Comment

The title complex, (I), was synthesized and crystallized in about 1978, and its structure published the following year as part of a synthetic and spectroscopic project (Wardeska et al., 1979). Crystals of this obviously robust material were recently rediscovered in perfect condition after 28 years in a glass vial and its structure has been redetermined in order to resolve some disorder in the earlier determination.

While the structure in the original report gave very good residuals, the disorder in the ethylenediamine ligand was not resolved and the determination of the absolute structure was based only on a comparison of the R values given by the correct versus the inverted structure. We also take this opportunity to present the first published structure from data collected on a new type of single-crystal diffraction instrument, the Rigaku SCXmini Benchtop Crystallography System. This structure was used as a test of the efficacy of this new paradigm for crystallographic instrumentation.

As shown in Fig. 1, there are two distinct conformations of the ethylenediamine ligand. The occupancy of the major orientation (specified by the letter A) refined to 0.66 (1).

The molecular structure of the cation (Table 1) and the hydrogen-bonding scheme (Table 2) involving all components of the unit-cell contents, are, of course, similar to those originally described in detail by Wardeska et al. (1979), although in the present determination the positions of the O-bound H atoms were fully refined.

Figure 1 A view of the cation in (I). The atoms and bonds in the minor orientation of the disordered ethylenediamine ligand are shown with dashed lines.

Experimental

The title compound was synthesized from a methanol-water solution of (1S,2S)-(+)-1-phenyl-2-amino-1,3-dihydroxypropane to which was added sodium hexanitrocobaltate(III). The resulting solids were dissolved in a 2:1 methanol-water solution and treated with ethylenediamine, warmed, filtered, and then converted to the iodide salt by recrystallizing twice from potassium iodide solution. The complete experimental preparation is described by Wardeska et al. (1979).

Crystal data

[Co(C9H12NO2)2(C2H8N2)]I·H2O Mr = 596.34 Orthorhombic, P 21 21 21 a = 6.7895 (2) Å b = 14.5013 (4) Å c = 24.8565 (8) Å V = 2447.29 (13) Å3 Z = 4 Dx = 1.619 Mg m-3 Mo K radiation Cell parameters from 19448 reflections = 3.0-27.5° = 2.00 mm-1 T = 294 (2) K Prism, translucent pale-brown 0.42 × 0.39 × 0.28 mm

Data collection

Rigaku SCXmini diffractometer scans Absorption correction: multi-scan(ABSCOR; Higashi, 1995)Tmin = 0.466, Tmax = 0.57 19627 measured reflections 5482 independent reflections 5172 reflections with I > 2(I) Rint = 0.029 max = 27.5° h = -8 8 k = -13 18 l = -30 32

Refinement

Refinement on F2 R[F2 > 2(F2)] = 0.027 wR(F2) = 0.062 S = 1.10 5482 reflections 291 parameters H atoms treated by a mixture of independent and constrained refinement w = 1/[2(Fo2) + (0.022P)2 + P] where P = (Fo2 + 2Fc2)/3 (/)max = 0.003 max = 0.58 e Å-3 min = -0.69 e Å-3 Absolute structure: Flack (1983), 2272 Friedel pairs Flack parameter: 0.007 (14)

Table 1 Selected geometric parameters (Å, °) Co1-O1 1.8793 (17) Co1-O2 1.9002 (18) Co1-N2 1.9456 (19) Co1-N4 1.955 (2) Co1-N1A 1.973 (2) Co1-N3A 1.987 (2) O1-Co1-O2 93.18 (8) O1-Co1-N2 85.45 (8) O1-Co1-N4 87.21 (8) O1-Co1-N1A 90.85 (8) O1-Co1-N3A 175.03 (9) O2-Co1-N2 88.43 (8) O2-Co1-N4 85.83 (8) O2-Co1-N1A 175.95 (9) O2-Co1-N3A 91.74 (9) N2-Co1-N4 170.41 (9) N2-Co1-N1A 92.23 (10) N2-Co1-N3A 93.98 (9) N4-Co1-N1A 94.03 (9) N4-Co1-N3A 93.87 (9) N1A-Co1-N3A 84.23 (9)

Table 2 Hydrogen-bond geometry (Å, °) D-HA D-H HA DA D-HA O4-H4O2i 0.899 (17) 1.73 (2) 2.594 (2) 159 (3) O5-H2WO4 0.906 (19) 1.99 (3) 2.792 (3) 146 (5) O5-H1WI1 0.90 (3) 2.91 (4) 3.639 (3) 140 (5) O3-H3O1ii 0.919 (18) 1.83 (2) 2.714 (3) 160 (4) N1A-H1A1I1iii 0.90 3.26 4.078 (2) 152 N1A-H1A2I1iv 0.90 2.92 3.709 (2) 147 N3A-H3A1I1 0.90 2.90 3.697 (2) 149 N3A-H3A2O4ii 0.90 2.35 3.094 (3) 140 N3A-H3A2O5ii 0.90 2.57 3.368 (4) 148 N1B-H1B2I1iv 0.90 2.91 3.709 (2) 148 N3B-H3B1I1 0.90 2.87 3.697 (2) 154 N3B-H3B2O5ii 0.90 2.61 3.368 (4) 142 N3B-H3B2O4ii 0.90 2.66 3.094 (3) 111 N2-H2AI1iii 0.90 2.80 3.632 (2) 155 N4-H4AO5 0.90 2.34 3.139 (4) 149 N4-H4BO3i 0.90 2.41 3.219 (3) 149 Symmetry codes: (i) x+1, y, z; (ii) x-1, y, z; (iii) ; (iv) .

The positions of the H atoms bonded to O atoms were fully refined. All other H atoms were placeed in idealized positions, with C-H = 0.98 (methine), 0.93 (phenyl) or 0.97 Å (methylene), and N-H = 0.90 Å. U_iso(H) values were set to 1.2U_eq(C,N) or 1.5U_eq(O). For the disordered group, only the positions of the two C atoms were split; the N positions were not distinct enough to allow modelling over two positions. The isotropic displacement parameters for disordered atoms C7A and C7B were constrained to be equal, as were those for C8A and C8B. The error in the C-C distance introduced by the disorder is greatly reduced in this resolved model compared with that in the earlier report. When these disordered C atoms are not resolved and they are allowed to refine anisotropically, the resulting apparent C-C distance is 1.395 (10) Å (Wardeska et al., 1979). The present refinement allows for two separate positions for this C-C group, and the distances refine to 1.506 (6) Å for the A group and 1.497 (10) Å for the lower-occupancy B group (i.e. statistically indistinguishable at the 2 level).

Data collection: SCXmini (Rigaku, 2006); cell refinement: PROCESS-AUTO (Rigaku, 1998); data reduction: PROCESS-AUTO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CrystalStructure (Rigaku, 2005); software used to prepare material for publication: SHELXL97.