Tetraaqua(4,5-diazafluoren-9-one-κ2 N,N′)nickel(II) dinitrate

The title compound, [Ni(C11H6N2O)(H2O)4](NO3)2, was prepared by the reaction of Ni(NO3)2 and 4,5-diazafluoren-9-one (dafo). The crystal packing consists of a three-dimensional network via O—H⋯O hydrogen bonds between the coordinated water molecules and the nitrate anions. The Ni atom lies on a special position (Wyckoff position 4e, site symmetry 2), as does the carbonyl O atom.

Here we report the synthesis and structure of the title compound, which formes a three-dimensional network by O-H···O bonding.
The title structure ( Fig. 1) features one Ni atom on a special position (Wyckoff position 4e, site symmetry 2), one 4,5diazafluoren-9-one (dafo) ligand, four coordination water molecules and two nitrate anion. Even the dafo ligand lies on a special position (Wyckoff position 4e, site symmetry 2 with the C=O bond containing the twofold axis). Ni is coordinated by the two N atoms from dafo ligand, and four water molecules, yielding an overall tetragonally distorted octahedral geometry.
The nitrogen donor atoms and two coordinated water molecules are found in the equatorial plane while the remaining two water molecules occupy the axial positions. The mean Ni-N and Ni-O bond lengths are similar to the reported (Swamy et al., 2001, Kramer et al., 2002. The torsion angles of O1W-Ni1-N2-C1, O2W-Ni1-N2-C1 are -91.30 (2) and -3.40 (2)°, respectively.
Hydrogen bonds are formed between the water molecules and O atoms from nitrate anions and the carbonyl group of the dafo ligand. O2w···O4 hydrogen-bond interactions link neighboring cations and form the one-dimensional chains. The anion NO 3 link these chains together by O1w···O and O2w···O hydrogen bonds, resulting in the three-dimensional network ( Fig.2).

Experimental
All commercially obtained reagent-grade chemicals were used without further purification. To a solution of dafo (0.452 g, 2.5 mmol) in methanol solution (30 ml) was added Ni(NO 3 ) 2 6(H 2 O) (0.581 g, 2.0 mmol) in water (20 ml). The solution was stirred for 1.5 h. The resultant dark green precipitate was filtered and dried thoroughly in air. The green crystals (yield 0.79 g) were grown by slow evaporation from the water and methanol (2:3 v/v) mixed solution.
supplementary materials sup-2 Refinement H atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H and O-H distances of 0.93 and 0.85 Å, respectively, and with U iso (H) = 1.2U eq of the parent atoms.