Studies of polyfunctional O-ligands: Formation and stability of Mg(2+) and Ca(2+) complexes of 1,2,4,5-benzenetetracarboxylic acid in aqueous solution at 25 degrees.
The stabilities of the Ca(2+) and Mg(2+) complexes with 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) were studied potentiometrically, at 25 degrees . The species ML, MHL, MH(2)L, and M(2)L [L = pyromellitate(4-); M = Ca(2+), Mg(2+)] were found to be present in solution (for Mg(2+) the species MH(3)L was also found). The dependence of the formation constants on ionic strength, and the stability trends of the Ca(2+) and Mg(2+) complexes with carboxylate ligands, are discussed.
De Robertis
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A
Istituto di Chimica Analitica dell'Università, Salita Sperone 31, P.O. Box 30, I-98166 S. Agata di Messina, Messina, Italy.
De Stefano
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C