Rhodium Pyrrolylphosphine Complexes as Highly Active and Selective Catalysts for Propene Hydroformylation: The Effect of Water and Aldehyde on the Reaction Regioselectivity

The hydroformylation of propene catalyzed by Rh(acac)(CO) 2 (acac=acetylacetonate) with a 13‐fold excess of N ‐pyrrolylphosphine ligands PPyr 3 , PPh 2 Pyr, or PPh(Pyr) 2 (Pyr=NC 4 H 4 ) was investigated under a pressure of 15 bar (propene/H 2 /CO=5:5:5) at 80 °C. The N ‐pyrrolylphosphine ligands facilitated an excellent regioselectivity towards n ‐butanal aldehyde, significantly better than PPh 3 and PCy 3 under the same conditions. In the presence of the strongest π‐acceptor, PPyr 3 , the linear‐to‐branched aldehyde (l/b) ratio was 8.6, which increased to 27.1 if water was added to the system. The application of a pure aldehyde as a solvent instead of toluene caused a significant increase in the aldehyde yield but with a decreased l/b ratio (2.9–7.6). The regioselectivity parameter l/b increased to 19.3 after the introduction of water as a cosolvent.