Redetermination of cis-bis(ethylenediamine-κ2 N,N′)bis(nitrito-κN)cobalt(III) (ethylenediamine-κ2 N,N′)tetrakis(nitrito-κN)cobaltate(III) monohydrate

The structure of the title compound, [Co(NO2)2(NH2CH2CH2NH2)2][Co(NO2)4(NH2CH2CH2NH2)]·H2O, was redetermined with a modern CCD-equipped diffractometer. In comparison with the original determination based on photographic data [Kushi et al. (1976 ▶). Inorg. Nucl. Chem. Lett. 12, 629–633], the current study allows the location of reliable postions for the H atoms and thus leads to better understanding of the interionic and intermolecular interactions. The crystal structure consists of an octahedrally coordinated cationic CoIII complex ion, an octahedrally coordinated anionic CoIII complex ion and a lattice water molecule. The complex cation, complex anion and lattice water molecule are connected by an intricate network of O—H⋯O and N—H⋯O hydrogen bonds, forming a three-dimensional structure.

The structure of the title compound, [Co(NO 2 ) 2 (NH 2 CH 2 -CH 2 NH 2 ) 2 ][Co(NO 2 ) 4 (NH 2 CH 2 CH 2 NH 2 )]ÁH 2 O, was redetermined with a modern CCD-equipped diffractometer. In comparison with the original determination based on photographic data [Kushi et al. (1976). Inorg. Nucl. Chem. Lett. 12,[629][630][631][632][633], the current study allows the location of reliable postions for the H atoms and thus leads to better understanding of the interionic and intermolecular interactions. The crystal structure consists of an octahedrally coordinated cationic Co III complex ion, an octahedrally coordinated anionic Co III complex ion and a lattice water molecule. The complex cation, complex anion and lattice water molecule are connected by an intricate network of O-HÁ Á ÁO and N-HÁ Á ÁO hydrogen bonds, forming a three-dimensional structure.
Data collection: APEX2 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2009); software used to prepare material for publication: publCIF (Westrip, 2010 (Angelici, 1969). The ethylenediamine complex cis-[bis (ethylenediamine-kN,N′)dinitritoκ-N-cobalt(III)] chloride is of particular interest due to its spontaneous resolution upon crystallization (Murmann, 1955;Bernal, 1985;Bernal & Kauffman, 1987). In an attempt to synthesize this compound, crystals of the title compound Although the crystal structure of the compound (I) has been determined previously from visually estimated photographic data (Kushi et al., 1976), it is of rather low quality (R = 0.13) compared to today's standard, and more importantly the extensive hydrogen bonding was not noted, in part due to the inability to locate the H atoms of the water molecule. In addition, the atomic coordinates have not been deposited with the Cambridge Structure Database (CSD; Allen, 2002) and hence are not available in the public domain. We report here the redetermination of the crystal structure at 100 K with data measured up to 30 ° in θ.
The crystal structure of (I) is centrossymmetric with a racemic mixture of the Δ and Λ isomers of the complex cation, the complex anion and a lattice water molecule. In the complex cation, the two ethylenediamine ligands chelate to the Co III ion, and the nitrito ligands bond via their N atoms to form an approximate octahedral coordination geometry. The complex anion is similar, with one ethylenediamine ligand and four nitrito ligands bonded to the central metal cation. The Co-N distances to the ethylenediamine ligands are similar in the two ion complexes, varying between 1.9141 (17) Å and 1.9811 (17) Å. This range is within the distribution for similar complexes with octahedrally coordinated Co(III) found in the CSD (Allen, 2002;version 5.33 as of November, 2011with Feb., 2011, Mar., 2012& May, 2012, viz 1.97 (2) Å for 756 distances. There is a slight trans influence in the the cation complex where the Co-N distance is marginally longer (by ca 0.02 Å) for the N atoms trans to the nitrito ligands. The Co-N distances for the nitrito ligands show a larger variation with shorter distances in the complex cation, 1.9141 (17)  The packing diagram (Fig. 2), shows alternating columns of complex cations and anions in the crystallographic a direction. The lattice water molecule is located between the complex cation and anion. There is an intricate threedimensional network of hydrogen bonding interactions between the NH 2 groups and O atoms of nitrito ligands of neighboring ions and also of the lattice water molecule, which forms hydrogen bonds to four complex anions ( Fig. 3

Experimental
The title compound was synthesized via the chloride, prepared following the procedure of Bailor & Rollinson (1946) with the hydrogen peroxide oxidation modification of Sharrock (1980), followed by subsitution of of the chloride ligand by nitrito ligand (Bernal, 1985). Yellow crystals suitable for single-crystal X ray diffraction were formed by slow evaporation of the reaction mixture as room temperature.

Refinement
The H atoms on N atoms and in the lattice water molecule were found in a difference Fourier map and their positions allowed to refine freely while isotropic displacement factors were set to 1.2 times those of the N atoms or to 1.5 of that the O atom. The H atoms on the ethylene C atoms were positioned geometrically and allowed to ride on their parent atoms, with C-H bond lengths of 0.99 Å and isotropic displacement parameters equal to 1.2 times U eq of the parent atom.

Crystal data
[Co(NO 2 ) 2 (C 2 H 8 N 2 ) 2 ][Co(NO 2 ) 4 (C 2 H 8 N 2 )]·H 2 O M r = 592.25 Monoclinic, P2 1 /n a = 14.7580 (5) Å b = 6.7060 (2) Å c = 20.6845 (7)  Special details Experimental. The data collection was performed under a cold nitritogen flow at 100 K. 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.