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Acta Cryst. (2008). E64, m714-m715    [ doi:10.1107/S1600536808011331 ]

Aquabis(1H-imidazole-[kappa]N3)bis(4-methylbenzoato-[kappa]2O,O')cadmium(II)

W.-D. Song, L.-L. Ji and X.-H. Huang

Abstract top

In the title compound, [Cd(C8H7O2)2(C3H4N2)2(H2O)], the CdII atom is coordinated by four carboxylate O atoms from two bidentate chelating 4-methylbenzoate ligands, two N atoms from two imidazole ligands and one water molecule in a distorted pentagonal bipyramidal geometry. Intermolecular O-H...O hydrogen bonds between the coordinated water molecule and the carboxylate O atoms of 4-methylbenzoate lead to an infinite chain. These chains are further self-assembled into a two-dimensional layer through N-H...O hydrogen bonds between the imidazole ligands and carboxylate groups. One of the imidazole ligands is disordered over two positions with site-occupancy factors of 0.737 (4) and 0.263 (4).

Comment top

In the structural investigation of 4-methylbenzoate complexes, it has been found that the 4-methylbenzoate functions as bidentate and monodentate ligands (Song et al., 2007). In this paper, we report the crystal structure of the title compound, a new Cd complex obtained by the reaction of 4-methylbenzoic acid, imidazole and cadmium chloride in alkaline aqueous solution.

As illustrated in Fig. 1, the CdII atom exists in a distorted pentagonal bipyramidal geometry, defined by four carboxylate O atoms from two bidentate chelating 4-methylbenzoate ligands, two N atoms from two imidazole ligands and one water molecule (Table 1). One of the imidazole ligands is disordered over two positions with site occupancy factors of 0.737 (4) and 0.263 (4). Intermolecular O—H···O hydrogen bonds (Table 2) lead to infinite chains, involving the coordinated water molecules as donors and the O atoms of 4-methylbenzoate ligands as acceptors. These chains are further self-assembled into a two-dimensional supramolecular network through intermolecular N—H···O hydrogen bonds between the imidazole ligands and carboxylate groups (Fig. 2).

Related literature top

For related literature, see: Song et al. (2007).

Experimental top

A mixture of cadmium chloride (0.183 g, 1 mmol), 4-methylbenzoic acid (0.136 g, 1 mmol), imidazole (0.068 g, 1 mmol), NaOH (0.06 g, 1.5 mmol) and H2O (12 ml) was sealed in a 23 ml Teflon-lined reactor, which was heated at 433 K for 3 d and then cooled to room temperature at a rate of 10 K h-1. The crystals obtained were washed with water and dried in air.

Refinement top

H atoms attached to C and N atoms were positioned geometrically and refined as riding atoms, with C—H = 0.93 (aromatic) and 0.96 (methyl) Å and N—H = 0.86 Å and with Uiso(H) = 1.2Ueq(C,N). H atoms of the water molecule were located in a difference Fourier map and refined with restraints of O—H = 0.82 (1) Å and H···H= 1.34 (2) Å and with Uiso(H) = 1.5Ueq(O). Site occupancy factors of the disordered imidazole ligand were refined.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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
[Figure 1] Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn as the 30% probability level. H atoms have been omitted for clarity.
[Figure 2] Fig. 2. A view of the two-dimensional layer in the title compound.
Aquabis(1H-imidazole-κN3)bis(4-methylbenzoato- κ2O,O')cadmium(II) top
Crystal data top
[Cd(C8H7O2)2(C3H4N2)2(H2O)]Z = 2
Mr = 536.85F000 = 544
Triclinic, P1Dx = 1.542 Mg m−3
Hall symbol: -P 1Mo Kα radiation
λ = 0.71073 Å
a = 6.1355 (1) ÅCell parameters from 3600 reflections
b = 12.4338 (3) Åθ = 1.4–28º
c = 15.4771 (3) ŵ = 0.98 mm−1
α = 91.396 (1)ºT = 296 (2) K
β = 97.765 (1)ºBlock, colorless
γ = 98.304 (1)º0.26 × 0.23 × 0.20 mm
V = 1156.46 (4) Å3
Data collection top
Bruker SMART APEXII CCD area-detector
diffractometer		4764 independent reflections
Radiation source: fine-focus sealed tube4515 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.037
T = 296(2) Kθmax = 26.5º
φ and ω scansθmin = 1.3º
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		h = −7→7
Tmin = 0.784, Tmax = 0.828k = −15→15
14653 measured reflectionsl = −18→19
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)] = 0.023H atoms treated by a mixture of
independent and constrained refinement
wR(F2) = 0.059  w = 1/[σ2(Fo2) + (0.0265P)2 + 0.2332P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max = 0.010
4764 reflectionsΔρmax = 0.27 e Å−3
314 parametersΔρmin = −0.46 e Å−3
37 restraintsExtinction correction: SHELXTL (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0610 (16)
Crystal data top
[Cd(C8H7O2)2(C3H4N2)2(H2O)]γ = 98.304 (1)º
Mr = 536.85V = 1156.46 (4) Å3
Triclinic, P1Z = 2
a = 6.1355 (1) ÅMo Kα
b = 12.4338 (3) ŵ = 0.98 mm−1
c = 15.4771 (3) ÅT = 296 (2) K
α = 91.396 (1)º0.26 × 0.23 × 0.20 mm
β = 97.765 (1)º
Data collection top
Bruker SMART APEXII CCD area-detector
diffractometer		4764 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		4515 reflections with I > 2σ(I)
Tmin = 0.784, Tmax = 0.828Rint = 0.037
14653 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.02337 restraints
