Crystal structure of dichlorido{2-[(2-hydroxyethyl)(pyridin-2-ylmethyl)amino]ethanolato-κ4 N,N′,O,O′}iron(III) dihydrate from synchrotron data

The FeIII ion in the title compound shows a slightly distorted FeCl2N2O2 octahedral coordination geometry. In the crystal, two complex molecules are linked by duplex O—H⋯O hydrogen bonds. Additional hydrogen-bonding interactions lead to the formation of undulating sheets parallel to (010).


Chemical context
Tetradentate ligands including pyridine and hydroxyl groups have attracted considerable attention in chemistry and materials science (Paz et al., 2012;Li et al., 2007). These ligands are able to form multinuclear complexes with various transition metal ions, leading to dimeric, trimeric, tetrameric or polymeric structures through the deprotonation of hydroxyl groups (Shin et al., 2010;Han et al., 2009). Such multinuclear complexes have potential applications in catalysis and magnetic materials. For example, Fe III and Co II/III complexes with aminoethanol moieties have been studied as oxidation catalysts of various olefins and investigated due to their magnetic properties (Shin et al., 2011(Shin et al., , 2014. Moreover, Mn II/III complexes containing hydroxyl substituents exhibit excellent single-molecular magnetic properties due to magnetic spin-orbit anisotropy (Wu et al., 2010).

Structural commentary
A view of the molecular structure of compound (I) is shown in Fig. 1. The coordination sphere of the Fe III ion can be described as distorted octahedral, consisting of the two N atoms and two O atoms from the Hpmide ligand, and two chloride anions. The chloride anions are trans to the deprotonated ethoxy O atom and the N atom of the pyridine group of the Hpmide ligand, respectively, and coordinate in cis position to each other. The average Fe-X Hpmide (X = N, O) bond length is 2.10 Å and the Fe-Cl bond lengths are 2.2773 (5) (equatorial) and 2.3581 (7) (axial) Å . Both the average Fe-N (2.182 Å ) and Fe-O (2.010 Å ) distances in (I) are comparable to those found in related N 2 O 2 -chelated highspin Fe III complexes (Shin et al., 2014;Cappillino et al., 2012). The bite angles of the five-membered chelate rings in (I) range from 76.59 (5) to 81.45 (4) .

Supramolecular features
The hydroxyl substituent of the Hpmide ligand forms a strong hydrogen bond with the O atom of the deprotonated ethoxy group of a neighbouring molecule. These duplex interactions lead to a dinuclear dimeric unit. The dimers are linked through O-HÁ Á ÁCl interactions to the lattice water molecules, that are likewise connected to each other through O-HÁ Á ÁO hydrogen bonds. All these hydrogen-bonding interactions (Steed & Atwood, 2009) lead to the formation of undulating sheets parallel to (010). Further weak hydrogen bonding between pyridine and methyl H atoms and chloride anions stabilizes this arrangement ( Fig. 2 and Table 1).

Database survey
A search of the Cambridge Structural Database (Version 5.35, November 2013 with three updates; Groom & Allen, 2014) indicated that five complexes derived from the H 2 pmide ligand have been reported. These include Ni II and Mn II/III ; Fe III complexes have been studied for their magnetic properties and catalytic effects (Saalfrank et al., 2001;Wu et al., 2010;Shin et al., 2014).

Synthesis and crystallization
The H 2 pmide ligand was prepared following a previously reported method (Wu et al., 2010). Compound (I) was prepared as follows: to a MeOH solution (4 ml) of FeCl 2 Á4H 2 O (81 mg, 0.408 mmol) was added dropwise a MeOH solution (3 ml) of H 2 pmide (80 mg, 0.408 mmol). The colour became yellow, and then the solution was stirred for 30 min at room temperature. Yellow crystals of (I) were obtained by diffusion of diethyl ether into the yellow solution for several days, and were collected by filtration and washed with diethyl ether and View of the molecular structure of the title compound, showing the atomlabelling scheme, with displacement ellipsoids drawn at the 50% probability level. H atoms and lattice water molecules are omitted for clarity except for the H atom of the hydroxyl group.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (