Crystal structure of aqua{μ-N-[3-(dimethylamino)propyl]-N′-2-(oxidophenyl)oxamidato}(1,10-phenanthroline-5,6-dione)dicopper(II) perchlorate hemihydrate

The N-[3-(dimethylamino)propyl]-N′-(2-hydroxyphenyl)oxamide trianion bridges two CuII cations to form the binuclear complex, in which the CuII cations have distorted square-planar and square-pyramidal coordination geometries.


Chemical context
It is known that oxamide ligands could be good candidates for forming polynuclear complexes because of their versatile coordinating abilities (Ojima & Nonoyama, 1988;Ruiz et al., 1999). Therefore, many oxamide complexes and their properties have been investigated extensively (Messori et al., 2003;Wang et al., 2013;Li et al., 2011).

Structural commentary
The title compound consists of a binuclear Cu II complex cation, a perchlorate anion and half of a solvent water molecule ( Fig. 1). Two copper(II) ions are bridged by a cisoxamido group. The Cu1 atom, located at the inner site of the oxamide ligand, has a distorted square-planar geometry and is displaced from the coordination plane by 0.0454 (15) Å , which is consistent with structures reported previously (Gao & Wang, 2010;Lu et al., 2011). The two exo-oxygen atoms of the oxamide ligand and two nitrogen atoms of the Phdo molecule chelate the Cu2 atom, forming the basal coordination plane [the maximum deviation being 0.0384 (14) Å for N4], and a water molecule (O4) occupies the apical position, completing a distorted square-pyramidal coordination geometry with a value of 0.06 (Addison et al., 1984). The Cu-O distance of 2.213 (3) Å in the apical direction is longer than those in the basal plane by 0.261 (4) and 0.266 (4) Å (Table 1). The Cu2 atom is displaced by 0.1610 (15) Å from the basal plane towards the apex.

Database survey
Several Cu II complexes of 1,10-phenanthroline-5,6-dione have been reported previously, for example, Chetana et al.  Zhang et al., 2013) and 1,10-phenanthroline-5,6dione (Phdo; Dickeson & Summers, 1970) were prepared by published procedures. The title compound was obtained as follows: A solution of Cu(ClO 4 ) 2 Á6H 2 O (0.0371 g, 0.1 mmol) in methanol (5 ml) was added dropwise to a solution of H 3 Dmapox (0.0133 g, 0.05 mmol) and piperidine (0.0128 g, 0.15 mmol) in methanol (5 ml). The solution was stirred continuously for 0.5 h. Then a solution of Phdo (0.011 g, 0.05 mmol) in methanol (5 ml) was added dropwise, and the mixture was stirred continuously at 313 K for 6 h and then filtered. Dark-blue crystals of the title compound suitable for X-ray analysis were obtained from the filtrate by slow evaporation at room temperature for 7 d.

Refinement
Crystal data, data collection, and refinement details are summarized in Table 3. Disorder occurs for four carbon atoms of the 3-(dimethylamino)propyl group [C10A-C13A, with occupancies of 0.561 (11); C10B-C13B, 0.439 (11) (10)]. The occupancies were refined freely except for the sum of atoms O7A and O7B which was fixed at 0.5. Some restraints on distances (DFIX) and anisotropic displacement parameters (SIMU) were applied to the disordered atoms to avoid unreasonable geometries. The hydrogen atoms of the water molecules were found in a difference Fourier map and then refined as riding. Other H atoms were placed in calculated positions, with C-H = 0.96 (methyl), 0.97 (methylene) and 0.93 Å (aromatic), and refined using a riding model, with U iso (H) = 1.2 U eq (C) or 1.5 for methyl groups.

Figure 3
A perspective view of thestacking interactions viewed perpendicular to the middle ring of the Phdo ligand. H atoms have been omitted for clarity [symmetry code: (iv) Àx, 1 À y, Àz]. Computer programs: SMART and SAINT (Bruker, 2002), SHELXS97, SHELXL97 and XP in SHELXTL (Sheldrick, 2008) and WinGX (Farrugia, 2012). Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP in SHELXTL (Sheldrick, 2008); software used to prepare material for publication: WinGX (Farrugia, 2012). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.76 e Å −3 Δρ min = −0.47 e Å −3 Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s 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 > 2σ(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.