wR(F2) = 0.059H atoms treated by a mixture of
independent and constrained refinement
S = 1.08Δρmax = 0.27 e Å−3
4764 reflectionsΔρmin = −0.46 e Å−3
314 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
C10.9109 (3)0.68747 (15)0.20150 (12)0.0325 (4)
C21.0359 (3)0.79413 (16)0.18052 (12)0.0360 (4)
C31.2641 (4)0.81996 (19)0.20736 (15)0.0462 (5)
H31.34050.77050.23830.055*
C41.3774 (5)0.9190 (2)0.18814 (17)0.0616 (7)
H41.52960.93540.20650.074*
C51.2686 (6)0.9941 (2)0.14216 (18)0.0694 (9)
C61.0429 (6)0.9680 (2)0.11549 (17)0.0636 (7)
H60.96711.01770.08440.076*
C70.9270 (4)0.86914 (19)0.13418 (15)0.0483 (5)
H70.77490.85310.11540.058*
C81.3923 (9)1.1036 (3)0.1231 (3)0.1242 (18)
H8A1.46161.09640.07170.186*
H8B1.50411.12890.17170.186*
H8C1.28951.15490.11390.186*
C90.7907 (3)0.29695 (15)0.32072 (12)0.0339 (4)
C100.8303 (3)0.18454 (15)0.34383 (12)0.0327 (4)
C111.0249 (3)0.14673 (16)0.33053 (14)0.0393 (4)
H111.13660.19250.30890.047*
C121.0542 (4)0.04120 (17)0.34930 (15)0.0422 (5)
H121.18430.01650.33840.051*
C130.8944 (4)−0.02866 (16)0.38390 (13)0.0388 (4)
C140.7012 (4)0.01078 (17)0.39875 (15)0.0460 (5)
H140.5927−0.03380.42320.055*
C150.6680 (4)0.11496 (17)0.37780 (15)0.0429 (5)
H150.53550.13890.38650.052*
C160.9287 (5)−0.14287 (18)0.40544 (17)0.0559 (6)
H16A1.0697−0.15600.39050.084*
H16B0.8119−0.19350.37280.084*
H16C0.9265−0.15190.46670.084*
C200.4871 (4)0.61585 (18)0.41076 (14)0.0424 (5)
H200.35090.62070.37770.051*
C210.5421 (4)0.64415 (19)0.49653 (15)0.0517 (6)
H210.45210.67090.53320.062*
C220.8214 (4)0.58717 (17)0.44726 (13)0.0396 (4)
H220.96190.56840.44510.047*
Cd10.68370 (2)0.491827 (10)0.250662 (8)0.02905 (7)
N10.6629 (3)0.57885 (13)0.38005 (10)0.0330 (3)
N20.7550 (4)0.62584 (15)0.51870 (12)0.0487 (5)
H20.83260.63720.56950.058*
O11.0144 (2)0.62012 (12)0.24245 (10)0.0424 (3)
O20.7032 (2)0.66821 (12)0.17868 (10)0.0408 (3)
O30.9568 (3)0.36908 (11)0.31565 (10)0.0420 (3)
O40.5945 (3)0.31678 (12)0.30732 (11)0.0468 (4)
O1W0.2938 (2)0.47353 (12)0.22005 (10)0.0395 (3)
H1W0.221 (4)0.4298 (14)0.2482 (15)0.059*
H2W0.228 (4)0.5262 (13)0.2184 (17)0.059*
C170.8273 (6)0.3438 (4)0.0917 (2)0.0580 (10)0.737 (4)
H170.95760.33150.12570.070*0.737 (4)
C180.7560 (6)0.3045 (4)0.0092 (2)0.0633 (11)0.737 (4)
H180.83120.2643−0.02510.076*0.737 (4)
C190.508 (3)0.3921 (12)0.0535 (6)0.0420 (16)0.737 (4)
H190.37280.41790.05380.050*0.737 (4)
N30.668 (2)0.4081 (12)0.1184 (10)0.0411 (13)0.737 (4)
N40.5551 (7)0.3347 (5)−0.0138 (5)0.0450 (11)0.737 (4)
H4A0.47190.3196−0.06320.054*0.737 (4)
