Hydrogenolysis of polychlorinated biphenyls by sodium borohydride with homogeneous and heterogeneous nickel catalysts

Abstract

The hydrogenolysis (hydrodechlorination) of a series of pure PCB congeners with sodium borohydride was studied. In the absence of nickel compounds, very little reaction occurred, but in the presence of solid Raney-type nickel or in the presence of a soluble Ni(0)triphenylphosphine complex, extensive hydrogenolysis occurred at ambient temperatures in DMF. The selectivity of one congener versus another was studied and found to be low. The selectivity for 2-, 3-, and 4-chloro displacement from di- and trichlorobiphenyls in the presence of Ni(0) complexes, however, was found to be high. The selectivities are interpreted with respect to the known mechanism of oxidative addition of aryl halides with Ni(0) complexes