Kinetics and mechanism of oxidative carbonylation of benzene catalyzed by rhodium complexes in the presence of copper salts

A kinetic study of benzene oxidative carbonylation was carried out in the medium of trifluoroacetic anhydride at 140°C in the presence of the catalytic system consisting of (PPh 3 ) 3 RhCl and Cu(OAc) 2 . The partial pressures of CO and O 2 and the concentrations of the substrate and catalyst components were found to affect the initial rates of the product buildup (benzoic acid and phenyl benzoate). These data were suggestive of the most probable mechanism of the process, which involves the activation of benzene by a Rh(III) complex via electrophilic substitution with the formation of a Rh-C σ-bond and reoxidation of Rh(I) complexes by molecular oxygen with the assistance of the heterobimetallic Rh-Cu intermediate. The kinetic model based on this mechanism agrees well with experimental observations.