Abstract
The nature of the complexes in aqueous solutions of Cu(II) and Ni(II) with diethylenetriamine (dien) and tetraethylenepentamine tetren) is pH-dependent. At M(II):dien = 2 and M(II):tetren = 1, the main complexes are [M(dien H)2(H2O)2]4+ and [M(tetren H)(H2O)2]3+. In excess ligand (pH = 10.30), the majority species are [M(dien)2]2+ and [M(tetren)(H2O)]2+, and considerable amounts of monoprotonated amines are adsorbed. The surface of hectorite prefers the tetragonally distorted complexes in all cases studied. The complexes readily lose their axially coordinated water molecules to form planar complexes on the interlamellar surface. The planar Ni(II)-complexes are diamagnetic, showing that the surface is a very weak axial ligand. The divalent complexes [M(dien)2]2+ and [M(tetren)(H2O]2+ can also be partially transformed to the corresponding planar forms on the surface, especially in the case of [Cu(dien)2]2+. The driving forces are thought to be the acid nature of the clay-adsorbed water and the gain in crystal field stabilization energy of the transition metal ions.
Резюме
Природа соединений в водных растворах Сu(II) и Ni(II) с диэтилентриамином (диен) и тетраэтиленпентамином (тетрен) зависит от рН. При М(II):диен = 2 и М(II):тетрен = 1, главными соединениями являются [М(диен Н)2(Н2O)2]4+ и М(тетрен Н)(Н2O)2]3+. При избытке лиганда (рН = 10,30) большинство соединений представляют собой [М(диен)2]2+ и [М(тетрен) (Н2O)]2+, при этом адсорбируются значительные количества монопротоновых аминов. Во всех исследованных случаях поверхность гекторита предпочитает тетрагонально искаженные соединения. Эти комплексы легко теряют свои координированные по оси водные молекулы, образуя плоские соединения на межслойной поверхности. Плоские Ni(II)-соединения являются диамагнитными, указывая, что поверхность образована очень слабым осевым лигандом. Двухвалентные соединения [М(диен)2]2+ и [М(тетрен) (Н2O)]2+ также могут быть частично преобразованы на поверхности в соответствующие плоские формы, особенно в случае [Си(диен)2]2+. Предполагается, что движущими силами являются кислотная природа адсорбированной глиной воды и увеличение в поле кристалла стабилизационной энергии ионов переходных металлов.
Resümee
Die Natur der Cu(II) und Ni(II) Komplexe mit diäthylentriamin (dien) und tetraäthylen-pentamin (tetren) in wäßrigen Lösungen ist pH abhängig. Bei M(II):dien = 2 und M(II):tetren = 1 sind die hauptsächlichen Komplexe [M(dien H)2(H2O)2]4+ und [M(tetren H)(H2O)2]3+. Bei Überschuß an Ligand (pH = 10,3) sind die Hauptsorten [M(dien)2]2+ und [M(tetren)(H2Ö)]2+ und beträchtliche Mengen monoprotonierter Amine werden adsorbiert. Die Oberfläche des Hektorit bevorzugt in allen untersuchten Fällen die tetraädrisch verformten Komplexe. Die Komplexe verlieren ihre axial koordinierten Wasser Moleküle, um planare Komplexe auf der interlamellaren Oberfläche zu formen. Die planaren Ni(II)-Komplexe sind diamagnetisch und zeigen, daß die Oberfläche ein sehr schwacher axialer Ligand ist. Die divalenten Komplexe [M(dien)2]2+ und [M(tetren)(H2O)]2+ können auch teilweise auf der Oberfläche in die entsprechenden planaren Formen übergehen, besonders im Falle von [Cu(dien)2]2+. Die saure Natur des auf Ton adsorbierten Wassers und die Zunahme in Kristallfeldstabilisierungs-energie der Übergangsmetallionen werden als treibende Kräfte angenommen.
Résumé
La nature des complexes en solutions aqueuses de Cu(II) et de Ni(II) avec la diethylene-triamine (dien) et la tétraethylenepentamine (tetren) est dépendante du pH. Pour M(II):dien = 2 et M(II):tetren = 1, les complexes principaux sont [M(dien H)2(H2O)2]4+ et [M(tetren H)(H2O)2]3+. En excès de ligand (pH = 10.30), les espèces majoritaires sont [M(dien)2]2+ et [M(tetren)(H2O)]2+, et des quantités considérables d’aminés monoprotonées sont adsorbées. La surface d’hectorite préfère les complexes déformés tétragonalement dans tous les cas étudiés. Les complexes perdent aisément leurs molécules d’eau coordonnées axialement pour former des complexes planes sur la surface interfeuillet. Les complexes planes Ni(II) sont diamagnétiques, montrant que la surface est un ligand axial très faible. Les complexes divalents [M(dien)2]2+ et [M(tetren)(H2O)]2+ peuvent aussi être partiellement transformés en les formes planes correspondantes sur la surface, surtout dans le cas de [Cu(dien)2]2+. On pense que les forces motrices sont la nature acide de l’eau adsorbée par l’argile et le gain d’énergie de stabilisation du champ cristallin par les ions du métal de transition.
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Schoonheydt, R.A., Velghe, F., Baerts, R. et al. Complexes of Diethylenetriamine (Dien) and Tetraethylenepentamine (Tetren) with Cu(II) and Ni(II) on Hectorite. Clays Clay Miner. 27, 269–278 (1979). https://doi.org/10.1346/CCMN.1979.0270405
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DOI: https://doi.org/10.1346/CCMN.1979.0270405