Crystal Structure of a Vermiculite-Anilinium Intercalate

P. G. Slade1, C. Dean2, P. K. Schultz2 and P. G. Self1
1 CSIRO, Division of Soils, Glen Osmond, South Australia 5064, Australia
2 Physical and Inorganic Chemistry Department, University of Adelaide Box 498 GPO, Adelaide 5001, Australia

Abstract: If anilinium ions are intercalated into Llano vermiculite, the stacking order of adjacent silicate layers is increased, resulting in a relatively sharp single crystal X-ray diffraction (XRD) pattern. The packing of intercalated organic members forms a superstructure and produces bonding from layer to layer which favors the stacking order. Superlattice reflections occur which, although sharp in the a*b* plane, are streaked along c*. Apparently there is little coherence between adjacent layers of ordered organic units.

A three-dimensional set of XRD reflections for a triclinic sub-cell having the following lattice parameters was measured: a = 5.326(3), b = 9.264(4), c = 14.82(5) Å, α = 90.31(7), β = 96.70(6), and γ = 89.55(5)°. In this unit cell (symmetry Cl), ditrigonal cavities in adjacent silicate layers are approximately opposite. Differential Fourier analyses and least-squares refinements showed that the principal axes of the anilinium ions, i.e., N-C(1)-C(4), are nearly perpendicular to the silicate layers. The planes of the aromatic rings, however, are about ±30° to X, neither parallel nor perpendicular to that direction, as indicated by earlier studies.

Inorganic cations and water molecules are also present in the interlayer; the former and some of the latter occupy sites near the middle of the layer. Anilinium-rich and anilinium-poor domains coexist. In the latter, the cation-water system predominates and apparently conforms to the superstructure. Although the cation-water structure could not be uniquely established from the reflections produced by the sub-cell, possible positional coordinates were obtained. From structural data for the silicate layers, no evidence was found for long-range Si/Al ordering in the tetrahedral sites.

Key Words: Anilinium ion • Crystal structure • Intercalate • Ordering • Vermiculite

Clays and Clay Minerals; June 1987 v. 35; no. 3; p. 177-188; DOI: 10.1346/CCMN.1987.0350303
© 1987, The Clay Minerals Society
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