Intercalation of montmorillonite clay with individual oligomeric rhodium(III) aqua cations

Abstract

A series of Rh(III) aqua cations, viz monomer, dimer and trimer, have been intercalated into montmorillonite for the first time. Since these aqua ions retain their integrity when intercalated between the clay layers, information has been obtained about the nature of the ion-exchange process. While the aqua ions can be exchanged from the wet gel, only partial exchange (dependent on aqua ion charge) is possible after drying in air at room temperature, indicating binding to the clay surface. This contrasts with the case of Cr(III)-intercalated montmorillonite where no exchange of the oligomers was possible after the same treatment. Full exchange of Na + by the Rh(III) aqua ions was possible. Glycolation of these clay is possible after drying in air at room temperature, indicating that there is considerable space between the clay layers. The Rh(III)-intercalated clays were found to exhibit reproducible properties, particularly powder XRD patterns, d 001 spacings of 14.0–14.6 Å were obtained for Rh(III) monomer, dimer and trimer intercalated montmorillonite, which are entirely consistent with the structures of these species. These products have significant thermal stability to 473 K with gallery heights of about 3 Å. Full glycolation is possible even for clays heated up to 573 K.