The immobilisation of phenoxaphosphine-modified xanthene-type ligand on polysiloxane support and application thereof in the hydroformylation reaction

For the first time a phenoxaphosphino-modified Xantphos-type ligand (1) has been covalently anchored to polysiloxane support (silica-1 and sol-gel-1). The use of these heterogenised ligands in the rhodium catalysed hydroformylation of 1-octene gives a system that is competitive with systems employing Xantphos (9) as ligand, but with the added advantages of immobilised systems, like facile catalyst recycling and facile product-catalyst separation. During the recycle experiments no rhodium leaching was detected by ICP analysis (<00.2% Rh-leaching of initial intake) when either silica-1 or sol-gel-1 were used. The application of sol-gel-1 for the hydroformylation of trans-2-octene resulted in an active and regio-selective catalyst, but under forced reaction conditions (T= 393 K, p(CO/H(2)) = 3.6 bar) significant catalyst deterioration was detected. The use of supercritical carbon dioxide as reaction medium in a continuous-flow set-up resulted in similar activities, but slightly lower regio-selectivities compared to batch-wise hydroformylation reactions in toluene. (C) 2004 Published by Elsevier B.V.