2,6-Bis(2,4-dichloro­benzyl­idene)cyclo­hexa­none

Guo, H.-M.; Liu, L.; Jian, F.-F.

doi:10.1107/S1600536808023003

organic compounds

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ISSN: 2056-9890

Volume 64| Part 8| August 2008| Page o1626

doi:10.1107/S1600536808023003

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2,6-Bis(2,4-dichlorobenzylidene)cyclohexanone

Huan-Mei Guo,^a Li Liu ^a and Fang-Fang Jian ^a ^*

^aMicroscale Science Institute, Department of Chemistry and Chemical Engineering, Weifang University, Weifang 261061, People's Republic of China
^*Correspondence e-mail: ffjian2008@163.com

(Received 10 July 2008; accepted 22 July 2008; online 31 July 2008)

The title compound, C₂₀H₁₄Cl₄O, was prepared from a mixture of 2,4-dichlorobenzophenone and cyclohexanone. The dihedral angles formed by the cyclohexane ring and two benzene rings are 39.18 (2) and 60.72 (2)°. There are some weak intramolecular C—H⋯O and C—H⋯Cl hydrogen-bond contacts in the crystal structure.

Related literature

For related literature, see: Butcher et al. (2006 ); Deli et al. (1984 ); Jia et al. (1989 ); Yu et al. (2000 ).

Experimental

Crystal data

C₂₀H₁₄Cl₄O
M_r = 412.11
Orthorhombic, P b c a
a = 14.469 (2) Å
b = 8.0602 (12) Å
c = 31.554 (4) Å
V = 3679.9 (9) Å³
Z = 8
Mo Kα radiation
μ = 0.65 mm⁻¹
T = 293 (2) K
0.20 × 0.15 × 0.10 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1997 ) T_min = 0.881, T_max = 0.938
21985 measured reflections
4570 independent reflections
2735 reflections with I > 2σ(I)
R_int = 0.053

Refinement

R[F² > 2σ(F²)] = 0.050
wR(F²) = 0.118
S = 1.03
4570 reflections
226 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.28 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C7—H7A⋯Cl2	0.93	2.74	3.055 (2)	101
C7—H7A⋯O1	0.93	2.33	2.732 (3)	105
C14—H14A⋯O1	0.93	2.39	2.759 (3)	103

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1997); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808023003/at2592sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808023003/at2592Isup2.hkl

checkCIF report

Comment top

As useful precursors to potentially bioactive pyrimidine derivatives, a,a-bis(substituted benzylidene) cycloalkanones have attracted considerable attention for many years (Deli et al., 1984). In recent years, a series of non-linear optically active bis(benzylidene) ketones have been synthesized (Yu et al., 2000). As part of our search for new non-linear optically active compounds, we synthesized the title compound (I), and describe its structure here.

In the structure of (I) (Fig. 1), all of the bond lengthes and bond angles fall in the normal range (Yu et al., 2000; Jia et al., 1989; Butcher et al., 2006). There are some weak C—H···O and C—H···Cl intramolecular hydrogen bonds in the crystal structure.

Related literature top

For related literature, see: Butcher et al. (2006); Deli et al. (1984); Jia et al. (1989); Yu et al. (2000).

Experimental top

A mixture of the 2,4-dichlorobenzophenone (0.2 mol), and cyclohexanone (0.1 mol) and 10% NaOH (10 ml) was stirred in ethanol (30 mL) for 5 h to afford the title compound [yield: 82%]. Single crystals suitable for X-ray measurements were obtained by recrystallization from ethanol at room temperature.

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART (Bruker, 1997); data reduction: SAINT (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

Fig. 1. The structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme.

2,6-Bis(2,4-dichlorobenzylidene)cyclohexanone top

Crystal data top

C₂₀H₁₄Cl₄O	Z = 8
M_r = 412.11	F(000) = 1680
Orthorhombic, Pbca	D_x = 1.488 Mg m⁻³
Hall symbol: -P 2ac 2ab	Mo Kα radiation, λ = 0.71073 Å
a = 14.469 (2) Å	µ = 0.65 mm⁻¹
b = 8.0602 (12) Å	T = 293 K
c = 31.554 (4) Å	Bar, yellow
V = 3679.9 (9) Å³	0.20 × 0.15 × 0.10 mm

