Effect of ligand modification on rhodium-catalyzed homogeneous hydroformylation in supercritical carbon dioxide

Several fluoroalkyl- and fluoroalkoxy-substituted tertiary arylphosphines w ere synthesized and investigated in the homogeneous catalytic hydroformylat ion of 1-octene using HRh(CO)L-3 (L = tertiary arylphosphine). The activity of the rhodium complex (formed in situ from Rh(CO)(2)(acac) and L) increas ed with decreasing basicity of the phosphine according to the series [3,5-( CF3)(2)C6H3](3)P > [4-CF3C6H4](3)P approximate to [3-CF3C6H4](3)P > [4-CF3O C6H4](3)P > [4-F(CF2)(4)(CH2)(3)C6H4](3)P. The very weakly basic phosphine (C6F5)(3)P did not complex with Rh(CO)(2)(acac), most likely due to a combi nation of electronic and steric factors. Steric effects did not play a role in either the activity or selectivity of the rhodium catalysts that were f ormed under hydroformylation conditions.