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Acta Cryst. (2009). E65, m1144-m1145    [ doi:10.1107/S1600536809033443 ]

(Cyclohexanecarboxylato)bis(di-2-pyridylamine)zinc(II) nitrate monohydrate

Y.-J. Cai, J. Yang, P. Huang, L. Lei and Q.-F. Zeng

Abstract top

In the title compound, [Zn(C7H11O2)(C10H9N3)2]NO3·H2O, the ZnII atom is five-coordinated by two bidentate di-2-pyridylamine ligands and one O atom from a cyclohexanecarboxyate anion, resulting in a ZnON4 square-based pyramidal coordination for the metal ion with the O atom in one of the basal positions. In the crystal, the components interact by way of O-H...O, O-H...N and N-H...O hydrogen bonds.

Comment top

There has been much research interest in the acid and amine metal complexes due to their molecular architectures (e.g. Yang et al., 2004). In this work, we report here the crystal structure of the title compound, (I). In (I), all bond lengths are within normal ranges (Allen et al., 1987) (Fig. 1). The ZnII atom is five-coordinated by four N atoms from di-2-pyridylamine and one O atom from cyclohexanecarboxylic acid.

Related literature top

For background to acid and amine metal complexes and their molecular architectures, see: Yang et al. (2004). For reference structural data, see: Allen et al. (1987).

Experimental top

A mixture of di-2-pyridylamine (342 mg, 2 mmol), cyclohexanecarboxylic acid (256 mg, 2 mmol) and ZnNO3.6H2O (1 mmol, 297 mg) in methanol (10 ml) was stirred for 3 h. After keeping the filtrate in air for 8 d, colourless blocks of (I) were formed.

