The catalytic activity of the complexes FeCl2(PPh3)(2), RuHCl (PPh3)(3), RuH2(CO)(PPh3)(3), RuHCl(CO)(AsPh3)(3), RuHCl(CO) ((PPr3)-Pr-i)(2), OsHCl(CO)((PPr3)-Pr-i)(2), OsH2Cl2((PPr3)-Pr-i)(3), CoCl(PPh3)(3), RhH2Cl((PPr3)-Pr-i)(2), IrH2Cl((PPr3)-Pr-i)(2), IrCl(PPh3)(3), and IrH2(SiEt3) (COD)(PCy3) (COD = 1,5-cyclooctadiene) in the simultaneous dehalogenation of 1,2,4-trichlorobenzene and the chlorination of HSiEt3 has been studied. The 3d metal complexes and the derivative IrH2(SiEt3)(COD)(PCy3) are unactive, while the 4d and 5d metal compounds simultaneously catalyze the dehalogenation of 1,2,4-trichlorobenzene and the chlorination of HSiEt3. The osmium and iridium derivatives are less effective catalysts than the derivatives of ruthenium and rhodium and undergo deactivation. Complexes RuHCl(PPh3)(3) and RhH2Cl((PPr3)-Pr-i)(2) also catalyze the dehalogenation of 1,2-, 1,3-, and 1,4-dichlorobenzene and chlorobenzene. The dehalogenation of 1,3-and 1,4-dichlorobenzene is favored over the dehalogenation of the 1,2-isomer.