EQUILIBRIUM STUDIES OF POLYNUCLEATING LIGANDS .2. METAL COMPLEXES OF TETRAKIS(AMINOMETHYL)METHANE

The interactions of tetrakis(aminomethyl)methane (tam) with Mn(II), Fe(II), Co(II), Ni(II), Zn(II), and Cd(II) have been studied. Equilibrium constants were determined by potentiometric methods in aqueous 0.1 M KNO3 at 25°. The species MH(tam)3+ was stable in all systems with the exception of Mn(II) and Fe(II) where hydrolysis of the metal ions resulted in precipitation and prevented equilibrium studies. All the metalligand association constants follow the Irving-Williams order. The monoprotic dissociation of MH(tam)3+ was determined for Co(II) and Ni(II). In the case of Zn(II), hydrolysis occurs in an overlapping step and results in the formation of Zn(tam)OH+ which slowly polymerizes. The measured and derived equilibrium constants obtained in the study are compared to constants previously determined with HC(CH2NH2)3. Trends in electrostatic interactions and entropy effects are discussed. © 1968, American Chemical Society. All rights reserved.