Abstract: The interactions of the following three kinds of racemic and enantiomeric cobalt(III) chelates with montmorillonite and saponite are studied: [Co(en)3]3+ (en = ethylenediamine), [Co(diNOsar)]3+ (diNOsar = (1,8-dinitro-3,6,10,13,16,19-hexaazabicyclo[6,6,6]-eicosane)cobalt(III)) and [Co(diAMsar)]3+ (diAMsar = (1,8-diamino-3,6,10,13,16,19-hexaazabicyclo-[6,6,6]eicosane)-cobalt(III)). At neutral pH, these complexes are adsorbed as a trivalent cation up to 90%–100% of the cation exchange capacity of a clay. No difference is observed in the maximum adsorption amount between the racemic and enantiomeric isomers. The basal spacings of the clay-chelate adducts are determined by the X-ray diffraction measurements of non-oriented powder samples: 14.3 Å for [Co(en)3]3+ montmorillonite, 16.5 Å for [Co(diNOsar)]3+ montmorillonite, and 16.9 Å for [Co(diAMsar)]3+ montmorillonite. The results imply that the chelates form a monolayer in the interlayer space. From the one-dimensional Fourier analyses of the diffraction pattern of [Co(diNOsar)]3+ montmorillonite, the chelate is concluded to be adsorbed with its three-fold symmetry axis in parallel with the layer surface. This is in contrast with the previous results of [Ru(phen)3]2+ and [Ru(bpy)3]2+, which are adsorbed with their three-fold symmetry axes perpendicular to the surface. The conclusion is consistent with the angular dependence of the infrared absorption spectrum of the film of the adduct.