Data collection top

Bruker SMART CCD area-detector diffractometer	4570 independent reflections
Radiation source: fine-focus sealed tube	2735 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.053
ϕ and ω scans	θ_max = 28.4°, θ_min = 1.3°
Absorption correction: multi-scan (SADABS; Bruker, 1997)	h = −19→18
T_min = 0.881, T_max = 0.938	k = −10→10
21985 measured reflections	l = −19→42

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.118	H-atom parameters constrained
S = 1.03	w = 1/[σ²(F_o²) + (0.0381P)² + 1.6278P] where P = (F_o² + 2F_c²)/3
4570 reflections	(Δ/σ)_max = 0.001
226 parameters	Δρ_max = 0.24 e Å⁻³
0 restraints	Δρ_min = −0.28 e Å⁻³

Crystal data top

C₂₀H₁₄Cl₄O	V = 3679.9 (9) Å³
M_r = 412.11	Z = 8
Orthorhombic, Pbca	Mo Kα radiation
a = 14.469 (2) Å	µ = 0.65 mm⁻¹
b = 8.0602 (12) Å	T = 293 K
c = 31.554 (4) Å	0.20 × 0.15 × 0.10 mm

Data collection top

Bruker SMART CCD area-detector diffractometer	4570 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 1997)	2735 reflections with I > 2σ(I)
T_min = 0.881, T_max = 0.938	R_int = 0.053
21985 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.050	0 restraints
wR(F²) = 0.118	H-atom parameters constrained
S = 1.03	Δρ_max = 0.24 e Å⁻³
4570 reflections	Δρ_min = −0.28 e Å⁻³
226 parameters

Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cl1	−0.37152 (7)	0.07869 (15)	−0.49524 (3)	0.1044 (4)
Cl2	−0.51233 (4)	0.04759 (9)	−0.33808 (2)	0.05594 (19)
Cl3	0.06595 (6)	0.60906 (12)	−0.04572 (3)	0.0852 (3)
Cl4	−0.21635 (6)	0.20911 (12)	−0.08713 (2)	0.0825 (3)
O1	−0.36351 (10)	0.3253 (2)	−0.22630 (5)	0.0557 (5)
C1	−0.42738 (15)	0.1234 (3)	−0.37207 (8)	0.0468 (6)
C2	−0.43315 (18)	0.0787 (4)	−0.41435 (8)	0.0578 (7)
H2A	−0.4804	0.0098	−0.4238	0.069*
C3	−0.36783 (19)	0.1381 (4)	−0.44228 (9)	0.0635 (8)
C4	−0.29917 (19)	0.2442 (4)	−0.42879 (9)	0.0663 (8)
H4A	−0.2572	0.2881	−0.4481	0.080*
C5	−0.29343 (17)	0.2844 (4)	−0.38653 (9)	0.0592 (7)
H5A	−0.2465	0.3550	−0.3776	0.071*
C6	−0.35581 (16)	0.2229 (3)	−0.35643 (8)	0.0466 (6)
C7	−0.34846 (15)	0.2620 (3)	−0.31106 (8)	0.0461 (6)
H7A	−0.4041	0.2752	−0.2967	0.055*
C8	−0.27162 (14)	0.2811 (3)	−0.28761 (8)	0.0419 (6)
C9	−0.17413 (14)	0.2600 (3)	−0.30424 (8)	0.0499 (6)
H9A	−0.1571	0.3581	−0.3202	0.060*
H9B	−0.1727	0.1661	−0.3235	0.060*
C10	−0.10328 (15)	0.2324 (3)	−0.26939 (8)	0.0502 (6)
H10A	−0.1142	0.1261	−0.2559	0.060*
H10B	−0.0417	0.2310	−0.2815	0.060*
C11	−0.11002 (15)	0.3693 (3)	−0.23677 (8)	0.0457 (6)
H11A	−0.0612	0.3563	−0.2160	0.055*
H11B	−0.1020	0.4760	−0.2505	0.055*
C12	−0.20266 (14)	0.3642 (3)	−0.21491 (8)	0.0412 (5)
C13	−0.28552 (15)	0.3230 (3)	−0.24158 (7)	0.0423 (6)
C14	−0.21556 (16)	0.3858 (3)	−0.17333 (8)	0.0466 (6)
H14A	−0.2751	0.3680	−0.1632	0.056*
C15	−0.14545 (15)	0.4349 (3)	−0.14198 (8)	0.0443 (6)
C16	−0.08247 (16)	0.5614 (3)	−0.15088 (8)	0.0512 (6)
H16A	−0.0840	0.6112	−0.1775	0.061*
C17	−0.01834 (18)	0.6150 (3)	−0.12186 (8)	0.0554 (7)
H17A	0.0227	0.6995	−0.1288	0.067*
C18	−0.01524 (17)	0.5426 (3)	−0.08242 (8)	0.0539 (7)
C19	−0.07653 (18)	0.4177 (3)	−0.07173 (8)	0.0555 (7)
H19A	−0.0746	0.3691	−0.0450	0.067*
C20	−0.14056 (17)	0.3665 (3)	−0.10137 (8)	0.0490 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.1071 (7)	0.1580 (10)	0.0482 (5)	−0.0068 (7)	0.0000 (5)	−0.0108 (5)
Cl2	0.0381 (3)	0.0687 (4)	0.0610 (4)	−0.0027 (3)	0.0010 (3)	0.0002 (3)
Cl3	0.0747 (5)	0.1149 (7)	0.0660 (5)	−0.0291 (5)	−0.0131 (4)	−0.0144 (5)
Cl4	0.0959 (6)	0.0945 (6)	0.0572 (5)	−0.0482 (5)	−0.0024 (4)	0.0122 (4)
O1	0.0313 (9)	0.0847 (14)	0.0509 (10)	−0.0009 (8)	0.0073 (8)	0.0041 (10)
C1	0.0355 (13)	0.0554 (16)	0.0497 (15)	0.0080 (11)	−0.0013 (11)	0.0045 (12)
C2	0.0506 (16)	0.0682 (19)	0.0546 (17)	0.0054 (13)	−0.0080 (13)	−0.0023 (14)
C3	0.0559 (17)	0.090 (2)	0.0445 (15)	0.0099 (16)	−0.0043 (14)	−0.0017 (15)
C4	0.0524 (16)	0.093 (2)	0.0531 (17)	0.0033 (16)	0.0063 (14)	0.0141 (16)
C5	0.0459 (15)	0.077 (2)	0.0549 (17)	−0.0076 (13)	−0.0001 (13)	0.0080 (15)
C6	0.0355 (12)	0.0555 (15)	0.0488 (15)	0.0069 (11)	−0.0019 (11)	0.0027 (12)
C7	0.0335 (12)	0.0547 (15)	0.0501 (15)	0.0002 (10)	0.0026 (11)	0.0034 (12)
C8	0.0331 (12)	0.0459 (14)	0.0468 (14)	−0.0012 (10)	0.0041 (10)	0.0056 (11)
C9	0.0331 (12)	0.0648 (17)	0.0517 (15)	−0.0026 (11)	0.0061 (11)	−0.0020 (13)
C10	0.0318 (12)	0.0576 (16)	0.0612 (16)	0.0049 (11)	0.0045 (12)	−0.0007 (13)
C11	0.0316 (12)	0.0537 (15)	0.0518 (15)	−0.0006 (11)	−0.0006 (11)	0.0023 (12)
C12	0.0327 (12)	0.0436 (14)	0.0473 (14)	0.0007 (10)	0.0024 (11)	0.0048 (11)
C13	0.0331 (12)	0.0458 (14)	0.0481 (14)	0.0018 (10)	0.0034 (11)	0.0096 (11)
C14	0.0340 (12)	0.0552 (15)	0.0507 (15)	−0.0003 (11)	0.0016 (11)	0.0050 (12)
C15	0.0370 (12)	0.0527 (15)	0.0431 (14)	0.0021 (11)	0.0027 (11)	−0.0019 (12)
C16	0.0490 (14)	0.0575 (16)	0.0471 (15)	−0.0007 (12)	0.0020 (12)	0.0047 (13)
C17	0.0513 (15)	0.0566 (17)	0.0583 (17)	−0.0101 (13)	0.0042 (13)	−0.0005 (14)
C18	0.0484 (14)	0.0633 (17)	0.0499 (16)	−0.0018 (13)	−0.0033 (12)	−0.0111 (14)
C19	0.0629 (17)	0.0642 (18)	0.0393 (14)	−0.0059 (14)	−0.0008 (12)	−0.0001 (13)
C20	0.0487 (14)	0.0513 (16)	0.0469 (15)	−0.0062 (12)	0.0052 (12)	−0.0013 (12)

