Synthesis, Thermal Behavior, and Structure of Hexaaquanickel(II) Chloro(hydrogenethylenediaminetetraacetato)ferrate(III): A Molecular Precursor for Stoichiometric Nickel Ferrite

Hexaaquanickel(II)
chloro(hydrogenethylenediaminetetraacetato)ferrate(III),
[Ni(H2O)6][FeCl(EDTA)H]2·4H2O, was prepared
by the reaction of nickel(II) chloride with (hydrogenethylenediammine)iron(III) in water at room temperature.
The compound readily loses water
at room temperature depending on drying conditions and the relative
humidity. The
molecular structure of the dihydrate was determined by single-crystal
X-ray crystallography.
The compound decomposes in stages involving, successively, loss of
water, pyrolysis of the
EDTA ligand, and loss of HCl to yield, finally, stoichiometric nickel
ferrite. Crystal data: 
C20H42N4O24Cl2Fe2Ni,
M = 963.88, monoclinic, space group
P21/c, a =
20.548(3) Å, b = 7.401(1) Å, c = 12.827(1) Å, β = 101.78(1)°,
V = 1909.6(7) Å3, Z = 2,
Dcalc = 1.68 g cm-3,
R =
0.028, and Rw = 0.040.