Synthetic, Thermochemical, and Catalytic Studies Involving Novel R2P(ORf) [R = Alkyl or Aryl; Rf = CH2CH2(CF2)5CF3] Ligands

Abstract

A series of mixed alkyl (or aryl) phosphinite compounds have been prepared from the alcohol CF3(CF2)5CH2CH2OH (RfOH) and an appropriate ClPR2 (R = ORf, Ph, iPr, Cy) in the presence of base. A bidentate analog, (RfO)2PCH2CH2P(ORf)2, was synthesized in a similar manner. The ligands react with [Rh(CO)2Cl]2 yielding the complexes RhCl(CO)(PR3)2. The structure of RhCl(CO)(PPh2ORf)2 (6) is reported. Infrared studies of the carbonyl complexes yield a relative ligand donor strength for this series. Solution calorimetry was performed on the rhodium reaction in order to quantify this donor strength scale. Both approaches lead to the same donor strength scale: PCy2ORf > PiPr2ORf > PPh2ORf > P(ORf)3. These phosphinite ligands can be used as ancillary ligation in rhodium-mediated hydrogenation. A cationic rhodium complex of the chelating ligand displays selected solubility in fluorous media and biphasic catalysis can be performed.