supplementary materials


zp2010 scheme

Acta Cryst. (2013). E69, o1730    [ doi:10.1107/S1600536813029401 ]

Ethyl 2-[6-(4-methyl­benzo­yl)-7-phenyl-2,3-di­hydro-1H-pyrrolizin-5-yl]-2-oxo­acetate

J. Zhong, W. Sun, F. Zhang, L. Liu and H. Liu

Abstract top

In the title compound, C25H23NO4, the pyrrolizine ring is approximately planar with an r.m.s deviation from planarity of 0.0053 Å, while the fused di­hydro­pyrrolizine ring adopts an envelope conformation with the C atom connected to two CH2 as the flap. The dihedral angles between the fused ring system and the phenyl and methyl­benzoyl rings are 41.65 (11) and 66.30 (8)°, respectively. In the crystal, weak C-H...O hydrogen bonds and C-H...[pi] inter­actions occur. One mol­ecule is linked to five adjacent ones through eight hydrogen bonds, forming a three-dimensional network.

Comment top

The title compound, (I) (Fig. 1), ethyl 2-(6-(4-methylbenzoyl)-7-phenyl -2,3-dihydro-1H-pyrrolizin-5-yl)-2-oxoacetate was synthesized from 6-(4-Methylbenzoyl)-7-phenyl-2,3-dihydro-pyrrolizine and ethyl oxalyl monochloride according to a general literature procedure of Itoh et al., (1984).

The title compound was an analogue of C20H19NOS (Liu, et al., 2013). The pyrrolizine ring is almost planar, while the fused dihydro-pyrrolizine ring adopts an envelope conformation. The dihedral angle between ring A (C1/C2/C3/N4/C5/C6/C7/C8) and phenyl ring B (C21—C26) is 41.65 (11)°, the dihedral angle between ring A and ring C (C13/C14/C15/C15/C17/C18/C19/C20) is 66.30 (8)°, and the dihedral angle between ring B and ring C is 74.31 (11)°. The torsion angle of O1/C9/C10/O2 was 131.5 (4)°. As a result, three side chains of ring A arranged themselves like propeller due to steric.

In the crystal, a series of weak intermolecular C—H···O (Table 1) hydrogen bonds can be found. Compared to C20H19NOS (Liu, et al., 2013), three O atoms of ethyloxalyl form three H-bonds, which help stablizing the crysatl packing. One molecule link to five adjacent ones through eight H-bonds to form three-dimensional infinite packing. An analysis by PLATON (Spek, 2009) shows C19—H19···π interaction with H19 to ring B centroid(Cg4) distance of 2.96 Å(Table 1, Fig2).

Related literature top

For the synthesis of the title compound, see: Itoh et al. (1984). For similar structures, see: Liu et al. (2007, 2013).

Experimental top

A stirred solution of 6-(4-Methylbenzoyl)-7-phenyl-2,3-dihydro- pyrrolizine in anhydrous CH2Cl2 was treated with AlCl3. A solution of ethyl oxalyl monochloride in anhydrous CH2Cl2 was added. The mixture was stirred for 4 h at room temperature, and cooled to 273 K, an aqueous solution of HCl(w/w10%) was then added and the resulting solution was stirred for 1 h. After addition of water to form a clear aqueous layer, the organic layer was separated and dried(anhydrous Na2SO4). Then the solution was evaporated under reduced pressure and purified by chromatography on silica gel column, eluting with a petroleum ether/acetone mixture (2:1) to give 65% yield of light yellow solid. The purity of the title compound was verified by elemental analysis: calculated for C25H23NO4: C 74.80, H 5.77, N 3.49; found C 65.72, H 4.39, N 3.83. EI—MS m/z: 402 (M+H)+.

The crystal appropriate for X-ray data collection was obtained from acetone solution at room temperature after two days.