Geometric parameters (Å, º) top

Cl1—C3	1.739 (3)	C9—H9B	0.9700
Cl2—C1	1.742 (2)	C10—C11	1.512 (3)
Cl3—C18	1.735 (3)	C10—H10A	0.9700
Cl4—C20	1.736 (3)	C10—H10B	0.9700
O1—C13	1.227 (2)	C11—C12	1.508 (3)
C1—C2	1.384 (3)	C11—H11A	0.9700
C1—C6	1.400 (3)	C11—H11B	0.9700
C2—C3	1.378 (4)	C12—C14	1.337 (3)
C2—H2A	0.9300	C12—C13	1.502 (3)
C3—C4	1.378 (4)	C14—C15	1.471 (3)
C4—C5	1.375 (4)	C14—H14A	0.9300
C4—H4A	0.9300	C15—C16	1.396 (3)
C5—C6	1.401 (3)	C15—C20	1.397 (3)
C5—H5A	0.9300	C16—C17	1.373 (3)
C6—C7	1.470 (3)	C16—H16A	0.9300
C7—C8	1.345 (3)	C17—C18	1.375 (4)
C7—H7A	0.9300	C17—H17A	0.9300
C8—C13	1.504 (3)	C18—C19	1.383 (4)
C8—C9	1.515 (3)	C19—C20	1.380 (3)
C9—C10	1.520 (3)	C19—H19A	0.9300
C9—H9A	0.9700

C2—C1—C6	122.2 (2)	H10A—C10—H10B	108.2
C2—C1—Cl2	117.4 (2)	C12—C11—C10	110.4 (2)
C6—C1—Cl2	120.4 (2)	C12—C11—H11A	109.6
C3—C2—C1	119.0 (3)	C10—C11—H11A	109.6
C3—C2—H2A	120.5	C12—C11—H11B	109.6
C1—C2—H2A	120.5	C10—C11—H11B	109.6
C2—C3—C4	120.8 (3)	H11A—C11—H11B	108.1
C2—C3—Cl1	119.9 (2)	C14—C12—C13	117.9 (2)
C4—C3—Cl1	119.3 (2)	C14—C12—C11	124.7 (2)
C5—C4—C3	119.3 (3)	C13—C12—C11	117.3 (2)
C5—C4—H4A	120.3	O1—C13—C12	120.7 (2)
C3—C4—H4A	120.3	O1—C13—C8	120.4 (2)
C4—C5—C6	122.4 (3)	C12—C13—C8	118.93 (19)
C4—C5—H5A	118.8	C12—C14—C15	126.8 (2)
C6—C5—H5A	118.8	C12—C14—H14A	116.6
C1—C6—C5	116.1 (2)	C15—C14—H14A	116.6
C1—C6—C7	121.3 (2)	C16—C15—C20	116.1 (2)
C5—C6—C7	122.5 (2)	C16—C15—C14	120.7 (2)
C8—C7—C6	128.4 (2)	C20—C15—C14	123.1 (2)
C8—C7—H7A	115.8	C17—C16—C15	122.5 (2)
C6—C7—H7A	115.8	C17—C16—H16A	118.8
C7—C8—C13	116.5 (2)	C15—C16—H16A	118.8
C7—C8—C9	124.5 (2)	C16—C17—C18	119.5 (2)
C13—C8—C9	118.96 (19)	C16—C17—H17A	120.3
C8—C9—C10	113.2 (2)	C18—C17—H17A	120.3
C8—C9—H9A	108.9	C17—C18—C19	120.6 (2)
C10—C9—H9A	108.9	C17—C18—Cl3	119.7 (2)
C8—C9—H9B	108.9	C19—C18—Cl3	119.8 (2)
C10—C9—H9B	108.9	C20—C19—C18	118.9 (2)
H9A—C9—H9B	107.8	C20—C19—H19A	120.6
C11—C10—C9	110.0 (2)	C18—C19—H19A	120.6
C11—C10—H10A	109.7	C19—C20—C15	122.5 (2)
C9—C10—H10A	109.7	C19—C20—Cl4	117.9 (2)
C11—C10—H10B	109.7	C15—C20—Cl4	119.59 (19)
C9—C10—H10B	109.7

