Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270199013116/ka1333sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270199013116/ka1333Isup2.hkl |
CCDC reference: 142723
The Δ-enantiomer of the title complex was synthesized according to the method of Broomhead et al. (1960) and crystallized by evaporation from an aqueous solution.
A linear correction for crystal decomposition was applied. H atoms were placed in calculated positions (C—H = 0.96 Å) and refined with a riding model. The H atoms of the disordered water molecules could not be observed and were omitted from the model. Calulations were carried out using the WinGX package (Farrugia, 1999).
Data collection: CAD-4 EXPRESS (Enraf Nonius, 1992); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1996); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX publication routines (Farrugia, 1999).
[Co(C2H8N2)3]2Cl6·NaCl·6H2O | Dx = 1.567 Mg m−3 |
Mr = 857.72 | Mo Kα radiation, λ = 0.71073 Å |
Trigonal, P3 | Cell parameters from 25 reflections |
Hall symbol: P 3 | θ = 11.6–22.5° |
a = 11.415 (4) Å | µ = 1.48 mm−1 |
c = 8.0552 (8) Å | T = 293 K |
V = 909.0 (5) Å3 | Approximate trapezoid cleaved from larger crystal, orange-brown |
Z = 1 | 0.7 × 0.6 × 0.4 mm |
F(000) = 448 |
Enraf Nonius Turbo CAD-4 diffractometer | Rint = 0.017 |
Graphite monochromator | θmax = 25.9°, θmin = 2.5° |
non–profiled ω/2θ scans | h = −14→12 |
Absorption correction: ψ scan (North et al., 1968) | k = −1→14 |
Tmin = 0.419, Tmax = 0.512 | l = −9→1 |
2484 measured reflections | 6 standard reflections every 118 reflections |
1440 independent reflections | intensity decay: 26% |
1429 reflections with I > 2σ(I) |
Refinement on F2 | Hydrogen site location: inferred from neighbouring sites |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.047 | w = 1/[σ2(Fo2) + (0.062P)2 + 3.2274P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.144 | (Δ/σ)max = 0.002 |
S = 1.20 | Δρmax = 0.64 e Å−3 |
1440 reflections | Δρmin = −0.61 e Å−3 |
130 parameters | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.040 (5) |
Primary atom site location: structure-invariant direct methods | Absolute structure: Flack (1983) |
Secondary atom site location: difference Fourier map | Absolute structure parameter: 0.07 (5) |
[Co(C2H8N2)3]2Cl6·NaCl·6H2O | Z = 1 |
Mr = 857.72 | Mo Kα radiation |
Trigonal, P3 | µ = 1.48 mm−1 |
a = 11.415 (4) Å | T = 293 K |
c = 8.0552 (8) Å | 0.7 × 0.6 × 0.4 mm |
V = 909.0 (5) Å3 |
Enraf Nonius Turbo CAD-4 diffractometer | 1429 reflections with I > 2σ(I) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.017 |
Tmin = 0.419, Tmax = 0.512 | 6 standard reflections every 118 reflections |
2484 measured reflections | intensity decay: 26% |
1440 independent reflections |
R[F2 > 2σ(F2)] = 0.047 | H-atom parameters constrained |
wR(F2) = 0.144 | Δρmax = 0.64 e Å−3 |
S = 1.20 | Δρmin = −0.61 e Å−3 |
1440 reflections | Absolute structure: Flack (1983) |
130 parameters | Absolute structure parameter: 0.07 (5) |
0 restraints |
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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Co1 | 0.0000 | 0.0000 | 0.0000 | 0.0218 (5) | |
Cl1 | 0.0510 (3) | 0.2329 (3) | 0.5216 (4) | 0.0345 (6) | |
C11 | −0.1076 (11) | 0.1688 (11) | −0.0846 (13) | 0.036 (2) | |
H11A | −0.1883 | 0.1715 | −0.1157 | 0.043* | |
H11B | −0.0302 | 0.2446 | −0.1366 | 0.043* | |
C12 | −0.0913 (11) | 0.1778 (10) | 0.1005 (12) | 0.033 (2) | |
H12A | −0.0682 | 0.2672 | 0.1395 | 0.040* | |
H12B | −0.1742 | 0.1114 | 0.1545 | 0.040* | |
N11 | −0.1187 (6) | 0.0394 (6) | −0.1406 (9) | 0.0261 (14) | |
H11C | −0.0935 | 0.0462 | −0.2476 | 0.031* | |
H11D | −0.2050 | −0.0281 | −0.1319 | 0.031* | |
N12 | 0.0208 (7) | 0.1496 (7) | 0.1353 (10) | 0.0319 (16) | |
H12C | 0.0198 | 0.1292 | 0.2434 | 0.038* | |
H12D | 0.1008 | 0.2238 | 0.1130 | 0.038* | |
Co2 | 0.3333 | 0.6667 | 0.5042 (3) | 0.0238 (5) | |
Cl2 | 0.2810 (3) | 0.4338 (3) | 0.0236 (4) | 0.0394 (7) | |
C21 | 0.4369 (12) | 0.4978 (11) | 0.4160 (12) | 0.037 (2) | |
H21A | 0.5154 | 0.4925 | 0.3808 | 0.045* | |
H21B | 0.3571 | 0.4237 | 0.3656 | 0.045* | |
C22 | 0.4245 (11) | 0.4890 (11) | 0.6063 (13) | 0.037 (2) | |
H22A | 0.4026 | 0.4000 | 0.6456 | 0.044* | |
H22B | 0.5075 | 0.5565 | 0.6589 | 0.044* | |
N21 | 0.4507 (7) | 0.6265 (7) | 0.3659 (10) | 0.0339 (16) | |
H21C | 0.4275 | 0.6227 | 0.2585 | 0.041* | |
H21D | 0.5374 | 0.6927 | 0.3774 | 0.041* | |
N22 | 0.3109 (8) | 0.5159 (8) | 0.6394 (10) | 0.0377 (17) | |
H22C | 0.3103 | 0.5354 | 0.7475 | 0.045* | |
H22D | 0.2314 | 0.4417 | 0.6153 | 0.045* | |
Na1A | 0.6667 | 0.3333 | 0.2632 (10) | 0.0451 (13) | 0.734 (16) |
Na1B | 0.6667 | 0.3333 | 0.7626 (8) | 0.0490 (10) | 0.266 (16) |
Cl3A | 0.6667 | 0.3333 | 0.7626 (8) | 0.0490 (10) | 0.734 (16) |
Cl3B | 0.6667 | 0.3333 | 0.2632 (10) | 0.0451 (13) | 0.266 (16) |
O1A | 0.7740 (12) | 0.2424 (13) | 0.4532 (17) | 0.054 (3) | 0.734 (16) |
O1B | 0.777 (2) | 0.251 (2) | 0.581 (3) | 0.026 (6)* | 0.266 (16) |
O2A | 0.8601 (12) | 0.4447 (12) | 0.0803 (14) | 0.047 (3) | 0.734 (16) |
O2B | 0.863 (3) | 0.437 (3) | −0.031 (4) | 0.038 (7)* | 0.266 (16) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Co1 | 0.0212 (6) | 0.0212 (6) | 0.0230 (9) | 0.0106 (3) | 0.000 | 0.000 |
Cl1 | 0.0421 (12) | 0.0338 (12) | 0.0230 (10) | 0.0155 (9) | 0.0010 (8) | 0.0016 (8) |
C11 | 0.042 (5) | 0.040 (6) | 0.037 (5) | 0.029 (5) | 0.007 (4) | 0.006 (4) |
C12 | 0.045 (5) | 0.031 (5) | 0.027 (4) | 0.022 (4) | −0.001 (4) | −0.005 (4) |
N11 | 0.031 (3) | 0.029 (3) | 0.019 (3) | 0.015 (3) | −0.001 (3) | −0.001 (3) |
N12 | 0.033 (3) | 0.028 (3) | 0.030 (4) | 0.013 (3) | 0.001 (3) | −0.004 (3) |
Co2 | 0.0223 (6) | 0.0223 (6) | 0.0267 (10) | 0.0112 (3) | 0.000 | 0.000 |
Cl2 | 0.0450 (12) | 0.0356 (13) | 0.0331 (12) | 0.0166 (10) | 0.0003 (9) | −0.0010 (9) |