Refinement top

The N- and O-bound H atoms were located in a difference map and their positions were freely refined. The C-bound H atoms were positioned geometrically (C—H = 0.93 Å for the aromatic H atoms and C—H = 0.96 Å for the aliphatic H atoms) and were refined as riding, with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); 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 (I) showing 30% probability displacement ellipsoids.
(Cyclohexanecarboxylato)bis(di-2-pyridylamine)zinc(II) nitrate monohydrate top
Crystal data top
[Zn(C7H11O2)(C10H9N3)2]NO3·H2OZ = 2
Mr = 614.96F(000) = 640
Triclinic, P1Dx = 1.411 Mg m−3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 10.4856 (3) ÅCell parameters from 25 reflections
b = 11.6116 (13) Åθ = 9–12°
c = 13.4876 (13) ŵ = 0.90 mm−1
α = 107.526 (3)°T = 296 K
β = 106.016 (3)°Block, colorless
γ = 99.706 (3)°0.32 × 0.26 × 0.20 mm
V = 1447.3 (2) Å3
Data collection top
Enraf–Nonius CAD-4
diffractometer		5178 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.014
graphiteθmax = 27.0°, θmin = 1.7°
ω/2θ scansh = −12→13
Absorption correction: ψ scan
(North et al., 1968)		k = −14→13
Tmin = 0.761, Tmax = 0.840l = −17→17
8944 measured reflections200 standard reflections every 3 reflections
6182 independent reflections intensity decay: 1%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.039Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.109H atoms treated by a mixture of independent and constrained refinement
S = 1.03 w = 1/[σ2(Fo2) + (0.0559P)2 + 0.6885P]
where P = (Fo2 + 2Fc2)/3
6182 reflections(Δ/σ)max = 0.001
386 parametersΔρmax = 0.46 e Å−3
3 restraintsΔρmin = −0.34 e Å−3
Crystal data top
[Zn(C7H11O2)(C10H9N3)2]NO3·H2Oγ = 99.706 (3)°
Mr = 614.96V = 1447.3 (2) Å3
Triclinic, P1Z = 2
a = 10.4856 (3) ÅMo Kα radiation
b = 11.6116 (13) ŵ = 0.90 mm−1
c = 13.4876 (13) ÅT = 296 K
α = 107.526 (3)°0.32 × 0.26 × 0.20 mm
β = 106.016 (3)°
Data collection top
Enraf–Nonius CAD-4
diffractometer		5178 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)		Rint = 0.014
Tmin = 0.761, Tmax = 0.840θmax = 27.0°
8944 measured reflections200 standard reflections every 3 reflections
6182 independent reflections intensity decay: 1%
Refinement top
R[F2 > 2σ(F2)] = 0.039H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.109Δρmax = 0.46 e Å−3
S = 1.03Δρmin = −0.34 e Å−3
6182 reflectionsAbsolute structure: ?
386 parametersFlack parameter: ?
3 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
C10.1292 (3)0.8840 (3)0.4961 (3)0.0615 (8)
H1A0.05110.88860.44020.074*
H1B0.20950.94860.50750.074*
