Efficient and Recyclable RuCl₃ ⋅ 3H₂O Catalyst Modified with Ionic Diphosphine for the Alkoxycarbonylation of Aryl Halides

Abstract

A series of ionic (mono‐/di‐)phosphines (L2, L4, and L6) with structural similarity and their corresponding neutral counterparts (L1, L3, and L5) were applied to modulate the catalytic performance of RuCl3 ⋅ 3H2O. With the involvement of the ionic diphosphine (L4), in which the two phosphino‐fragments were linked by butylene group, RuCl3 ⋅ 3H2O with advantages of low cost, robustness, and good availability was found to be an efficient and recyclable catalyst for the alkoxycarbonylation of aryl halides. The L4‐based RuCl3 ⋅ 3H2O system corresponded to the best conversion of PhI (96 %) along with 99 % selectivity to the target product of methyl benzoate as well as the good generality to alkoxycarbonylation of different aryl halides (ArX, X=I and Br) with alcohols MeOH, EtOH, i‐PrOH and n‐BuOH. The electronic and steric effects of the applied phosphines, which were analyzed by the 31P NMR for 1 J 31 P‐ 77 Se 1 J measurement and single‐crystal X‐ray diffraction, were carefully co‐related to the performance RuCl3 ⋅ 3H2O catalyst. In addition, the L4‐based RuCl3 ⋅ 3H2O system could be recycled successfully for at least eight runs in the ionic liquid [Bmim]PF6.