Diaquabis(4-bromobenzoato-κO)bis(N,N-diethylnicotinamide-κN 1)copper(II)

The title CuII complex, [Cu(C7H4BrO2)2(C10H14N2O)2(H2O)2], contains two 4-bromobenzoate (PBB), two diethylnicotinamide (DENA) monodentate ligands and two water molecules. The four O atoms in the equatorial plane around the CuII ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by two N atoms of the DENA ligands in the axial positions. Intramolecular O—H⋯O hydrogen bonds link the water molecules to the carboxylate groups. The dihedral angles between the carboxylate groups and the adjacent benzene rings are 3.1 (3) and 3.74 (17)°, while the pyridine rings and the benzene rings are oriented at dihedral angles of 6.81 (10) and 3.38 (12)°. In the crystal, intermolecular O—H⋯O hydrogen bonds link the molecules into double chains along the b axis. C—H⋯O interactions are also observed. π–π contacts between pyridine rings [centroid–centroid distance = 3.485 (2) Å] may further stabilize the crystal structure.

The title Cu II complex, [Cu(C 7 H 4 BrO 2 ) 2 (C 10 H 14 N 2 O) 2 -(H 2 O) 2 ], contains two 4-bromobenzoate (PBB), two diethylnicotinamide (DENA) monodentate ligands and two water molecules. The four O atoms in the equatorial plane around the Cu II ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by two N atoms of the DENA ligands in the axial positions. Intramolecular O-HÁ Á ÁO hydrogen bonds link the water molecules to the carboxylate groups. The dihedral angles between the carboxylate groups and the adjacent benzene rings are 3.1 (3) and 3.74 (17) , while the pyridine rings and the benzene rings are oriented at dihedral angles of 6.81 (10) and 3.38 (12) . In the crystal, intermolecular O-HÁ Á ÁO hydrogen bonds link the molecules into double chains along the b axis. C-HÁ Á ÁO interactions are also observed.contacts between pyridine rings [centroid-centroid distance = 3.485 (2) Å ] may further stabilize the crystal structure.
In the copper(II) complex mentioned above the two benzoate ions coordinate to the Cu II atom as bidentate ligands, while in the other structures all the ligands coordinate in a monodentate manner.
In the title complex ( Fig. 1), the four O atoms (O1, O3, O7 and O8) in the equatorial plane around the Cu II ion form a slightly distorted square-planar arrangement, while the slightly distorted octahedral coordination is completed by the two N atoms of the DENA ligands (N1 and N3) in the axial positions. The intramolecular O-H···O hydrogen bonds link the water molecules to the carboxylate groups (Table 1) (11) and C/D = 6.81 (10) °.

supplementary materials sup-2 Experimental
The title compound was prepared by the reaction of CuSO 4 .5H 2 O (1.23 g, 5 mmol) in H 2 O (20 ml) and DENA (1.78 g, 10 mmol) in H 2 O (20 ml) with sodium 4-bromobenzoate (2.23 g, 10 mmol) in H 2 O (50 ml) at room temperature. The mixture was filtered and set aside to crystallize at ambient temperature for two weeks, giving blue single crystals.

Refinement
The compound crystallized as an inversion twin: refined BASF parameter = 0.412 (7), for 2353 Friedel pairs (50.5% coverage). Atoms H71, H72, H81 and H82 (for water molecules) were located in a difference Fourier map and were freely refined. The C-bound H-atoms were positioned geometrically with C-H = 0.93, 0.97 and 0.96 Å, for aromatic, methylene and methyl H-atoms, respectively, and constrained to ride on their parent atoms, with U iso (H) = k × U eq (C), where k = 1.5 for methyl H-atoms and k = 1.2 for all other H-atoms. Fig. 1. The molecular structure of the title molecule with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. The intramolecular O-H···O hydrogen bonds are shown as dashed lines [see Table 1 for details].  Table 1 for details; Hatoms not involved in hydrogen bonding have been omitted for clarity].

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 > 2sigma(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.