catena-Poly[[(1,10-phenanthroline)cobalt(II)]-di-μ-azido]

In the crystal structure of the binuclear title complex, [Co(N3)2(C12H8N2)]n, each CoII cation is coordinated by two N atoms from one chelating 1,10-phenanthroline ligand and four azide ligands in a slightly distorted octahedral coordination. The two CoII cations of the binuclear complex are related by an inversion centre and are bridged by two symmetry-related azide ligands in both μ1,1 and μ1,3 modes. The μ1,3 bridging mode gives rise to an infinite one-dimensional chain along the a axis, whereas the μ1,1 bridging mode is responsible for the formation of the binuclear CoII complex.


Related literature
For general background to metal-azide complexes, see: Zhao et al. (2009). For a closely related Ni-azide structure, see: Li et al. (2000).

catena-Poly[[(1,10-phenanthroline)cobalt(II)]-di-µ-azido]
Xue-Miao Gao, Jiong-Peng Zhao and Fu-Chen Liu Comment Some metal-azido complexes with unique structural features have been reported in the past (Zhao et al., 2009). Coligands are often encountered in metal azido complex, e.g. the 1,10-phenanthroline ligand which are used frequently in assembling metal azido complexes. One 1D nickel-azido complex with 1,10-phenanthroline as co-ligand was reported in 2000(Li et al., 2000. However, its isomorphic Co II compound was not reported until this work. That may be due to the fact that Co II cations are easy oxidated to Co III with 1,10-phenanthroline as co-ligand. In the title complex the Co II ion is coordinated by one chelating 1,10-phenanthroline and four azido anions forming a distorted CoN 6 octahedral environment (Fig. 1). The azido anions take two different coordinated types, in which one bridges two Co II ions in µ 1,1 mode while the other one bridges two Co II ions in µ 1,3 mode. The two µ 1,1 azido anions link two Co II ions forming a binuclear dimer whereas the dimers linked by the two µ 1,3 azido anions yield a 1D chain of bunuclear Co II complexes ( Fig. 2). π-π stacking of the phenanthroline aromatic rings between adjacent chains assists in the forming of a 3D supermolecular structure (Fig. 3). The smallest centroid to centroid distances between the aromatic rings of phenanthroline aromatic rings between adjacent chains are 3.589 (2) Å and 3.605 (2) Å, respectively. A weak CH···N interaction is present between the aromatic H5 proton and the terminal N3 azide nitrogen (2.54 Å), reinforcing slightly the packing of adjacent chains.

Experimental
The complex was hydrothermally synthesized under auto-generated pressure. A mixture of cobalt formate (1 mmol), NaN 3 (1 mmol) and 1,10-phenanthroline (1 mmol) in methanol was sealed in a Teflon-lined stainless-steel Parr bomb that was heated at 413 K for 48 h. Red crystals of the title complex were collected after the bomb was allowed to cool to room temperature. Yield 20% based on metal salt.

Refinement
H atoms were included in calculated positions and treated as riding on their parent C atoms with C-H = 0.93Å and U iso (H) = 1.2U eq (C).  The coordinated mode and linkage of the complex. Atomic displacement ellipsoids are drawn at the 30% probability level. Symmetry codes:

Figure 2
The 1D chain of the complex along the a-axis.   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.