Crystal structure of tetrakis(μ-4-benzyl-4H-1,2,4-triazole-κ2 N 1:N 2)tetrafluoridodi-μ2-oxido-dioxidodisilver(I)divanadium(V)

The title heterobimetallic silver(I)–vanadium(V) oxide-fluoride compound is built on the {Ag2(VO2F2)2(tr)4} secondary building unit supported by 1,2,4-triazole ligands [4-benzyl-(4H-1,2,4-triazol-4-yl)].


Chemical context
There is considerable interest in the chemistry of organicinorganic hybrids, including the vanadium oxide-fluoride (VOF) matrix, which is motivated by the numerous potential applications in catalysis, magnetism, optics, etc. (Dolbecq et al., 2010;Monakhov et al., 2015). Incorporation of silver(I) in VOF solid can afford materials such as Ag 4 V 2 O 6 F 2 (Sorensen et al., 2005;Albrecht et al., 2009) and Ag 3 VO 2 F 4 (Chamberlain et al., 2010), which are attractive candidates for solid-state battery technologies. The formation of Ag I -VOF heterobimetallic secondary building units (SBUs) in coordination compounds remains a non-trivial challenge. The 1,2,4-triazole heterocycle, as a functional group, demonstrates a favorable coordination affinity towards Ag I cations, connecting them into polynuclear units (Aromí et al., 2011). At the same time, it possesses a hidden capability to bind two different metal ions through a short -NN-bridge, usually Cu II -tr-Mo VI (Tian et al., 2011;Lysenko et al., 2016;Senchyk et al., 2017;Zhu et al., 2012) but there are some other rare examples including Cu Itr-V IV (Sharga et al., 2010) and Ag I -tr-Mo VI (Tian et al., 2017). This may be realized in the case of constructing SBUs with a terminal N 1 -triazole function that has an open site accessible to coordination. We demonstrated this principle in the self-association of Ag I -VOF heterobimetallic coordination compounds based on {Ag I 2 (V V O 2 F 2 ) 2 (tr) 4 } SBUs with bi-1,2,4-triazole ligands with different geometries (Senchyk et al., 2012). Such units seem to be very favorable and stable, and form even in the presence of a heterobifunctional 1,2,4-triazole-carboxylate ligand (Senchyk et al., 2019). In the present contribution we extend the library of Ag I -VOF compounds, adding the title complex [Ag 2 (VO 2 F 2 ) 2 (tr-CH 2 Ph) 4 ] (I), which has the ligand 4-benzyl-(4H-1,2,4-triazol-4-yl) (tr-CH 2 Ph).

