Studies on clathrasils. IX*

Abstract

Deca-dodecasil 3R, 120 SiO₂ · 6M¹⁰ · 9M¹² · 6M¹⁹ with M¹² = N₂ and M¹⁹ = C₁₀NH₁₇ (1-aminoadamantane), crystallizes in space group R[unk]m with a = 13.860(3) Å and c = 40.891(8) Å. Its crystal structure is built by corner-sharing [SiO₄] tetrahedra. The tetrahedra are connected to pseudohexagonal layers of face-sharing pentagonal dodecahedra ([5¹²] cages). These layers are stacked in ABCABC sequence and interconnected by additional [SiO₄] tetrahedra which form six-membered rings between the layers. Thus two new types of cage arise, another small decahedron, [4³5⁶6¹] cage and a large 19-hedron, [4³5¹²6¹8³] cage, the latter housing the 1-aminoadamantane guest molecule.

The 19-hedra are interconnected through 8-membered rings (pore width 4.5 Å), forming a two-dimensional pore system between the dodecahedral layers. Untreated deca-dodecasil 3 R is a member of the clathrasil family because the guest molecules trapped during synthesis are too large to pass through the 8-membered rings of the 19-hedra. However, on thermal treatment of deca-dodecasil 3 R the guest molecules are decomposed and the fragments are driven out of the cages, transforming the clathrasil to a phase possessing zeolitic properties.