supplementary materials


HTML versionpdf versioncif file3d viewstructure factorssupplementary materialsCIF check reportcited insimilar papers Open access

ci5079 scheme

Acta Cryst. (2010). E66, m601-m602    [ doi:10.1107/S1600536810015564 ]

Di-[mu]-thiocyanato-[kappa]4N:N-bis({5-methoxy-2-[3-(methylamino)propyliminomethyl]phenolato-[kappa]3O1,N,N'}copper(II))

N. Wang, R. Xue, B. Li, Y.-P. Yang and M. Cao

Abstract top

The title thiocyanate-bridged dinuclear copper(II) complex, [Cu2(C12H17N2O2)2(NCS)2], possesses crystallographic inversion symmetry. Each CuII atom is five-coordinated by one imine N, one amine N and one phenolate O atom of the Schiff base ligand, and by two N atoms from two bridging thiocyanate ligands, forming a square-pyramidal geometry. Beside the two thiocyanate bridges, there are two intramolecular N-H...O hydrogen bonds, which further link the two Cu(C12H17N2O2)(NCS) units. The Cu...Cu separation is 3.261 (2) Å. Parts of the methylaminopropylimino segment are disordered over two sites with occupancies of 0.669(9) and 0.331(9).

Comment top

An extensive effort has been made to prepare and characterize a variety of coordination complexes in an attempt to model the physical and chemical behaviour of copper-containing enzymes (Reddy et al., 2000). The peculiarity of copper lies in its ability to form complexes with coordination numbers of four, five, and six (Ray et al. 2003; Arnold et al., 2003; Raptopoulou et al., 1998). As a continuation of our own work in this area (Wang & Li, 2005; Wang et al., 2006), the title compound, a new copper(II) complex, is reported here.

The title compound is a thiocyanate-bridged dinuclear copper(II) complex (Fig. 1), with a Cu···Cu separation of 3.2608 (7) Å. The complex possesses a crystallographic inversion centre symmetry. Each CuII atom is five-coordinated by one imine N, one amine N, and one phenolate O atom of the Schiff base ligand, and by two N atoms from two thiocyanate ligands, forming a square-pyramidal geometry. The bond lengths and angles (Table 1) are typical and comparable with those in other copper(II) complexes with Schiff bases and thiocyanate ligands (Elmali et al., 2000; You & Zhu, 2005; Liu et al., 2004; Datta et al., 2008; Habibi et al., 2007). Beside the two thiocyanate bridges, there exist two N—H···O hydrogen bonds (Table 2) in the complex, which further link the two [Cu(C12H17N2O2)(NCS)] units together (Fig. 2).

Related literature top

For general background to copper complexes, see: Reddy et al. (2000); Ray et al. (2003); Arnold et al. (2003); Raptopoulou et al. (1998). For our previous reports of copper(II) complexes, see: Wang & Li (2005); Wang et al. (2006). For related structures, see: Elmali et al. (2000); You & Zhu (2005); Liu et al. (2004); Datta et al. (2008); Habibi et al. (2007).

Experimental top

4-Methoxysalicylaldehyde (0.1 mmol, 15.2 mg), N-methylpropane-1,3-diamine (0.1 mmol, 8.8 mg), NH4NCS (0.1 mmol, 7.6 mg) and Cu(CH3COO)2.H2O (0.1 mmol, 19.9 mg) were dissolved in methanol (20 ml). The mixture was stirred at room temperature for 1 h to give a blue solution. The resulting solution was allowed to stand in air for a few days, and blue block-shaped crystals were formed.

Refinement top

Atoms C9, C10 and C11 of the methylaminopropylimino segment are disordered over two sites with occupancies of 0.669 (9) and 0.331 (9). The N—C and also the C—C distances involving the disordered atoms were restrained to be equal. The Uij parameters of the disordered atoms, and atom C12 were restrained to an approximate isotropic behaviour. H atoms were placed in idealized positions and constrained to ride on their parent atoms, with C—H distances in the range 0.93-0.97 Å, N—H distances in the range 0.90-0.91 Å and with Uiso(H) = 1.2Ueq(C,N) and 1.5Ueq(methyl C).

