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Zur Stabilität der Metallkomplexe von Methantriessigsäure und cis, cis ‐1,3,5‐Cyclohexantricarbonsäure
Author(s) -
Wu YiHe,
Kaden Thomas A.
Publication year - 1983
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19830660527
Subject(s) - chemistry , protonation , denticity , carboxylate , glutaric acid , metal , stereochemistry , stability constants of complexes , medicinal chemistry , metal ions in aqueous solution , ion , organic chemistry
The stabilities of the Mn 2+ ‐, Co 2+ ‐, Ni 2+ ‐, Cu 2+ ‐ and Zn 2+ ‐complexes with 2‐(carboxymethyl)glutaric acid ( 2 ) and cis , cis ‐1,3,5‐cyclohexanetricarboxylic acid ( 3 ) were measured potentiometrically at 25° and I = 0.5 (KNO 3 ). Beside the complexes ML − protonated species MLH and MLH 2 +are also formed. Their stability constants are given in Table 1 . A comparison between the stabilities of 2 or 3 and those of acetate, as a model for a monocarboxylate, or succinate and glutarate, as examples for dicarboxylates, indicates that in all species only one carboxylate is strongly bound whereas the second and third ones are probably not. The observation that Δlog K 1 = log K MLH LH− log K MLH 2LH 2as well as Δlog K 2 = log K ML L− log K MLH LHare practically constants with values of 0.34 ± 0.05 and 0.49 ± 0.07, respectively, for both ligands and the five metal ions studied is also in line with the proposed monodentate structures of the complexes ML − , MLH and MLH + 2 .