C6—C1—C2—C3	−1.9 (4)	C11—C12—C13—O1	−176.1 (2)
Cl2—C1—C2—C3	179.2 (2)	C14—C12—C13—C8	−173.9 (2)
C1—C2—C3—C4	−1.9 (4)	C11—C12—C13—C8	3.0 (3)
C1—C2—C3—Cl1	178.0 (2)	C7—C8—C13—O1	5.7 (3)
C2—C3—C4—C5	3.2 (4)	C9—C8—C13—O1	−173.0 (2)
Cl1—C3—C4—C5	−176.7 (2)	C7—C8—C13—C12	−173.4 (2)
C3—C4—C5—C6	−0.8 (4)	C9—C8—C13—C12	7.9 (3)
C2—C1—C6—C5	4.1 (4)	C13—C12—C14—C15	−176.6 (2)
Cl2—C1—C6—C5	−176.99 (19)	C11—C12—C14—C15	6.7 (4)
C2—C1—C6—C7	−176.9 (2)	C12—C14—C15—C16	43.5 (4)
Cl2—C1—C6—C7	1.9 (3)	C12—C14—C15—C20	−140.1 (3)
C4—C5—C6—C1	−2.8 (4)	C20—C15—C16—C17	0.8 (4)
C4—C5—C6—C7	178.3 (3)	C14—C15—C16—C17	177.5 (2)
C1—C6—C7—C8	145.0 (3)	C15—C16—C17—C18	0.0 (4)
C5—C6—C7—C8	−36.1 (4)	C16—C17—C18—C19	−0.5 (4)
C6—C7—C8—C13	179.4 (2)	C16—C17—C18—Cl3	179.7 (2)
C6—C7—C8—C9	−2.0 (4)	C17—C18—C19—C20	0.3 (4)
C7—C8—C9—C10	−161.0 (2)	Cl3—C18—C19—C20	−180.0 (2)
C13—C8—C9—C10	17.6 (3)	C18—C19—C20—C15	0.6 (4)
C8—C9—C10—C11	−53.5 (3)	C18—C19—C20—Cl4	179.8 (2)
C9—C10—C11—C12	64.1 (3)	C16—C15—C20—C19	−1.1 (4)
C10—C11—C12—C14	138.1 (3)	C14—C15—C20—C19	−177.7 (2)
C10—C11—C12—C13	−38.5 (3)	C16—C15—C20—Cl4	179.69 (18)
C14—C12—C13—O1	7.0 (4)	C14—C15—C20—Cl4	3.1 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7A···Cl2	0.93	2.74	3.055 (2)	101
C7—H7A···O1	0.93	2.33	2.732 (3)	105
C14—H14A···O1	0.93	2.39	2.759 (3)	103

Experimental details

Crystal data
Chemical formula	C₂₀H₁₄Cl₄O
M_r	412.11
Crystal system, space group	Orthorhombic, Pbca
Temperature (K)	293
a, b, c (Å)	14.469 (2), 8.0602 (12), 31.554 (4)
V (Å³)	3679.9 (9)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.65
Crystal size (mm)	0.20 × 0.15 × 0.10

Data collection
Diffractometer	Bruker SMART CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 1997)
T_min, T_max	0.881, 0.938
No. of measured, independent and observed [I > 2σ(I)] reflections	21985, 4570, 2735
R_int	0.053
(sin θ/λ)_max (Å⁻¹)	0.669

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.050, 0.118, 1.03
No. of reflections	4570
No. of parameters	226
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.24, −0.28

Computer programs: SMART (Bruker, 1997), SAINT (Bruker, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C7—H7A···Cl2	0.93	2.74	3.055 (2)	100.8
C7—H7A···O1	0.93	2.33	2.732 (3)	105.3
C14—H14A···O1	0.93	2.39	2.759 (3)	103.3

Acknowledgements

The authors thank the National Science Foundation of Weifang University (grant: No.2008Z04).

References

Bruker (1997). SADABS, SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Butcher, R. J., Yathirajan, H. S., Sarojini, B. K., Narayana, B. & Indira, J. (2006). Acta Cryst. E62, o1910–o1912. Web of Science CSD CrossRef IUCr Journals Google Scholar
Deli, J., Lorand, T., Szabo, D. & Foldesi, A. (1984). Pharmazie, 39, 539–544. CAS PubMed Web of Science Google Scholar
Jia, Z., Quail, J. W., Arora, V. K. & Dimmock, J. R. (1989). Acta Cryst. C45, 285–289. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Yu, R. C., Yakimansky, A. V., Kothe, H., Voigt-Martin, I. G., Schollmeyer, D., Jansen, J., Zandbergen, H. & Tenkovtsev, A. V. (2000). Acta Cryst. A56, 436–450. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar