Disodium tetraaquabis(sulfato)iron(II)

In the title compound, [FeNa2(SO4)2(H2O)4], the Fe2+ cation is situated on a centre of inversion and is hexacoordinated by four O atoms from water molecules and two O atoms from two sulfate anions in an octahedral geometry. The coordination environment of Na+ comprises six O atoms in a more distorted octahedral arrangement, with Na—O distances between 2.368 (1) and 2.612 (1) Å. The structure contains an extensive three-dimensional network of O—H⋯O hydrogen bonds.

In the title compound, [FeNa 2 (SO 4 ) 2 (H 2 O) 4 ], the Fe 2+ cation is situated on a centre of inversion and is hexacoordinated by four O atoms from water molecules and two O atoms from two sulfate anions in an octahedral geometry. The coordination environment of Na + comprises six O atoms in a more distorted octahedral arrangement, with Na-O distances between 2.368 (1) and 2.612 (1) Å . The structure contains an extensive three-dimensional network of O-HÁ Á ÁO hydrogen bonds.

Comment
In order to find convenient crystals as model compounds for investigation of the electronic structure of Fe II complexes, the title compound was prepared. The unit cell contains two Fe II cations situated on centres of inversion, four Na + cations, four SO 4 2− anions and eight water molecules. The structure contains a three-dimensional network of O-H···O hydrogen bonds.
In the title compound ( Fig. 1)

Experimental
A solution of 1.0 mmol of Fe(SO 4 ) 2 in 2 ml water with one drop of diluted H 2 SO 4 (aq) and a piece of Fe metal was mixed with a solution of 2.0 mmol NaNO 2 NCN in 10 ml water and a solution of 2.0 mmol of imidazole in 10 ml me thanol. From this system, pale yellow crystals were isolated after a few days standing.

Refinement
H atoms were located in difference Fourier maps and refined freely with isotropic displacement parameters.
Figures Fig. 1. The asymmetric unit of the title compound with displacement ellipsoids shown at the 30% probability level for non-H atoms. as large as those based on F, and R-factors based on ALL data will be even larger.