C17'0.8520 (17)0.4185 (11)0.0683 (6)0.0580 (10)0.263 (4)
H17'0.99190.45710.08830.070*0.263 (4)
C18'0.7834 (18)0.3789 (12)−0.0139 (6)0.0633 (11)0.263 (4)
H18'0.87120.3675−0.05680.076*0.263 (4)
C19'0.512 (7)0.379 (4)0.0592 (19)0.0420 (16)0.263 (4)
H19'0.36900.38110.07210.050*0.263 (4)
N3'0.690 (7)0.394 (4)0.117 (3)0.0411 (13)0.263 (4)
N4'0.561 (2)0.3591 (18)−0.0207 (18)0.0450 (11)0.263 (4)
H4'0.46830.3381−0.06700.054*0.263 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0379 (10)0.0348 (10)0.0259 (9)0.0070 (8)0.0076 (8)−0.0024 (7)
C20.0439 (11)0.0367 (10)0.0281 (9)0.0036 (8)0.0108 (8)−0.0024 (8)
C30.0432 (11)0.0526 (13)0.0419 (12)0.0010 (10)0.0103 (9)−0.0041 (10)
C40.0575 (15)0.0704 (17)0.0511 (14)−0.0175 (13)0.0183 (12)−0.0110 (13)
C50.097 (2)0.0552 (15)0.0481 (15)−0.0246 (15)0.0208 (15)−0.0025 (12)
C60.095 (2)0.0448 (13)0.0475 (14)0.0013 (14)0.0059 (14)0.0121 (11)
C70.0587 (14)0.0435 (12)0.0412 (12)0.0043 (10)0.0039 (10)0.0052 (10)
C80.179 (5)0.079 (2)0.092 (3)−0.065 (3)0.025 (3)0.011 (2)
C90.0439 (11)0.0332 (10)0.0256 (9)0.0082 (8)0.0060 (8)0.0000 (7)
C100.0386 (10)0.0293 (9)0.0291 (9)0.0033 (7)0.0032 (8)−0.0003 (7)
C110.0404 (11)0.0339 (10)0.0454 (12)0.0041 (8)0.0138 (9)0.0038 (8)
C120.0431 (11)0.0362 (11)0.0506 (13)0.0127 (9)0.0113 (10)0.0007 (9)
C130.0500 (12)0.0281 (9)0.0363 (10)0.0036 (8)0.0023 (9)−0.0014 (8)
C140.0474 (12)0.0357 (11)0.0548 (13)−0.0016 (9)0.0135 (10)0.0081 (9)
C150.0363 (10)0.0381 (11)0.0554 (13)0.0048 (8)0.0108 (9)0.0032 (9)
C160.0824 (18)0.0313 (11)0.0546 (14)0.0106 (11)0.0091 (13)0.0045 (10)
C200.0400 (11)0.0468 (12)0.0405 (11)0.0038 (9)0.0100 (9)−0.0049 (9)
C210.0681 (16)0.0471 (12)0.0410 (12)−0.0028 (11)0.0259 (12)−0.0112 (10)
C220.0473 (11)0.0346 (10)0.0341 (11)0.0025 (8)−0.0010 (9)0.0037 (8)
Cd10.03054 (9)0.03191 (10)0.02451 (9)0.00588 (5)0.00252 (5)−0.00215 (5)
N10.0391 (8)0.0324 (8)0.0271 (8)0.0045 (6)0.0050 (7)−0.0009 (6)
N20.0710 (14)0.0416 (10)0.0264 (9)−0.0088 (9)0.0009 (8)−0.0006 (7)
O10.0410 (8)0.0393 (8)0.0496 (9)0.0120 (6)0.0089 (7)0.0074 (6)
O20.0381 (8)0.0463 (8)0.0358 (8)0.0026 (6)0.0008 (6)0.0045 (6)
O30.0522 (9)0.0313 (7)0.0417 (8)0.0018 (6)0.0085 (7)0.0054 (6)
O40.0481 (9)0.0409 (8)0.0545 (10)0.0159 (7)0.0080 (7)0.0059 (7)
O1W0.0303 (7)0.0441 (8)0.0447 (8)0.0086 (6)0.0041 (6)0.0038 (7)
C170.0427 (15)0.089 (3)0.0413 (17)0.0138 (19)0.0016 (13)−0.0240 (18)
C180.0542 (18)0.092 (3)0.0433 (18)0.013 (2)0.0090 (14)−0.0268 (19)
C190.0507 (14)0.040 (4)0.0335 (17)0.008 (2)−0.0013 (14)0.001 (2)
N30.040 (3)0.053 (4)0.0312 (11)0.0127 (18)0.0034 (19)−0.013 (2)
