Novel reactions of hydrocarbon complexes of metal-substituted sheet silicates: thermal dimerisation of trans-stilbene

Abstract

TRANSITION metal, ion-exchanged montmorillonites form complexes^1,2, often of an interlamellar kind (intercalates), with a range of aromatic molecules, including benzene, toluene and the xylenes, anisole, and other species such as trans-stilbene and indene^3–5. The aromatic molecules can form two main types of complex with the interlayer transition-metal ions, for example Cu(II). In the first type there is thought to be an edge-π-bonded copper arene moiety, similar to the bonding situation which exists in C₆H₆CuAlCl₄ (ref. 6), and in the second instance it is considered to be a type of bond which causes associated distortion of the aromatic ring and some localisation of the circumferential double bonds¹. Although detailed crystallographic analyses of the organic intercalates of sheet silicates has only recently commenced (ref. 7, and J. M. Adams et al., unpublished) and in spite of the paucity of information relating to the precise nature of the bonding of organic entities to encaged metal ions, it is clear^2–4 that these organic complexes display a rich range of unusual reactions, some new examples of which we report here.