C20.1004 (4)0.9075 (3)0.6045 (3)0.0724 (10)
H2A0.18220.91140.66230.087*
H2B0.07980.98780.62670.087*
C3−0.0192 (4)0.8051 (4)0.5925 (3)0.0811 (11)
H3A−0.02980.81880.66400.097*
H3B−0.10350.80860.54220.097*
C40.0032 (3)0.6775 (4)0.5488 (3)0.0757 (10)
H4A0.08020.67030.60390.091*
H4B−0.07830.61350.53630.091*
C50.0320 (3)0.6546 (3)0.4428 (3)0.0630 (8)
H5A−0.04890.65270.38530.076*
H5B0.05050.57350.41980.076*
C60.1545 (3)0.7559 (3)0.4557 (2)0.0450 (6)
H60.16070.74120.38190.054*
C70.2903 (2)0.7493 (2)0.52994 (18)0.0344 (5)
C80.5875 (3)0.8287 (3)0.4789 (2)0.0449 (6)
H80.57340.90750.50500.054*
C90.5912 (3)0.7849 (3)0.3745 (2)0.0601 (8)
H90.58060.83320.33040.072*
C100.6110 (3)0.6673 (3)0.3351 (2)0.0602 (8)
H100.61140.63460.26320.072*
C110.6299 (3)0.5993 (3)0.4021 (2)0.0468 (6)
H110.64290.51980.37670.056*
C120.6293 (2)0.6519 (2)0.51007 (17)0.0320 (4)
C130.7019 (2)0.6277 (2)0.69238 (19)0.0367 (5)
C140.7804 (3)0.5631 (3)0.7447 (3)0.0608 (8)
H140.79790.49170.70310.073*
C150.8314 (4)0.6060 (4)0.8583 (3)0.0803 (11)
H150.88510.56490.89460.096*
C160.8021 (4)0.7106 (4)0.9178 (3)0.0787 (11)
H160.83520.74110.99490.094*
C170.7240 (3)0.7685 (3)0.8619 (2)0.0610 (8)
H170.70600.84000.90290.073*
C180.8081 (3)1.0300 (3)0.7532 (2)0.0543 (7)
H180.83500.96320.71460.065*
C190.8960 (3)1.1469 (3)0.7940 (2)0.0580 (7)
H190.98051.15980.78350.070*
C200.8562 (3)1.2454 (3)0.8512 (2)0.0598 (8)
H200.91381.32670.88010.072*
C210.7314 (3)1.2231 (2)0.8654 (2)0.0532 (7)
H210.70301.28910.90360.064*
C220.6474 (2)1.1005 (2)0.82200 (19)0.0389 (5)
C230.4434 (2)0.9739 (2)0.84199 (18)0.0366 (5)
C240.3436 (3)0.9918 (3)0.8921 (2)0.0487 (6)
H240.33251.07160.92020.058*
C250.2633 (3)0.8919 (3)0.8994 (2)0.0569 (7)
H250.19640.90270.93170.068*
C260.2822 (3)0.7736 (3)0.8580 (2)0.0558 (7)
H260.22980.70410.86340.067*
C270.3796 (3)0.7623 (3)0.8094 (2)0.0488 (6)
H270.39220.68300.78170.059*
H6A0.524 (2)0.360 (2)0.983 (3)0.081 (13)*
H6B0.386 (2)0.322 (3)0.921 (3)0.087 (13)*
N10.60361 (18)0.76244 (17)0.54675 (15)0.0325 (4)
N30.6709 (2)0.72807 (19)0.74978 (16)0.0398 (4)
N40.6839 (2)1.00475 (19)0.76529 (17)0.0429 (5)
N60.4594 (2)0.85966 (18)0.79898 (16)0.0375 (4)
N70.7893 (3)0.5522 (2)0.1219 (2)0.0611 (6)
O10.30686 (18)0.64659 (15)0.53325 (15)0.0455 (4)
O20.38469 (16)0.85182 (15)0.58651 (13)0.0378 (4)
O30.8755 (3)0.5011 (3)0.1033 (3)0.1179 (12)
O40.8103 (3)0.6659 (2)0.1560 (2)0.0860 (8)
O50.6740 (3)0.4912 (3)0.1109 (3)0.1178 (12)
O60.4564 (4)0.2978 (2)0.9418 (3)0.0855 (8)
N110.6563 (2)0.58533 (19)0.57844 (16)0.0363 (4)
N120.5229 (2)1.0789 (2)0.83921 (19)0.0437 (5)
Zn10.54528 (3)0.81698 (2)0.67867 (2)0.03606 (10)
