Termoquimica de adultos de ligantes heterociclicos com cloretos de zinco, cadmio e mercurio

AUTOR(ES)
DATA DE PUBLICAÇÃO

1985

RESUMO

The adducts ZnCl2.L2(L = py and pyO), ZnCl2.L (L = bipy and phen), 2ZnCl2.3bipyO2 and MCl2,L (where M = Cd e Hg and L = py, pyO, bipy, bipyO2, phen), were characterized by elemental analysis, melting point, thermogravimetry and infrared spectra. From the values of standard enthalpy of dissolution of chloride, ligands and adducts in appropriate calorimetric solvents, it was calculated the standard enthalpies of the reaction MCl2(s) + nL(s,l) = (MCl2.Ln) (s); DHR The standard enthalpies of formation (DH f ) were calculated b y using DH R values, the standard enthalpies of formation of ligands, whose values were determined by means of combustion calorimetry. It was also determined, other thermochemical parameters, such as standard enthalpies DHD and DHM concerning to the equations: MCl2,Ln(s) = MCl2(s) + nL(g); DHD MCl2,Ln(s) = MCl2(g) + nL(g); DHM Except for pyridine, the standard enthalpies of vaporization and sublimation of ligands were determined. The melting point, thermogravimetric and mass spectra data indicated that these compounds possibly do not exist in appreciable amount in gaseous phase. The metal-ligand bond enthalpies could be also estimated. DHR parameter enable us to establish the relative acidity order of the metallic chlorides concerning the bases(py, pyO, bipy, bipyO2 and phen), resulting the sequence Zn >Cd >Hg, as well as the relative basicity order for the CdCl2 and HgCl2 compounds: bipyO2>PyO >py >bipy >phen. DHM is proposed as a better parameter to characterize energetically the adducts studied.

ASSUNTO(S)

compostos heterociclicos termoquimica ligações quimicas

ACESSO AO ARTIGO

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