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); 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, showing 30% displacement ellipsoids (arbitrary spheres for the H atoms). Unlabelled atoms are at the symmetry position (1 - x, - y, - z). Only the major disorder component is shown.
[Figure 2] Fig. 2. The crystal packing of the title compound. Intramolecular N—H···O hydrogen bonds are shown as dashed lines.
Di-µ-thiocyanato-κ4N:N-bis({5-methoxy-2-[3- (methylamino)propyliminomethyl]phenolato- κ3O1,N,N'}copper(II)) top
Crystal data top
[Cu2(C12H17N2O2)2(NCS)2]F(000) = 708
Mr = 685.79Dx = 1.531 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 2304 reflections
a = 11.8003 (18) Åθ = 2.5–25.1°
b = 15.373 (2) ŵ = 1.61 mm−1
c = 8.6740 (13) ÅT = 298 K
β = 108.972 (7)°Block, blue
V = 1488.0 (4) Å30.20 × 0.20 × 0.18 mm
Z = 2
Data collection top
Bruker SMART CCD area-detector
diffractometer		3544 independent reflections
Radiation source: fine-focus sealed tube2496 reflections with I > 2σ(I)
graphiteRint = 0.030
ω scansθmax = 28.5°, θmin = 1.8°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		h = −15→15
Tmin = 0.739, Tmax = 0.760k = −20→19
9297 measured reflectionsl = −11→10
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)] = 0.040Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.108H-atom parameters constrained
S = 1.05 w = 1/[σ2(Fo2) + (0.0508P)2 + 0.2175P]
where P = (Fo2 + 2Fc2)/3
3544 reflections(Δ/σ)max = 0.001
211 parametersΔρmax = 0.48 e Å−3
50 restraintsΔρmin = −0.41 e Å−3
Crystal data top
[Cu2(C12H17N2O2)2(NCS)2]V = 1488.0 (4) Å3
Mr = 685.79Z = 2
Monoclinic, P21/cMo Kα radiation
a = 11.8003 (18) ŵ = 1.61 mm−1
b = 15.373 (2) ÅT = 298 K
c = 8.6740 (13) Å0.20 × 0.20 × 0.18 mm
β = 108.972 (7)°
Data collection top
Bruker SMART CCD area-detector
diffractometer		3544 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)		2496 reflections with I > 2σ(I)
Tmin = 0.739, Tmax = 0.760Rint = 0.030
9297 measured reflectionsθmax = 28.5°
Refinement top
R[F2 > 2σ(F2)] = 0.040H-atom parameters constrained
wR(F2) = 0.108Δρmax = 0.48 e Å−3
S = 1.05Δρmin = −0.41 e Å−3
3544 reflectionsAbsolute structure: ?
211 parametersFlack parameter: ?
50 restraintsRogers parameter: ?
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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*/UeqOcc. (<1)
Cu10.44981 (3)0.09693 (2)0.01842 (4)0.04380 (14)
S10.77288 (9)0.09042 (7)−0.17937 (13)0.0751 (3)
O10.33324 (18)0.07895 (14)−0.1912 (2)0.0557 (6)
O2−0.03088 (19)0.11364 (15)−0.6308 (3)0.0612 (6)
