Chemical Modification of the Gallery Surfaces in Layered Silicate Clays (LSC's) for Catalytic Applications in Nucleophilic Displacement Reactions

Ordinary swelling layered silicate clays (LSC's) are poor phase transfer catalysts for nucleophilic displacement reactions because of their inability to bind substantial quantities of anions. However, by electrostatically binding large, positively charged tris polypyridyl complexes to the gallery surfaces, the negative charge of the host layers is sufficiently shielded to permit formation of an intersalate, wherein binding of anions occurs as cation-anion pairs. Anions in the LSC-intersalate are labile and accessible for nucleophilic displacement reactions. The LSC-intersalated catalysts exhibit impressive substrate selectivities based on the size of the alkyl groups. Analogous selectivities are not found for nucleophilic displacements under biphasic reaction conditions.