The first coordination complex of (5R,6R,7S)-5-(furan-2-yl)-7-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-6-amine with zinc(II) acetate-chloride

The first coordination complex with (5R,6R,7S)-5-(furan-2-yl)-7-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-α]pyrimidin-6-amino as a bridged ligand coordinating two zinc atoms has been synthesized and studied.


Chemical context
Multicomponent reactions of 3-amino-1,2,4-triazole and carbonyl compounds have divergent selectivity, allowing the synthesis of alternative products from the same set of starting reagents (Sedash et al., 2012). Such a phenomenon is used in diversity-oriented synthesis to increase the molecular space of biologically active compounds. In previous research, we suggested a plausible reaction mechanism for the annulation of triazole with a tetrahydropyrimidine ring occurring in reactions of 3-amino-1,2,4-triazole, aromatic aldehydes and ketocompounds (Gü mü ş et al., 2017a,b). Generally, such reactions proceed via the intermediate formation of a Schiff base from the aminoazole and the aldehyde. One of the key stages of the mechanism is a nucleophilic attack of the electron-rich enol carbon atom onto the electron-deficit azomethine carbon, with the formation of a C-C bond in the cyclization. If the suggested hypothesis is true, other reagents with a polar C C bond similar to the C C bond in enoles should possess similar reactivity. Using this analogy, we performed a multicomponent reaction between 3-amino-1,2,4triazole, -nitrostyrene and furfural. As expected, a derivative of tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidine 1 was obtained in high regio-and stereoselectivity. Further reduction of the nitro group in this compound unexpectedly resulted in formation of the zinc polycomplex 2. A single crystal of this compound was characterized by X-ray diffraction.

Structural commentary
The title compound 2 is a coordination complex (Fig. 1) in which the zinc cation forms a salt with a chlorine anion and deprotonated acetic acid and is coordinated additionally by 5-furan-2-yl-7-phenyl-4,5,6,7-tetrahydro-[1,2,4]triazolo[1,5-a]pyrimidin-6-amine through interaction with the electron lone pairs of the N4 atom of the triazole ring and the pyramidal amino group [the sum of bond angles, centered at the N5 atom, is 324 ]. Thus, the zinc coordination polyhedron is tetrahedral.

Supramolecular features
In the crystal, the coordination complex forms polymeric chains in the [010] direction, in which the neutral organic molecule is bridged between two zinc cations (Fig. 2). The coordination polymer exists as a monohydrate in the crystal. The organic molecule is linked to the chlorine and acetic anions by N1-HÁ Á ÁCl and N5-H5AÁ Á ÁO3 i hydrogen bonds (Table 1). Neighbouring polymeric chains are connected through the water molecules by O1S-H1SAÁ Á ÁO2, O1S-H1SBÁ Á ÁCl and N5-H5BÁ Á ÁO1S ii hydrogen bonds (Table 1).

Hirshfeld surface analysis
Hirshfeld surface analysis (Turner et al., 2017) was used to identify and visualize different types of intra-and intermolecular interactions in the crystal structure. The molecular Hirshfeld surface of the coordination complex was constructed using a standard surface resolution with threedimensional d norm surfaces. The areas coloured red on the d norm surfaces correspond to strong intermolecular O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds (Fig. 3) Symmetry codes: (i) Àx þ 1; y þ 1 2 ; Àz þ 3 2 ; (ii) x; Ày þ 1 2 ; z þ 1 2 .

Figure 2
The chain of molecules of 2 linked by N-HÁ Á ÁCl and N-HÁ Á ÁO hydrogen bonds.

Figure 1
The molecular structure of compound 2 (solvent molecule and hydrogen atoms are omitted for clarity). Displacement ellipsoids are shown at the 50% probability level.

Synthesis and crystallization
Microwave irradiation experiments were carried out using an Emrys TM Creator EXP (Biotage, Uppsala) equipped with an outer IR temperature sensor. The reaction was performed in a sealed microwave process vial using the 'very high' mode, which decreased the initial power to 90 W. Reaction time under microwave conditions refers to the time that the reaction mixture was kept at the set temperature (fixed hold time).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2

tetrahydro[1,2,4]triazolo[1,5-a]pyrimidin-6-amine] monohydrate]
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.36 e Å −3 Δρ min = −0.32 e Å −3 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.

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