Crystal structure of poly[{μ-N,N′-bis[(pyridin-4-yl)methyl]oxalamide}-μ-oxalato-cobalt(II)]

In the polymeric title compound, [Co(C2O4)(C14H14N4O2)]n, the CoII atom is six-coordinated by two N atoms from symmetry-related bis[(pyridin-4-yl)methyl]oxalamide (BPMO) ligands and four O atoms from two centrosymmetric oxalate anions in a distorted octahedral coordination geometry. The CoII atoms are linked by the oxalate anions into a chain running parallel to [100]. The chains are linked by the BPMO ligands into a three-dimensional architecture. In addition, N—H⋯O hydrogen bonds stabilize the crystal packing.


Data collection
Bruker SMART APEXII CCD diffractometer Absorption correction: multi-scan (SADABS; Sheldrick, 1996) T min = 0.740, T max = 0.785 11121 measured reflections 4254 independent reflections 2027 reflections with I > 2(I) R int = 0.085 Table 1 Hydrogen-bond geometry (Å , ). Data collection: APEX2 (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXTL and publCIF (Westrip, 2010 Design of effective ligands and the proper choice of metal centers are the keys to design and construct novel metalorganic frameworks (Kitagawa et al., 2004;Ma et al., 2009). These complexes can be specially designed by the careful selection of metal cations with preferred coordination geometries, the nature of the anions, the structure of the connecting ligands, and the reaction conditions Wang et al., 2007). We selected oxalic acid as an organic carboxylate anion and N,N′-Bis-pyridin-4-ylmethyl-oxalamide (BPMO) as a N-donor neutral ligand, generating a coordination compound, [Co(C 2 O 4 )(BPMO)] n , which is reported here.
In the asymmetric unit of the title compound, [Co(C 2 O 4 )(BPMO)] n , the central Co II is six-coordinated by two nitrogen atoms from different BPMO ligands and four oxygen atoms from two oxalate anions in a distorted octahedral coordination geometry. The Co-N and Co-O distances are comparable to those found in other crystallographically characterized Co II complexes . The Co II atoms are linked by the oxalate anions to give a one-dimensional chain. The chains are linked by BPMO ligands and extend the chains into a three-dimensional supramolecular architecture. Moreover, the hydrogen bonds between the N-donor neutral ligand and oxalate, are crucial for stabilizing the three-dimensional framework.

S2. Experimental
The synthesis was performed under hydrothermal conditions. A mixture of Co(CH 3 COO) 2 . 4(H 2 O),(0.2 mmol, 0.05 g), N,N′-Bis-pyridin-4-ylmethyl-oxalamide (0.2 mmol, 0.054 g), sodium oxalate (0.2 mmol,0.026 g) and H 2 O(15 ml) in a 25 ml stainless steel reactor with a Teflon liner was heated from 293 to 443 K in 2 h and a constant temperature was maintained at 443 K for 72 h, after which the mixture was cooled to 298 K. Pink crystals of (I) were recovered from the reaction.

S3. Refinement
All H atoms on C and N atoms atoms were poisitioned geometrically and refined as riding atoms with U iso (H) = 1.2 U eq (C, N).

Figure 1
A view of the molecule of (I). Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
View of the three-dimensional structure of (I).

Poly[{µ-N,N′-bis[(pyridin-4-yl)methyl]oxalamide}-µ-oxalato-cobalt(II)]
Crystal data  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.