HYDROGENOLYSIS OF POLYCHLORINATED-BIPHENYLS BY SODIUM-BOROHYDRIDE WITH HOMOGENEOUS AND HETEROGENEOUS NICKEL-CATALYSTS

The hydrogenolysis (hydrodechlorination) of a series of pure PCB conge ners with sodium borohydride was studied. In the absence of nickel com pounds, very little reaction occurred, but in the presence of solid Ra ney-type nickel or in the presence of a soluble Ni(0)triphenylphosphin e complex, extensive hydrogenolysis occurred at ambient temperatures i n 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, ho wever, was found to be high. The selectivities are interpreted with re spect to the known mechanism of oxidative addition of aryl halides wit h Ni(0) complexes.