Crystal structure of tetraaqua(5,5′-dimethyl-2,2′-bipyridyl-κ2 N,N′)iron(II) sulfate

In the crystal structure of the title compound, [Fe(dmbpy)(H2O)4][SO4], the charged components form an extensive hydrogen-bonding network. Eight O—H⋯O hydrogen bonds [d(O⋯H) < 2.00 Å], form a two-dimensional network parallel to the ab plane.


Chemical context
Coordination compounds containing polynitrile anions as ligands are of current interest for their magnetic properties and their rich architectures and topologies (Setifi et al., 2003;Gaamoune et al., 2010;Vá hovská & Potočň á k, 2012;Setifi, Domasevitsch et al., 2013;Potočň á k et al., 2014). Given the crucial role of these anionic ligands, we are interested in using them in combination with other chelating or bridging neutral co-ligands to explore their structural and electronic characteristics in the large field of molecular materials exhibiting the spin crossover (SCO) phenomenon. In an attempt to prepare such a complex, we obtained the title compound, [Fe(dmbpy)(H 2 O) 4 ]SO 4 , (I), where dmbpy is 5,5 0 -dimethyl-2,2 0 -bipyridyl.

Structural commentary
A molecular view of complex (I), together with the atomnumbering scheme is given in Fig. 1. The crystal structure of (I) consists of the cationic complex [Fe(dmbpy)(H 2 O) 4 ] 2+ and a free [SO 4 ] 2À counter-ion. The Fe II atom is in a distorted octahedral coordination environment and the equatorial plane of the octahedron is formed by a pair of nitrogen donors from the 5,5 0 -dimethyl-2,2 0 -bipyridyl ligand and two molecules of water, while the axial sites are occupied by two other water molecules. The equatorial donor atoms are nearly coplanar (r.m.s. deviation = 0.0062 Å ), while the deviation of the Fe atom from the least-squares plane is somewhat larger [0.021 (2) Å ]. The bipyridine chelating angle N1-Fe-N2 of 75.6 (1) shows the most significant deviation from an ideal octahedral geometry. The other angular distortions from an ideal octahedral geometry are in the range 0.1 (1) to 9.1 (1

Supramolecular features
Within the crystal packing, the charged components are connected by an extensive hydrogen-bonding network (  The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms. Hydrogen bonds are indicated by dashed lines.
arrangement leads to the formation of a two-dimensional hydrogen-bonded network parallel to the ab plane (Fig. 2b).

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms bonded to C atoms were placed at geometrically calculated positions and refined using a riding model. C-H distances were fixed at 0.93 and 0.96 Å from aromatic and methyl C atoms, respectively. The U iso (H) values were equal to 1.2 and 1.5 times U eq of the corresponding C(sp 2 ) and C(sp 3 ) atoms. The H atoms of the four water molecules were initially located in a difference Fourier map. During the refinement, these H atoms were allowed to ride on their parent O atoms and also to rotate about the corresponding Fe-O bonds. The U iso (H) values were set equal to 1.2 times U eq of the parent O atom. The reflections (100) and (002) were excluded from the refinement because they were nearly completely obscured by the beamstop.  Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2006); software used to prepare material for publication: CALC-OH (Nardelli, 1999). Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.