Crystal Structure of Ferric Chloride Hexahydrate

Abstract

The crystal structure of ferric chloride hexahydrate has been determined from three‐dimensional single‐crystal x‐ray‐diffraction data. In the crystals two chloride ions and four water molecules are arranged around each ferric ion to form octahedral trans‐[FeCl₂(OH₂)₄]⁺ ions with C_2h−2/m symmetry. Fe–Cl and Fe–OH₂ interatomic distances in the complex ion are 2.30±0.02 Å and 2.07±0.02 Å, respectively. The crystals are monoclinic, space group C_2h³—C2/m, with a=11.89±0.02, b=7.05±0.01, c=5.99±0.01 Å, and β=100.5±0.2°. The unit cell contains two [FeCl₂(OH₂)₄]Cl·2H₂O units. The arrangement of the [FeCl₂(OH₂)₄]⁺ ions, chloride ions, and water molecules in the crystals indicates hydrogen bonding in addition to the electrostatic forces between oppositely charged ions.