Highly active polymer-anchored bimetallic palladium-based catalysts (PVP-PdCl2-MY, PVP = poly(N-vinyl-2-pyrrolidone, MY = the second transition metal component) exhibit very high catalytic activity and selectivity for the carbonylation of allyl halides (CH2=CH-CH(2)X, X = Cl or Br) in toluene/dilute alcoholic-aqueous solution at 40 degrees C and atmospheric pressure in the presence of NaOH. These catalysts were prepared by the addition of a second transition metal compound to the alcoholic or aqueous solution of the polymer-anchored monometallic palladium catalyst PVP-PdCl2, i.e. FeCl3 . 6H(2)O, Co(OAc)(2) . 4H(2)O, NiCl2 . 6H(2)O, RhCl3 . 3H(2)O, or RhCl3 . H2O was added to PVP-PdCl2/EtOH, and [RuCl2(TPPTS)(2)](2), RhH(CO)(TPPTS)(3), H2IrCl6, IrH(CO)(TPPTS)(3) or IrCl(CO)(TPPTS)(2) was added to PVP-PdCl2/H2O (TPPTS = (m-NaSO3C6H4)(3)P). For allyl chloride, a remarkable synergic effect of the polymer-anchored bimetallic catalysts led to an obvious increase in the carbonylation rate and/or selectivity for the desired product, beta, gamma-butenoic acid. For allyl bromide, only a weak synergic effect was observed by the addition of RhCl3 . 3H(2)O or IrCl(CO)(TPPTS)(2) to the monometallic catalyst.