N10.3347 (2)0.14948 (17)0.1093 (3)0.0578 (7)
N20.5877 (3)0.1033 (2)0.2257 (4)0.0775 (10)
H2A0.63210.05480.22620.093*0.669 (9)
H2B0.63240.05720.21740.093*0.331 (9)
N30.5707 (2)0.06534 (19)−0.0884 (3)0.0608 (7)
C10.1697 (2)0.15468 (16)−0.1467 (3)0.0412 (6)
C20.2230 (2)0.10933 (17)−0.2462 (4)0.0433 (7)
C30.1564 (3)0.09443 (17)−0.4110 (4)0.0447 (7)
H30.19060.0638−0.47740.054*
C40.0408 (2)0.12515 (19)−0.4741 (4)0.0458 (7)
C5−0.0121 (3)0.1713 (2)−0.3762 (4)0.0558 (8)
H5−0.08970.1925−0.42010.067*
C60.0507 (3)0.18466 (18)−0.2176 (4)0.0516 (7)
H60.01450.2146−0.15280.062*
C70.0149 (3)0.0685 (2)−0.7408 (4)0.0664 (9)
H7A0.08270.0993−0.75130.080*
H7B−0.04610.0646−0.84540.080*
H7C0.03910.0110−0.69980.080*
C80.2262 (3)0.16936 (18)0.0221 (4)0.0516 (7)
H80.17990.19650.07680.062*
C90.3506 (5)0.1469 (5)0.2885 (6)0.0633 (17)0.669 (9)
H9A0.33220.08890.31780.076*0.669 (9)
H9B0.29510.18720.31170.076*0.669 (9)
C100.4770 (5)0.1705 (5)0.3900 (8)0.068 (2)0.669 (9)
H10A0.49720.22590.35220.082*0.669 (9)
H10B0.47980.17800.50220.082*0.669 (9)
C110.5706 (8)0.1048 (6)0.3857 (7)0.080 (3)0.669 (9)
H11A0.64590.11910.46890.096*0.669 (9)
H11B0.54620.04750.40980.096*0.669 (9)
C9A0.3884 (12)0.1980 (8)0.2722 (11)0.068 (4)0.331 (9)
H9AA0.44890.23910.26550.082*0.331 (9)
H9AB0.32650.22930.30040.082*0.331 (9)
C10A0.4432 (15)0.1287 (10)0.397 (2)0.086 (5)0.331 (9)
H10C0.38080.08880.40190.103*0.331 (9)
H10D0.47580.15590.50330.103*0.331 (9)
C11A0.5414 (14)0.0777 (10)0.3617 (15)0.085 (6)0.331 (9)
H11C0.60960.07730.46130.102*0.331 (9)
H11D0.51370.01810.34140.102*0.331 (9)
C120.6695 (4)0.1786 (3)0.2263 (7)0.1234 (19)
H12A0.62820.23230.22760.148*
H12B0.69300.17620.13030.148*
H12C0.73940.17530.32140.148*
C130.6548 (3)0.07722 (19)−0.1263 (4)0.0500 (7)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0406 (2)0.0484 (2)0.0408 (2)0.00958 (15)0.01100 (16)−0.00055 (14)
S10.0543 (5)0.1109 (8)0.0669 (6)−0.0065 (5)0.0290 (5)0.0033 (5)
O10.0440 (12)0.0789 (15)0.0409 (11)0.0279 (10)0.0095 (9)−0.0046 (10)
O20.0424 (12)0.0714 (15)0.0598 (15)0.0034 (10)0.0026 (11)−0.0030 (11)
N10.0597 (16)0.0727 (18)0.0399 (14)0.0239 (14)0.0149 (13)−0.0057 (12)
N20.0566 (18)0.093 (2)0.063 (2)0.0254 (16)−0.0074 (15)−0.0285 (16)
N30.0474 (15)0.0776 (18)0.0592 (17)0.0080 (14)0.0195 (14)0.0049 (14)
C10.0389 (14)0.0394 (14)0.0484 (16)0.0053 (12)0.0185 (13)0.0028 (12)
C20.0404 (15)0.0425 (16)0.0472 (17)0.0080 (12)0.0146 (13)0.0073 (12)
C30.0411 (15)0.0495 (16)0.0435 (16)0.0043 (12)0.0140 (13)0.0037 (12)
