Poly[[diaquahexa-μ-cyanido-cerium(III)ferrate(III)] dihydrate]

In the structure of the title complex, {[CeFe(CN)6(H2O)2]·2H2O}n, the CeIII and FeIII atoms exhibit square antiprismatic [CeN6(H2O)2] (site symmetry m2m) and octahedral [FeC6] (site symmetry 2/m) coordination geometries, respectively. The metal atoms are linked alternately through the cyanide groups, forming a three-dimensional framework in which the {Ce2Fe2(CN)4} puckered square unit is the basic building block. The crystal packing is enforced by O—H⋯O and O—H⋯N hydrogen bonds, including the uncoordinated water molecule which is located on a mirror plane.

In the structure of the title complex, {[CeFe(CN) 6 (H 2 O) 2 ]Á-2H 2 O} n , the Ce III and Fe III atoms exhibit square antiprismatic [CeN 6 (H 2 O) 2 ] (site symmetry m2m) and octahedral [FeC 6 ] (site symmetry 2/m) coordination geometries, respectively. The metal atoms are linked alternately through the cyanide groups, forming a three-dimensional framework in which the {Ce 2 Fe 2 (CN) 4 } puckered square unit is the basic building block. The crystal packing is enforced by O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen bonds, including the uncoordinated water molecule which is located on a mirror plane.

Comment
In the past few years, hexacyanometalate-based lanthanide assemblies have received much attention due to their intriguing topologies and interesting functionalities (Andruh et al., 2009). The chelated ligands have played an important role in the construction of low-dimensional complexes. Along this line, we have employed the K 3 Fe(CN) 6 presusor to react with the Ce 3+ ion in the presence of the bidentate chelated ligand 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen).
Single crystal X-ray diffraction analysis revealed that the asymmetric unit of the title complex ( Fig. 1) consists of one fourth of a [Ce(H 2 O) 2 ] 3+ cation, one fourth of a [Fe(CN) 6 ] 3anion and one half of a water molecules of crystallization.
Each iron(III) atom is six-coordinated by six bridging CN groups in a distorted octahedral geometry. The average Fe-C and C-N bond distances are 1.928 (5) and 1.166 (7) Å, respectively. The Fe-CN angles deviate slightly from the linearity, ranging from 178.3 (6) to 178.7 (8)°. Each cerium(III) atom is eight-coordinated with six cyano nitrogen atoms and two oxygen atoms from two coordinated water molecules, forming a square antiprismatic geometry. The Ce-O and the mean Ce-N bond distances are 2.351 (7) and 2.458 (5) Å, respectively. Due to the large ionic radii of the lanthanide atom, the cyanide bridges are exceptionally long and the Ce-N-C bonds are strongly bent with a mean angle of 160.0 (5)°, in opposition to the linearity of the Fe-C-N angle. As a consequence, adjacent Ce and Fe metals are connected through cyano groups to generate a three-dimensional open framework (Fig. 2). The 12-membered puckered square unit Ce 2 Fe 2 (CN) 4 is the basic building block, in which the Ce and Fe atoms occupy the corners and the CN linkages the edges. The crystal structure is stabilized by O-H···O and O-H···N hydrogen bonds (Table 1).

Experimental
Single crystals of the title complex were prepared at room temperature by slow diffusion of an ethanol solution (3 ml) of After about one month, red block crystals were obtained.

Refinement
All non-hydrogen atoms were refined with anisotropic thermal parameters. The water H atoms were located from a difference Fourier map and refined as riding with O-H = 0.85 Å and U(H) set to 1.5U eq (O).

Poly[[diaquahexa-µ-cyanido-cerium(III)ferrate(III)] dihydrate]
Crystal data Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.