Metallkomplexe mit Polyaminen II: Mit Triamino‐triäthylamin = „tren”︁
TL;DR: In this article, die Gleichgewichte bei der Komplexbildung with β,β′,β″-Triaminotriathylamin (= „tren”) und den folgenden Metallkationen: Mn+2, Fe+2.
Abstract: Es wurden die Gleichgewichte bei der Komplexbildung mit β,β′,β″-Triaminotriathylamin (= „tren”) und den folgenden Metallkationen: Mn+2, Fe+2, Co+2, Ni+2, Cu+2, Zn+2 Cd+2, Hg+2 und Ag+ untersucht. Bei den zweiwertigen Metallen bilden sich einzig bei Nickel und Quecksilber sehr unstabile Hydrogenkomplexe von der Zusammensetzung: MH2tren+4 und MHtren+3 als Zwischenstufen. Bei den andern ist das Gleichgewicht sehr einfach, indem daran einzig das Metall-kation, die Tetraminomolekel in den Neutralisationsstufen: H3tren+3, H2tren+2, Htren+, tren und der Komplex M(tren) teilnehmen. Bei Silber ist es komplizierter, indem die folgenden Partikeln auftreten: AgH2tren+2, AgHtren+2, Ag(tren)+ und Ag2tren+2. Von all diesen 16 Komplexionen sind die Bildungskonstanten ermittelt worden.
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TL;DR: The coordination chemistry of tripodal tetrammine ligands is reviewed in this paper, with emphasis being placed on structural features of the resulting metal complexes, and references to methods for the synthesis of these ligands, and the coordination chemistry with both transition metals and lanthanide ions is detailed.
188 citations
TL;DR: In this paper, the synthesis of the new complexing agents tris-(2-pyridylmethyl)-amine and N,N,N′, N′-tetrakis-( 2pyridine methylenediamine) is described, and their protonation constants given.
Abstract: The synthesis of the new complexing agents tris-(2-pyridylmethyl)-amine and N,N,N′,N′-tetrakis-(2-pyridylmethyl)-ethylenediamine is described, and their protonation constants are given.
175 citations
TL;DR: In this paper, the synthesis of polyguanidinium salts of potential interest as anion complexones is described, which are most conveniently prepared from polyamines via polynitroguanidine intermediates.
Abstract: The synthesis of a series of polyguanidinium salts of potential interest as anion complexones is described. Among the various synthetic methods investigated, the polyguanidinium salts were found to be most conveniently prepared from polyamines via polynitroguanidine intermediates. The complexation of phosphate and carboxylate anions by these complexones and by related polyammonium salts were studied by analysis of pH-metric titration data. The ligands studied from relatively stable complexes (log Ks = 2.0–4.0 for PO in water) which also present good selectivities in some cases. Both the stability and the selectivity of complexation are primarily governed by electrostatic forces and thus depend on charge accumulation in the interacting species; structural effects are also observed. Since the binding is primarily electrostatic, polyammonium salts from more stable complexes (at a given charge) than do polyguanidinium salts. However, whereas the complexation properties of the latter are independent of pH, the complexes of the former are observed only in the limited ranges of pH where both the protonated polyamine and the anion of interest can coexist. The polycationic ligands may, in principle, form chelate type anion complexes. Comparison with the corresponding single binding sites reveals an increase in complexation constant of about two or three orders of magnitude; this may be considered as a thermodynamic indication of a chelate effect for the polydentate ligands (by analogy with the well known effects displayed by cation complexones); however, structural data on the formation of chelate ‘rings’ are not yet available. The nature of the complexes and the prospects of anion complexones in various fields are discussed.
162 citations
TL;DR: In this article, the authors measured the stability constants of the cryptate complexes formed by ligands 1−4 with alkali, alkaline-earth, transition metal and toxic heavy metal cations.
Abstract: We have measured the stability constants of the cryptate complexes formed by ligands 1–4 with alkali, alkaline-earth, transition metal and toxic heavy metal cations. Stabilities and selectivities of complexation of the alkali and alkaline-earth cations are less pronounced in 1–4 than in the parent compounds 5 and 6 and decrease as the number of nitrogen sites increase. Remarkable complexation properties are found towards transition metal and toxic heavy metal cations. The intramolecular cavity of ligands 1–3 is too large for small cations like Co2+, Ni2+, Zn2+ so that the complexes formed are comparatively weak; however these cations are strongly complexed by ligand 4 whose intramolecular cavity has a much smaller size, compatible with their ionic radius. On the other hand, ligands 1–4 all form highly stable cryptates with Cd2+, Hg2+, Pb2+. Thus by the combined operation of the two structural parameters, cavity size and nature of the binding sites, cryptands 2 et 3 present very high selectivities for the complexation of these toxic heavy metal cations with respect to the biologically important ones Na+, K+, Mg2+, Ca2+, Zn2+. The selectivities of ligand 2 for Cd2+, Hg2+ and Pb2+ with respect to Zn2+ are as high as 106, 1018 and 109 respectively. They are much more pronounced than those of previously known complexing agents. Cryptands like 2 and 3 thus present a unique selectivity sequence of special interest in detoxication (decorporation, depollution). Further structural elaboration may allow to design ligands which present a given selectivity pattern of potential use in “cryptatotherapy” and “environment pollution control”. The results also provide evidence for the existence, at low pH, of protonated complexes which probably participate in an acid catalysed process for dissociation of the complexes.
85 citations
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TL;DR: In this article, a Methode zur Ermittlung der Bildungskonstanten sehr stabiler Chelatkomplexe beschrieben is described.
Abstract: Es wird eine Methode zur Ermittlung der Bildungskonstanten sehr stabiler Chelatkomplexe beschrieben. Sie fuhrt uber die aus einer Neutralisationskurve erhaltliche Gleichgewichtskonstante einer Reaktion, bei der das Metall vom zu untersuchenden Chelatkomplex MX auf einen Hilfskomplexpartner tren ubertritt oder umgekehrt:
wobei M′ ein Metallion ist, das nur mit dem Komplexon, nicht aber mit tren einen Komplex zu bilden vermag.
43 citations
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