Rates of racemization and dissociation of [Fe(phen)3I2+ were measured in water, methanol, acetone, formamide, N,N-dimethylformamide, acetonitrile, and acetic acid, and in mixtures of water with methanol, acetone, formamide, and N,N-dimethylformamide. The rate of racemization was also measured in mixtures of water with glycerol and ethylene glycol. In all cases the dissociation rate was much slower than the racemization rate, indicating that racemization is predominantly intramolecular in all these solvents. Ion association (with clod-), when it occurs, has a retarding effect on the rate of racemization. The effect of a solvent on the racemization rate appears to be due to solvation of the aromatic phenanthroline ligands in the transition state, and to the viscous resistance to reorganization of the solvent in the vicinity of the complex ion when the latter undergoes inversion. Supporting this view is the fact that the rate constants can be empirically represented by the equation log k = c -(0.26AClig,,,j/2.303RT) -0. 48 log ( q V , ) . where a c l i g a n d is the free energy of solvation of the aromatic ligands, q is the coefficient of viscosity of the solvent, and V , is the molar volume of the solvent. The effect of solvent on the dissociation rate appears to be due to solvation of the ligands in the transition state, and the solvent's ability to act as a replacing ligand

A model for the solvation of the [Fe(phen)3]2+ cation is proposed based on the geometry of the complex. The solvation energy is considered to be the sum of two parts: that due to the ion-dipole interaction with the solvent and that due to the van der Waals interaction between the solvent and the aromatic ligands. The model was tested, and verified, by measuring the solubilities of Fe(phen)3(C104)2 and naphthalene in ten pure solvents, and in mixtures of water with methanol, acetone, and JV.TV-dimethylformamide. The van der Waals interaction with the ligands was shown to parallel the interaction with naphthalene. The NMR chemical shifts of the 5,6 protons on Fe(phen)32+ were measured in some of the solvent systems.

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