C40.0387 (16)0.0446 (15)0.0500 (17)0.0000 (12)0.0088 (14)0.0074 (13)
C50.0328 (15)0.0577 (19)0.073 (2)0.0075 (13)0.0113 (16)0.0021 (16)
C60.0410 (16)0.0481 (17)0.070 (2)0.0043 (13)0.0239 (16)−0.0047 (14)
C70.061 (2)0.079 (2)0.0491 (19)−0.0022 (18)0.0044 (17)0.0007 (17)
C80.0577 (19)0.0498 (17)0.0539 (18)0.0126 (14)0.0271 (16)0.0011 (14)
C90.072 (4)0.075 (4)0.044 (3)0.013 (3)0.021 (3)−0.004 (3)
C100.080 (4)0.073 (4)0.042 (3)0.010 (3)0.007 (3)−0.021 (3)
C110.104 (5)0.086 (5)0.030 (3)0.029 (4)−0.007 (3)−0.017 (3)
C9A0.070 (7)0.080 (7)0.053 (6)0.028 (6)0.018 (5)−0.008 (5)
C10A0.089 (9)0.106 (9)0.062 (7)0.005 (7)0.024 (7)0.018 (7)
C11A0.100 (9)0.085 (8)0.038 (7)0.041 (7)−0.022 (6)−0.032 (6)
C120.066 (3)0.138 (4)0.148 (4)−0.020 (3)0.010 (3)−0.070 (3)
C130.0459 (17)0.0568 (18)0.0452 (17)0.0038 (14)0.0118 (15)0.0024 (13)
Geometric parameters (Å, °) top
Cu1—O11.910 (2)C5—H50.93
Cu1—N11.953 (2)C6—H60.93
Cu1—N21.997 (3)C7—H7A0.96
Cu1—N31.998 (3)C7—H7B0.96
Cu1—N3i2.598 (4)C7—H7C0.96
S1—C131.616 (3)C8—H80.93
O1—C21.317 (3)C9—C101.509 (6)
O2—C41.359 (3)C9—H9A0.97
O2—C71.421 (4)C9—H9B0.97
N1—C81.294 (4)C10—C111.506 (6)
N1—C91.504 (5)C10—H10A0.97
N1—C9A1.540 (8)C10—H10B0.97
N2—C111.467 (6)C11—H11A0.97
N2—C121.505 (5)C11—H11B0.97
N2—C11A1.506 (9)C9A—C10A1.507 (8)
N2—H2A0.91C9A—H9AA0.97
N2—H2B0.90C9A—H9AB0.97
N3—C131.157 (4)C10A—C11A1.510 (8)
C1—C21.407 (4)C10A—H10C0.97
C1—C61.415 (4)C10A—H10D0.97
C1—C81.416 (4)C11A—H11C0.97
C2—C31.408 (4)C11A—H11D0.97
C3—C41.378 (4)C12—H12A0.96
C3—H30.93C12—H12B0.96
C4—C51.399 (4)C12—H12C0.96
C5—C61.350 (4)
O1—Cu1—N193.67 (10)H7A—C7—H7B109.5
O1—Cu1—N2171.12 (10)O2—C7—H7C109.5
N1—Cu1—N294.96 (12)H7A—C7—H7C109.5
O1—Cu1—N385.70 (10)H7B—C7—H7C109.5
N1—Cu1—N3169.45 (12)N1—C8—C1127.6 (3)
N2—Cu1—N386.20 (12)N1—C8—H8116.2
N3i—Cu1—N199.91 (15)C1—C8—H8116.2
N3i—Cu1—N287.06 (15)N1—C9—C10111.3 (5)
N3i—Cu1—N390.57 (15)N1—C9—H9A109.4
N3i—Cu1—O189.50 (15)C10—C9—H9A109.4
C2—O1—Cu1127.91 (18)N1—C9—H9B109.4
C4—O2—C7119.1 (2)C10—C9—H9B109.4
C8—N1—C9112.2 (3)H9A—C9—H9B108.0
C8—N1—C9A117.1 (5)C11—C10—C9114.7 (6)
C8—N1—Cu1123.2 (2)C11—C10—H10A108.6
C9—N1—Cu1122.4 (3)C9—C10—H10A108.6
C9A—N1—Cu1116.0 (5)C11—C10—H10B108.6
C11—N2—C12105.7 (5)C9—C10—H10B108.6
C12—N2—C11A126.4 (7)H10A—C10—H10B107.6
C11—N2—Cu1122.0 (4)N2—C11—C10111.2 (5)
C12—N2—Cu1112.0 (3)N2—C11—H11A109.4
C11A—N2—Cu1107.2 (7)C10—C11—H11A109.4
C11—N2—H2A105.3N2—C11—H11B109.4
C12—N2—H2A105.3C10—C11—H11B109.4
C11A—N2—H2A97.8H11A—C11—H11B108.0
Cu1—N2—H2A105.3C10A—C9A—N1105.7 (11)
C11—N2—H2B110.6C10A—C9A—H9AA110.6
C12—N2—H2B102.4N1—C9A—H9AA110.6
