Browsing by Author "Peigneur, Paul"

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    Complexes of Ammonia and Ethylenediamine with Cu" on Zeolite A
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (09-12), 1978) Schoonheydt, Robert A.; Peigneur, Paul; Uytterhoeven, Jan B.
    Adsorption of NH3 on a dehydrated CuA zeolite gives Cu(NH3)2+4 and a small amount of tetrahedrally coordinated CuII ions. These complexes are unstable and decompose by vacuum heating in the range 295–373 K to yield lattice-bonded CuII ions characterized by an e.p.r. signal with g‖= 2.3087, A‖= 0.015 09 cm–1, g⊥= 2.067 and A⊥= 0.000 96 cm–1. Above 373 K this signal transforms to g‖= 2.3715, A‖= 0.013 63 cm–1, g⊥= 2.062 and A⊥= 0.001 92 cm–1. Adsorption of ethylenediamine on a dehydrated CuA zeolite gives only Cu(en)2+, stable up to 473 K. However, in the presence of water, Cu(en)2+2 and Cu(en)2+3 can also be synthesized on the surface. The latter two complexes are unstable and decompose by vacuum heating to the mono-complex. Cu(en)2+ can also be loaded on NaA by ion-exchange from aqueous solution, but Cu(en)2+2 cannot, due to space requirements and the instability of the bis-complex in the supercages of zeolite A. First it is necessary to exchange the mono-complex and to synthesize the bis-complex in situ by adding large excesses of ethylenediamine to the aqueous suspension. The e.p.r. and reflectance spectra of the various complexes depend slightly but consistently on the environment in the supercages of zeolite A. Their analysis, however, shows that this does not induce major changes in the CuII—N bonding characteristics.
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    Stability of Metal Uncharged Ligand Complexes in Ion Exchangers: Part 2.—The Copper + Ethylenediamine Complex in Montmorillonite and Sulphonic Acid Resin
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (1), 1978) Maes, Andre; Peigneur, Paul; Cremers, Adrien
    The thermodynamic stability of the copper+ethylenediamine complex is determined in montmorillonite and a macroreticular sulphonic acid resin using ion exchange data and the complex formation function. Both methods are in excellent agreement and correspond to an increase in the overall stability constant of 103 for montmorillonite and 101·3 for the resin. The stepwise formation constants K1K2 of the ion exchanged complex are 1011·6 and 1011·5 for montmorillonite and 1011·65 and 109·7 for the resin, as compared with values of 1010·7 and 109·3 for the bulk solution. Some tentative interpretation is offered in terms of a decreased ligand solvation in the ion exchanger.