Bis[bis(3,5-diamino-1H-1,2,4-triazol-4-ium)copper(I)] tris(hexafluoridosilicate)

In the title compound, [Cu(C2H6N5)2]2(SiF6)3, the asymmetric unit is composed of one [Cu(HL)2]3+ cation (where L is 3,5-diamino-1,2,4-triazole) and one and a half SiF6 2− anions. The rather large positively charged guanazole ligand moiety promotes the low metal coordination number of 2 for the CuI atom. The compound was obtained using the electrochemical alternating-current technique starting from an ethanol–methanol solution of CuSiF6·4H2O and guanazole. In the crystal, N—H⋯F hydrogen bonds play an important role in the formation of a three-dimensional network. As a result of these hydrogen bonds, there are also π–π interactions [centroid–centroid distance = 3.3024 (14) Å] involving one of the triazole groups in molecules related by an inversion center, and short Cu⋯N interactions [2.909 (3) Å] involving an –NH2 group, leading to the formation of a dimer-like arrangement.

In the title compound, [Cu(C 2 H 6 N 5 ) 2 ] 2 (SiF 6 ) 3 , the asymmetric unit is composed of one [Cu(HL) 2 ] 3+ cation (where L is 3,5diamino-1,2,4-triazole) and one and a half SiF 6 2À anions. The rather large positively charged guanazole ligand moiety promotes the low metal coordination number of 2 for the Cu I atom. The compound was obtained using the electrochemical alternating-current technique starting from an ethanol-methanol solution of CuSiF 6 Á4H 2 O and guanazole. In the crystal, N-HÁ Á ÁF hydrogen bonds play an important role in the formation of a three-dimensional network. As a result of these hydrogen bonds, there are alsointeractions [centroid-centroid distance = 3.3024 (14) Å ] involving one of the triazole groups in molecules related by an inversion center, and short CuÁ Á ÁN interactions [2.909 (3) Å ] involving an -NH 2 group, leading to the formation of a dimer-like arrangement.
Bis[bis(3,5-diamino-1H-1,2,4-triazol-4-ium)copper(I)] tris(hexafluoridosilicate) M. Mys'kiv and E. Goreshnik Comment 1,2,4-triazole and its functionalized derivatives, particularly 3,5-diamino-1,2,4-triazole (L), have attracted great interest and are actively studied as ligands in the synthesis of coordination compounds, biologically active compounds with a wide range efficiency, and as components of high-energy compositions [Potts, 1984]. On the other hand only a few X-ray crystal structures of complexes of this triazole have been reported (Aznar et al., 2006). The formation of low soluble polynuclear metal derivatives is one of the hindrances for structural studies of such compounds. It may be expected that the protonated form of the ligand (LH) will possess lower affinity to metal centers. Herein, we report on the synthesis and crystal structure of the title copper(I) hexafluorosilicate complex of LH.
Beside the positively charged state, the LH moiety demonstrates ability of metal coordination. In the structure of [Cu(LH) 2 ] 2 (SiF 6 ) 3 each metal atom is bound to two nitrogen atoms from two LH moieties ( Fig. 1). A similar linear copper(I) surrounding comprising of two nitrogen atoms from two voluminous ligand molecules was observed, for example, in the structure of bis(2-methylbenzimidazole)copper(I) dichlorocuprate(I) (Goreshnik et al., 2004). Because of the low copper(I) ion coordination number both Cu-N distances appear to be rather short, 1.8747 (18) and 1.8749 (17) Å. Despite the cationic status of the ligand moiety the Cu -N bond length is practically the same [1.874 (2) Å] as in the above mentioned bis(2methylbenzimidazole)copper(I) cation.
In the crystal each NH and NH 2 hydrogen atom participates in the formation of strong N-H···F hydrogen bonds (Table   1). The closest NH 2 group to the coordinated copper ion [Cu1···N10 i = 2.9092 (29) Å, symmetry code (i) = -x + 1, -y, -z + 1], forms noticeably shorter hydrogen bonds than all the others. Each of the two crystallographically independent SiF 6 2anions is bound to six LH units (Fig. 2). The [Cu(LH)] 3+ and SiF 6 2units are interconnected by N-H···F bonds to form a three dimensional network (Fig. 3). In the crystal there are also π-π interactions involving triazole rings (N1-N3,C3,C4 = Cg2) related by an inversion center, with a centroid-to-centroid distance of 3.3024 (14) As was already mentioned, the guanazolium moiety in this structure acts as a ligand despite its cationic status. Such behaviour was observed previously in the structure of platinum(II) dibromo bis(3,5-diamino-1(2)-triazolium) dibromide (Fabretti, 1992). It emphasizes the high affinity of this triazole derivative towards metal ions. The relatively large size of the LH units and their positive charge lead to the low coordination number of the copper ion.

Experimental
The title compound was prepared using electrochemical synthesis. An ethanol solution of (LH) 2 SiF 6 (where L = 3,5-diamino- This solution was then placed in a small test-tube and copper-wire electrodes were inserted. By usage of the alternating-supplementary materials sup-2 current electrochemical technique at 0.5 V of tension during some days colourless crystals of the title compound appeared on the electrodes.

Refinement
The N-bound H-atoms could all be located in difference Fourier maps. In the final cycles of least-squares refinement they were refined with distance restraints of 0.86 (2) Å with U iso (H) = 1.2U eq (N).    supplementary materials sup-8