Crystal structure of diaquatris(1-ethyl-1H-imidazole-κN 3)(sulfato-κO)nickel(II)

The NiII ion atom is octahedrally coordinated in diaquatris(1-ethyl-1H-imidazole)sulfatonickel(II). There are three organic ligands, two water and the sulfate anion coordinated around the NiII centre. Two complex molecules form an inversion dimer via two pairs of O—H⋯O hydrogen bonds between the coordinating sulfate anion and a water molecule in the unit cell.

In the title complex, [Ni(SO 4 )(C 5 H 8 N 2 ) 3 (H 2 O) 2 ], the Ni II ion is coordinated by three facial 1-ethyl-1H-imidazole ligands, one monodentate sulfate ligand and two water molecules in a slightly distorted octahedral coordination environment. In the crystal, two pairs of O-HÁ Á ÁO hydrogen bonds link complex molecules, forming inversion dimers incorporating R 2 4 (8), R 2 2 (8) and R 2 2 (12) rings. The dimeric unit also contains two symmetry-unique intramolecular O-HÁ Á ÁO hydrogen bonds. In addition, weak C-HÁ Á ÁO hydrogen bonds, weak C-HÁ Á Á interactions andinteractions with a centroid-centroid distance of 3.560 (2) Å combine to form a three-dimensional network. One of the ethyl groups is disordered over two sets of sites with occupancies in the ratio 0.586 (7):0.414 (7).

Chemical context
In spite of efforts in the past decades to synthesize structurally highly varying metal-organic complexes, no structures up to this point have been reported which contain the combination of a hydrophilic sulfate anion, water molecules and hydrophobic 1-ethyl-1H-imidazole molecules as ligands. The title compound was prepared by the reaction of NiSO 4 Á6H 2 O and 1-ethyl-1H-imidazole. The crystal structure of the title compound is presented herein.

Figure 3
An inversion dimer of the title compound. Hydrogen bonds are shown as dotted blue lines.
actions with a centroid-centroid distance of 3.560 (2) Å combine to form a three-dimensional network. Theinteraction is observed between the N11/C21/N31/C41/C51 ring and the inversion-related ring at (1 À x, Ày, 1 À z).  (Mukherjee et al., 1995), and with Cu: ODAHEI, ODAHOS (Adarsh et al., 2011), XIHSAI (Gó mez-Saiz et al., 2002 and QUSJAP (Calatayud et al., 2000). A similar type of hydrogen bonding occurs between the sulfate anion and water molecules in the complex BEDSEJ. In ARUZIW, one of the hydrogen bonds of the sulfate anion involves the protonated hydrogen-acceptor nitrogen atom. Unlike the title compound, one of the water ligands in FOXRAM, REHKUL and ZAMFUO is trans to the sulfate ligand. This also the case in the copper-containing structure QUSJUP, but in ODAHEI, ODAHOS and XIHSAI the two aqua ligands are trans to each other.

Database survey
Complexes with one Ni II ion and at least three 1-ethyl-1Himidazole ligands have already been reported in the literature

Synthesis and crystallization
NiSO 4 Á6H 2 O and 1-ethyl-1H-imidazole in a 1:1 stoichiometric ratio formed an exothermic reaction. The compound was dissolved in methanol and the solution was precipitated with ethyl acetate. After one week, blue crystals suitable for X-ray diffraction grew in the vessel.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Six reflections were found to be shaded by the beamstop and removed from the data set. The hydrogen atoms of the water molecules were located in a difference map and refined freely. Hydrogen atoms bonded to C atoms were placed in calculated positions and refined in a riding-model approximation. One of the ethyl groups is disordered over two sets of sites with occupancies in the ratio 0.586 (7)