metal-organic compounds
Dichloridobis[2-(2-chloroethyl)-1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole-κN]cobalt(II)
aCoordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093, People's Republic of China
*Correspondence e-mail: zzkltl@163.com
In the title compound, [CoCl2(C12H14ClN3)2], the central CoII ion lies on a twofold rotation axis and adopts a distorted tetrahedral coordination geometry defined by two N atoms from two 2-(2-chloroethyl)-1,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole ligands and two chloride anions. The Cl atom located in the side chain of the ligand is involved in intermolecular C—H⋯Cl hydrogen bonding, which links neutral complex units into a one-dimensional right-handed helical chain running along a crystallographic 41 axis. Such hydrogen-bonded helical chains are connected to each other to form a homochiral three-dimensional supramolecular network. One C atom of the 2-chloroethyl chain is disordered over two positions, with site-occupancy factors of 0.52 and 0.48.
Related literature
For related literature, see: Balamurugan et al. (2004); Matrick & Day (1961); Parker et al. (2004); Sundberg et al. (1977).
Experimental
Crystal data
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Data collection: SMART (Bruker, 2000); cell SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 1998) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S1600536808018011/om2235sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808018011/om2235Isup2.hkl
The ligand 2-(2-chloroethyl)-l,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole was synthesized according to a literature method (Matrick & Day, 1961).
The title compound was prepared by adding a methanol solution (10 ml) of CoCl2.6H2O (1 mmol) into a methanol solution (10 ml) of 2-(2-chloroethyl)-l,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole (2 mmol). The resulting mixture was refluxed for two hours and filtered after cooling to room temperature. Blue single crystals of the title compound suitable for X-ray
were obtained by slow diffusion of diethyl ether into the filtrate. Elemental analysis found: C 47.80; H 4.60; N 14.03%; calculated for C24H28Cl4CoN6: C 47.94; H 4.69; N 13.98%.The 2-chloroethyl chain attached to N atom displays rotational disorder and its C12 atom was split into two positions (C12A and C12B) with site-occupancy factors of 0.52 and 0.48. A l l H atoms were placed in calculated positions and refined using a riding model, with C—H = 0.93 - 0.97 Å and with Uiso(H) = 1.2 Ueq(C).
Data collection: SMART (Bruker, 2000); cell
SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1998) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).[CoCl2(C12H14ClN3)2] | Dx = 1.458 Mg m−3 |
Mr = 601.25 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, P41212 | Cell parameters from 835 reflections |
Hall symbol: P 4abw 2nw | θ = 2.5–16.9° |
