Structure of Iron (III) Chloride–Methanol Solutions

The structure of the solute species in concentrated iron(III) chloride–methanol solutions has been examined by diffraction techniques. Solute association is established by colligative measurements and indirectly by diffraction results and Fe2Cl6 emerges as a realistic solute species. The radial-distribution functions of the solutions and those obtained from electron diffraction studies of vapor-phase Fe2Cl6 are comparable. The average iron(III)–chloride bond distance is 2.25 Å, and each iron atom has four chloride nearest neighbors; both facts are consistent with the dimer model. Crystal radii serve to interpret bond distances.