catena-Poly[[(2,2′-bipyidine-2κ2 N,N′)-μ-cyanido-1:2κ2 N:C-dicopper(I)]-μ-bromido-[(2,2′-bipyidine-2κ2 N,N′)-μ-cyanido-1:2κ2 N:C-dicopper(I)]-μ-cyanido-κ2 N:C]

In the title complex, [Cu4Br(CN)3(C10H8N2)2]n, the four independent CuI atoms are all in distorted trigonal-planar geometries. One is formed by one N atom and one C atom from two cyanide groups and one Br atom, one is formed by two N atoms from two cyanide groups and one Br atom, and the other two are formed by two N atoms from a chelating 2,2′-bipyridine (bpy) ligand and one C atom from a cyanide group. The structure exhibits a zigzag chain backbone along [101] constructed by bromide and cyanide anions bridging the CuI atoms, with the [Cu(bpy)(CN)] units pointing laterally.

In the title complex, [Cu 4 Br(CN) 3 (C 10 H 8 N 2 ) 2 ] n , the four independent Cu I atoms are all in distorted trigonal-planar geometries. One is formed by one N atom and one C atom from two cyanide groups and one Br atom, one is formed by two N atoms from two cyanide groups and one Br atom, and the other two are formed by two N atoms from a chelating 2,2 0bipyridine (bpy) ligand and one C atom from a cyanide group. The structure exhibits a zigzag chain backbone along [101] constructed by bromide and cyanide anions bridging the Cu I atoms, with the [Cu(bpy)(CN)] units pointing laterally.

Experimental
Crystal data [Cu 4 Br(CN) 3 (C 10   Considerable attention has been paid to the study of copper cyanide coordination polymers due to their fascinating structural frameworks, physical and chemical properties, and potential applications in many fields (Korzeniak et al., 2005;Yi et al., 2004). Cyanide group is a versatile ligand that can act as a monodentate ligand as well as a µ 2 -, µ 3 -or µ 4bridging ligand, exhibiting intriguing topological architectures (Zhang et al., 2000). Copper atom has versatile coordination properties and normally adopts two-, three-, four-, five-, or six-coordination, forming diverse geometries (He et al., 2006). Herein, we report a copper cyanide coordination polymers derived from 2,2′-bipyidine ligand. The title complex contains four unique Cu I ions, which are all in distorted trigonal-planar geometries. However, the detailed coordination environments of these Cu I atoms are different, as Cu1 and Cu2 are each coordinated by two N atoms of a 2,2′-bipyidine ligand and one µ 2 -cyanide group. Cu3 and Cu4 are each coordinated by two µ 2 -cyanide groups and one bromide ion (Fig. 1, Table 1). The structure exhibits by a zigzag chain backbone, [Cu 2 Br(CN)] n , along [1 0 1] (Fig. 2).

Experimental
A mixture of CuBr 2 (0.33 g, 1.48 mmol), K 4 Fe(CN) 6 .3H 2 O (0.42 g, 0.99 mmol), 2,2′-bipyridine (0.156 g, 1.00 mmol) and 24 ml H 2 O was stirred for 30 min in air. The resulting gel was then transferred to a 30 ml Teflon-lined autoclave and kept at 160°C for 5 days. After the mixture was slowly cooled to room temperature, yellow block crystals of the title complex were filtered, washed with water and dried at room temperature (yield: 0.17 g, 66%).

Figure 2
The zigzag chain in the title complex.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq