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 C2h-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 C2h3-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·2H 2O units. The arrangement of the [FeCl2(OH 2)4]+ ions, chloride ions, and water molecules in the crystals indicates hydrogen bonding in addition to the electrostatic forces between oppositely charged ions.