Refinement top

All H atoms were placed in geometically idealized positions and constrained to ride on their parent atoms with C—H distances of 0.93(0.97 for CH2)Å for CH, and Uiso(H) = 1.2(1.5 for CH3)Ueq(C). Four H atoms taking part in the hydrogen-bonds can be found on the difference Fourier maps although the position of H20B was not perfect.

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); 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) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. View of the molecule of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
[Figure 2] Fig. 2. The C—H···π interaction, dashed lines. Non-essential H atoms are omitted for clarity. Symmetry code: (i) -x, -y, -z.
Ethyl 2-[6-(4-methylbenzoyl)-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl]-2-oxoacetate top
Crystal data top
C25H23NO4F(000) = 848
Mr = 401.44Dx = 1.311 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 9483 reflections
a = 8.8949 (18) Åθ = 3.1–27.5°
b = 9.0003 (18) ŵ = 0.09 mm1
c = 25.580 (5) ÅT = 296 K
β = 96.75 (3)°Needle, yellow
V = 2033.7 (7) Å30.26 × 0.15 × 0.10 mm
Z = 4
Data collection top
Bruker APEXII CCD
diffractometer
1930 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.070
Graphite monochromatorθmax = 25.5°, θmin = 3.2°
φ and ω scansh = 1010
16259 measured reflectionsk = 1010
3775 independent reflectionsl = 3030
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.062H-atom parameters constrained
wR(F2) = 0.194 w = 1/[σ2(Fo2) + (0.1076P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.97(Δ/σ)max < 0.001
3775 reflectionsΔρmax = 0.16 e Å3
274 parametersΔρmin = 0.36 e Å3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.007 (2)
Crystal data top
C25H23NO4V = 2033.7 (7) Å3
Mr = 401.44Z = 4
Monoclinic, P21/cMo Kα radiation
a = 8.8949 (18) ŵ = 0.09 mm1
b = 9.0003 (18) ÅT = 296 K
c = 25.580 (5) Å0.26 × 0.15 × 0.10 mm
β = 96.75 (3)°
Data collection top
Bruker APEXII CCD
diffractometer
1930 reflections with I > 2σ(I)
16259 measured reflectionsRint = 0.070
3775 independent reflectionsθmax = 25.5°
Refinement top
R[F2 > 2σ(F2)] = 0.062H-atom parameters constrained
wR(F2) = 0.194Δρmax = 0.16 e Å3
S = 0.97Δρmin = 0.36 e Å3
3775 reflectionsAbsolute structure: ?
274 parametersAbsolute structure parameter: ?
0 restraintsRogers parameter: ?
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
