Ionic Rh(I)-complexes containing π-accepting and hemilabile P,N-ligands as efficient catalysts for hydroformylation of 1-octene

• Ionic Rh(I)-complexes containing π-accepting and hemilabile P,N-ligands.
• Efficient catalysts for homogeneous hydroformylation of 1-octene.
• In situ high-pressure FT-IR characterization of active RhH species.

The ionic hybrid P,N-ligands of 1 and 2 have been synthesized as one type of unconventional tertiary phosphines with the advantages of both the π-accepting ligands and the hemilabile ligands. The corresponding ionic Rh(I)-complexes of 1A and 2A proved to be more efficient catalysts for hydroformylation of 1-octene over isomerization than the traditional RhI(acac)(CO)(PPh3), due to the π-backdonation interaction in Rh → P linkage and the hemilabile ligation of N,P-coordinating sites to Rh-center. The in situ high-pressure FT-IR analysis indicated that: (1) the formation and lifetime of the active RhH species (2047 cm−1) derived from 1A are facilitated by the presence of ligand 1; (2) the formation of the active RhH species is depressed without the aid of the P,N-hemilabile ligation; and (3) the active RhH species derived from RhI(acac)(CO)(PPh3) is unstable and susceptible to the formation of the inactive carbonyl-bridged Rh-dimer.

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