Optical Resolution and Asymmetric Syntheses by use of Adsorption on Clay Minerals

Abstract

The interactions of metal complexes with layer clay minerals are reviewed with a special attention to the aggregate behaviours of bound species. Experimental evidences have been presented for the formation of stereoregular adsorbate layers from a solution of a racemic metal complex. The opposite enantiomers of a complex are adsorbed in an alternative way in the interlayer space of a clay mineral. The causes for such stereoregularity have been discussed from the viewpoint of stereochemical interactions between adsorbed molecules. The phenomena are extended to the development of the novel mdehods of optical resolution and asymmetric syntheses by use of clay minerals. In these methods, an adduct of a clay and a chelate is used as a chiral adsorbent. Chirality has been recognized or induced due to the stacking interactions of an adsorbed molecule with a pre-adsorbed optically active chelate. The methods are further extended to the electrochemical syntheses of an opticaly active molecule by use of an electrode modified with a film of a clay-chelate abduct.