For the transesterification of DMT(dimethyl terephthalate)and polycondensation of BHET[bis(2-hydroxyethyl)terephthalate)], catalytic activity of various metal complex can be correlated with acidity of metal ion, which is expressed as modified electronegativity. Based on correlations mode of catalysis for the formation of PET[poly(ethylene terephthalate)] was suggested.