Dehalogenation of Chloroarenes with Sodium Dihydridobis(2-methoxyethoxo)aluminate in the Presence of Transition Metal Compounds

Dehalogenation of low-chlorinated arenes such as p-dichlorobenzene or chlorobenzene with the title hydride is accelerated in the presence of transition metal species formed in situ from the corresponding 2,4-pentanedionates. Their efficiency decreases in the order: Co ≈ Ni ≈ Pd > Cu >> Mn > Fe which results from changes of their activity and stability. The dehalogenation is well described by a kinetic model consisting of the set of dehalogenation steps which are first order in the chloroarene combined with the catalyst deactivation which is second order in the transition metal compound.