Monte Carlo simulations are used to investigate the intercalation structures of a metal complex within a smectite clay. The investigated model system is [M(phen)3]2+ (phen = 1,10-phenanthroline) intercalated between two linked [SiO4]4- and [AlO4]5- tetrahedra sheets. The free energy of binding, the roles of the upper and lower sheets in determining the orientation of a bound chelate, and the effects of water medium on the binding free energy are investigated. For interlayer distances from 10 to 18 Å, the chelate is bound by the sheets with the 3-fold (C3) symmetry axis perpendicular to the sheet surface. The chelate rotates around the C3 axis by 15-60° from the equilibrium position. A comparison with experimental data shows that agreement with Monte Carlo simulations is satisfactory, although the theoretical treatments predict more details about the bound structures of the chelate than the experimental results. © 1992 American Chemical Society.