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

P. G. Slade1, P. K. Schultz2 and E. R. T. Tiekink2
1 CSIRO, Division of Soils, Glen Osmond, South Australia 5064, Australia
2 Department of Physical and Inorganic Chemistry, University of Adelaide, Box 498 GPO, Adelaide 5001, Australia

Abstract: 1-4-diazabicyclo[2,2,2]octane dihydrochloride (DABCO·2HCl) was reacted with two vermiculite samples to produce intercalates which, at room temperature, had relatively sharp, single crystal X-ray diffraction patterns. At higher temperatures (250°C) the stacking order decreased, and consequently the 0kl reflections with k ≠ 3n became increasingly diffuse. The stacking order of previously heated samples returned when they were cooled. A superstructure was present in which DABCO cations occupied the corners and center of a cell 3a × b, compared with the standard vermiculite cell.

DABCO-intercalated Nyasaland vermiculite had the following monoclinic subcell (symmetry C1) parameters under ambient conditions: a = 5.341(2), b = 9.249(3), c = 14.50(1) Å, and β = 96.98(5)°. Differential Fourier analyses and least-squares refinement led to a final R value of 12.6% for 1814 reflections. The crystal structure analysis showed that individual DABCO ions were not symmetrically positioned between the silicate layers. A network of inorganic cations and water molecules was also present and governed the interlayer separation. At 250°C the d value was 13.7Å, consistent with a dehydrated structure, in which each organic pillar has one amino group keyed into a ditrigonal cavity and the other amino group riding on the basal oxygens of an opposite tetrahedron.

Key Words: Crystal structure • DABCO • Intercalate • Stacking ordering • Vermiculite

Clays and Clay Minerals; February 1989 v. 37; no. 1; p. 81-88; DOI: 10.1346/CCMN.1989.0370110
© 1989, The Clay Minerals Society
Clay Minerals Society (www.clays.org)