Wilkinson Catalysis

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Wilkinson Catalysis
Student Presentation On 5 January 07

• Mr. Nirawat Thammajak 4605015
• Ms. Saowalak Tapala 4605639

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Wilkinson's catalyst

• The common name for chlorotris(triphenylphosphine)
  rhodium(I), a chemical compound with the formula
  RhCl(PPh3)3.
• It is named after the late organometallic chemist
  and 1973 Nobel Laureate, Sir Geoffrey Wilkinson
  who popularlized its use.

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Basic Properties Synthesis

• The compound is a square planar, 16-electron
  complex.
• Isolated in the form of a red-violet crystalline
  solid from the reaction of rhodium trichloride
  with triphenylphosphine. The synthesis is
  conducted in refluxing ethanol.1Ethanol serves
  as the reducing agent.

RhCl3(H2O)3 CH3CH2OH 3PPh3 ? RhCl(PPh3)3
CH3CHO
2HCl 3H2O
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Catalytic applications

• Wilkinson's catalyst is catalyzes the
  hydrogenation of alkenes.
• Mechanism involves the initial dissociation of
  one or two triphenylphosphine ligands to give 14
  or 12-electron complexes, respectively.
• Followed by oxidative addition of H2 to the
  metal.
• Subsequent p-complexation of alkene,
  intramolecular hydride transfer, and reductive
  elimination results in extrusion of the alkane
  product.
• Other applications of Wilkinsons catalyst
  include catalytic hydroboration of alkenes and
  the selective 1,4-reduction of a, ß-unsaturated
  carbonyl compounds in concert with triethylsilane.

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Ex
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Other reactions of RhCl(PPh3)3

• RhCl(Ph3P)3 reacts with CO to give
  RhCl(CO)(PPh3)2, which is structurally analogous
  to Vaska's complex. The complex will also
  decarbonylate aldehydes, although the reaction is
  stoiochiometric
• RhCl(PPh3)3 RCHO ? RhCl(CO)(PPh3)2 RH PPh3
• Upon stirring in benzene solution, RhCl(PPh3)3
  loses PPh3 to give the poorly soluble red-colored
  species Rh2Cl2(PPh3)4. This conversion
  demonstrates the lability of the
  triphenylphosphine ligands.

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Comparison with other catalysts
Wilkinson catalyst is more active and so faster
reactions are possible. Another advantage of this
catalyst is that in comparison with the reactant
and product phases, the catalyst can either be
homogeneous or heterogeneous, whilst the other 2
catalyst are normally in the solid phase.
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References

• Osborn, J. A. Jardine, F. H. Young, J. F.
  Wilkinson, G. Journal of the Chemical Society A,
  1966, pp. 1711 - 1732, DOI 10.1039/J19660001711.
  
• A. J. Birch, D. H. Williamson, Organic Reactions,
  1976, vol. 24, pp. 1ff
• B.R. James, Homogeneous Hydrogenation. John Wiley
  Sons, New York, 1973.
• D. A. Evans, G. C. Fu, and A. H. Hoveyda, Journal
  of the American Chemical Society, 1988, vol. 110,
  pp. 6917.
• I. Ojima, T. Kogure, Y. Nagai, Tetrahedron Lett.
  1972, pp. 5035.
• http//en.wikipedia.org/wiki/Wilkinson's_catalyst
• http//www.ch.ic.ac.uk/wiki/index.php/Itwilkinson