catena-Poly[[copper(II)-bis[μ-bis(pyridin-3-yl)methanone-κ2 N:N′]] bis(tetrafluoridoborate)]

In the title complex, {[Cu(C11H8N2O)2](BF4)2}n, the CuII ion is situated on an inversion centre and adopts an N4F2 octahedral coordination geometry with four N atoms from four different bis(pyridin-3-yl)methanone ligands at the equatorial sites and two independent tetrafluoridoborate anions weakly bonded at the axial sites via two F atoms [Cu⋯F = 2.613 (3) Å]. Chains with the bridging ligands are formed along the a axis. C—H⋯F interactions stabilize the structure. C—O⋯π interactions also occur.

In the title complex, {[Cu (C 11 H 8 N 2 O) 2 ](BF 4 ) 2 } n , the Cu II ion is situated on an inversion centre and adopts an N 4 F 2 octahedral coordination geometry with four N atoms from four different bis(pyridin-3-yl)methanone ligands at the equatorial sites and two independent tetrafluoridoborate anions weakly bonded at the axial sites via two F atoms [CuÁ Á ÁF = 2.613 (3) Å ]. Chains with the bridging ligands are formed along the a axis. C-HÁ Á ÁF interactions stabilize the structure. C-OÁ Á Á interactions also occur.

Comment
The transition metal complexes of di-2-pyridinylmethanone (di-2-pyridyl ketone) have been widely studied in the passed decade (Dendrinou-Samara et al., 2003;Boudalis et al., 2003). The positional isomer di-3-pyridinylmethanone (di-3-pyridyl ketone) was mostly used as a flexible linker in construction various coordination frameworks. The angular C(sp 2 )-CO-C(sp 2 ) moiety and the rotatable C-C σ bond exhibit subtile tuning on the ligand conformation and subsequent on the formation of various coordination frameworks, such as one-dimensional helical and zigzag chains , two-dimensional nets  as well as honeycomb-like three-dimensional frameworks (Chen et al., 2009) were constructed.
In the title complex, C 22 H 16 B 2 CuF 8 N 4 O 2 , the Cu II ion adopts an N4F2-octahedral coordination geometry with four separate di-3-pyridinylmethanone ligands providing four N atoms at the equatorial sites, while two independent tetrafluoridoborate weakly bonding at the axial sites via two F atoms (Fig. 1). The Cu1···F1 distance is 2.613 (2) Å, comparable to , wherein the Cu II adopts a similar N4F2-octahedral geometry. Along the a axis, one double bridged chain with the bidentate bridging ligands is formed in the title complex, which is remarkable different from the (4,4) net in [(CuL 2 )(BF 4 ) 2 ] ∞ (L = di-3-pyridinylmethanone, . The chains are arranged in a shoulder-to-shoulder mode and interconnected through C═O···π(pyridyl) interaction, forming a layer in the ac plane (Fig. 2). For the C═O···π(pyridyl) interaction, each C6═O1 points to the opposite chain and is embraced by two pyridyl rings. The O1···Cg(pyridyl) distances lie within the 3.123 (4)-3.237 (3) Å range (Table 1), well comparable to that 2.916-3.125 Å in Cu(L) 2 (BF 4 ) 2 (L = 2,6-pyridinediylbis(3-pyridinyl)methanone) reported by Wan et al. (Wan et al. 2008). The formed layers are almost parallel and stacked along the b direction to furnish a three-dimensional framework, with the tetrafluoridoborate anions embedded among the interstices (Fig. 3). C-H(pyridyl)···F interactions is also found to stabilize the full framework (Table 1).

Experimental
Di-3-pyridinylmethanone was prepared according to the previously reported procedure .
Cu(BF 4 ) 2 .xH 2 O (40 mg) and di-3-pyridylmethanone (19mg, 0.1 mmol) were mixed and dissolved in 4 ml acetonitrile with stirring at room temperature. To the solution 1 ml methanol was subsequently dropped, obtaining a clear solution. Filtration was conducted the filtrate was left to evaporate in air. The needle-like crystals were deposited after one week (15.4 mg, 51% yield based on ligand).

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.