a = 9.5706 (8) Å | µ = 1.04 mm−1 |
c = 29.911 (4) Å | T = 293 K |
V = 2739.7 (5) Å3 | Prism, blue |
Z = 4 | 0.32 × 0.21 × 0.18 mm |
F(000) = 1236 |
Bruker SMART APEX CCD area-detector diffractometer | 2703 independent reflections |
Radiation source: sealed tube | 2219 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.061 |
ϕ and ω scans | θmax = 26.0°, θmin = 2.2° |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | h = −11→7 |
Tmin = 0.763, Tmax = 0.829 | k = −11→11 |
14573 measured reflections | l = −36→35 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.055 | H-atom parameters constrained |
wR(F2) = 0.131 | w = 1/[σ2(Fo2) + (0.0877P)2 + 1.82P] where P = (Fo2 + 2Fc2)/3 |
S = 1.01 | (Δ/σ)max < 0.001 |
2703 reflections | Δρmax = 0.54 e Å−3 |
169 parameters | Δρmin = −0.80 e Å−3 |
2 restraints | Absolute structure: Flack (1983), 1274 Friedel pairs |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.07 (5) |
[CoCl2(C12H14ClN3)2] | Z = 4 |
Mr = 601.25 | Mo Kα radiation |
Tetragonal, P41212 | µ = 1.04 mm−1 |
a = 9.5706 (8) Å | T = 293 K |
c = 29.911 (4) Å | 0.32 × 0.21 × 0.18 mm |
V = 2739.7 (5) Å3 |
Bruker SMART APEX CCD area-detector diffractometer | 2703 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2000) | 2219 reflections with I > 2σ(I) |
Tmin = 0.763, Tmax = 0.829 | Rint = 0.061 |
14573 measured reflections |
R[F2 > 2σ(F2)] = 0.055 | H-atom parameters constrained |
wR(F2) = 0.131 | Δρmax = 0.54 e Å−3 |
S = 1.01 | Δρmin = −0.80 e Å−3 |
2703 reflections | Absolute structure: Flack (1983), 1274 Friedel pairs |
169 parameters | Absolute structure parameter: 0.07 (5) |
2 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 | 0.99857 (7) | 0.99857 (7) | 0.0000 | 0.0305 (2) | |
C1 | 0.7722 (5) | 0.8869 (5) | 0.07778 (15) | 0.0312 (10) | |
H1A | 0.7825 | 0.7909 | 0.0679 | 0.037* | |
H1B | 0.8635 | 0.9211 | 0.0866 | 0.037* | |
C2 | 0.7177 (5) | 0.9724 (5) | 0.04111 (16) | 0.0327 (11) | |
C3 | 0.6905 (5) | 1.0950 (5) | −0.01903 (17) | 0.0336 (11) | |
C4 | 0.7080 (5) | 1.1677 (5) | −0.05859 (18) | 0.0332 (11) | |
H4 | 0.7945 | 1.1750 | −0.0726 | 0.040* | |
C5 | 0.5873 (5) | 1.2300 (5) | −0.07639 (16) | 0.0339 (11) | |
H5 | 0.5940 | 1.2775 | −0.1034 | 0.041* | |
C6 | 0.4595 (6) | 1.2234 (5) | −0.05550 (17) | 0.0368 (12) | |
H6 | 0.3826 | 1.2693 | −0.0675 | 0.044* | |
C7 | 0.4469 (5) | 1.1478 (5) | −0.01639 (16) | 0.0317 (11) | |
H7 | 0.3604 | 1.1398 | −0.0024 | 0.038* | |
C8 | 0.5617 (5) | 1.0847 (5) | 0.00170 (18) | 0.0335 (11) | |
C9 | 0.4822 (5) | 0.9696 (5) | 0.07306 (16) | 0.0325 (11) | |
H9A | 0.3964 | 0.9399 | 0.0587 | 0.039* | |
H9B | 0.4612 | 1.0496 | 0.0918 | 0.039* | |
C10 | 0.5382 (5) | 0.8555 (5) | 0.10051 (16) | 0.0354 (12) | |
H10A | 0.4780 | 0.8397 | 0.1261 | 0.042* | |
H10B | 0.5418 | 0.7701 | 0.0831 | 0.042* | |
C11 | 0.7325 (6) | 0.8092 (5) | 0.15130 (16) | 0.0348 (11) | |
H11A | 0.7724 | 0.7247 | 0.1387 | 0.042* | 0.520 (13) |