C21 | 0.051 (6) | 0.051 (6) | 0.028 (5) | 0.040 (5) | 0.002 (4) | −0.003 (4) |
C22 | 0.042 (5) | 0.034 (5) | 0.043 (5) | 0.025 (4) | −0.002 (5) | 0.006 (4) |
N21 | 0.035 (3) | 0.036 (3) | 0.029 (4) | 0.016 (3) | −0.001 (3) | 0.001 (3) |
N22 | 0.041 (4) | 0.044 (4) | 0.029 (4) | 0.022 (3) | 0.000 (3) | 0.001 (3) |
Na1A | 0.0456 (15) | 0.0456 (15) | 0.044 (3) | 0.0228 (7) | 0.000 | 0.000 |
Na1B | 0.0556 (13) | 0.0556 (13) | 0.036 (2) | 0.0278 (7) | 0.000 | 0.000 |
Cl3A | 0.0556 (13) | 0.0556 (13) | 0.036 (2) | 0.0278 (7) | 0.000 | 0.000 |
Cl3B | 0.0456 (15) | 0.0456 (15) | 0.044 (3) | 0.0228 (7) | 0.000 | 0.000 |
O1A | 0.051 (6) | 0.051 (7) | 0.058 (8) | 0.022 (5) | −0.001 (6) | 0.005 (6) |
O2A | 0.058 (7) | 0.050 (6) | 0.024 (6) | 0.021 (5) | −0.004 (4) | 0.003 (4) |
Co1—N12i | 1.938 (7) | Na1A—O2Av | 2.420 (12) |
Co1—N12 | 1.938 (7) | Na1A—O2A | 2.420 (12) |
Co1—N12ii | 1.938 (7) | Na1A—O2Avi | 2.420 (12) |
Co1—N11i | 1.983 (7) | Na1A—O1A | 2.488 (13) |
Co1—N11 | 1.983 (7) | Na1A—O1Avi | 2.488 (13) |
Co1—N11ii | 1.983 (7) | Na1A—O1Av | 2.488 (13) |
C11—N11 | 1.487 (12) | Na1A—Na1B | 4.023 (10) |
C11—C12 | 1.499 (14) | Na1A—Na1Bvii | 4.032 (10) |
C12—N12 | 1.494 (12) | Na1B—O1B | 2.41 (2) |
Co2—N22iii | 1.942 (8) | Na1B—O1Bv | 2.41 (2) |
Co2—N22iv | 1.942 (8) | Na1B—O1Bvi | 2.41 (2) |
Co2—N22 | 1.942 (8) | Na1B—O2Bviii | 2.55 (3) |
Co2—N21iv | 1.965 (8) | Na1B—O2Bix | 2.55 (3) |
Co2—N21iii | 1.965 (8) | Na1B—O2Bx | 2.55 (3) |
Co2—N21 | 1.965 (8) | Na1B—Na1Aviii | 4.032 (10) |
C21—N21 | 1.454 (12) | O1A—O1B | 1.03 (3) |
C21—C22 | 1.538 (14) | O2A—O2B | 0.90 (3) |
C22—N22 | 1.498 (13) | O2B—Na1Bvii | 2.55 (3) |
N12i—Co1—N12 | 91.5 (3) | O2A—Na1A—O1Av | 178.2 (5) |
N12i—Co1—N12ii | 91.5 (3) | O2Avi—Na1A—O1Av | 92.3 (4) |
N12—Co1—N12ii | 91.5 (3) | O1A—Na1A—O1Av | 86.1 (5) |
N12i—Co1—N11i | 85.3 (3) | O1Avi—Na1A—O1Av | 86.1 (5) |
N12—Co1—N11i | 174.6 (3) | O2Av—Na1A—Na1B | 127.5 (3) |
N12ii—Co1—N11i | 92.9 (3) | O2A—Na1A—Na1B | 127.5 (3) |
N12i—Co1—N11 | 92.9 (3) | O2Avi—Na1A—Na1B | 127.5 (3) |
N12—Co1—N11 | 85.3 (3) | O1A—Na1A—Na1B | 52.0 (4) |
N12ii—Co1—N11 | 174.6 (3) | O1Avi—Na1A—Na1B | 52.0 (4) |
N11i—Co1—N11 | 90.6 (3) | O1Av—Na1A—Na1B | 52.0 (4) |
N12i—Co1—N11ii | 174.6 (3) | O2Av—Na1A—Na1Bvii | 52.5 (3) |
N12—Co1—N11ii | 92.9 (3) | O2A—Na1A—Na1Bvii | 52.5 (3) |
N12ii—Co1—N11ii | 85.3 (3) | O2Avi—Na1A—Na1Bvii | 52.5 (3) |
N11i—Co1—N11ii | 90.6 (3) | O1A—Na1A—Na1Bvii | 128.0 (4) |
N11—Co1—N11ii | 90.6 (3) | O1Avi—Na1A—Na1Bvii | 128.0 (4) |
N11—C11—C12 | 108.4 (8) | O1Av—Na1A—Na1Bvii | 128.0 (4) |
N12—C12—C11 | 105.2 (8) | Na1B—Na1A—Na1Bvii | 180.000 (1) |
C11—N11—Co1 | 108.9 (6) | O1B—Na1B—O1Bv | 86.8 (8) |
C12—N12—Co1 | 110.1 (6) | O1B—Na1B—O1Bvi | 86.8 (8) |
N22iii—Co2—N22iv | 91.7 (3) | O1Bv—Na1B—O1Bvi | 86.8 (8) |
N22iii—Co2—N22 | 91.7 (3) | O1B—Na1B—O2Bviii | 94.0 (9) |
N22iv—Co2—N22 | 91.7 (3) | O1Bv—Na1B—O2Bviii | 176.2 (10) |
N22iii—Co2—N21iv | 92.5 (3) | O1Bvi—Na1B—O2Bviii | 97.0 (9) |
N22iv—Co2—N21iv | 85.1 (3) | O1B—Na1B—O2Bix | 97.0 (9) |
N22—Co2—N21iv | 174.8 (3) | O1Bv—Na1B—O2Bix | 94.0 (9) |
N22iii—Co2—N21iii | 85.1 (3) | O1Bvi—Na1B—O2Bix | 176.2 (10) |
N22iv—Co2—N21iii | 174.8 (3) | O2Bviii—Na1B—O2Bix | 82.2 (11) |
N22—Co2—N21iii | 92.5 (3) | O1B—Na1B—O2Bx | 176.2 (10) |
N21iv—Co2—N21iii | 91.0 (3) | O1Bv—Na1B—O2Bx | 97.0 (9) |
N22iii—Co2—N21 | 174.8 (3) | O1Bvi—Na1B—O2Bx | 94.0 (9) |
N22iv—Co2—N21 | 92.5 (3) | O2Bviii—Na1B—O2Bx | 82.2 (11) |
N22—Co2—N21 | 85.1 (3) | O2Bix—Na1B—O2Bx | 82.2 (11) |
N21iv—Co2—N21 | 91.0 (3) | O1B—Na1B—Na1A | 52.5 (6) |
N21iii—Co2—N21 | 91.0 (3) | O1Bv—Na1B—Na1A | 52.5 (6) |
N21—C21—C22 | 107.6 (8) | O1Bvi—Na1B—Na1A | 52.5 (6) |
N22—C22—C21 | 103.0 (8) | O2Bviii—Na1B—Na1A | 130.6 (7) |
C21—N21—Co2 | 109.6 (6) | O2Bix—Na1B—Na1A | 130.6 (7) |
C22—N22—Co2 | 109.8 (6) | O2Bx—Na1B—Na1A | 130.6 (7) |
O2Av—Na1A—O2A | 86.8 (4) | O1B—Na1B—Na1Aviii | 127.5 (6) |
O2Av—Na1A—O2Avi | 86.8 (4) | O1Bv—Na1B—Na1Aviii | 127.5 (6) |
O2A—Na1A—O2Avi | 86.8 (4) | O1Bvi—Na1B—Na1Aviii | 127.5 (6) |
O2Av—Na1A—O1A | 92.3 (4) | O2Bviii—Na1B—Na1Aviii | 49.4 (7) |
O2A—Na1A—O1A | 94.8 (4) | O2Bix—Na1B—Na1Aviii | 49.4 (7) |
O2Avi—Na1A—O1A | 178.2 (5) | O2Bx—Na1B—Na1Aviii | 49.4 (7) |
O2Av—Na1A—O1Avi | 178.2 (5) | Na1A—Na1B—Na1Aviii | 180.000 (2) |
O2A—Na1A—O1Avi | 92.3 (4) | O1B—O1A—Na1A | 124.9 (16) |
O2Avi—Na1A—O1Avi | 94.8 (4) | O1A—O1B—Na1B | 130.2 (18) |
O1A—Na1A—O1Avi | 86.1 (5) | O2B—O2A—Na1A | 128 (2) |
O2Av—Na1A—O1Av | 94.8 (4) | O2A—O2B—Na1Bvii | 129 (2) |
Symmetry codes: (i) −y, x−y, z; (ii) −x+y, −x, z; (iii) −x+y, −x+1, z; (iv) −y+1, x−y+1, z; (v) −x+y+1, −x+1, z; (vi) −y+1, x−y, z; (vii) x, y, z−1; (viii) x, y, z+1; (ix) −x+y+1, −x+1, z+1; (x) −y+1, x−y, z+1. |
Experimental details
Crystal data | |
Chemical formula | [Co(C2H8N2)3]2Cl6·NaCl·6H2O |
Mr | 857.72 |
Crystal system, space group | Trigonal, P3 |
Temperature (K) | 293 |
a, c (Å) | 11.415 (4), 8.0552 (8) |
V (Å3) | 909.0 (5) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 1.48 |
Crystal size (mm) | 0.7 × 0.6 × 0.4 |
Data collection | |
Diffractometer | Enraf Nonius Turbo CAD-4 diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.419, 0.512 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2484, 1440, 1429 |
Rint | 0.017 |
(sin θ/λ)max (Å−1) | 0.614 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.144, 1.20 |
No. of reflections | 1440 |
No. of parameters | 130 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.64, −0.61 |
Absolute structure | Flack (1983) |
Absolute structure parameter | 0.07 (5) |
Computer programs: CAD-4 EXPRESS (Enraf Nonius, 1992), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1996), SIR92 (Altomare et al., 1993), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX publication routines (Farrugia, 1999).
Co1—N12 | 1.938 (7) | C22—N22 | 1.498 (13) |
Co1—N11 | 1.983 (7) | Na1A—O2A | 2.420 (12) |
C11—N11 | 1.487 (12) | Na1A—O1A | 2.488 (13) |
C11—C12 | 1.499 (14) | Na1A—Na1B | 4.023 (10) |
C12—N12 | 1.494 (12) | Na1B—O1B | 2.41 (2) |
Co2—N22 | 1.942 (8) | Na1B—O2Bi | 2.55 (3) |
Co2—N21 | 1.965 (8) | O1A—O1B | 1.03 (3) |
C21—N21 | 1.454 (12) | O2A—O2B | 0.90 (3) |
C21—C22 | 1.538 (14) | ||
N12ii—Co1—N12 | 91.5 (3) | N22iv—Co2—N22 | 91.7 (3) |
N12ii—Co1—N11 | 92.9 (3) | N22iv—Co2—N21 | 92.5 (3) |
N12—Co1—N11 | 85.3 (3) | N22—Co2—N21 | 85.1 (3) |
N12—Co1—N11iii | 92.9 (3) | N21iv—Co2—N21 | 91.0 (3) |
Symmetry codes: (i) x, y, z+1; (ii) −y, x−y, z; (iii) −x+y, −x, z; (iv) −y+1, x−y+1, z. |
l | F2(calc) | F2(obs) | σ |
-9 | 72.76 | 177.30 | 3.57 |
-8 | 2097.26 | 2106.88 | 14.15 |
-7 | 32.59 | 21.10 | 1.42 |
-6 | 1078.48 | 1091.35 | 8.24 |
-5 | 58.99 | 111.37 | 1.73 |
-4 | 1847.87 | 1652.23 | 7.03 |
-3 | 370.18 | 1176.73 | 4.99 |
-2 | 18204.96 | 19443.56 | 74.78 |
-1 | 18.84 | 44.08 | 0.56 |
1 | 18.78 | 50.40 | 0.59 |
The complex cation [Co(en)3]3+ (en is ethylenediamine) has been of historic importance in the development of transition metal optical activity. The title complex, (I), was the first transition metal complex to have its absolute configuration determined by the anomalous scattering of X-rays (Saito et al., 1954, 1955). The same compound was the first transition metal complex to have its electronic CD spectrum measured in both the solid state and in solution (Mathieu, 1953; McCaffery & Mason, 1963), and as such has been the complex of choice for testing the various theories of transition metal CD in the visible region (Mason & Seal, 1976; Ernst & Royer, 1993). The measurement of natural CD has recently been extended to the X-ray region (Alagna et al., 1998) and the present redetermination was undertaken as a basis for ab initio and multiple scattering calculations of CD at the Co K-edge. [CD = ?]
The crystal structure of (I) was first determined by Shiro and co-workers (Nakatsu et al., 1957) from photographic data. On the basis of the observed 6/m Laue symmetry, the data were analysed in terms of a twinned structure in the hexagonal space group P63. However, these authors noted that the arrangement of the Na+ and Cl− ions, and the two independent water molecules was only consistent with the lower symmetry trigonal space group P3. Despite their clear statement in the summary that `the space group is P3', the coordinates given in this paper, and those deposited in the Cambridge Structural Database (refcode SAETCO; Allen & Kennard, 1993) refer to the hexagonal space group.
A distinction between the two space groups in terms of systematic absences can only be made from the intensities of the set of 00 l reflections having l odd. These reflections are observed by us to be systematically weak, contributing ca 8.4% to the total 00 l intensities, but are definitely present as Bragg reflections (see Table 2). The reflections 003 and 006 were monitored at several different azimuthal angles. They were found to have normal profiles and were not subject to the Renninger effect. Moreover, in concurrence with the earlier study (Nakatsu et al., 1957), the 003 reflection was found to be the strongest of these. The presence of these reflections in both the photographic (Nakatsu et al., 1957) and diffractometric data precludes the possibility that they arise from scan overlap involving neighbouring strong reflections.
Although the Laue symmetry is very close to 6/m (Rint is 0.075 for 2473 observations of 629 independent data), the merging statistics are significantly better for the Laue symmetry 3 (Rint is 0.017 for 2218 observations of 915 independent data). Nevertheless, the overall crystal structure is very close to P63. The coordinates of the non-H atoms in cation 1 (x1, y1, z1) are all nearly related to those in cation 2 (x2, y2, z2) by the relationships x2 = 1/3 − x1, y2 = 2/3 − y1, z2 = 1/2 + z1, and all atoms are within 0.05 Å of the idealized P63 structure. The data may be satisfactorily refined in this space group (see supplementary material). Using the standard procedure of merging equivalent reflections (SHELXL instruction MERG2), a final R(F) value of 0.0409 is obtained for 80 parameters and 719 independent data, suggesting this refinement is superior. However, the merging process forces the higher symmetry on the data and is slightly misleading. It is more illuminating to compare the refinements in both space groups without any data merging (i.e. treating all data as independent observations). The corresponding final R(F) values are 0.0471 (space group P3, 130 parameters, 2484 data) and 0.0614 (space group P63, 80 parameters, 2478 data). This evidence, together with the Rint values, is strongly suggestive of the lower symmetry trigonal space group P3. Moreover, following the comment of Marsh (1995) that `it is a solid tenet of crystallography that even a single violation of an extinction condition should be taken as proof that the symmetry is not present', we find that the strongest evidence in favour of space group P3 over P63 lies in the observed intensities of the 00 l reflections for l odd (Table 2).
The asymmetric unit consists of two independent Δ-[Co(en)3]Cl3 moieties and an [Na(H2O)6]Cl unit, all of which reside on sites of crystallographic threefold symmetry. As expected, the two independent [Co(en)3]3+ cations have very similar geometry (see Table 1). The Co—N distances within each molecule are significantly different from each other but are similar in the two independent molecules. In excess of 55 structural determinations on the [Co(en)3]3+ cation are found in the Cambridge Structural Database and the observed geometry in the title complex is unremarkable and merits no further comment. Each cation is associated with a Cl− ion which shows no unusually short contacts to other atoms.
The [Na(H2O)6]Cl unit effectively forms an infinite chain along the c axis (Fig. 1). A view of the unit-cell contents is shown in Fig. 2. The problem of the unusual coordination geometry for the Na+ and Cl− ions which was discussed earlier (Nakatsu et al., 1957) has been resolved with the observation of four partially occupied O-atom positions. The disordered O-atom positions are separated by ca 1 Å, allowing for anisotropic refinement of the more populated positions. The Na+ and Cl− ions occupy the same lattice positions in the structure and only the Na+ ions are labelled in Fig. 1. Thus, the position indicated by Na1A is actually occupied by a Na+ ion of occupancy 0.734 which is octahedrally coordinated by O atoms O1A and O2A at distances of 2.420 (12) and 2.488 (13) Å, respectively. This site is also occupied by a Cl− ion (Cl3B) of occupancy 0.266, which is also coordinated octahedrally by the O1B and O2B atoms at distances of 3.19 (3) and 3.06 (3) Å, respectively. These latter Cl···O contact distances are suggestive of hydrogen bonding, but since the water H atoms could not be located directly, this conclusion is tentative. A similar situation pertains to the site labelled Na1B atom. In space group P63, there is only one independent Na/Cl lattice site and the Na+ and Cl− ions are thus required to be statistically (i.e. 50:50) disordered. This is the only significant difference arising between the two refinements.