N40.0624 (13)0.041 (3)0.0262 (17)−0.0024 (13)−0.0035 (9)−0.002 (2)
C17'0.0427 (15)0.089 (3)0.0413 (17)0.0138 (19)0.0016 (13)−0.0240 (18)
C18'0.0542 (18)0.092 (3)0.0433 (18)0.013 (2)0.0090 (14)−0.0268 (19)
C19'0.0507 (14)0.040 (4)0.0335 (17)0.008 (2)−0.0013 (14)0.001 (2)
N3'0.040 (3)0.053 (4)0.0312 (11)0.0127 (18)0.0034 (19)−0.013 (2)
N4'0.0624 (13)0.041 (3)0.0262 (17)−0.0024 (13)−0.0035 (9)−0.002 (2)
Geometric parameters (Å, °) top
C1—O11.256 (2)C20—N11.369 (3)
C1—O21.262 (3)C20—H200.9300
C1—C21.499 (3)C21—N21.358 (3)
C2—C71.383 (3)C21—H210.9300
C2—C31.393 (3)C22—N11.315 (3)
C3—C41.384 (3)C22—N21.331 (3)
C3—H30.9300C22—H220.9300
C4—C51.381 (5)Cd1—N32.257 (13)
C4—H40.9300Cd1—N12.2805 (15)
C5—C61.379 (5)Cd1—O1W2.3514 (13)
C5—C81.516 (4)Cd1—O42.3842 (16)
C6—C71.386 (3)Cd1—O12.4128 (14)
C6—H60.9300Cd1—O22.4788 (15)
C7—H70.9300Cd1—O32.5507 (16)
C8—H8A0.9600N2—H20.8600
C8—H8B0.9600O1W—H1W0.82 (2)
C8—H8C0.9600O1W—H2W0.82 (2)
C9—O41.254 (3)C17—C181.347 (4)
C9—O31.269 (2)C17—N31.444 (10)
C9—C101.496 (3)C17—H170.9300
C10—C111.383 (3)C18—N41.345 (5)
C10—C151.390 (3)C18—H180.9300
C11—C121.382 (3)C19—N31.298 (4)
C11—H110.9300C19—N41.337 (6)
C12—C131.386 (3)C19—H190.9300
C12—H120.9300N4—H4A0.8600
C13—C141.391 (3)C17'—N3'1.33 (5)
C13—C161.504 (3)C17'—C18'1.343 (8)
C14—C151.380 (3)C17'—H17'0.9300
C14—H140.9300C18'—N4'1.343 (9)
C15—H150.9300C18'—H18'0.9300
C16—H16A0.9600C19'—N3'1.300 (9)
C16—H16B0.9600C19'—N4'1.337 (10)
C16—H16C0.9600C19'—H19'0.9300
C20—C211.350 (3)N4'—H4'0.8600
O1—C1—O2121.53 (18)N3—Cd1—O196.7 (5)
O1—C1—C2119.37 (18)N1—Cd1—O186.88 (5)
O2—C1—C2119.09 (18)O1W—Cd1—O1141.36 (5)
C7—C2—C3118.6 (2)O4—Cd1—O1137.19 (5)
C7—C2—C1120.66 (19)N3—Cd1—O288.6 (4)
C3—C2—C1120.8 (2)N1—Cd1—O289.81 (5)
C4—C3—C2120.2 (2)O1W—Cd1—O288.32 (5)
C4—C3—H3119.9O4—Cd1—O2169.31 (5)
C2—C3—H3119.9O1—Cd1—O253.35 (5)
C5—C4—C3121.2 (3)N3—Cd1—O389.8 (3)
C5—C4—H4119.4N1—Cd1—O395.21 (5)
C3—C4—H4119.4O1W—Cd1—O3134.30 (5)
C6—C5—C4118.4 (2)O4—Cd1—O353.05 (5)
C6—C5—C8120.6 (4)O1—Cd1—O384.34 (5)
C4—C5—C8121.0 (3)O2—Cd1—O3137.09 (4)
C5—C6—C7121.1 (3)C22—N1—C20105.43 (17)
C5—C6—H6119.4C22—N1—Cd1123.23 (14)
C7—C6—H6119.4C20—N1—Cd1130.55 (14)
C2—C7—C6120.5 (2)C22—N2—C21107.39 (19)
C2—C7—H7119.8C22—N2—H2126.3
C6—C7—H7119.8C21—N2—H2126.3
O4—C9—O3122.22 (19)C1—O1—Cd194.15 (12)
O4—C9—C10118.90 (18)C1—O2—Cd190.92 (12)
O3—C9—C10118.88 (18)C9—O3—Cd187.86 (12)
C11—C10—C15118.59 (18)C9—O4—Cd195.91 (13)
C11—C10—C9121.38 (17)Cd1—O1W—H1W117.5 (18)
C15—C10—C9120.02 (18)Cd1—O1W—H2W121.9 (18)
C10—C11—C12120.31 (18)H1W—O1W—H2W103.8 (15)
C10—C11—H11119.8C18—C17—N3108.7 (6)
C12—C11—H11119.8C18—C17—H17125.6
