Estimating the value of the metal-ligand bond dissociation enthalpy<D> (M-L) for adducts using empirical equations supported by TG data

Abstract

Recebido em 11/12/97; aceito em 10/11/98In this work is presented and tested (for 106 adducts, mainly of the zinc group halides) two empirical equations supported in TG data to estimate the value of the metal-ligand bond dissociation enthalpy for adducts: <D> (M-O) = ti / γ if ti < 420 K and <D> (M-O) = (ti / γ ) -7,75 . 10 -2 . ti if t i > 420 K. In this empirical equations, ti is the thermodynamic temperature of the beginning of the thermal decomposition of the adduct, as determined by thermogravimetry, and γ is a constant factor that is function of the metal halide considered and of the number of ligands, but is not dependant of the ligand itself. To half of the tested adducts the difference between experimental and calculated values was less than 5%. To about 80% of the tested adducts, the difference between the experimental (calorimetric) and the calculated (using the proposed equations) values are less than 15%.