xyzUiso*/Ueq
O10.3855 (4)0.7209 (3)0.14060 (9)0.1067 (10)
O20.5168 (3)1.0611 (3)0.16709 (9)0.0918 (8)
O30.3842 (3)0.9266 (3)0.21838 (8)0.0818 (7)
O40.3274 (3)1.2999 (3)0.07415 (9)0.0829 (7)
N40.3342 (3)0.8148 (3)0.03486 (9)0.0588 (7)
C10.2962 (4)0.7905 (4)0.05606 (12)0.0695 (9)
H1A0.37530.82160.07680.083*
H1B0.20010.78970.07830.083*
C20.3308 (4)0.6400 (4)0.03159 (13)0.0814 (10)
H2A0.40760.59000.04910.098*
H2B0.24040.57890.03500.098*
C30.3874 (4)0.6643 (4)0.02624 (13)0.0738 (9)
H3A0.34340.59300.04850.089*
H3B0.49690.65810.03260.089*
C50.3345 (3)0.9074 (3)0.07784 (11)0.0579 (7)
C60.2855 (3)1.0463 (3)0.05824 (10)0.0532 (7)
C70.2560 (3)1.0339 (3)0.00275 (11)0.0554 (7)
C80.2900 (3)0.8895 (3)0.00953 (11)0.0556 (7)
C90.3779 (4)0.8520 (4)0.12995 (12)0.0671 (8)
C100.4326 (4)0.9619 (4)0.17365 (12)0.0662 (8)
C110.4400 (5)1.0161 (5)0.26432 (12)0.0886 (11)
H11A0.40171.11690.26030.106*
H11B0.54971.01930.26860.106*
C120.3840 (5)0.9433 (5)0.31076 (13)0.1027 (13)
H12A0.42070.99670.34220.154*
H12B0.41990.84270.31350.154*
H12C0.27530.94360.30650.154*
C130.2684 (3)1.1863 (3)0.08767 (11)0.0597 (8)
C140.1747 (3)1.1872 (3)0.13189 (11)0.0587 (8)
C150.1881 (4)1.3048 (4)0.16630 (14)0.0828 (10)
H15A0.25621.38110.16220.099*
C160.0987 (6)1.3085 (5)0.20733 (15)0.1011 (13)
H16A0.11091.38590.23160.121*
C170.0070 (4)1.2007 (5)0.21290 (13)0.0822 (11)
C180.0224 (4)1.0875 (5)0.17767 (12)0.0796 (10)
H18A0.09521.01460.18050.096*
C190.0685 (3)1.0794 (4)0.13783 (11)0.0645 (8)
H19A0.05790.99970.11450.077*
C200.1077 (8)1.2103 (7)0.2552 (2)0.164 (2)
H20A0.20451.16780.24290.247*
H20B0.12061.31260.26440.247*
H20C0.06321.15670.28560.247*
C210.1933 (3)1.1473 (3)0.03498 (11)0.0552 (7)
C220.0754 (4)1.2406 (4)0.02484 (14)0.0726 (9)
H22A0.03591.23240.00710.087*
C230.0156 (4)1.3444 (4)0.06075 (17)0.0873 (11)
H23A0.06251.40610.05280.105*
C240.0712 (5)1.3571 (5)0.10828 (18)0.0975 (13)
H24A0.03161.42770.13260.117*
C250.1858 (5)1.2647 (5)0.11977 (14)0.0901 (11)
H25A0.22291.27220.15220.108*
C260.2464 (4)1.1607 (4)0.08351 (12)0.0696 (9)
H26A0.32391.09880.09180.083*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.170 (3)0.0612 (18)0.0835 (16)0.0110 (17)0.0077 (17)0.0117 (14)
O20.1034 (19)0.091 (2)0.0803 (16)0.0263 (16)0.0085 (14)0.0017 (14)
O30.0979 (17)0.0886 (18)0.0579 (13)0.0101 (13)0.0045 (12)0.0020 (12)
