Crystal Structure of a Vermiculite-Anilinium Intercalate

Abstract

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) A, a = 90.31(7),/3 = 96.70(6), and 3' = 89.55(5) ~ In this unit cell (symmetry C1), 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 subcell, possible positional coordinates were obtained. From structural data for the silicate layers, no evidence was found for long-range Si/A1 ordering in the tetrahedral sites.

Arrangement of n-Alkylammonium Ions in Phlogopite and Vermiculite: An XRD and TEM Study

“…Based on electron microprobe analyses, Slade et al (1987) give an interlayer charge for Na-saturated Llano vermiculite of 0.93 per [Ore(OH)2]. This is similar to the interlayer charge of Ontario phlogopite (0.94), whereas our Llano vermiculite has an interlayer charge of 0.88, as shown above.…”

“…Thus, a perpendicular arrangement of alkyl chains in weathered mica may not be possible. Slade et al (1987) also reported that some interlayer sites in Llano vermiculite were still occupied by inorganic cations after intercalation of anilinium ions. However, energy-dispersive X-ray analysis of both phlogopite and K-depleted phlogopite (Ca-phlogopite) revealed that the remaining K was derived from nonexpanded K-layers in the alkylammonium-treated sample.…”

Identification of vermiculite by transmission electron microscopy and X-ray diffraction

“…Thus, the intercalation of alkylammonium ions in the interlayers of vermiculite appears to improve the degree of ordering of 2 : 1 layers in these minerals. Three dimensional X-ray patterns of Llano vermiculite intercalated with anilinium ions (Slade et al, 1987) confirm this observation.…”

Structure of a 1,4-Diazabicyclo[2,2,2]Octane-Vermiculite Intercalate

“…A trial model for the silicate structure was derived from the atomic coordinates given by Slade et aL (1987).…”

“…Alcover et al (1973) suggested that the exchangeable inorganic cations and water molecules in a Kenya vermiculite were also distributed over the lattice points in a C-face centered cell with dimensions 3a x b, which, by inference, represented t h e charge distribution in the silicate layers. For the Vermiculite from Llano County, Texas (LV), de la Calle et aL (1976), Thompson (1984), and Slade et aL (1987) showed that only short-range ordering of tetrahedral cations exists in local domains. Consequently, if local charge balance operates in LV, its interlayer cations should also be ordered only in local domains; however, for the Nyasaland and Kenya vermiculites, the local domains of short-range order may well be larger.…”