New Ligands for Rh‐Catalysed Hydroformylation of 1‐Octene in Supercritical Carbon Dioxide – X‐ray Structure of [Rh{PPh 2 (OC 9 H 19 )} 4 ]PF 6

The new P‐donor ligands PPh 3– n (OC 9 H 19 ) n ( n = 3, 2, 1) containing branched alkyl chains were synthesised and their coordination to Rh I and Pd II studied. The X‐ray structure of [Rh{PPh 2 (OC 9 H 19 )} 4 ]PF 6 was determined. Reaction of the [Rh(acac)(CO) 2 ]/PPh 3– n (OC 9 H 19 ) n systems with CO/H 2 at 5 atm and 80 °C in toluene led to the formation of [RhH(CO){PPh 3– n (OC 9 H 19 ) n } 3 ] as the main species. The Rh‐catalysed hydroformylation of 1‐octene with these ligands was investigated in supercritical carbon dioxide (scCO 2 ) and toluene as solvents. Although the catalytic systems are not soluble in scCO 2 , they are active. The activities are higher in toluene than in scCO 2 but the selectivities for aldehydes in the case of the phosphonite derivative are higher in the supercritical medium than in toluene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)