The hydroformylation of decene-1 was studied in the presence of the fluorous-soluble P[CH2CH2(CF2)5CF3]3 modified rhodium catalyst at 100 °C and 1.1 MPa of CO/H2 (1:1) in a 50/50 vol % toluene/C6F11CF3 solvent mixture, which forms a homogeneous liquid phase at and above 100 °C. P[CH2CH2(CF2)5CF3]3 was selected on the basis of a semiempirical calculation of the electronic properties of P[(CH2)x(CF2)yCF3]3 (x = 0, y = 2, 4 and x = 0−5, y = 2) and prepared by the reaction of PH3 with CH2CH(CF2)5CF3. The solution structure of HRh(CO){P[CH2CH2(CF2)5CF3]3}3 (1) in C6F11CF3 is similar to that of HRh(CO)(PPh3)3 (2) in toluene and HRh(CO){P(m-C6H4SO3Na)3}3 (3) in water. High-pressure NMR of 1 under 2.1−8.3 MPa of CO/H2 (1:1) revealed that 1 is in equilibrium with HRh(CO)2{P[CH2CH2(CF2)5CF3]3}2 (4). Kinetic studies show that the reaction is first order in both rhodium and decene-1. While the reaction is inhibited by P[CH2CH2(CF2)5CF3]3, the normal/iso (n/i) ratio of the aldehyde increases with increasing phosphine ...