C11—C12—C13121.63 (19)N3—C17—H17125.6
C11—C12—H12119.2C17—C18—N4106.7 (5)
C13—C12—H12119.2C17—C18—H18126.6
C12—C13—C14117.65 (19)N4—C18—H18126.6
C12—C13—C16121.4 (2)N3—C19—N4113.3 (12)
C14—C13—C16121.0 (2)N3—C19—H19123.3
C15—C14—C13121.05 (19)N4—C19—H19123.3
C15—C14—H14119.5C19—N3—C17102.8 (11)
C13—C14—H14119.5C19—N3—Cd1130.1 (8)
C14—C15—C10120.7 (2)C17—N3—Cd1126.5 (8)
C14—C15—H15119.6C19—N4—C18108.0 (9)
C10—C15—H15119.6C19—N4—H4A126.0
C21—C20—N1109.4 (2)C18—N4—H4A126.0
C21—C20—H20125.3N3'—C17'—C18'110 (2)
N1—C20—H20125.3N3'—C17'—H17'125.1
C20—C21—N2106.33 (19)C18'—C17'—H17'125.1
C20—C21—H21126.8C17'—C18'—N4'105.1 (14)
N2—C21—H21126.8C17'—C18'—H18'127.5
N1—C22—N2111.4 (2)N4'—C18'—H18'127.5
N1—C22—H22124.3N3'—C19'—N4'111 (4)
N2—C22—H22124.3N3'—C19'—H19'124.3
N3—Cd1—N1174.2 (3)N4'—C19'—H19'124.3
N3—Cd1—O1W85.9 (3)C19'—N3'—C17'103 (4)
N1—Cd1—O1W88.49 (6)C19'—N4'—C18'106 (3)
N3—Cd1—O488.0 (5)C19'—N4'—H4'127.1
N1—Cd1—O492.50 (6)C18'—N4'—H4'127.1
O1W—Cd1—O481.32 (5)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1W—H1W···O3i0.82 (2)2.104 (14)2.881 (2)157 (2)
O1W—H2W···O1i0.82 (2)1.943 (13)2.723 (2)160 (2)
N2—H2···O3ii0.862.062.905 (3)167
N4—H4A···O2iii0.861.982.813 (8)163
Symmetry codes: (i) x−1, y, z; (ii) −x+2, −y+1, −z+1; (iii) −x+1, −y+1, −z.
Table 1
Selected geometric parameters (Å, °) top
Cd1—N32.257 (13)Cd1—O12.4128 (14)
Cd1—N12.2805 (15)Cd1—O22.4788 (15)
Cd1—O1W2.3514 (13)Cd1—O32.5507 (16)
Cd1—O42.3842 (16)
N3—Cd1—N1174.2 (3)N1—Cd1—O289.81 (5)
N3—Cd1—O1W85.9 (3)O1W—Cd1—O288.32 (5)
N1—Cd1—O1W88.49 (6)O4—Cd1—O2169.31 (5)
N3—Cd1—O488.0 (5)O1—Cd1—O253.35 (5)
N1—Cd1—O492.50 (6)N3—Cd1—O389.8 (3)
O1W—Cd1—O481.32 (5)N1—Cd1—O395.21 (5)
N3—Cd1—O196.7 (5)O1W—Cd1—O3134.30 (5)
N1—Cd1—O186.88 (5)O4—Cd1—O353.05 (5)
O1W—Cd1—O1141.36 (5)O1—Cd1—O384.34 (5)
O4—Cd1—O1137.19 (5)O2—Cd1—O3137.09 (4)
N3—Cd1—O288.6 (4)
Table 2
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1W—H1W···O3i0.82 (2)2.104 (14)2.881 (2)157 (2)
O1W—H2W···O1i0.82 (2)1.943 (13)2.723 (2)160 (2)
N2—H2···O3ii0.862.062.905 (3)167
N4—H4A···O2iii0.861.982.813 (8)163
Symmetry codes: (i) x−1, y, z; (ii) −x+2, −y+1, −z+1; (iii) −x+1, −y+1, −z.
Acknowledgements top

The authors acknowledge Guangdong Ocean University for supporting this work.

references
References top

Bruker (2007). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.

Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.

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

Song, W.-D., Gu, C.-S., Hao, X.-M. & Liu, J.-W. (2007). Acta Cryst. E63, m1023–m1024.