O40.1009 (17)0.0537 (15)0.0960 (16)0.0161 (13)0.0199 (14)0.0042 (12)
N40.0605 (14)0.0468 (16)0.0676 (15)0.0063 (11)0.0018 (12)0.0051 (13)
C10.069 (2)0.069 (2)0.0695 (19)0.0092 (17)0.0026 (16)0.0146 (17)
C20.097 (3)0.058 (2)0.089 (2)0.0014 (19)0.013 (2)0.0175 (19)
C30.075 (2)0.050 (2)0.094 (2)0.0097 (16)0.0015 (18)0.0107 (17)
C50.0598 (17)0.0507 (18)0.0615 (17)0.0002 (14)0.0002 (14)0.0015 (15)
C60.0529 (16)0.0460 (18)0.0601 (17)0.0029 (13)0.0043 (13)0.0000 (13)
C70.0504 (16)0.0538 (19)0.0618 (17)0.0000 (14)0.0049 (13)0.0000 (15)
C80.0520 (16)0.0535 (19)0.0607 (17)0.0015 (14)0.0040 (13)0.0046 (15)
C90.077 (2)0.055 (2)0.068 (2)0.0061 (17)0.0021 (16)0.0057 (17)
C100.069 (2)0.069 (2)0.0587 (19)0.0076 (18)0.0027 (16)0.0032 (17)
C110.111 (3)0.091 (3)0.0593 (19)0.009 (2)0.010 (2)0.0042 (19)
C120.140 (4)0.099 (3)0.069 (2)0.000 (3)0.014 (2)0.010 (2)
C130.0639 (18)0.049 (2)0.0635 (17)0.0015 (15)0.0021 (15)0.0010 (15)
C140.0654 (18)0.053 (2)0.0555 (16)0.0093 (15)0.0005 (15)0.0057 (14)
C150.097 (3)0.063 (2)0.090 (2)0.0023 (19)0.016 (2)0.0190 (19)
C160.132 (4)0.085 (3)0.089 (3)0.009 (3)0.024 (3)0.031 (2)
C170.090 (2)0.094 (3)0.064 (2)0.025 (2)0.0157 (19)0.004 (2)
C180.078 (2)0.097 (3)0.0652 (19)0.001 (2)0.0114 (18)0.002 (2)
C190.0686 (19)0.065 (2)0.0590 (17)0.0005 (17)0.0047 (15)0.0028 (15)
C200.196 (6)0.182 (6)0.121 (4)0.035 (5)0.043 (4)0.005 (4)
C210.0528 (16)0.0464 (17)0.0653 (17)0.0040 (13)0.0015 (14)0.0011 (14)
C220.067 (2)0.064 (2)0.086 (2)0.0044 (17)0.0057 (18)0.0089 (18)
C230.075 (2)0.067 (3)0.116 (3)0.0088 (19)0.005 (2)0.014 (2)
C240.105 (3)0.074 (3)0.104 (3)0.004 (2)0.025 (3)0.024 (2)
C250.114 (3)0.083 (3)0.073 (2)0.019 (3)0.006 (2)0.019 (2)
C260.071 (2)0.068 (2)0.0695 (19)0.0078 (17)0.0073 (17)0.0037 (17)
Geometric parameters (Å, º) top
O1—C91.211 (4)C12—H12B0.9600
O2—C101.190 (4)C12—H12C0.9600
O3—C101.308 (4)C13—C141.482 (4)
O3—C111.463 (4)C14—C151.373 (4)
O4—C131.218 (3)C14—C191.375 (4)
N4—C81.339 (4)C15—C161.389 (5)
N4—C51.380 (3)C15—H15A0.9300
N4—C31.460 (4)C16—C171.370 (6)
C1—C81.493 (4)C16—H16A0.9300
C1—C21.509 (5)C17—C181.356 (5)
C1—H1A0.9700C17—C201.486 (6)
C1—H1B0.9700C18—C191.375 (4)
C2—C31.521 (4)C18—H18A0.9300
C2—H2A0.9700C19—H19A0.9300
C2—H2B0.9700C20—H20A0.9600
C3—H3A0.9700C20—H20B0.9600
C3—H3B0.9700C20—H20C0.9600
C5—C61.397 (4)C21—C261.384 (4)
C5—C91.433 (4)C21—C221.392 (4)
C6—C71.417 (4)C22—C231.373 (5)
