Shvo's complex
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| Names | |
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IUPAC name
1-Hydroxytetraphenylcyclopentadienyl-(tetraphenyl-2,4-cyclopentadien-1-one)-μ-hydrotetracarbonyldiruthenium(II)
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| Identifiers | |
| Properties | |
| C62H42O6Ru2 | |
| Molar mass | 1085.13 |
| Appearance | orange solid |
| Melting point | 223 to 227 °C (433 to 441 °F; 496 to 500 K) |
| polar organic solvents | |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
The Shvo catalyst, named after Youval Shvo, is an organoruthenium compound that is used for transfer hydrogenation. Related derivatives are known where p-tolyl replaces some of the phenyl groups. The compound is of academic interest as an early example of a catalyst for transfer hydrogenation that operates by an "outer sphere mechanism."
Commonly, industrial hydrogenation processes involve heterogeneous catalysts containing one or more transition metals. While this approach facilitates efficient production on an industrial scale, heterogeneous catalysis is not always suitable for the asymmetric synthesis of more structurally complex molecules, which demands the increased versatility precluded by necessary interaction with a solid metal surface.
One half of the 2001 Nobel Prize in Chemistry was awarded jointly to William S. Knowles and Ryoji Noyori "for their work on chirally catalysed hydrogenation reactions", and the other half was awarded to K. Barry Sharpless "for his work on chirally catalysed oxidation reactions", highlighting the growing importance of homogeneous catalysis as an industrially applicable redox technique for asymmetric synthesis. Shvo's catalyst represents a subset of homogeneous hydrogenation catalysts that involves both metal and ligand in its mechanism, and it therefore presents unique opportunities for customizing selectivity.
The complex was originally prepared by the reaction of diphenylacetylene and triruthenium dodecacarbonyl. This synthetic route is efficient, despite the complicated pathway, which includes formation of cyclopentadienone-like ligands. Related syntheses use the preformed cyclopentadienone. A related iron analogue is also known, see Knölker complex.
The compound contains a pair of equivalent Ru centres that are bridged by a strong hydrogen bond and a bridging hydride. In solution, the complex dissociates unsymmetrically:
The hydride (η5-C5Ph4OH)RuH(CO)2 transfers H2, especially to polar substrates such as ketones and iminium cations. The cyclopentadienone species (η6-C5Ph4O)Ru(CO)2 abstracts H2 from substrates.
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