Complexes and cations supported on the surface and between the layers of zirconium phosphate. 1. Copper(II) and its ammonia complexes
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The nature of the Cu(II)-aquo and -ammine complexes which form on the surface of the layered inorganic ion exchanger α-zirconium phosphate, Zr(HPO4)2·H2O, has been examined by means of ESR and UV-visible reflectance spectra. At low surface coverage, the ESR spectra of both the highly crystalline and semicrystalline exchangers are mainly due to isolated hexaaquocopper ions. However, resonances due to nonlinear pairs and species that yield reversed g parameters (g⊥ > g∥) are also observed. As the loading increases, the concentration of nonlinear pairs increases proportionately until finally at ∼20% coverage only this species is obtained. The copper complexes are octahedral with tetragonal distortion. In the amorphous form of the exchanger the Cu(II) species are free to tumble much as in aqueous solution. When the protons were exchanged out with Na+, nonlinear Cu(II) pairs were not observed even up to 25% coverage of the surface by Cu(II). On dehydration, diffusion of copper ions into the interior takes place with an accompanying change of symmetry to trigonal. Sorption of NH3 by Cu(II) on hydrated zirconium phosphate results in formation of [Cu(NH3)5H2O]2+. However, in the dehydrated state the tetraammine complex forms. Explanations for the observed behavior are given on the basis of the known structure of the host lattice. © 1982, American Chemical Society. All rights reserved.
author list (cited authors)
Clearfield, A., & Quayle, L. R.