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

The complexation of IrCl 3 ⋅3H 2 O 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 IrCl 3 ⋅3H 2 O 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 IrCl 3 ⋅3H 2 O system immobilized in RTIL of [Bmim]PF 6 could be recycled for 6 runs without the obvious activity loss or metal leaching.