catena-Poly[[[[N′-(4-cyanobenzylidene)nicotinohydrazide]silver(I)]-μ-[N′-4-cyanobenzylidene)nicotinohydrazide]] hexafluoridoarsenate]

In the title compound, {[Ag(C14H10N4O)2]AsF6}n, the AgI ion is coordinated by two N atoms from two different pyridyl rings and one N atom from one carbonitrile group of three different N′-(4-cyanobenzylidene)nicotinohydrazide ligands in a distorted T-shaped geometry. The Ag—Ncarbonitrile bond distance is significant longer than those of Ag—Npyridyl. The bond angles around the AgI atom are also not in line with those in an ideal T-shaped geometry. One type of ligand acts as the bridge that connects AgI atoms into chains along [01]. These chains are linked to each other via N—H⋯O hydrogen bonds and Ag⋯O interactions with an Ag⋯O separation of 2.869 (2) Å. In addition, the [AsF6]− counter-anions are linked to the hydrazone groups through N—H⋯F hydrogen bonds. Four of the F atoms of the [AsF6]− anion are disordered over two sets of sites with occupancies of 0.732 (9) and 0.268 (9).

In the title compound, {[Ag (C 14 H 10 N 4 O) 2 ]AsF 6 } n , the Ag I ion is coordinated by two N atoms from two different pyridyl rings and one N atom from one carbonitrile group of three different N 0 -(4-cyanobenzylidene)nicotinohydrazide ligands in a distorted T-shaped geometry. The Ag-N carbonitrile bond distance is significant longer than those of Ag-N pyridyl . The bond angles around the Ag I atom are also not in line with those in an ideal T-shaped geometry. One type of ligand acts as the bridge that connects Ag I atoms into chains along [101]. These chains are linked to each other via N-HÁ Á ÁO hydrogen bonds and AgÁ Á ÁO interactions with an AgÁ Á ÁO separation of 2.869 (2) Å . In addition, the [AsF 6 ] À counter-anions are linked to the hydrazone groups through N-HÁ Á ÁF hydrogen bonds. Four of the F atoms of the [AsF 6 ] À anion are disordered over two sets of sites with occupancies of 0.732 (9) and 0.268 (9).

Experimental
Crystal data [Ag(C 14
The compound 4-Cyanobenzylidene nicotinohydrazide act as the µ 2 -bridging ligands only by coordinations of pyridyl and carbonitrile nitrogen atoms. Each of these bridging ligands connects two silver atoms together by one pyridyl nitrogen atom N1 and one carbonitrile nitrogen atom N8 to form a one-dimensional chain along [-1,0,1] direction. The shortest distance between two silver atoms in one chain is about 16.28 Å. Meanwhile, the rest half of all ligands acting as terminal ligands are coordinated to silver atoms in chains only through pyridyl nitrogen atoms with the carbonitrile nitrogen atoms uncoordinating (Fig.2).
There are hydrogen bondings between uncoordinating groups, including pyridyl rings of terminal ligands and all hydrazone groups and counteranions. On one hand, counteranions AsF 6are attached to ligands of chains by N-H···F hydrogen bondings (Table 2). On the other hand, there are also N-H···O hydrogen bondings (Table 2) between two neighbouring antiparallel chains. In addition to these intermolecular hydrogen bondings, there are weak Ag···O interactions between one oxygen atom O1 of the terminal ligand in one chain and one silver atom in the neighbouring chain with the Ag···O separations of 2.876 (2) Å (Fig. 3).

S2. Experimental
A solution of AgAsF 6 (0.032 g, 0.1 mmol) in CH 3 OH (10 ml) was carefully layered on a CH 3 OH/CHCl 3 solution (5 ml/10 ml) of 4-Cyanobenzylidene nicotinohydrazide (0.025 g, 0.1 mmol) in a straight glass tube. About ten days later, colourless single crystals suitable for X-ray analysis were obtained (yield about 30%). One very strong bonds at 699 cm -1 in the IR spectra was assigned to AsF 6 -. disordered F atoms were also performed. The final difference Fourier map had a max and min electron density of 0.63 and -0.47 e Å -3 , respectively, but were otherwise featureless.

Figure 1
A view of the Ag I coordination environment in the polymeric structure of (I), showing the atom-labelling scheme.

Figure 2
A e llipsoid diagram at the 50% probability level showing the one-dimensional chain. All counteranions and H atoms have been omitted for clarity.