C11A—N2—H2B103.1C10A—C9A—H9AB110.6
Cu1—N2—H2B102.5N1—C9A—H9AB110.6
C13—N3—Cu1154.3 (3)H9AA—C9A—H9AB108.7
C2—C1—C6118.3 (3)C9A—C10A—C11A113.5 (12)
C2—C1—C8124.0 (3)C9A—C10A—H10C108.9
C6—C1—C8117.7 (3)C11A—C10A—H10C108.9
O1—C2—C1122.6 (3)C9A—C10A—H10D108.9
O1—C2—C3118.0 (3)C11A—C10A—H10D108.9
C1—C2—C3119.3 (3)H10C—C10A—H10D107.7
C4—C3—C2120.1 (3)N2—C11A—C10A121.4 (11)
C4—C3—H3120.0N2—C11A—H11C107.0
C2—C3—H3120.0C10A—C11A—H11C107.0
O2—C4—C3124.5 (3)N2—C11A—H11D107.0
O2—C4—C5114.7 (2)C10A—C11A—H11D107.0
C3—C4—C5120.8 (3)H11C—C11A—H11D106.7
C6—C5—C4119.4 (3)N2—C12—H12A109.5
C6—C5—H5120.3N2—C12—H12B109.5
C4—C5—H5120.3H12A—C12—H12B109.5
C5—C6—C1122.1 (3)N2—C12—H12C109.5
C5—C6—H6118.9H12A—C12—H12C109.5
C1—C6—H6118.9H12B—C12—H12C109.5
O2—C7—H7A109.5N3—C13—S1178.1 (3)
O2—C7—H7B109.5
N1—Cu1—O1—C210.5 (3)C7—O2—C4—C5179.3 (3)
N3—Cu1—O1—C2−159.0 (3)C2—C3—C4—O2−179.5 (3)
O1—Cu1—N1—C8−8.2 (3)C2—C3—C4—C50.0 (4)
N2—Cu1—N1—C8173.9 (3)O2—C4—C5—C6178.6 (3)
N3—Cu1—N1—C878.0 (7)C3—C4—C5—C6−0.9 (4)
O1—Cu1—N1—C9153.7 (4)C4—C5—C6—C11.0 (5)
N2—Cu1—N1—C9−24.2 (4)C2—C1—C6—C5−0.2 (4)
N3—Cu1—N1—C9−120.1 (6)C8—C1—C6—C5−177.8 (3)
O1—Cu1—N1—C9A−165.8 (6)C9—N1—C8—C1−160.8 (4)
N2—Cu1—N1—C9A16.3 (6)C9A—N1—C8—C1160.1 (7)
N3—Cu1—N1—C9A−79.5 (8)Cu1—N1—C8—C12.8 (5)
N1—Cu1—N2—C1125.6 (5)C2—C1—C8—N14.5 (5)
N3—Cu1—N2—C11−164.9 (5)C6—C1—C8—N1−178.0 (3)
N1—Cu1—N2—C12−101.1 (3)C8—N1—C9—C10−150.3 (5)
N3—Cu1—N2—C1268.4 (3)C9A—N1—C9—C10−44.3 (8)
N1—Cu1—N2—C11A41.7 (6)Cu1—N1—C9—C1046.0 (7)
N3—Cu1—N2—C11A−148.9 (6)N1—C9—C10—C11−68.3 (9)
O1—Cu1—N3—C13123.7 (6)C12—N2—C11—C1081.1 (7)
N1—Cu1—N3—C1336.7 (10)C11A—N2—C11—C10−97 (2)
N2—Cu1—N3—C13−60.0 (6)Cu1—N2—C11—C10−48.3 (8)
Cu1—O1—C2—C1−6.7 (4)C9—C10—C11—N269.8 (9)
Cu1—O1—C2—C3174.05 (19)C8—N1—C9A—C10A132.2 (9)
C6—C1—C2—O1−180.0 (2)C9—N1—C9A—C10A41.3 (8)
C8—C1—C2—O1−2.5 (4)Cu1—N1—C9A—C10A−68.8 (12)
C6—C1—C2—C3−0.8 (4)N1—C9A—C10A—C11A60.8 (18)
C8—C1—C2—C3176.7 (3)C11—N2—C11A—C10A78 (2)
O1—C2—C3—C4−179.9 (2)C12—N2—C11A—C10A75.1 (16)
C1—C2—C3—C40.9 (4)Cu1—N2—C11A—C10A−60.6 (15)
C7—O2—C4—C3−1.2 (4)C9A—C10A—C11A—N27(2)
Symmetry codes: (i) −x+1, −y, −z.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···O1i0.912.142.999 (3)157
Symmetry codes: (i) −x+1, −y, −z.
Table 1
Selected geometric parameters (Å) top
Cu1—O11.910 (2)Cu1—N31.998 (3)
Cu1—N11.953 (2)Cu1—N3i2.598 (4)
Cu1—N21.997 (3)
Symmetry codes: (i) −x+1, −y, −z.
Table 2
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···O1i0.912.142.999 (3)157
Symmetry codes: (i) −x+1, −y, −z.
Acknowledgements top