Supramolecular features
Since the organic ligand contains a hydrophobic benzyl tail, the crystal structure of I involves no solvate water molecules. Thus, the only hydrogen bonds observed are of the type C-HÁ Á ÁO, C-HÁ Á ÁF and C-HÁ Á Á contacts (Figs. 2 and 3, Symmetry code: (i) Àx; Ày þ 1; Àz.
other triazole group, which provides the heterometallic Ag-V linkage, forms bifurcated C-HÁ Á ÁO and C-HÁ Á ÁF contacts with vanadium oxofluoride anions of neighboring molecular complexes. Additionally, methylene -CH 2 -fragments show directed C-HÁ Á ÁO and C-HÁ Á ÁF contacts to the VOF fragments. The phenyl rings are here oriented towards each other in an edge-to-face C-HÁ Á Á interaction mode. Supramolecular interactions in the title structure were studied through Hirshfeld surface analysis (Spackman & Byrom, 1997;McKinnon et al., 2004;Hirshfeld, 1977;Spackman & McKinnon, 2002), performed with Crystal-Explorer17 (Turner et al., 2017), taking into account only the major contribution of the disordered group. The Hirshfeld surface, mapped over d norm using a fixed color scale of À0.488 (red) to 1.385 (blue) a.u. visualizes the set of shortest intermolecular contacts (Fig. 4). All of them correspond to the hydrogen-bond interactions, which fall into three categories. The strongest hydrogen bonds to F-atom acceptors are reflected by the most prominent red spots (À0.469 to À0.488 a.u.), whereas a group of medium intensity spots (À0.182 to À0.261 a.u.) identify weaker C-HÁ Á ÁO bonds with the terminal oxide O2. However, even more distal interactions with the bridging oxide O1 are still distinguishable on the surface, in the form of very diffuse, less intense spots (À0.066 to À0.142 a.u.).
The contribution of different kinds of interatomic contacts to the Hirshfeld surface is shown in the fingerprint plots in Fig. 5. A significant fraction of the EÁ Á ÁH/HÁ Á ÁE (E = C, N, O, F) contacts (in total 60.1%) suggests the dominant role of the hydrogen-bond interactions. The strongest ones (E = O, F) have a similar nature and they are reflected by pairs of spikes pointing to the lower left of the plot. However, the contribution from the contacts with F-atom acceptors is higher (15.6% for FÁ Á ÁH/HÁ Á ÁF and 11.6% for OÁ Á ÁH/HÁ Á ÁO) and they are also essentially shorter, as indicated by different lengths of the spikes (the shortest contacts are FÁ Á ÁH = 2.0 and OÁ Á ÁH = 2.2 Å ). One may suppose that the preferable sites for hydrogen bonding of the vanadium oxofluoride groups are the F atoms. This is consistent with the results of Hirshfeld analysis for the [VOF 5 ] 2À anion 4,4 0 -(propane-1,3-diyl)bis(4H-1,2,4triazol-1-ium) salt (Senchyk et al., 2020).
The plots indicate close resemblance of the NÁ Á ÁH/HÁ Á ÁN The Hirshfeld surface of the title compound mapped over d norm in the color range À0.488 (red) to 1.385 (blue) a.u., in the environment of the closest neighbor [symmetry code: Àx + 1, Ày + 1, Àz], with the red spots indicating different kinds of intermolecular interactions.

Figure 2
Projection on the bc plane showing the crystal packing of compound I. Vanadium oxofluoride anions are shown as polyhedra. [Atoms are colored as follows: silver -cyan, vanadium -dark green, oxygen -red, fluorine -green, nitrogen -blue, carbon -gray, hydrogen -white.]
(NÁ Á ÁH = 2.9 and CÁ Á ÁH = 2.9 Å ). Both of them correspond to edge-to-face stacking or C-HÁ Á Á interactions involving either the phenyl or triazole rings. The contribution from mutualinteractions of the latter delivers minor fractions of the CÁ Á ÁC, NÁ Á ÁN and CÁ Á ÁN/NÁ Á ÁC contacts, which account in total for only 2.6%. The shortest contact of this series [CÁ Á ÁN = 3.5 Å ] exceeds the sum of the van der Waals radii [3.25 Å ] andinteractions are not associated with red spots of the d norm surface. A comparable contribution is due to the distal anagostic contacts AgÁ Á ÁH/HÁ Á ÁAg (2.9%) with the polarized methylene H atoms. There are no mutualinteractions involving phenyl rings, which are responsible for larger fractions of the CÁ Á ÁC contacts in the case of polycyclic species (Spackman & McKinnon, 2002

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. For one of the organic ligands, the benzyl linkage (C12-C18) is unequally disordered over two overlapping positions with refined partial contribution factors of 0.68 (3) and 0.32 (3). The major part of the disorder was freely refined anisotropically, while atoms of the minor contributor were refined anisotropically with a restrained geometry for the phenyl ring, rigid-bond restraints applied to the -CH 2 C 6 H 5 linkage and similarity restraints applied to the closely separated contributions of C12 and C12A, C13 and C13A. H atoms were positioned geometrically and refined as   (Sheldrick, 2015), DIAMOND (Brandenburg, 1999) and WinGX (Farrugia, 2012).  riding, with C-H = 0.93 Å (CH) and 0.97 Å (CH 2 ) and with U iso (H) = 1.2U eq (C). program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014/7 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 2012).

Tetrakis(µ-4-benzyl-4H-1,2,4-triazole-κ 2 N 1 :N 2 )tetrafluoridodi-µ 2 -oxido-dioxidodisilver(I)divanadium(V)
Crystal data 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.