Bis(4-dimethylamino-1-ethylpyridinium) bis(1,2-dicyanoethene-1,2-dithiolato-κ2 S,S′)nickelate(II)

The asymmetric unit of the title complex, (C9H15N2)2[Ni(C4N2S2)2], comprises one 4-dimethylamino-1-ethylpyridinium cation and one half of a [Ni(mnt)2]2− (mnt2− = maleonitriledithiolate) anion; the complete anion is generated by the application of a centre of inversion. The NiII ion is coordinated by four S atoms of two mnt2− ligands and exhibits a square-planar coordination geometry.

The asymmetric unit of the title complex, (C 9 H 15 N 2 ) 2 - [Ni(C 4 N 2 S 2 ) 2 ], comprises one 4-dimethylamino-1-ethylpyridinium cation and one half of a [Ni(mnt) 2 ] 2À (mnt 2À = maleonitriledithiolate) anion; the complete anion is generated by the application of a centre of inversion. The Ni II ion is coordinated by four S atoms of two mnt 2À ligands and exhibits a square-planar coordination geometry.

Shan-Shan Yu, Hong Zhou and Xiao-Ming Ren Comment
Bis-1,2-dithiolene complexes of transition metals have been widely studied due to their novel properties in the areas of magnetic and conducting materials for example (Belo & Almedia, 2010;Nishijo et al., 2000;Duan et al., 2010;Ni et al., 2005). The mesomorphous neutral nickel-dithiolene complexes, with a focus on aspects of crystalline to liquid crystal transition behaviour has attracted attention and our research focus has been to try to design and assemble ionic and planar nickel-dithiolene mesogens with novel magnetic behaviour (Ni et al., 2004;Ren et al., 2004). Herein, we report the crystal structure of the title complex (I).
The molecular structure of (I) is illustrated in Fig. 1. and selected bond lengths and bond angles are given in Table 1.
Complex (I) crystallizes in the triclinic space group P1 at 293 K and the asymmetric units comprises one half of a [Ni(mnt) 2 ] 2anion and one 1-ethyl-4-N,N-dimethylpyridinium cation. The Ni II ion in the centrosymmetric [Ni(mnt) 2 ] 2anion is coordinated by four sulfur atoms of two mnt 2ligands, and exhibits square-planar coordination geometry. Bond lengths and angles of the anion are in good agreement with the other [Ni(mnt) 2 ] 2compounds (e.g. Yao et al., 2008). In the crystal packing, the cations and anions are arranged in alternate layers, which are parallel to bc plane.

Experimental
All reagents and chemicals were purchased from commercial sources and used without further purification. The staring materials disodium maleonitriledithiolate, and 1-ethyl-4-N,N-dimethylpyridinium bromide were synthesized following the literature procedures (Davison & Holm, 1967;Duan et al., 2011). Disodium maleonitriledithiolate (456 mg, 2.5 mmol) and nickel chloride hexahydrate (297 mg, 1.25 mmol) were mixed under stirring in water (20 ml) at room temperature. Subsequently, a solution of 1-ethyl-4-N,N-dimethylpyridinium bromide (2.5 mmol) in water (10 ml) was added to the mixture, and the red precipitate that was immediately formed was filtered off and washed with water. The crude product was recrystallized in acetone to give red blocks.

Refinement
Carbon-bound H-atoms were placed in calculated positions [C-H 0.93 to 0.97 Å, U iso (H) 1.2 to 1.5U eq (C)] and were included in the refinement in the riding model approximation.

Bis(4-dimethylamino-1-ethylpyridinium) bis(1,2-dicyanoethene-1,2-dithiolato-κ 2 S,S′)nickelate(II)
Crystal data (C 9 H 15 N 2 ) 2 [Ni(C 4  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 R-factors(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.