This work was supported by the Science and Technology Support Projects of Gansu Province (grant No. 097 GKCA028) and by the `Qing Lan' Talent Engineering Funds of Lanzhou Jiaotong University.

references
References top

Arnold, P. J., Davies, S. C., Durrant, M. C., Griffiths, D. V., Hughes, D. L. & Sharpe, P. C. (2003). Inorg. Chim. Acta, 348, 143–149.

Bruker (1998). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.

Datta, A., Huang, J.-H. & Lee, H. M. (2008). Acta Cryst. E64, m1497.

Elmali, A., Zeyrek, C. T., Elerman, Y. & Svoboda, I. (2000). Acta Cryst. C56, 1302–1304.

Habibi, M. H., Mokhtari, R., Harrington, R. W. & Clegg, W. (2007). Acta Cryst. E63, m1998.

Liu, H., Wang, H., Niu, D. & Lu, Z. (2004). Acta Cryst. E60, m1941–m1942.

Raptopoulou, C. P., Papadopoulos, A. N., Malamatari, D. A., Ioannidis, E., Moisidis, G., Terzis, A. & Kessissoglou, D. P. (1998). Inorg. Chim. Acta, 272, 283–290.

Ray, M. S., Bhattacharya, R. B., Chaudhuri, S., Righi, L., Bocelli, G., Mukhopadhyay, G. & Ghosh, A. (2003). Polyhedron, 22, 617–624.

Reddy, P. A. N., Datta, R. & Chakravarty, A. R. (2000). Inorg. Chem. Commun. 3, 322–324.

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

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

Wang, N., Han, X.-E. & Wen, X.-G. (2006). Acta Cryst. E62, m369–m370.

Wang, N. & Li, J.-P. (2005). Acta Cryst. E61, m1223–m1225.

You, Z.-L. & Zhu, H.-L. (2005). Acta Cryst. C61, m421–m423.