H11A0.667 (3)0.528 (2)0.553 (2)0.027 (7)*
H120.505 (3)1.135 (3)0.861 (2)0.037 (8)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0498 (16)0.0601 (17)0.083 (2)0.0269 (14)0.0102 (15)0.0427 (16)
C20.066 (2)0.067 (2)0.073 (2)0.0456 (17)0.0105 (16)0.0076 (16)
C30.056 (2)0.121 (3)0.085 (2)0.048 (2)0.0373 (18)0.040 (2)
C40.0456 (17)0.090 (2)0.116 (3)0.0254 (16)0.0374 (19)0.060 (2)
C50.0374 (14)0.0568 (17)0.075 (2)0.0109 (13)0.0036 (14)0.0128 (15)
C60.0397 (13)0.0597 (16)0.0391 (13)0.0209 (12)0.0104 (10)0.0218 (12)
C70.0345 (11)0.0421 (12)0.0335 (11)0.0168 (10)0.0169 (9)0.0154 (10)
C80.0436 (13)0.0501 (14)0.0537 (15)0.0196 (11)0.0218 (12)0.0279 (12)
C90.0623 (18)0.086 (2)0.0517 (16)0.0263 (16)0.0260 (14)0.0439 (16)
C100.0665 (19)0.084 (2)0.0364 (14)0.0240 (16)0.0255 (13)0.0226 (14)
C110.0501 (15)0.0530 (15)0.0358 (12)0.0157 (12)0.0206 (11)0.0086 (11)
C120.0262 (10)0.0358 (11)0.0314 (11)0.0059 (8)0.0114 (9)0.0088 (9)
C130.0381 (12)0.0401 (12)0.0372 (12)0.0152 (10)0.0171 (10)0.0152 (10)
C140.076 (2)0.0703 (19)0.0535 (16)0.0487 (17)0.0255 (15)0.0284 (15)
C150.097 (3)0.107 (3)0.0597 (19)0.068 (2)0.0225 (19)0.045 (2)
C160.090 (3)0.118 (3)0.0367 (15)0.062 (2)0.0150 (16)0.0287 (17)
C170.0690 (19)0.083 (2)0.0332 (13)0.0451 (17)0.0160 (13)0.0129 (13)
C180.0391 (14)0.0557 (16)0.0552 (16)0.0088 (12)0.0171 (12)0.0042 (13)
C190.0411 (14)0.0645 (18)0.0552 (16)−0.0017 (13)0.0155 (13)0.0138 (14)
C200.0596 (18)0.0477 (16)0.0573 (17)−0.0043 (13)0.0121 (14)0.0167 (14)
C210.0624 (17)0.0370 (13)0.0538 (16)0.0108 (12)0.0182 (14)0.0115 (12)
C220.0408 (12)0.0394 (12)0.0345 (12)0.0118 (10)0.0108 (10)0.0124 (10)
C230.0392 (12)0.0414 (12)0.0290 (11)0.0167 (10)0.0111 (9)0.0101 (9)
C240.0515 (15)0.0582 (16)0.0423 (13)0.0253 (13)0.0236 (12)0.0141 (12)
C250.0533 (16)0.078 (2)0.0512 (16)0.0224 (15)0.0314 (14)0.0246 (15)
C260.0579 (17)0.0620 (17)0.0546 (16)0.0104 (14)0.0288 (14)0.0260 (14)
C270.0596 (16)0.0433 (14)0.0465 (14)0.0137 (12)0.0241 (13)0.0157 (11)
N10.0304 (9)0.0378 (10)0.0343 (9)0.0121 (8)0.0149 (8)0.0155 (8)
N30.0423 (11)0.0490 (11)0.0309 (9)0.0230 (9)0.0135 (8)0.0121 (9)
N40.0361 (10)0.0399 (11)0.0455 (11)0.0080 (8)0.0160 (9)0.0054 (9)
N60.0414 (11)0.0384 (10)0.0350 (10)0.0139 (8)0.0172 (8)0.0113 (8)
N70.0612 (16)0.0498 (15)0.0746 (17)0.0120 (12)0.0294 (14)0.0227 (13)
O10.0478 (10)0.0371 (9)0.0546 (10)0.0202 (8)0.0181 (8)0.0160 (8)
O20.0335 (8)0.0392 (9)0.0431 (9)0.0148 (7)0.0138 (7)0.0152 (7)
O30.101 (2)0.087 (2)0.199 (4)0.0436 (18)0.093 (3)0.051 (2)
O40.0831 (18)0.0619 (15)0.116 (2)0.0114 (13)0.0389 (16)0.0373 (14)
