cis-Diaquatetrakis(1-butyl-1H-imidazole-κN 3)nickel(II) dichloride

In the title compound, [Ni(C7H12N2)4(H2O)2]Cl2, the nickel(II) ion has a distorted octahedral coordination environment. It is surrounded by three N atoms and one O atom occupying the equatorial plane, and one N and one O atom in the axial positions. The imidazole ring systems are inclined to one another with dihedral angles varying between 38.3 (4) and 74.1 (4)°. In the crystal, molecules are linked via O—H⋯Cl hydrogen bonds involving one Cl− anion and the water molecule in the equatorial plane, forming an inversion dimer-like arrangement. The water molecule in the axial position is hydrogen-bonded to both Cl− anions. There are also a number of C—H⋯Cl hydrogen bonds present, forming a three-dimensional structure. All four alkyl chains are disordered over two positions with refined occupancy ratios of 0.395 (15):0.605 (15), 0.658 (14):0.342 (14), 0.332 (11):0.668 (11) and 0.622 (12):0.378 (12).

In the title compound, [Ni(C 7 H 12 N 2 ) 4 (H 2 O) 2 ]Cl 2 , the nickel(II) ion has a distorted octahedral coordination environment. It is surrounded by three N atoms and one O atom occupying the equatorial plane, and one N and one O atom in the axial positions. The imidazole ring systems are inclined to one another with dihedral angles varying between 38.3 (4) and 74.1 (4) . In the crystal, molecules are linked via O-HÁ Á ÁCl hydrogen bonds involving one Cl À anion and the water molecule in the equatorial plane, forming an inversion dimer-like arrangement. The water molecule in the axial position is hydrogen-bonded to both Cl À anions. There are also a number of C-HÁ Á ÁCl hydrogen bonds present, forming a three-dimensional structure. All four alkyl chains are disordered over two positions with refined occupancy ratios of 0.395 (15)
Knowledge of the detailed coordination behaviour of imidazoles and their limitation in the possible use in complexes with specific catalytic activity is of great current importance. Imidazoles, namely 1,3-diazacyclopenta-2,4-diene and its derivatives, have found a wide range of applications in coordination chemistry because of their multiple coordination modes as ligands to metal ions and for the construction of novel metal-organic frameworks (Huang et al., 2008(Huang et al., , 2011. The chemistry of imidazole occupies an extremely important position within the family of five-membered heterocyclic compounds. Synthesis of imidazole derivatives has attracted great interest in recent years due to their broad spectrum of biological activities (Gaonkar et al., 2009). This paper describes the synthesis and crystal structure of the nickel(II) complex of the imidazole ligand 1-butyl-1H-imidazole.
In the crystal, molecules are linked via O-H···Cl hydrogen bonds, involving one Clanion (Cl2) and the water molecule (O2) in the equatorial plane, to form an inversion dimer-like arrangement. The water molecule in the axial position (O1) is hydrogen-bonded to both Clanions. There are a number of C-H···Cl interactions present forming a three-dimensional structure. Details are given in Table 1.

Experimental
NiCl 2 .6H 2 O (6.0 g) was dissolved in warm ethanol (3 ml). The solution was cooled in ice while adding slowly a solution of 1-butylimidazole (5.0 g in 5.6 ml EtOH); the reaction is quite exothermic. Cold ethanol (15 ml) was then added to initiate crystallization. The colourless crystalline solid was filtered and kept cold for 10 min then washed with two 5 ml portions of ethanol and dried in air.

Refinement
Thy water H atoms were located in a difference Fourier map and freely refined. The C-bound H atoms were included in calculated positions and treated as riding atoms: C-H = 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl and =

Figure 1
View of the molecular structure of the title compound, with atom labelling. The displacement ellipsoids are drawn at the 30% probability level. The H atoms have been omitted for clarity. The minor fraction of the disordered alkyl chains are indicated by dashed bonds and a suffix ′ to the atom label.

Figure 2
The crystal packing of the title compound viewed along the c axis. The O-H···Cl hydrogen bonds are shown as dashed Primary atom site location: structure-invariant direct methods Secondary atom site location: difference Fourier map Hydrogen site location: inferred from neighbouring sites H atoms treated by a mixture of independent and constrained refinement

cis-Diaquatetrakis(1-butyl-1H-imidazole-κN 3 )nickel(II) dichloride
Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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 > 2sigma(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.