Tris(ethane-1,2-diamine-κ2 N,N′)nickel(II) diiodide

The title compound, [Ni(C2H8N2)3]I2, crystallizes with an [Ni(en)3 2+] cation (en is ethane-1,2-diamine) and two iodide ions in the asymmetric unit. Two of the en ligands surrrounding the Ni2+ ion have disordered C atoms, while the third exhibits extensive weak N—H⋯I interactions with the two iodide ions that extend throughout the crystalline lattice, producing an infinite network along (011).

The title compound, [Ni(C 2 H 8 N 2 ) 3 ]I 2 , crystallizes with an [Ni(en) 3 2+ ] cation (en is ethane-1,2-diamine) and two iodide ions in the asymmetric unit. Two of the en ligands surrrounding the Ni 2+ ion have disordered C atoms, while the third exhibits extensive weak N-HÁ Á ÁI interactions with the two iodide ions that extend throughout the crystalline lattice, producing an infinite network along (011).
Structural studies of the thiocyanate salts reveal a linear polymeric anion, [(M(SCN) 3 ) 2-] n . [Ni(en) (Dvorkin et al., 1991) and [Ni(en) 3 ](SeCN) 2 .K(SeCN) (Farago et al., 1967) or [Zn(en) 3 ](SCN) 2 .K(SCN) (Dvorkin et al., 1989). Many of these structures also reveal a linear polymeric anion, [(MX 3 ) 2-] n (X=ClO 4 or BF 4 -), similar to that observed above suggesting that anions of this type are stable in certain settings and may be used in other reactions. The anions in all of the above complexes are tethered to the cations through hydogen bonds involving either amine, -NH 2 or the bidentate hydrogen bonding donor, In an effort to determine the nature of the interactions between the amine, -NH 2 (in the cation building unit used in the formation of double salts) and the anion in stabilizing these salts we report the crystal structure of the title compound, C 6 H 24 N 6 NiI 2 , (I).
The presence of I1 and I2 in the crystal lattice allows for the formation of a collection of weak intermolecular N-H···I interactions which thereby influences crystal stability (Table 1).

Experimental
Nickel(II) chloride hexahydrate was dissolved in water and excess ethylenediamine was added to the green solution. The resulting violet/purple solution was allowed to go to dryness. The crude [Ni(en) 3 ]Cl 2 was redissolved in water saturated supplementary materials sup-2 with potassium iodide. The dark blockish crystals suitable for x-ray studies, in space group Pbca, were collected by filtration on standing.

Refinement
All of the H atoms were placed in their calculated positions and then refined using the riding model with N-H = 0.93 Å, C-H = 0.95-0.99 Å, and with U iso (H) = 1.18-1.51U eq (C,N).  Crystal data [Ni(C 2