Poly[(μ2-2,2′-bipyridine-κ2 N:N′)bis(μ3-2,2,2-trifluoroacetato-κ3 O:O:O′)disilver(I)]

In the title salt, [Ag2(CF3CO2)2(C10H8N2)]n, which may also be regarded as a coordination polymer if long Ag⋯O interactions are considered, each of the N atoms of the somewhat twisted 2,2′-bipyridine molecule [N—C—C—N = −27.5 (4)°] binds to an Ag atom, and each of the carboxylate ligands is tridentate, linking to three Ag atoms. The bidentate carboxylate O atoms bridge the same two Ag atoms, resulting in the formation of Ag2O2 rings. These rings are bridged by the 2,2′-bipyridine ligands, forming a chain along the b axis. The chains are linked into double chains via the remaining Ag—O bonds and Ag⋯Ag contacts. As a consequence of the Ag⋯Ag contacts, the NO4 donor set about each Ag atom is heavily distorted. Finally, the chains are linked into a three-dimensional network by a combination of C—H⋯O and C—H⋯F interactions.

In the title salt, [Ag 2 (CF 3 CO 2 ) 2 (C 10 H 8 N 2 )] n , which may also be regarded as a coordination polymer if long AgÁ Á ÁO interactions are considered, each of the N atoms of the somewhat twisted 2,2 0 -bipyridine molecule [N-C-C-N = À27.5 (4) ] binds to an Ag atom, and each of the carboxylate ligands is tridentate, linking to three Ag atoms. The bidentate carboxylate O atoms bridge the same two Ag atoms, resulting in the formation of Ag 2 O 2 rings. These rings are bridged by the 2,2 0 -bipyridine ligands, forming a chain along the b axis. The chains are linked into double chains via the remaining Ag-O bonds and AgÁ Á ÁAg contacts. As a consequence of the AgÁ Á ÁAg contacts, the NO 4 donor set about each Ag atom is heavily distorted. Finally, the chains are linked into a threedimensional network by a combination of C-HÁ Á ÁO and C-HÁ Á ÁF interactions.

Related literature
For structural diversity in the supramolecular structures of silver salts, see: Kundu et al. (2010). For a related Ag salt, see: Arman et al. (2010).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB5622).  (Kundu et al., 2010). During the course of on-going crystal engineering studies on silver salts (Arman et al., 2010), the title salt was isolated and characterized.
The asymmetric unit of (I) comprises two Ag cations, a 2,2'-bipyridine molecule and two trifluoroacetate anions, Fig.   1. Each of the 2,2'-bipyridine-N atoms coordinates to a Ag atom bringing into close proximity the Ag1 and Ag2 atoms [Ag1···Ag2 = 3.1941 (7) Å]. In order to relive steric pressure, the 2,2'-bipyridine molecule is twisted as seen in the torsion angle [N1-C5-C6-N2 = -27.5 (4) °] and the dihedral angle formed between the pyridine rings of 26.93 (15) °. Each Ag atom forms a close Ag-O bond to a carboxylate-O, i.e. Ag1-O1 and Ag2-O3, Table 1, and each of the O1 and O3 atoms also bridges a neighbouring Ag atom to form a non-planar Ag 2 O 2 ring. The second carboxylate-O atom in each case, i.e. O2 and O4, bridges to a different Ag atom so that each carboxylate ligand is tridentate. The supramolecular assembly is a double chain along the b axis whereby one row of Ag 2 O 2 rings bridged by 2,2'-bipyridine molecules is connected to a second row via the Ag1-O2 and Ag2-O4 bonds and vice versa. Additional stability to the double chain is afforded by Ag1···Ag1 and Ag2···Ag2 interactions, Fig. 2 and Table 1. In terms of coordination geometry, each Ag atom exists within a NO 3 donor set which is grossly distorted owing to the presence of two close Ag···Ag contacts. Chains are consolidated in the crystal packing by a combination of C-H···O and C-H···F contacts, Table 2.
Experimental 2,2'-Bipyridine (0.015 g, 0.1 mmol) was dissolved in 5 ml of methanol. Added to this was silver trifluoroacetate (0.044 g, 0.2 mmol) dissolved in 7 ml of methanol. The resulting solution was gently heated and allowed to stand for slow evaporation affording colourless blocks of (I) after five days.  Poly   (9)