Heats of protonation and formation of Ni(II), Cu(II), and Zn(II) complexes of the quadridentate ligand 1,5,9,13-tetraazatridecane were detd. calorimetrically at 25° in 0.1M NaNO3 and the corresponding entropies were calcd.; the complexes contain 3 linked 6-membered rings. Comparison of ΔH and ΔS of complex formation with those of other linear aliphatic polyamines which give 5- and 6-membered ring complexes showed that there are 2 different steric constraints, those present in an individual chelate ring, and those arising from progressive linking of chelate rings. The individual ring strain is greater in 6-membered rings, while the cumulative ring strain is more destabilizing in linked 5-membered rings. In complexes contg. 6-membered rings the std. molar entropies of metal complexes are linearly related to the std. molar entropies of the free ligands.
Thermodynamics of complex formation of aliphatic linear tetraamines. ΔH and ΔS for the reactions of 1,5,9,13-tetraazatridecane with protons and bivalent transition-metal ions
FABBRIZZI, LUIGI;
1972-01-01
Abstract
Heats of protonation and formation of Ni(II), Cu(II), and Zn(II) complexes of the quadridentate ligand 1,5,9,13-tetraazatridecane were detd. calorimetrically at 25° in 0.1M NaNO3 and the corresponding entropies were calcd.; the complexes contain 3 linked 6-membered rings. Comparison of ΔH and ΔS of complex formation with those of other linear aliphatic polyamines which give 5- and 6-membered ring complexes showed that there are 2 different steric constraints, those present in an individual chelate ring, and those arising from progressive linking of chelate rings. The individual ring strain is greater in 6-membered rings, while the cumulative ring strain is more destabilizing in linked 5-membered rings. In complexes contg. 6-membered rings the std. molar entropies of metal complexes are linearly related to the std. molar entropies of the free ligands.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.