O50.0797 (19)0.0729 (18)0.176 (3)−0.0024 (15)0.059 (2)0.0110 (19)
O60.094 (2)0.0605 (15)0.097 (2)0.0444 (16)0.0289 (17)0.0132 (14)
N110.0434 (11)0.0309 (10)0.0356 (10)0.0146 (9)0.0171 (9)0.0081 (9)
N120.0512 (13)0.0375 (11)0.0473 (12)0.0212 (10)0.0235 (10)0.0116 (10)
Zn10.03508 (15)0.03867 (16)0.03545 (15)0.01457 (11)0.01437 (11)0.01066 (11)
Geometric parameters (Å, °) top
C1—C61.518 (4)C16—C171.356 (4)
C1—C21.529 (5)C16—H160.9300
C1—H1A0.9700C17—N31.356 (3)
C1—H1B0.9700C17—H170.9300
C2—C31.511 (5)C18—N41.351 (3)
C2—H2A0.9700C18—C191.357 (4)
C2—H2B0.9700C18—H180.9300
C3—C41.506 (5)C19—C201.372 (4)
C3—H3A0.9700C19—H190.9300
C3—H3B0.9700C20—C211.367 (4)
C4—C51.497 (5)C20—H200.9300
C4—H4A0.9700C21—C221.392 (4)
C4—H4B0.9700C21—H210.9300
C5—C61.519 (4)C22—N41.326 (3)
C5—H5A0.9700C22—N121.383 (3)
C5—H5B0.9700C23—N61.337 (3)
C6—C71.527 (3)C23—N121.373 (3)
C6—H60.9800C23—C241.406 (3)
C7—O11.246 (3)C24—C251.360 (4)
C7—O21.272 (3)C24—H240.9300
C8—N11.356 (3)C25—C261.389 (4)
C8—C91.360 (4)C25—H250.9300
C8—H80.9300C26—C271.361 (4)
C9—C101.382 (4)C26—H260.9300
C9—H90.9300C27—N61.357 (3)
C10—C111.365 (4)C27—H270.9300
C10—H100.9300N7—O31.204 (4)
C11—C121.402 (3)N7—O41.218 (3)
C11—H110.9300N7—O51.239 (4)
C12—N11.332 (3)Zn1—N11.9984 (18)
C12—N111.373 (3)Zn1—N32.0192 (19)
C13—N31.337 (3)Zn1—N42.166 (2)
C13—N111.376 (3)Zn1—N62.0405 (19)
C13—C141.395 (3)Zn1—O21.9803 (16)
C14—C151.370 (4)O6—H6A0.838 (10)
C14—H140.9300O6—H6B0.836 (10)
C15—C161.374 (5)N11—H11A0.70 (2)
C15—H150.9300N12—H120.71 (3)
C6—C1—C2110.8 (2)N3—C17—C16123.7 (3)
C6—C1—H1A109.5N3—C17—H17118.2
C2—C1—H1A109.5C16—C17—H17118.2
C6—C1—H1B109.5N4—C18—C19124.1 (3)
C2—C1—H1B109.5N4—C18—H18118.0
H1A—C1—H1B108.1C19—C18—H18118.0
C3—C2—C1111.4 (3)C18—C19—C20117.9 (3)
C3—C2—H2A109.3C18—C19—H19121.1
C1—C2—H2A109.3C20—C19—H19121.1
C3—C2—H2B109.3C21—C20—C19119.6 (3)
C1—C2—H2B109.3C21—C20—H20120.2
H2A—C2—H2B108.0C19—C20—H20120.2
C4—C3—C2111.1 (2)C20—C21—C22119.2 (3)
C4—C3—H3A109.4C20—C21—H21120.4
C2—C3—H3A109.4C22—C21—H21120.4
C4—C3—H3B109.4N4—C22—N12119.7 (2)
C2—C3—H3B109.4N4—C22—C21121.8 (2)
H3A—C3—H3B108.0N12—C22—C21118.6 (2)
C5—C4—C3112.1 (3)N6—C23—N12121.9 (2)
C5—C4—H4A109.2N6—C23—C24121.3 (2)
C3—C4—H4A109.2N12—C23—C24116.8 (2)
C5—C4—H4B109.2C25—C24—C23119.6 (2)
C3—C4—H4B109.2C25—C24—H24120.2
H4A—C4—H4B107.9C23—C24—H24120.2
C4—C5—C6111.6 (3)C24—C25—C26119.4 (2)
C4—C5—H5A109.3C24—C25—H25120.3
C6—C5—H5A109.3C26—C25—H25120.3
C4—C5—H5B109.3C27—C26—C25118.0 (3)
C6—C5—H5B109.3C27—C26—H26121.0
H5A—C5—H5B108.0C25—C26—H26121.0
C1—C6—C5109.8 (2)N6—C27—C26123.9 (3)
C1—C6—C7112.4 (2)N6—C27—H27118.0
C5—C6—C7112.2 (2)C26—C27—H27118.0
