(2,9-Dimethyl-1,10-phenanthroline-κ2 N,N′)bis(2-methoxybenzoato-κ2 O 1,O 1′)cadmium

In the title compound, [Cd(C8H7O3)2(C14H12N2)], the CdII ion is coordinated by two N atoms from a 2,9-dimethyl-1,10-phenanthroline (dmphen) ligand and four O atoms from two 2-methoxybenzoate anions in a distorted octahedral environment. Two O atoms of one bidentate 2-methoxybenzoate ligand are each disordered over two positions, with site-occupancy factors of 0.579 (4) and 0.421 (4). In the crystal, molecules are linked by C—H⋯O hydrogen bonds, forming a two-dimensional network lieing parallel to the bc plane. The crystal packing is further stablized by π–π stacking interactions between the dmphen rings of neighboring molecules, with distances between their parallel dmphen ring planes of 3.517 (3) and 3.610 (3) Å.


Heng Zhang and Pei-Zheng Zhao Comment
The transition metal complexes with 1,10-phenanthroline and their derivatives have attracted much attention because of their peculiar features (Dhar et al., 2003;Mizuno et al., 2002;Wall et al., 1999). Some Cd(II)-phenanthroline complexes have been synthesized and their structures were determined (Harvey et al., 2000;Ding et al., 2005;Cui et al., 2011).
Recently, we obtained the title Cadmium(II) complex which contains two different kinds of chelating ligands, by reaction of 2,9-dimethyl-1,10-phenanthroline, 2-methoxy-benzoate and cadmium acetate in an ethanol/water mixture. The structure of the title compound, Cd(C 14 H 12 N 2 )(C 8 H 7 O 3 ) 2 ,(I), is presented below.
In the crystal structure, molecules are linked into a broad one-dimensional framework by C-H···O hydrogen bonds and π-π stacking interactions between the dmphen rings of neighboring molecules, where vicinal aromatic groups present a face-to-face separations of 3.517 (3) and 3.610 (3) Å. (Fig. 2). Experimental 2,9-dimethyl-1,10-phenanthroline hemihydrate (C 14 H 12 N 2 .0.5H 2 O, 0.1086 g, 0.5 mmol) was dissolved in ethanol (10 ml) and Cd(CH 3 COO) 2 .2H 2 O (0.1333 g, 0.5 mmol) in distilled water (5 ml) were added. This solution was added to a solution of 2-methoxy-benzoic acid (C 8 H 8 O 3 , 0.1522 g, 1 mmol) in ethanol (5 ml). The mixture was stirred at 323 K and then refluxed for 11 h, cooled to room temperature and filtered. Colourless single crystals of (I) appeared over a period of two weeks by slow evaporation of the mixture at room temperature.

Refinement
Methyl H atoms were placed in calculated positions,with C-H=0.96 Å, and refined with free torsion angles to fit the electron density; U iso (H) = 1.5U eq (carrier). Other H atoms were placed in calculated positions, with C-H=0.93 Å, and refined in the riding-model approximation with U iso (H) = 1.2U eq (C). Two O atoms of one bidentate 2-methoxy-benzoate are disordered over two positions, with site occupancy factors of 0.579 (4) and 0.421 (4). The disordreed moieties were refined with similarity restraints both in distances as in U's.

Figure 1
The molecular structure of the title complex(I), with atom labels and 30% probability displacement ellipsoids.  The hydrogen-bonding motifs in the crystal structure of (I). Dashed lines indicate hydrogen bonds and π-π interaction between the dmphen rings of neighboring molecules in the crystal structure of (I).[Symmetry codes:(B)x, y + 1, z; (C)x, y + 2, z; (D)-x + 1, -y, -z; (E)-x + 1, -y + 1, -z; (F)-x + 1, -y + 2, -z + 1/2] (2,9-Dimethyl-1,10-phenanthroline-κ 2 N,N′)bis ( 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. 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 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.