Hydroformylation reactions in supercritical carbon dioxide using insoluble metal complexes

P(OPh)3, P(OC6H4-4-C9H19)3 (1) and Ph2PCH2CH(CO2C16H33)CH2CO2C16H33 (2) provide rhodium catalysts which are insoluble in scCO2 but which can show high activity and selectivity in the hydroformylation of hex-1-ene; removing the products from the reaction by flushing them into a second autoclave and decompressing gives the aldehyde product containing undetectable amounts of rhodium and the catalyst can be reused several times.