Bis(2,2′,2′′-nitrilotriacetamide-κ3 O,N,O′)cobalt(II) dinitrate tetrahydrate

In the centrosymmetric title compound, [Co(C6H12N4O3)2](NO3)2·4H2O, the CoII ion, lying on an inversion center, is O,N,O′-chelated by two nitrilotriacetamide molecules, forming a distorted octahedral geometry. In the crystal, extensive O—H⋯O and N—H⋯O hydrogen bonds link the complex cations, nitrate anions and lattice water molecules into a three-dimensional network.

In the centrosymmetric title compound, [Co(C 6 H 12 N 4 O 3 ) 2 ]-(NO 3 ) 2 Á4H 2 O, the Co II ion, lying on an inversion center, is O,N,O 0 -chelated by two nitrilotriacetamide molecules, forming a distorted octahedral geometry. In the crystal, extensive O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds link the complex cations, nitrate anions and lattice water molecules into a three-dimensional network.

Related literature
For related structures, see: Kumari et al. (2012). For the synthesis of the ligand, see: Smith et al. (1995).

Experimental
The ligand was prepared according to the literature method (Smith et al., 1995). The title compound was synthesized by adding water solution of Co(NO 3 ) 2 .6H 2 O (291 mg, 2 mmol) to a solution of the ligand (752 mg, 4 mmol) in methanol/water (v/v 3:1, 20 ml). The mixture was stirred for 30 min at room temperature. The solution was filtered and the filtrate was allowed to stand in air for 1 week, and pink crystals were formed at the bottom of the vessel on slow evaporation of the solvent at room temperature (yield: 30%).

Refinement
H atoms on C and N atoms were positioned geometrically and refined as riding atoms, with C-H = 0.97, N-H = 0.86 Å, and with U iso (H) = 1.2U eq (C,N). The water H atoms were located from a difference Fourier map and refined with restraints of O-H = 0.86 (1) Å and U iso (H) = 1.5U eq (O).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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.