Transition metals are commonly used for carbon-carbon coupling reactions throughout modern synthetic chemistry. Reactions such as arylation and vinylation of olefins can be catalysed by palladium complexes for example in the Heck reaction. Such reactions have been widely studied for industrial-scale-up over the last ten years. However, catalytic power - turnover number - has generally been achieved at less than 100.
  In 1995, Wolfgang Herrmann of the Technical University in Berlin discovered that palladacyclic complexes could achieve turnovers of up to about 500,000. Now, a French team has achieved turnover numbers still greater, some 10^8, for the asymmetric hydroarylation of norbornene.
  Gérard Buono and his colleagues at the Laboratory of Asymmetric Synthesis (UMR CNRS) in Marseilles, France, have synthesised a chiral o-tolyldiazaphospholidine ligand in 89% yield using an exchange reaction in refluxing toluene from bis(dimethylamino)(o-tolyl)phosphine and (S)-anilinomethylpyrrolidine. They confirmed the structure of this ligand using NMR spectroscopy and X-ray analysis. They could then produce the active palladacycle by treating palladium(II) acetate with this ligand in refluxing toluene. The product was as a thermally, air and moisture stable yellow solid although they are yet to crystallise it.
  The researchers have found that this phosphapalladacycle catalyst mediates the arylation of the standard starting material norbornene under reductive conditions - triethylamine in HCO2H - so that reaction of phenyl triflate or iodobenzene with norbornene produced the corresponding exo-phenylnorbornane.
  The team report exceptional turnover numbers up to 1.96 × 10^8 mol product and yields of some 98%. These values are the highest turnover numbers reported to date for palladium catalysis involving chiral palladacycle complexes, they claim.
  The researchers concede that the enantiomeric excesses (ee) they have achieved are low - just 25% ee (2mol% of catalyst) - but they point out that this is the first successful asymmetric reaction using a chiral phosphapalladacycle catalyst. They are now working on relating their results to the catalyst's structure and finding ways to modify the chiral component in order to increase the selectivity.

The team reports their results in more detail in Chem Commun (DOI: 10.1039/b005521m) and in Angew. Chem. Eng. Edn. 2000, 39, 1946.