Bis(3,5,7-triaza-1-azoniatricyclo[3.3.1.13,7]decane) bis(1,2-dicyanoethene-1,2-dithiolato)nickelate(II)

The asymmetric unit of the title complex, (C6H13N4)2[Ni(C4N2S2)2], comprises one 1-azonia-3,5,7-triazatricyclo[3.3.1.13,7]decane cation and one half of an [Ni(mnt)2]2− (mnt2− is maleonitriledithiolate or 1,2-dicyanoethene-1,2-dithiolate) dianion. The Ni2+ ion is located on a center of inversion and is coordinated by four S atoms from two mnt2− ligands in a square-planar coordination mode. Intermolecular N—H⋯N hydrogen-bond interactions link one anion and two cations in the crystal structure.


Related literature
For general background to square-planar M[dithiolene] 2 complexes acting as magnetic materials or showing non-linear optical properties, see: Duan et al. (2010). For the synthesis, see: Pei et al. (2010). For related structures, see: Ren et al. (2002). For related literature on spectroscopic properties, see: Bigoli et al. (2002).

Comment
Square-planar M[dithiolene] 2 complexes have been widely studied due to their novel properties and application in the areas of conducting and magnetic materials, dyes, non-linear optics, catalysis and others. These applications arise due to a combination of functional properties, specific geometries and intermolecular interactions (Duan et al., 2010;Pei et al., 2010).
Herein we report the crystal structure of the title compound.
The molecular structure of (I) is illustrated in Fig. 1., bond distances and bond angles are given as Supplementary Material.
The N-H···N hydrogen bond properties are given in Table 1.

Experimental
Disodium maleonitriledithiolate (456 mg, 2.5 mmol) and nickel chloride hexahydrate (297 mg, 1.25 mmol) were mixed under stirring in water (20 ml) and heated to boiling about 20 min. After filtering the red solution, an aequeous solution of hexamethylenetetramine hydrochloride (442 mg, 2.5 mmol) was added dropwise to the filtrate. The immediately formed dark red precipitate was filtered off, washed with water and dried in vacuum. The crude product was recrystallized to give red crystals (yield: 645 mg, 83%). Single crystals with block shape suitable for X-ray analysis were obtained via recrystallization of the corresponding complex in acetone.

Refinement
Non-hydrogen atoms were refined anisotropically, whereas the H atom of the NH function was found in a difference Fourier map and was refined isotropically with N-H = 0.86 Å; and the H atoms of methylene protons were calculated and placed to the bonded parent atoms in geometrically idealized positions (C-H = 0.97 Å) and refined as riding atoms, with U iso (H) = 1.2U eq (C).
Crystal data (C 6