Phosphine-ligated Ir(III)-complex as a bi-functional catalyst for one-pot tandem hydroformylation-acetalization

The complexation of IrCl₃⋅3H₂O with the electron-deficient phosphines (L1-L6) respectively afforded a bi-functional catalyst possessing the dual functions of transition metal complex (Ir^III-P) and Ir^III-Lewis acid for tandem hydroformylation-acetalization of olefins. The best result was obtained over L5-based IrCl₃⋅3H₂O catalytic system which corresponded to 97% conversion of 1-hexene along with 92% selectivity to the target acetals free of any additive. The crystal structure of the novel Ir^III-complex of Ir^III-L4 indicated that the electron-deficient nature of the involved phosphine warranted Ir-center in +3 valence state without reduction, which served as the Lewis acid catalyst for the subsequent acetalization of the aldehydes as well. Moreover, as an ionic phosphine, L6-based IrCl₃⋅3H₂O system immobilized in RTIL of [Bmim]PF₆ could be recycled for 6 runs without the obvious activity loss or metal leaching.