INTERCALATION OF MONTMORILLONITE CLAY WITH INDIVIDUAL OLIGOMERIC RHODIUM(III) AQUA CATIONS

A series of Rh(III) aqua cations, viz, monomer, dimer and trimer, have been intercalated into montmorillonite for the first time. Since thes e aqua ions retain their integrity when intercalated between the clay layers, information has been obtained about the nature of the ion-exch ange process. While the aqua ions can be exchanged from the wet gel, o nly partial exchange (dependent on aqua ion charge) is possible after drying in air at room temperature, indicating binding to the clay surf ace. This contrasts with the case of Cr(III)-intercalated montmorillon ite where no exchange of the oligomers was possible after the same tre atment. Full exchange of Na+ by the Rh(III) aqua ions was possible. Gl ycolation of these clays is possible after drying in air at room tempe rature, indicating that there is considerable space between the clay l ayers. The Rh(III)-intercalated clays were found to exhibit reproducib le properties, particularly powder XRD patterns. d(001) spacings of 14 .0-14.6 Angstrom were obtained for Rh(III) monomer, dimer and trimer i ntercalated montmorillonite, which are entirely consistent with the st ructures of these species. These products have significant thermal sta bility to 473 K with gallery heights of about 3 Angstrom. Full glycola tion is possible even for clays heated up to 573 K.