Dichloridobis(7-amino-2,4-dimethyl-1,8-naphthyridine-κ2 N,N′)cobalt(II) methanol disolvate

The title compound, [CoCl2(C10H11N3)2]·2CH3OH, crystallizes with an elongated Co coordination polyhedron in a very distorted octahedral geometry. Both naphthyridine ligands coordinate to the Co atom via two N atoms in a bidentate chelating mode. The remaining coordination sites are occupied by two Cl atoms. Two uncoordinated solvent methanol molecules are hydrogen bonded to the Cl atoms. Additional N—H⋯O, C—H⋯Cl and N—H⋯Cl hydrogen bonds, and π–π stacking interactions [centroid–centroid distance 3.664 (4) Å], give rise to a three-dimensional network structure.

The title compound was obtained as violet crystals by reacting cobalt chloride hexahydrate and L in methanol. The compound is air stable and light insensitive, and does not dissolve in water and most organic solvents. X-ray structural analysis shows that the complex is mononuclear, its molecular structure is shown in Fig. 1. The Co atom is positioned on an inversion center and is bonded to two L ligands and two chloride ions. Both of the two ligands coordinate to the metal center via two nitrogen atoms in a bidentate chelating fashion. The two chloride anions coordinated to the Co ion complete a very distorted octahedral geometry. With a N-Co-N bite angle of only 58.86 (11), and 60.39 (11) ° the structure can also be seen as a pseudotetrahedral complex with each of the naphthyridine ligands L counted as a singly bonded entity. The N-Co-N angle is of necessity quite small, thereby allowing for the Cl(2)-Co(1)-Cl(1) angle to expand to 96.99 (5) °.
Perhaps as a result of the smaller spatial requirements of the chelating naphthyridine, the chloride ions are in cis-arrangement which is different from reported results (Harvey et al., 2004).
The two naphthyridine rings are basically planar with an r.m.s. deviation of only 0.0098, and 0.0183 ° respectively, and both ligands are almost perpendicular to each other with an angle between the root mean square planes of the two ligands of 85.4 °.
The free methanol molecules are connected to the (Co(L) 2 (Cl) 2 ) moieties via O-H···Cl and N-H···O hydrogen bonds, and the (Co(L) 2 (Cl) 2 ) moieties themselves are connected with each other by N-H···Cl hydrogen bonds (see Table 1). The closest C-C distance between adjacent parallel naphthyridyl rings is 3.378 (4) Å, the corresponding centroid to centroid distance for the naphthyridyl rings is 3.664 Å, which implies the presence of π-π stacking interactions between the naphthyridyl rings. Via all these interactions the compound forms a three-dimensional network structure as shown in Fig. 2.

Experimental
All reagents and solvents were used as obtained without further purification. The CHN elemental analyses were performed on a Perkin-Elmer model 2400 elemental analyzer.
supplementary materials sup-2 To a methanol solution of cobalt chloride hexahydrate (24 mg, 0.1 mmol), was added L (17.4 mg, 0.1 mmol) in 10 ml of methanol. The solution was stirred for three minutes, then the solution was filtered. The solution was left standing at room temperature for several days, and violet crystals were isolated after slow evaporation of the methanol solution in air. Yield: 38 mg, 70.3%. Anal. Calcd for C 22 H 30 Cl 2 CoN 6 O 2 : C,48.86;H,5.55;N,15.55;Found: C,48.81;H,5.52;N,15.49.

Refinement
All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with aromatic C-H = 0.93 Å, and methyl C-H = 0.96 Å. Hydrogen atoms bound to methanol molecules and amine groups were fixed, and restrained to O-H = 0.85 (1) Å, and N-H = 0.86 (1) Å.