Empirical correlations involving calorimetric, thermogravimetric and infrared data for zinc halides adducts

The use of the non-isothermal Coats-Redfern method to obtain the activation energy values for the processes ZnX2.2hmpa(c) --> ZnX2(C) + 2hmpa(g) (X = Cl, Br, I and hmpa = hexamethylphosphoramide), by using thermogravimetric data, gave the values 44; 94 and 215 U mol(-1) for the given sequence of halides, These values correlated to the standard molar enthalpy of formation in the condensed phase for the same sequence of adducts: -1596, -1532 and -1408 kJ mol(-1), respectively, providing the equation: DeltafH(mdegrees) = 1.086 x E-a - 1639.738, which shows a linear correlation between the thermodynamic and kinetic parameters for such solid adducts. The IR spectroscopy data for a series of adducts of zinc halides with amides enabled the acquisition of an equation to estimate the mean metal-ligand bond enthalpy <D>(M-L) values: the spectroscopic data were adjusted to the expression <D>(M-L) = alpha + beta + Delta(v), where alpha and beta are related to Lewis acidity and basicity coordination features, respectively, and Deltav is the difference between C=O or P=O stretching vibrations of the coordinated and uncoordinated ligands. This equation was applied for 15 adducts, showing a deviation less than 10% from the thermochemical values. (C) 2002 Published by Elsevier Science Ltd.