Abstract The effect of the addition of metal salts as catalysts for the acid interchange polycondensation of tetrachlorobisphenol A diacetate with phthalic acids was examined. The acetate salts of some transition metals were found to have an effect upon the molecular weights of the polyesters produced, but inherent viscosities above 0.50 dL/g were not achieved with these catalysts. Modification of the nature of the salts by either the use of a mixture of acetate and strong acid anionic species, or by addition of an equivalent of strong acid to the metal acetate, to generate a mixed salt in situ, gave the most effective catalyst for the polycondensation. Inherent viscosities as high as 0.82 dL/g were achieved with a catalyst system consisting of an equimolar mixture of nickel acetate and nickel perchlorate. As an approach to explaining the activity of the metal salt catalysis, it is proposed that a metal salt complex, consisting of a central divalent, tetracoordinate transition metal, surrounded by the oxy...