C1—C6—H6107.4C12—N1—C8117.9 (2)
C5—C6—H6107.4C12—N1—Zn1123.08 (14)
C7—C6—H6107.4C8—N1—Zn1117.45 (16)
O1—C7—O2122.0 (2)C13—N3—C17117.2 (2)
O1—C7—C6120.5 (2)C13—N3—Zn1123.65 (15)
O2—C7—C6117.4 (2)C17—N3—Zn1119.08 (17)
N1—C8—C9122.9 (3)C22—N4—C18117.5 (2)
N1—C8—H8118.5C22—N4—Zn1122.70 (16)
C9—C8—H8118.5C18—N4—Zn1119.52 (17)
C8—C9—C10118.7 (3)C23—N6—C27117.6 (2)
C8—C9—H9120.6C23—N6—Zn1122.08 (15)
C10—C9—H9120.6C27—N6—Zn1117.11 (16)
C11—C10—C9119.7 (2)O3—N7—O4122.9 (3)
C11—C10—H10120.1O3—N7—O5121.4 (3)
C9—C10—H10120.1O4—N7—O5115.7 (3)
C10—C11—C12118.5 (3)C7—O2—Zn1108.91 (14)
C10—C11—H11120.7H6A—O6—H6B109.5 (17)
C12—C11—H11120.7C12—N11—C13129.1 (2)
N1—C12—N11120.21 (19)C12—N11—H11A113 (2)
N1—C12—C11122.0 (2)C13—N11—H11A115 (2)
N11—C12—C11117.8 (2)C23—N12—C22131.3 (2)
N3—C13—N11120.1 (2)C23—N12—H12114 (2)
N3—C13—C14121.9 (2)C22—N12—H12113 (2)
N11—C13—C14118.0 (2)O2—Zn1—N189.03 (7)
C15—C14—C13119.2 (3)O2—Zn1—N3162.61 (8)
C15—C14—H14120.4N1—Zn1—N388.38 (7)
C13—C14—H14120.4O2—Zn1—N685.24 (7)
C14—C15—C16119.1 (3)N1—Zn1—N6172.28 (8)
C14—C15—H15120.4N3—Zn1—N695.55 (8)
C16—C15—H15120.4O2—Zn1—N4100.52 (8)
C17—C16—C15118.8 (3)N1—Zn1—N499.74 (8)
C17—C16—H16120.6N3—Zn1—N496.86 (9)
C15—C16—H16120.6N6—Zn1—N486.42 (8)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N12—H12···O6i0.71 (3)2.10 (3)2.806 (3)174 (3)
N11—H11A···O1ii0.70 (2)2.11 (3)2.810 (3)177 (3)
O6—H6B···N7ii0.84 (1)2.59 (1)3.406 (4)167 (3)
O6—H6B···O5ii0.84 (1)2.48 (3)3.164 (4)139 (3)
O6—H6B···O4ii0.84 (1)2.09 (1)2.904 (4)165 (3)
O6—H6A···O5iii0.84 (1)1.97 (2)2.787 (4)164 (4)
Symmetry codes: (i) x, y+1, z; (ii) −x+1, −y+1, −z+1; (iii) x, y, z+1.
Table 1
Selected geometric parameters (Å) top
Zn1—N11.9984 (18)Zn1—N62.0405 (19)
Zn1—N32.0192 (19)Zn1—O21.9803 (16)
Zn1—N42.166 (2)
Table 2
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N12—H12···O6i0.71 (3)2.10 (3)2.806 (3)174 (3)
N11—H11A···O1ii0.70 (2)2.11 (3)2.810 (3)177 (3)
O6—H6B···N7ii0.84 (1)2.59 (1)3.406 (4)167 (3)
O6—H6B···O5ii0.84 (1)2.48 (3)3.164 (4)139 (3)
O6—H6B···O4ii0.84 (1)2.09 (1)2.904 (4)165 (3)
O6—H6A···O5iii0.84 (1)1.97 (2)2.787 (4)164 (4)
Symmetry codes: (i) x, y+1, z; (ii) −x+1, −y+1, −z+1; (iii) x, y, z+1.
references
References top

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.

Enraf–Nonius (1989). CAD-4 Software. Enraf–Nonius, Delft, The Netherlands.

Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.

North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351–359.

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

Yang, H.-L., You, Z.-L. & Zhu, H.-L. (2004). Acta Cryst. E60, m1213–m1214.