Structure of Λ(δλλ)-[Co(en)3]I3(I)2

The structure, coordination geometry and extended hydrogen-bonded network of tris(ethane-1,2-diamine-κ2 N,N′)cobalt(III) bis(iodide) triiodide is discussed.

As part of a study involving potential effects of non-chiral counter-ions, an attempt was made to grow crystals with [Co(en) 3 ]I 3 and Na[Co(edta)]. However, in the presence of I À , the mildly oxidizing [Co(edta)] À was reduced and an unexpected product, [Co(en) 3 ]I 3 (I) 2 was obtained. The structure of the corresponding cobalt(II) complex, [Co(en) 3 ]I 3 I, has been reported (Du et al., 2007). The larger cobalt(II) complex supports an lel 3 geometry of the bidentate ligands around the cobalt center. The Co-N bond distances in [Co(en) 3 ] 2+ average 2.28 Å , significantly longer than the 1.97 Å average in [Co(en) 3 ] 3+ and consistent with the sluggish redox exchange between the complexes (Jolley et al., 1990). In [Co(en) 3 ]I 3 I, the I À ions are located along the quasi-C 2 axis of the [Co(en) 3 ] 2+ complex ion with close hydrogen-bond contacts from N-H protons of 2.91 Å . The terminal iodine atoms of the I 3 À ions likewise form hydrogen bonds with N-H protons at 2.93 Å , resulting in an alternating chain of linear I 3 À ions at 90 to one another down the c-axis direction.

Structural commentary
The complex, [Co(en) 3 ](I 3 )(I) 2 crystallizes as dark-red, rodlike crystals. The asymmetric unit of the primitive, acentric, orthorhombic space group P2 1 2 1 2 1 consists of one [Co(en) 3 ] 3+ cation, two iodide anions and a triiodide anion (Fig. 1). The correct enantiomorph of the space group was determined by comparison of intensities of Friedel pairs of reflections, yielding a Flack x parameter of 0.017 (9) (Parsons et al., 2013) and a Hooft y parameter of 0.006 (8) (Hooft et al., 2008). Values close to zero indicate the correct enantiomorph of the space group. This determination allows an accurate assessment of the configuration of the cobalt cation. The cobalt center is located in a slightly distorted octahedral environment by the nitrogen atoms of three ethylene diamine ligands (see Table 1 for details). The ligands adopt a Ã() lel ob ob (lelob 2 ) geometry about the cobalt center, Fig. 1. Bond distances and angles within the molecules are unexceptional.
The amine hydrogen atoms were initially located from a difference-Fourier map and were refined freely. All of the amine hydrogen atoms are involved in hydrogen bonds to nearby iodine/triiodide moieties, Fig. 2. This interconnectivity results in a three-dimensional hydrogen-bonded network throughout the entire structure.

Supramolecular features
The iodide ion I À (1) is hydrogen bonded to N-H protons from N4 on one [Co(en) 3 ] 3+ ion at 2.77 Å , bridging to N-H protons on N4 and N5 from the two ligands with a -configuration on an adjacent cation with distances of 2.90 (5) and 2.95 (5) Å (Fig. 2, Table 2). The pairwise interactions create a hydrogen-bonded chain along the crystallographic a-axis direction, forming a layer with the complex cations separated by channels formed by I 3 À ions in an alternating herringbone pattern punctuated by I2 À ions. The iodide I2 À forms a hydrogen-bonded network bridging the layers with N-H protons from three separate cations at 2.79 (5), 2.80 (5) and 2.83 (5) Å . The I 3 À ion has a close N-H contact with N6 at 2.89 (5) Å .

Database survey
A survey of Co(en) 3 coupled with iodine reveals 23 structures in the Cambridge Structural Database (CSD v5.42, November Table 1 Selected geometric parameters (Å , ).
A mixed Cl/I species was reported by Huang and co-workers (FAXMEX, Zhang et al., 2005). All of these reports also contain water of crystallization. There is one report of Co(en) 3 that has both an iodide and a triodide pair of counter-ions that crystallizes in the tetragonal space group I42d (HIQYUC, Du et al., 2007). However, that report is of the Co II complex, Co(en) 3 (I 3 )I.

Synthesis and crystallization
Crystals were obtained from an attempt to co-crystallize optically active [Co (en)

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. The structure was solved by dualspace methods (Sheldrick, 2015a) and refined routinely (Sheldrick, 2015b). Amine hydrogen atoms were refined freely and methylene hydrogen atoms were refined as riding on the carbon to which they are bonded with C-H = 0.99 Å and U iso (H) = 1.2U eq (C).

Crystal data
[Co(C 2 H 8 N 2 ) 3 ]I 3 (I) 2 M r = 873.74 Orthorhombic, P2 1 2 1 2 1 a = 8.7508 (12)  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq I1 0.32971 (