C6—C131.485 (4)C22—H22A0.9300
C7—C81.379 (4)C23—C241.370 (5)
C7—C211.469 (4)C23—H23A0.9300
C9—C101.529 (4)C24—C251.374 (6)
C11—C121.493 (5)C24—H24A0.9300
C11—H11A0.9700C25—C261.382 (5)
C11—H11B0.9700C25—H25A0.9300
C12—H12A0.9600C26—H26A0.9300
C10—O3—C11116.9 (3)C11—C12—H12C109.5
C8—N4—C5110.2 (2)H12A—C12—H12C109.5
C8—N4—C3114.0 (2)H12B—C12—H12C109.5
C5—N4—C3135.3 (3)O4—C13—C14120.8 (3)
C8—C1—C2103.3 (3)O4—C13—C6119.7 (3)
C8—C1—H1A111.1C14—C13—C6119.5 (3)
C2—C1—H1A111.1C15—C14—C19118.8 (3)
C8—C1—H1B111.1C15—C14—C13118.7 (3)
C2—C1—H1B111.1C19—C14—C13122.4 (3)
H1A—C1—H1B109.1C14—C15—C16119.3 (4)
C1—C2—C3107.6 (3)C14—C15—H15A120.4
C1—C2—H2A110.2C16—C15—H15A120.4
C3—C2—H2A110.2C17—C16—C15121.5 (3)
C1—C2—H2B110.2C17—C16—H16A119.3
C3—C2—H2B110.2C15—C16—H16A119.3
H2A—C2—H2B108.5C18—C17—C16118.7 (3)
N4—C3—C2101.8 (3)C18—C17—C20120.3 (4)
N4—C3—H3A111.4C16—C17—C20120.9 (4)
C2—C3—H3A111.4C17—C18—C19120.6 (4)
N4—C3—H3B111.4C17—C18—H18A119.7
C2—C3—H3B111.4C19—C18—H18A119.7
H3A—C3—H3B109.3C14—C19—C18121.1 (3)
N4—C5—C6106.5 (2)C14—C19—H19A119.5
N4—C5—C9120.4 (3)C18—C19—H19A119.5
C6—C5—C9133.1 (3)C17—C20—H20A109.5
C5—C6—C7107.6 (3)C17—C20—H20B109.5
C5—C6—C13128.6 (3)H20A—C20—H20B109.5
C7—C6—C13123.8 (3)C17—C20—H20C109.5
C8—C7—C6106.4 (3)H20A—C20—H20C109.5
C8—C7—C21125.6 (3)H20B—C20—H20C109.5
C6—C7—C21127.9 (3)C26—C21—C22117.3 (3)
N4—C8—C7109.3 (2)C26—C21—C7120.4 (3)
N4—C8—C1110.0 (3)C22—C21—C7122.2 (3)
C7—C8—C1140.7 (3)C23—C22—C21121.8 (3)
O1—C9—C5123.4 (3)C23—C22—H22A119.1
O1—C9—C10117.5 (3)C21—C22—H22A119.1
C5—C9—C10118.9 (3)C24—C23—C22119.9 (4)
O2—C10—O3125.7 (3)C24—C23—H23A120.0
O2—C10—C9122.3 (3)C22—C23—H23A120.0
O3—C10—C9111.9 (3)C23—C24—C25119.6 (4)
O3—C11—C12106.5 (3)C23—C24—H24A120.2
O3—C11—H11A110.4C25—C24—H24A120.2
C12—C11—H11A110.4C24—C25—C26120.5 (4)
O3—C11—H11B110.4C24—C25—H25A119.8
C12—C11—H11B110.4C26—C25—H25A119.8
H11A—C11—H11B108.6C25—C26—C21120.9 (3)
C11—C12—H12A109.5C25—C26—H26A119.6
C11—C12—H12B109.5C21—C26—H26A119.6
H12A—C12—H12B109.5
C8—C1—C2—C316.0 (4)O1—C9—C10—O344.2 (4)
C8—N4—C3—C214.4 (3)C5—C9—C10—O3141.7 (3)
C5—N4—C3—C2175.1 (3)C10—O3—C11—C12173.4 (3)
C1—C2—C3—N418.3 (3)C5—C6—C13—O4127.9 (3)
C8—N4—C5—C60.8 (3)C7—C6—C13—O450.6 (4)
C3—N4—C5—C6171.6 (3)C5—C6—C13—C1454.4 (4)
C8—N4—C5—C9179.9 (3)C7—C6—C13—C14127.2 (3)
C3—N4—C5—C99.3 (5)O4—C13—C14—C1517.5 (5)
N4—C5—C6—C70.1 (3)C6—C13—C14—C15164.8 (3)