H11B | 0.6558 | 0.7816 | 0.1706 | 0.042* | 0.520 (13) |
H11C | 0.8335 | 0.8174 | 0.1515 | 0.042* | 0.480 (13) |
H11D | 0.7095 | 0.7120 | 0.1458 | 0.042* | 0.480 (13) |
C12A | 0.8428 (10) | 0.8809 (9) | 0.1796 (3) | 0.033 (3) | 0.520 (13) |
H12A | 0.9132 | 0.9212 | 0.1601 | 0.039* | 0.520 (13) |
H12B | 0.8883 | 0.8121 | 0.1984 | 0.039* | 0.520 (13) |
C12B | 0.6908 (11) | 0.8567 (10) | 0.1978 (3) | 0.034 (3) | 0.480 (13) |
H12C | 0.7154 | 0.7845 | 0.2192 | 0.040* | 0.480 (13) |
H12D | 0.5903 | 0.8691 | 0.1988 | 0.040* | 0.480 (13) |
N1 | 0.6779 (4) | 0.8924 (5) | 0.11560 (13) | 0.0345 (9) | |
N2 | 0.7894 (4) | 1.0231 (4) | 0.00683 (13) | 0.0341 (9) | |
N3 | 0.5833 (4) | 1.0082 (5) | 0.03979 (13) | 0.0359 (9) | |
Cl1 | 0.77153 (12) | 1.01254 (13) | 0.21326 (4) | 0.0341 (3) | |
Cl2 | 1.10525 (13) | 1.08043 (13) | 0.06139 (4) | 0.0345 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Co1 | 0.0302 (3) | 0.0302 (3) | 0.0311 (4) | −0.0010 (4) | 0.0031 (3) | −0.0031 (3) |
C1 | 0.033 (3) | 0.030 (2) | 0.030 (2) | −0.004 (2) | −0.003 (2) | 0.001 (2) |
C2 | 0.036 (3) | 0.032 (3) | 0.031 (2) | 0.003 (2) | 0.012 (2) | 0.005 (2) |
C3 | 0.035 (3) | 0.028 (3) | 0.038 (3) | 0.000 (2) | −0.009 (2) | −0.007 (2) |
C4 | 0.029 (3) | 0.032 (3) | 0.039 (3) | 0.001 (2) | −0.005 (2) | 0.007 (2) |
C5 | 0.036 (3) | 0.028 (3) | 0.037 (3) | −0.006 (2) | −0.002 (2) | 0.017 (2) |
C6 | 0.038 (3) | 0.032 (3) | 0.040 (3) | 0.005 (2) | −0.002 (2) | −0.003 (2) |
C7 | 0.032 (3) | 0.032 (3) | 0.031 (2) | 0.005 (2) | 0.000 (2) | −0.0074 (19) |
C8 | 0.031 (3) | 0.035 (3) | 0.035 (2) | 0.005 (2) | −0.009 (2) | −0.007 (2) |
C9 | 0.031 (3) | 0.035 (3) | 0.031 (2) | −0.005 (2) | 0.002 (2) | 0.0002 (19) |
C10 | 0.036 (3) | 0.041 (3) | 0.029 (2) | 0.001 (2) | 0.003 (2) | 0.016 (2) |
C11 | 0.040 (3) | 0.036 (3) | 0.029 (3) | 0.002 (2) | −0.002 (2) | −0.003 (2) |
C12A | 0.036 (5) | 0.031 (5) | 0.031 (5) | 0.000 (4) | −0.002 (4) | 0.007 (4) |
C12B | 0.032 (6) | 0.032 (6) | 0.036 (6) | 0.001 (4) | −0.003 (4) | 0.002 (4) |
N1 | 0.039 (2) | 0.035 (2) | 0.030 (2) | 0.0055 (19) | 0.0004 (18) | 0.0035 (18) |
N2 | 0.035 (2) | 0.037 (2) | 0.0303 (19) | 0.0010 (18) | −0.0003 (17) | −0.0028 (17) |
N3 | 0.036 (2) | 0.035 (2) | 0.037 (2) | −0.0003 (19) | 0.0060 (18) | 0.005 (2) |
Cl1 | 0.0330 (6) | 0.0355 (6) | 0.0339 (6) | −0.0082 (5) | −0.0012 (5) | −0.0007 (5) |
Cl2 | 0.0367 (7) | 0.0333 (7) | 0.0336 (6) | −0.0011 (5) | −0.0071 (5) | −0.0038 (5) |
Co1—N2i | 2.026 (4) | C9—N3 | 1.436 (6) |
Co1—N2 | 2.026 (4) | C9—C10 | 1.468 (6) |
Co1—Cl2 | 2.2423 (13) | C9—H9A | 0.9700 |
Co1—Cl2i | 2.2423 (13) | C9—H9B | 0.9700 |
C1—N1 | 1.448 (6) | C10—N1 | 1.454 (7) |
C1—C2 | 1.465 (6) | C10—H10A | 0.9700 |
C1—H1A | 0.9700 | C10—H10B | 0.9700 |
C1—H1B | 0.9700 | C11—N1 | 1.431 (6) |
C2—N2 | 1.325 (6) | C11—C12A | 1.517 (10) |
C2—N3 | 1.332 (6) | C11—C12B | 1.517 (10) |
C3—C4 | 1.383 (7) | C11—H11A | 0.9700 |
C3—C8 | 1.383 (7) | C11—H11B | 0.9700 |
C3—N2 | 1.403 (6) | C11—H11C | 0.9700 |
C4—C5 | 1.405 (7) | C11—H11D | 0.9700 |
C4—H4 | 0.9300 | C12A—Cl1 | 1.752 (9) |
C5—C6 | 1.374 (7) | C12A—H11C | 1.0395 |
C5—H5 | 0.9300 | C12A—H12A | 0.9700 |
C6—C7 | 1.381 (7) | C12A—H12B | 0.9700 |
C6—H6 | 0.9300 | C12B—Cl1 | 1.742 (9) |
C7—C8 | 1.366 (7) | C12B—H12C | 0.9700 |
C7—H7 | 0.9300 | C12B—H12D | 0.9700 |
C8—N3 | 1.370 (7) | ||
N2i—Co1—N2 | 103.8 (2) | N1—C10—C9 | 109.2 (4) |
N2i—Co1—Cl2 | 112.03 (12) | N1—C10—H10A | 109.8 |
N2—Co1—Cl2 | 109.08 (12) | C9—C10—H10A | 109.8 |
N2i—Co1—Cl2i | 109.08 (12) | N1—C10—H10B | 109.8 |
N2—Co1—Cl2i | 112.03 (12) | C9—C10—H10B | 109.8 |
Cl2—Co1—Cl2i | 110.64 (7) | H10A—C10—H10B | 108.3 |
N1—C1—C2 | 110.0 (4) | N1—C11—C12A | 114.8 (5) |
N1—C1—H1A | 109.7 | N1—C11—C12B | 114.9 (5) |
C2—C1—H1A | 109.7 | N1—C11—H11A | 108.6 |
N1—C1—H1B | 109.7 | C12A—C11—H11A | 108.6 |
C2—C1—H1B | 109.7 | N1—C11—H11B | 108.6 |
H1A—C1—H1B | 108.2 | C12A—C11—H11B | 108.6 |
N2—C2—N3 | 112.5 (4) | H11A—C11—H11B | 107.6 |
N2—C2—C1 | 126.8 (5) | N1—C11—H11C | 109.0 |
N3—C2—C1 | 120.6 (4) | C12B—C11—H11C | 103.4 |
C4—C3—C8 | 121.8 (5) | N1—C11—H11D | 109.0 |
C4—C3—N2 | 129.6 (5) | C12B—C11—H11D | 112.5 |
C8—C3—N2 | 108.6 (4) | H11C—C11—H11D | 107.8 |
C3—C4—C5 | 116.0 (5) | C11—C12A—Cl1 | 112.0 (6) |
C3—C4—H4 | 122.0 | C11—C12A—H12A | 109.2 |
C5—C4—H4 | 122.0 | Cl1—C12A—H12A | 109.2 |
C6—C5—C4 | 122.7 (4) | C11—C12A—H12B | 109.2 |
C6—C5—H5 | 118.7 | Cl1—C12A—H12B | 109.2 |
C4—C5—H5 | 118.7 | H12A—C12A—H12B | 107.9 |
C5—C6—C7 | 119.2 (5) | C11—C12B—Cl1 | 112.5 (6) |
C5—C6—H6 | 120.4 | C11—C12B—H12C | 109.1 |
C7—C6—H6 | 120.4 | Cl1—C12B—H12C | 109.1 |
C8—C7—C6 | 119.8 (5) | C11—C12B—H12D | 109.1 |
C8—C7—H7 | 120.1 | Cl1—C12B—H12D | 109.1 |
C6—C7—H7 | 120.1 | H12C—C12B—H12D | 107.8 |
C7—C8—N3 | 133.4 (5) | C11—N1—C1 | 109.6 (4) |
C7—C8—C3 | 120.5 (5) | C11—N1—C10 | 115.6 (4) |
N3—C8—C3 | 106.1 (4) | C1—N1—C10 | 108.8 (4) |
N3—C9—C10 | 109.4 (4) | C2—N2—C3 | 104.9 (4) |
N3—C9—H9A | 109.8 | C2—N2—Co1 | 123.2 (3) |
C10—C9—H9A | 109.8 | C3—N2—Co1 | 131.9 (3) |
N3—C9—H9B | 109.8 | C2—N3—C8 | 107.9 (4) |
C10—C9—H9B | 109.8 | C2—N3—C9 | 124.4 (4) |
H9A—C9—H9B | 108.2 | C8—N3—C9 | 127.7 (4) |
Symmetry code: (i) y, x, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C1—H1A···Cl1ii | 0.97 | 2.87 | 3.812 (5) | 164 |
C5—H5···Cl2iii | 0.93 | 2.79 | 3.709 (5) | 171 |
Symmetry codes: (ii) −x+3/2, y−1/2, −z+1/4; (iii) y−1/2, −x+5/2, z−1/4. |
Experimental details
Crystal data | |
Chemical formula | [CoCl2(C12H14ClN3)2] |
Mr | 601.25 |
Crystal system, space group | Tetragonal, P41212 |
Temperature (K) | 293 |
a, c (Å) | 9.5706 (8), 29.911 (4) |
V (Å3) | 2739.7 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.04 |
Crystal size (mm) | 0.32 × 0.21 × 0.18 |
Data collection | |
Diffractometer | Bruker SMART APEX CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2000) |
Tmin, Tmax | 0.763, 0.829 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 14573, 2703, 2219 |
Rint | 0.061 |
(sin θ/λ)max (Å−1) | 0.617 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.055, 0.131, 1.01 |
No. of reflections | 2703 |
No. of parameters | 169 |
No. of restraints | 2 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.54, −0.80 |
Absolute structure | Flack (1983), 1274 Friedel pairs |
Absolute structure parameter | 0.07 (5) |
Computer programs: SMART (Bruker, 2000), SAINT (Bruker, 2000), SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 1998) and ORTEP-3 (Farrugia, 1997).
Co1—N2 | 2.026 (4) | Co1—Cl2 | 2.2423 (13) |
N2i—Co1—N2 | 103.8 (2) | Cl2—Co1—Cl2i | 110.64 (7) |
N2—Co1—Cl2 | 109.08 (12) |
Symmetry code: (i) y, x, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
C1—H1A···Cl1ii | 0.97 | 2.87 | 3.812 (5) | 164 |
C5—H5···Cl2iii | 0.93 | 2.79 | 3.709 (5) | 171 |
Symmetry codes: (ii) −x+3/2, y−1/2, −z+1/4; (iii) y−1/2, −x+5/2, z−1/4. |
Acknowledgements
This project was supported by the Nature Science Foundation of China (grant No. 20475026).
References
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Nitrogen mustards that contain a reactive N,N-bis-(2-chloroethyl)amine group are widely used as alkylating agents in cancer chemotherapy. However, these nitrogen mustards exhibit high chemical reactivity and usually show no selectivity of DNA alkylation. Recently, it has been proved that complexation of macrocyclic nitrogen mustards with metals may be an effective strategy in the design of hypoxia-selective antitumor prodrugs (Parker et al., 2004). As part of our work, some metal complexes of a monofunctional mustard, 2-(2-chloroethyl)-l,2,3,4-tetrahydropyrazino[1,2-a]benzimidazole (L), were prepared in order to evaluate their antitumor and antimalarial activities. Here, we report the crystal structure of a novel Co(II) mustard complex.
As depicted in Fig. 1, the complete complex molecule is generated by a twofold symmetry operation, with the CoII ion located on the rotation axis. The distorted tetrahedral coordination sphere around the CoII center consists of two benzimidazole N atoms from two L ligands and two chloride anions. The Co—N distance of 2.026 (4) Å and Co—Cl length of 2.2423 (13) Å (Table 1) are comparable to those reported in the literature (Sundberg et al., 1977).
In the crystal packing, intermolecular C—H···Cl hydrogen bonding play a key role. Fig. 2 illustrates that adjacent neutral complex units are connected by C1—H1A···Cl1 interactions into a one-dimensional right-handed helical architecture running along a crystallographic 41 screw axis in the c direction. Five complex fragments form a helix turn with a long pitch of 29.911 (4) Å. The shortest intrachain Co—Co distance is 10.072 Å. Further C—H···Cl hydrogen bond linkages (Table 2) extend such one-dimensional helical chains into a homochiral three-dimensional hydrogen-bonded network (Balamurugan et al., 2004).