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CATALYSIS AND SUPRAMOLECULAR CHEMISTRY

 

Generation of phosphine low-coordinated species

 

We previously showed that, in the presence of β-CD or Rame-β-CD, TPPTS low-coordinated rhodium species could be formed.

 

β-CD ; G=H RAME-β-CD ; G=H ou CH3 (11,8 on average)

 

To emphasize the phenomenon, we synthesized a new hydrosoluble phosphine, named tBuTPPDS (TertioButylTriPhenylPhosphineDiSulfonated) and bearing a tertiobutylphenyle group whose presence provide a very high CD/ligand association constant (400 000 M-1 vs. 1 200 M-1 for the β-CD/TPPTS couple).

The behaviour of the tBuTPPDS-based rhodium, palladium or platinum complexes has been studied by NMR. Addition of β-CD or Rame-β-CD to these species led to the formation of phosphine low-coordinated species. It is worth noting that these low-coordinated species are in equilibrium with species bearing CDs as second-sphere ligands. The equilibrium is dependant on the CD amount and the temperature [P1]..

 

 

A similar behaviour has been observed with sulfonated alkyldiphosphines. Actually, the mobility of the alkyle chain originates in the formation of phosphine low-coordinated species with one CD as second-sphere ligand [P2].

 

 

Publications :

 

• P 1. Supramolecular trapping of phosphanes by cyclodextrins: A general approach to generate phosphane coordinatively unsaturated organometallic complexes.

  C. Binkowski-Machut, M. Canipelle, H. Bricout, S. Tilloy, F. Hapiot, E. Monflier,
  Eur. J. Inorg. Chem. (2006) 1611-1619.

• P 2. Hydroformylation of 1-decene in aqueous medium catalyzed by rhodium/alkyl sulfonated diphosphines system in the presence of methylated β-cyclodextrins. How the flexibility of the diphosphine backbone influences the regioselectivity.

  S. Tilloy, G. Crowyn, E. Monflier, P. W. N. M. van Leeuwen, J. N. H. Reek,
  New. J. Chem. 30 (2006) 377-383.

 

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