C9—C5—C6—C7178.9 (3)O4—C13—C14—C19158.4 (3)
N4—C5—C6—C13178.6 (3)C6—C13—C14—C1919.3 (4)
C9—C5—C6—C132.5 (5)C19—C14—C15—C162.7 (5)
C5—C6—C7—C80.8 (3)C13—C14—C15—C16178.7 (3)
C13—C6—C7—C8177.9 (3)C14—C15—C16—C172.8 (6)
C5—C6—C7—C21175.8 (3)C15—C16—C17—C180.8 (6)
C13—C6—C7—C215.4 (5)C15—C16—C17—C20176.6 (4)
C5—N4—C8—C71.4 (3)C16—C17—C18—C191.4 (5)
C3—N4—C8—C7174.3 (2)C20—C17—C18—C19178.8 (4)
C5—N4—C8—C1177.6 (2)C15—C14—C19—C180.6 (5)
C3—N4—C8—C14.7 (3)C13—C14—C19—C18176.5 (3)
C6—C7—C8—N41.3 (3)C17—C18—C19—C141.5 (5)
C21—C7—C8—N4175.4 (2)C8—C7—C21—C2641.7 (4)
C6—C7—C8—C1177.1 (4)C6—C7—C21—C26142.2 (3)
C21—C7—C8—C16.1 (6)C8—C7—C21—C22135.5 (3)
C2—C1—C8—N47.4 (3)C6—C7—C21—C2240.6 (5)
C2—C1—C8—C7174.2 (4)C26—C21—C22—C231.5 (5)
N4—C5—C9—O115.8 (5)C7—C21—C22—C23178.8 (3)
C6—C5—C9—O1163.1 (3)C21—C22—C23—C240.7 (6)
N4—C5—C9—C10158.0 (3)C22—C23—C24—C250.5 (6)
C6—C5—C9—C1023.2 (5)C23—C24—C25—C260.8 (6)
C11—O3—C10—O20.7 (5)C24—C25—C26—C210.1 (5)
C11—O3—C10—C9174.8 (3)C22—C21—C26—C251.2 (5)
O1—C9—C10—O2131.5 (4)C7—C21—C26—C25178.5 (3)
C5—C9—C10—O242.7 (5)
Hydrogen-bond geometry (Å, º) top
Cg4 is the centroid of the C21–C26 phenyl ring.
D—H···AD—HH···AD···AD—H···A
C20—H20B···O3i0.962.643.268 (6)123
C12—H12B···O2ii0.962.633.579 (5)170
C12—H12A···O1iii0.962.663.376 (5)132
C2—H2A···O4iv0.972.703.391 (5)128
C19—H19···Cg4v0.932.963.769 (5)147
Symmetry codes: (i) x, y+1/2, z+1/2; (ii) x+1, y1/2, z+1/2; (iii) x+1, y+1/2, z+1/2; (iv) x+1, y+2, z; (v) x, y, z.
Hydrogen-bond geometry (Å, º) top
Cg4 is the centroid of the C21–C26 phenyl ring.
D—H···AD—HH···AD···AD—H···A
C20—H20B···O3i0.962.643.268 (6)123.1
C12—H12B···O2ii0.962.633.579 (5)169.9
C12—H12A···O1iii0.962.663.376 (5)132.1
C2—H2A···O4iv0.972.703.391 (5)128.4
C19—H19···Cg4v0.932.963.769 (5)147.0
Symmetry codes: (i) x, y+1/2, z+1/2; (ii) x+1, y1/2, z+1/2; (iii) x+1, y+1/2, z+1/2; (iv) x+1, y+2, z; (v) x, y, z.
references
References top

Bruker (2009). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.

Itoh, O., Nagata, T., Nomura, I., Takanaga, T., Sugita, T. & Ichikawa, K. (1984). Bull. Chem. Soc. Jpn, 57, 810–814.

Liu, Y., Hu, Y., Li, X. & Chen, W. (2007). Acta Cryst. E63, o1106–o1107.

Liu, Y., Zhong, J., Sun, W., Zhang, F. & Liu, H. (2013). Acta Cryst. E69, o1513.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.

Spek, A. L. (2009). Acta Cryst. D65, 148–155.