A triclinic polymorph of catena-poly[[bis(N,N-dimethylformamide-κO)cobalt(II)]-di-μ-1,5-dicyanamido-κ4 N 1:N 5]

The title compound, [Co(C2N3)2(C3H7NO)2]n, is a triclinic polymorph of the previously reported monoclinic structure [Tong et al. (2003 ▶). Acta Cryst. E59, m405–m407]. The CoII ion lies on an inversion centre and adopts an almost regular octahedral N4O2 coordination geometry. Adjacent CoII atoms are connected by two bridging dicyanamide ligands, resulting in the formation of neutral chains parallel to the b axis. The title complex is isotypic with the MnII analogue but not with the NiII analogue.

The title compound, [Co(C 2 N 3 ) 2 (C 3 H 7 NO) 2 ] n , is a triclinic polymorph of the previously reported monoclinic structure [Tong et al. (2003). Acta Cryst. E59, m405-m407]. The Co II ion lies on an inversion centre and adopts an almost regular octahedral N 4 O 2 coordination geometry. Adjacent Co II atoms are connected by two bridging dicyanamide ligands, resulting in the formation of neutral chains parallel to the b axis. The title complex is isotypic with the Mn II analogue but not with the Ni II analogue.

Related literature
For the design and synthesis of metal-organic compounds, see: Long & Yaghi (2009). For the structures of the Mn II and Ni II analogues, see: Batten et al. (1999); Shen & Yuan (2005). For the structure of the monoclinic polymorph, see: Tong et al. (2003).

Experimental
Crystal data [Co(C 2  Data collection: CrystalClear (Rigaku, 2008); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL. The design and synthesis of metal-organic compounds have attracted great attention in recent years (Long & Yaghi, 2009), in particular focusing on the properties of flexible bridging ligands able to construct metal-organic compounds with various structures. The title compound is constructed by the flexible dicyanamide bridging ligand through diffusion reaction.
As illustrated in Fig. 1, the cobalt(II) ion lies on an inversion centre and adopts an octahedral coordination geometry.
Metal atoms are connected by two dicyanamide bridging ligands, resulting in the formation of neutral chains parallel the b axis. The title complex is isotypic with the Mn analogue (Batten et al., 1999) but not with the Ni analogue (Shen & Yuan, 2005). A monoclinic polymorph of the title compound was previously reported (Tong et al., 2003).

Experimental
Co(NO 3 ) 2 .6H 2 O (116.6 mg, 0.4 mmol) was added into 1 ml dmf with thorough stir for 5 minutes. After filtration, the purple filtrate was carefully laid on the surface with a solution of NaN(CN) 2 (89.1 mg, 1 mmol) in 1 ml dmf and 4 ml i-PrOH. Purple block crystals were obtained after five days.

Refinement
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.96 Å, and with U iso (H) = 1.5U eq (C) or 1.2U eq (C) for methyl and formyl H atoms, respectively.

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.  (13)