Diaquabis(ethylenediamine-κ2 N,N′)copper(II) bis(4-phenylbenzoate) 2.66-hydrate

In the title complex, [Cu(C2H8N2)2(H2O)2](C13H9O2)2·2.66H2O, the CuII centre (located at an inversion centre) is coordinated by two bidentate ethylenediamine (en) ligands and two water O atoms in a typical Jahn–Teller distorted octahedral geometry. The amino groups and the water molecules are disordered over two distinct crystallographic positions with occupancies of 1/3 and 2/3. In the crystal, the cations and anions are disposed in alternating layers. One of the water molecules of crystallization is disordered and the other has a fractional occupation. In the 2/3 occupancy component, water molecules are organized into a chain composed of hexameric units interconnected by carboxylate bridges.

In the title complex, [Cu(C 2 H 8 N 2 ) 2 (H 2 O) 2 ](C 13 H 9 O 2 ) 2 Á-2.66H 2 O, the Cu II centre (located at an inversion centre) is coordinated by two bidentate ethylenediamine (en) ligands and two water O atoms in a typical Jahn-Teller distorted octahedral geometry. The amino groups and the water molecules are disordered over two distinct crystallographic positions with occupancies of 1/3 and 2/3. In the crystal, the cations and anions are disposed in alternating layers. One of the water molecules of crystallization is disordered and the other has a fractional occupation. In the 2/3 occupancy component, water molecules are organized into a chain composed of hexameric units interconnected by carboxylate bridges.  (2008). For a description of the graph-set notation for hydrogen-bonded aggregates, see: Grell et al. (1999).
The asymmetric unit of (I) contains one 4-phenylbenzoate anion, 1.33 water molecules of crystallisation, and 1/2 of the [Cu(en) 2 (H 2 O) 2 ] 2+ cation; the latter is situated about a centre of inversion. The species are distributed in alternating layers along the b axis (Fig. 1a). An ordered hydrophobic layer is composed by the aromatic rings from pband occupies the unit cell regions located between ca. 0.1 < b < 0.4 and 0.6 < b < 0.9 (Fig. 1a). Along the c axis, these moieties are distributed in two alternating layers, from which the aromatic rings of a specific layer are off-set from those of the layers directly above and below, avoiding efficient π-π stacking ( Fig. 1b). The two average planes containing the phenyl rings are mutually rotated by ca. 40°, which increases the distance between hydrogen atoms of neighbouring pbanions.
The hydrophilic layer, which is formed by the carboxylate groups, the [Cu(en) 2 (H 2 O) 2 ] 2+ cations and the water molecules of crystallisation, exhibits extensive crystallographic disorder. On the one hand, the centrosymmetric cation has two possible mutually-tilted crystallographic positions (rates of occupancy of 1/3 and 2/3; see Fig. 2), which have in common the two carbon atoms and the Cu centre. For each possibility the Cu centre exhibits a typical octahedral coordination environment with a strong Jahn-Teller distortion: the Cu-N bonds (equatorial planes) range from 2.006 (2) to 2.035 (4) Å, and the Cu-O water (apical positions) are either 2.601 (2) Å (2/3 occupancy) or 2.495 (4) Å (1/3 occupancy); however, the cis octahedral angles fall within a rather short range around the ideal value: 84.65 (15) -95.35 (15) ° (Table 1).
The crystal structure is rich with a variety of hydrogen bonds due to the presence of amines, carboxylates and water molecules (both coordinated and uncoordinated). The formed hydrogen bonding sub-network is strongly affected by the aforementioned crystal disorder plus some additional disorder associated with the two uncoordinated water molecules (O2W and O4W). The coordinated O3W and uncoordinated O2W water molecules, plus the O1 oxygen atom of the carboxylate group are engaged in a series of strong [O···O distances ranging from 2.668 (2) to 2.932 (3) Å; Table 2] and rather directional [angles in the range 156 (5) -168 (5) °; Table 2] O-H···O hydrogen bonds, forming an almost planar supramolecular hexagon (longest distance to the average plane of ca. 0.17 Å) with a graph set motif R 6 4 (12) (Grell et al., 1999) (Fig. 3). Remarkably, the carboxylate group further establishes bridges between adjacent supramolecular hexagons [O2W-H2M···O2 at 1.731 (10) Å; Fig. 3], leading to a 1-D hydrogen bonded chain running parallel the a axis (Fig. 3). The amino groups supplementary materials sup-2 also participate in the hydrogen bonding network with rather directional interactions [angles are in the range 141 -174 °;

Refinement
Hydrogen atoms bound to carbon and nitrogen were located at their idealized positions and were included in the final structural model in riding-motion approximation with: C-H = 0.95 Å (aromatic) and 0.95 Å (-CH 2 moieties); N-H = 0.92 Å. The isotropic thermal displacement parameters for these atoms were fixed at 1.2 times U eq of the respective parent atom.
H atoms associated with the four crystallographically independent water molecules were directly located from difference Fourier maps and included in the structure with the O-H and H···H distances restrained to 0.95 (1) and 1.55 (1) Å, respectively, in order to ensure a chemically reasonable geometry for these moieties. The U iso of these H-atoms were fixed at 1.5 times U eq of the parent O-atoms.
The crystallographically independent ethylendiamine moiety was found to be disordered over two distinct positions with rates of occupancy of 2/3 and 1/3, respectively (calculated from unrestrained refinements for the respective sites occupancies). The analogous pairs of carbon atoms of these moieties (C1 and C1'; C2 and C2') were located at the same crystallographic positions and were further included in the final structural model with identical anisotropic displacement parameters.   The organic part of the pbligand has been omitted for clarity. Symmetry operations used to generate equivalent atoms have been omitted for simplicity.

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.
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 Rfactors(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.