A new pathway of preparation and refined structure of (NH4)2[FeCl5(H2O)]

The title compound, (NH₄)₂[FeCl₅H₂O] has been prepared by reaction between iron(III) chloride and ammonium chloride which was formed by hydrolysis of isonicotinamide or thionicotinamide in ethanol. The characterization was based on elemental analysis and infrared spectra. The crystal structure of the title compound has been refined by single crystal X-ray diffraction method at 293 K. Crystals are orthorhombic, Pnma, with unit cell parameters: a = 13.760(1) A, b = 9.960(1) A, c = 7.060(1) A, Z = 4 and R = 3.5 %. The iron(III) atom in [FeCl₅(H₂O)]²- ion is approximately octahedrally coordinated by five Cl atoms and one O atom of H₂O molecule. This distortion is caused by the extensively hydrogen-bonded lattice. Structural parameters and IR spectra of similar compounds are compared and discussed.