Hydroformylation in fluorous solvents

The fluorous solvent alone had a minimal effect on the outcome of the reaction. However, with the flnorinated ligand, the n iso ratio was found to increase with increasing phosphine concentration, reaching a valne of almost 8 1 at a phosphine to rhodium ratio of 103 1. The beauty of this system was demonstrated by its use in a semicontinnous hydroformylation experiment. After each 

Despite this setback, this catalyst system could also be used for the hydroformylation of ethylene and indeed the long-term stability of the catalyst was found to be better than that of the catalyst derived from triphenylphosphine. Hence, this catalyst system allowed the hydroformylation of both high and low molecular weight alkenes under homogeneous conditions combined with facile product separation by simple decantation. 

Investigation of the derivatized triarylphosphine in PP2 demonstrated that this catalyst system was much more stable under the same reaction conditions compared to that derived from the phosphite. The rhodium leaching level was dramatically reduced (0.05 % in one case). Omission of toluene from this system allows development of a process which is nearing the rigorous retention that would be required for commercial application, whilst retaining a high rate and good selectivity to the linear aldehyde product. The refined system also compares well with commercial processes. 

The hydroformylation of long chain alkenes using the perfluoroalkyl-deri-vatized phosphites illustrated in Figme 8.10 has also been examined [30]. 

CH2CH2 spacer groups insulated the aryl rings from the perfluorooctyl groups. This was found to markedly increase the stability of the phosphites towards hydrolysis. 

Although much effort has been directed towards making catalysts soluble in the alternative solvents described in this book, insoluble metal complexes have actu- 

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