cis-Dichloridobis(1,10-phenanthroline)cobalt(II) dimethylformamide solvate

In the title complex, [CoCl2(C12H8N2)2]·C3H7NO, which has twofold rotation symmetry, the CoII cation is coordinated by two 1,10-phenanthroline (phen) molecules and two chloride ligands in a distorted octahedral geometry. In the crystal structure, a cavity is created by six complex molecules connected by C—H⋯π interactions and non-classical C—H⋯Cl hydrogen bonds. The cavities are occupied by the disordered dimethylformamide solvent molecule. The C and N atoms of the C—N bond in the solvent molecule also lie on a crystallographic twofold rotation axis; the remaining atoms of the solvent are statistically disordered (ratio 0.5:0.5) about this axis.

In the title complex, [CoCl 2 (C 12 H 8 N 2 ) 2 ]ÁC 3 H 7 NO, which has twofold rotation symmetry, the Co II cation is coordinated by two 1,10-phenanthroline (phen) molecules and two chloride ligands in a distorted octahedral geometry. In the crystal structure, a cavity is created by six complex molecules connected by C-HÁ Á Á interactions and non-classical C-HÁ Á ÁCl hydrogen bonds. The cavities are occupied by the disordered dimethylformamide solvent molecule. The C and N atoms of the C-N bond in the solvent molecule also lie on a crystallographic twofold rotation axis; the remaining atoms of the solvent are statistically disordered (ratio 0.5:0.5) about this axis.
Data collection: CrystalClear (Rigaku & Molecular Structure Corporation, 2000); cell refinement: CrystalClear; data reduction: CrystalClear program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2005); software used to prepare material for publication: SHELXTL Comment ML m X n coordination compounds (L = α,α'-diimine chelate ligands, such as 2,2'-bipyridine, 1,10-phenanthroline, and their derivatives; X = halide or pseudohalide ligands) have been receiving extensive attention due to their importance in crystal engineering and supramolecular chemistry. They also serve as models to aid the understanding of phenomena such as photosensitization and crystallization (Forster et al., 2000;Holder et al., 2007;Ma et al., 2002). In such molecules a variety of weak intermolecular interactions involving the halide anions, aromatic ligands and solvent molecules can stabilise and regulate the supramolecular architecture in different aggregation states (Matsumoto et al., 2002;Xie et al., 2006). Herein, we report the crystal structure of a new cobalt(II) chloride complex with a phenanthroline ligand, Fig 1. The crystallographic asymmetric unit of (I) consists of one half occuapncy Co II atom that lies on a two-fold rotation axis, one phenanthroline molecule, one Clanion, and half a molecule of dimethylformamide. In the complex, the Co II atom is in a distorted octahedral coordination environment provided by four N atoms from two bidentate phen ligands and two terminal Clanions. The Co-N and Co-Cl bond lengths (Table 1) are normal, and are comparable to those found in a related octahedral cobalt(II) complex [CoCl 2 (C 12 H 8 N 2 ) 2 ].1.5CH 3 CN [Hazell et al., 1997].
Interestingly in the crystal structure, a cavity is created by six complex molecules connected by C-H···π interactions and non-classical C-H···Cl hydrogen bonds (Table 2, Fig. 2) which is occupied by the disordered dmf solvate molecule.
The solvate lies with the C14 and N3 on a crystallographic 2-fold rotation axis; the remaining atoms of the solvate are statistically disordered about this axis. The calculated void space of the cavity was estimated to be 557.6 Å 3 per unit cell, which corresponds to 23.2% of the total volume (2489.8 Å 3 ) (Fig 2) (Spek, 2003).

Experimental
[CoCl 2 .6(H 2 O)] (238 mg) was dissolved in a mixture of dimethylformamide (10 ml) and tetrahydrofuran (10 ml) with stirring. A color change from blue to dark blue was observed after the phenanthroline (40 mg) was added to the solution. The mixture was cooled down to room temperature after stirring for 1 h at 90 o C. The resulting mixture was then filtered, and the filtrate was concentrated to ca 13 ml by rotary evaporation and left in a refrigerator at 4 o C. Transparent blue prismatic crystals suitable for X-ray diffraction were produced in a few days (yield 21%). Analysis calculated for C 27 H 23 C l2 CoN 5 O: C 57.57, N 12.43, H 4.12%; found: C 57.72, N 12.56, H 3.97%.

Refinement
The H atoms bonded to C atoms were placed in calculated positions and treated using a riding-model approximation (C-H = 0.96 Å and U iso (H) = 1.5U eq (C) for the methyl group; C-H = 0.93 Å and U iso (H) = 1.2U eq (C) for the 1,10-phenanthroline and aldehyde groups).   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.