosphine)ruthenium. Both generations of the catalyst are commercially available through Aldrich.
An interesting application of Grubbs' Catalyst is in the aerospace industry. A spaceship's hull is a necessarily very strong material, but over time small microcracks in the structure can form. A new material used in the construction of spaceship hulls contains Grubbs' Catalyst, as well as capsules of dicyclopentadiene, which can undergo ROMP. 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.
References
1. Schwab, P.; Grubbs, R. H.; Ziller, J. W. Journal of the American Chemical Society, 1996, 118, 100-110.
2. Louie, J.; Grubbs, R. H. Organometallics, 2002, 21, 2153-2164.
3. Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Organic Letters, 1999, 1, 953-956.
4. Trnka, T. M.; Grubbs, R. H. Accounts of Chemical Research, 2001, 34, 18-29.
5. Bonser, K. http://science.howstuffworks.com/self-healing-spacecraft1.htm
6. Grubbs, R.H. Handbook of Metathesis; Wiley VCH: United Kingdon, 2003.
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