Bis(μ-4-amino-3,5-dimethyl-4H-1,2,4-triazole)bis[diiodidozinc(II)]

In the title compound, [Zn2I4(C4H8N4)2], the ZnII atom is coordinated in a distorted tetrahedral geometry by two N atoms from the triazole rings of two 4-amino-3,5-dimethyl-4H-1,2,4-triazole (admt) ligands and two iodide ligands. Doubly bridging admt ligands connect two ZnII atoms, forming a centrosymmetric dimer. Weak N—H⋯I and C—H⋯I hydrogen bonds play an important role in the intermolecular packing.

In the title compound, [Zn 2 I 4 (C 4 H 8 N 4 ) 2 ], the Zn II atom is coordinated in a distorted tetrahedral geometry by two N atoms from the triazole rings of two 4-amino-3,5-dimethyl-4H-1,2,4-triazole (admt) ligands and two iodide ligands. Doubly bridging admt ligands connect two Zn II atoms, forming a centrosymmetric dimer. Weak N-HÁ Á ÁI and C-HÁ Á ÁI hydrogen bonds play an important role in the intermolecular packing.

Structure Reports Online
The structure of the title compound is made up of neutral dimeric metallacycle. THe title compound has the same molecular structure as its chloro derivative [Zn 2 (admt) 2 Cl 4 ], but the two compounds have different packing patterns and are not isotructural (Lavrenova et al., 1992). In each dimeric metallacycle, as shown in Fig. 1, two zinc II centers are connected by two admt ligands, resulting in a discrete Zn 2 (admt) 2 6-membered metallacycle which represents the smallest closed cyclic structure with a 1:1 metal-to-ligand ratio. Two triazole rings are coplanar. Each zinc II center is four-coordinated with two nitrogen donors of two admt ligands (Zn1-N1 2.013 (5) Å; Zn1-N2 i (symmetry code i: -x + 1,-y + 1,-z) 2.046 (5) Å)and two Ianions ligands (Zn1-I1 2.560 (1) Å; Zn1-I2 2.549 (1) Å), forming a distorted tetrahedral geometry. The Zn-N (triazole) bond lengths in the title compound are consistent with values in other Zn-triazole complexes (Zhang et al., 2007;Lavrenova et al., 1992). The N-Zn-N, N-Zn-I and I-Zn-I bond angles in the title compound are in the range of 106.8 (2) to 113.75 (3)°, near to the ideal tetrahedral value of ca. 109.5°.
The ligand admt is a 4-substituted 1,2,4-triazole and exhibits in the title compound the N1,N2-bidentate bridging coordination mode. Two admt ligands bridge two Zn(II) atoms to form a dimer with a Zn···Zn distance of 3.803 (2) Å. For a 4-substituted 1,2,4-triazole, by blocking the N4 donor position through substitution, only the N1 monodentate and N1,N2bidentate coordination modes are possible. The N1,N2-bidentate coordination mode in the dimer has been observed.

Refinement
The H atoms of the amino group were obtained from difference Fourier maps and were refined with N-H distances of 0.86Å and U iso (H) = 1.2U eq (N). All other H atoms were placed in idealized positions and refined as riding with C-H distances of 0.96Å and U iso (H) = 1.5U eq (C).

Bis(µ-4-amino-3,5-dimethyl-4H-1,2,4-triazole)bis[diiodidozinc(II)]
Crystal data [  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 Rfactors(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.