Reactions of smectites with binuclear oxo-bridged iron complexes of N-alkyl-N,N-bis(2-pyridylmethyl)amines
Cationic binuclear oxo- and carboxylate bridged Fe(III) complexes of N-alkyl-N,N-bis(2-pyridylmethyl)amines are introduced into the interlayer region of smectites by cation exchange reactions. The reaction can be divided into three steps. After a predominant loading of external surfaces, cation exchange sites at internal surfaces react, accompanied by considerable structural expansion. Both reaction stages belong to the steep section of the exchange isotherms. At a certain loading, which depends on the complex substituents and the layer charge of the smectite, the isotherms become flat. With bulky shaped complex cations and highly charged smectites, exchange is not quantitative; vermiculite-type minerals show a very small complex uptake. For this behaviour, both thermodynamic and kinetic reasons must be considered. From these results the number of cation exchange positions at external surfaces of smectite crystals may be estimated.
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Document Type: Research Article
Affiliations: Institut fu ¨r Anorganische Chemie der Universita ¨t Mu ¨nchen, Meiserstraûe 1, D-80333 Mu ¨nchen, Germany
Publication date: 1998-03-01