Efficient and recyclable IrCl₃·3H₂O-based catalyst modified by ionic ^tBu-substituted-phosphine for highly selective hydroformylation of olefins

Given the depletion of natural resources and relentless price inflation of Rh-compounds, the development of Ir-catalyst as an alternative to this precious Rh-metal has been highly in demand, especially using the easily available IrCl₃·3H₂O as precursor. The novel ionic phosphine ligands of L1 and L2 were synthesized as the unconventional tert-butyl-substituted phosphine-analogues, which were featured with excellent air/moisture insensitivity in contrast to the notorious P(^tBu)₃, due to the strong electron-withdrawing effect of the neighbored imidazolium cation to delocalize the electron density of phosphorus-atom. Fortunately, L1 and L2 enabled IrCl₃·3H₂O exhibited the superior catalytic performance in terms of activity, selectivity and stability for hydroformylation of aliphatic α-olefins. The in situ high-pressure FT-IR spectral studies confirmed the favorable formation and stability of iridium-hydride (Ir-H) active species with L1-IrCl₃·3H₂O catalytic system, responsible for the observed efficient hydroformylation.