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Acta Cryst. (2007). E63, m2416-m2417    [ doi:10.1107/S1600536807041281 ]

Poly[bis[[mu]-1,4-bis(1,2,4-triazol-1-ylmethyl)benzene]dicyanatonickel(II)]

W.-B. Wang, L.-Y. Wang, B.-L. Li and Y. Zhang

Abstract top

The coordination geometry of the NiII atom in the title complex, [Ni(NCO)2(C12H12N6)2]n or [Ni(NCO)2(bbtz)2]n, where bbtz is 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, is distorted octahedral, in which the NiII atom lies on an inversion center and is bonded to four N atoms from the triazole rings of four symmetry-related bbtz ligands and two N atoms from two symmetry-related monodentate NCO- ligands. The NiII atoms are bridged by four bbtz ligands to form a two-dimensional (4,4) network.

Comment top

The design and assembly of coordination polymers have been intensely studied for their interesting topologies and potential application as functional materials. The structural motifs of coordination polymers rest on several factors, such as the central atom, the performance of the ligands, the coordinated and/or non-coordinated counter ions and the reaction conditions. The ligand is no doubt the key factor of manipulating the topologies of the coordination polymers. Some novel coordination polymers with the flexible bis(triazole) ligands have been synthesized (Haasnoot, 2000; Albada et al., 2000; Zhao et al., 2002; Meng et al., 2004; Li et al., 2005).

In our previous studies, we synthesized several coordination polymers with the flexible ligands 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (bbtz) (Li et al., 2004; Li et al., 2005; Wang et al., 2007). In the present paper, we report the preparation and crystal structure of a two-dimensional (4,4) network coordination polymer [Ni(bbtz)2(NCO)2]n (I).

The structure of (I) is similar to that of [Ni(bbtz)2(N3)2]n (Wang et al., 2007). Fig. 1 shows the local coordination of the NiII atom in (I). The complex has a center of symmetry and the NiII atom occupies an inversion center. The coordination geometry of the NiII atom is distorted octahedral; it is coordinated equatorially by four nitrogen atoms from the triazole rings of four symmetry-related bbtz ligands [Ni1—N3, 2.1156 (3) Å; Ni1—N6 (−x + 1, y − 1/2, −z − 1/2), 2.1195 (14) Å], and axially by two nitrogen atoms from two symmetry-related cyanate anions [Ni1—N7, 2.0672 (16) Å]. The Ni—N(triazole) bond lengths [2.1156 (3) and 2.1195 (14) Å] at equatorial plane in (I) are corresponding to the values [2.1012 (16) and 2.1162 (16) Å] reported in [Ni(bbtz)2(N3)2]n (Wang et al., 2007). The cyanato ligand in (I) is quasi-linear as expected [the N—C—O bond angle is 178.3 (2)°]. The Ni—N—C (NCO) bond angle is 169.80 (15)°.

Because the methyl carbon atoms of bbtz can freely rotate to adjust itself to the coordination environment, bbtz can exhibit the trans-gauche and gauche-gauche conformations. The bbtz ligands exhibit the trans-gauche conformation in (I), similar to the situation in the free bbtz molecule (Peng et al., 2004), [Ni(bbtz)2(N3)2]n (Wang et al., 2007) and [Co(bbtz)2(N3)2]n (Li et al., 2004). The three rings (two triazole rings and one benzene ring) of one bbtz ligand are not coplanar in (I), [Ni(bbtz)2(N3)2]n, [Co(bbtz)2(N3)2]n and the free bbtz molecule. The dihedral angle between the two triazole planes in (I) is 58.8 (1)°, compared with the values 63.70 (9)° in [Ni(bbtz)2(N3)2]n, 61.94 (19)° in [Co(bbtz)2(N3)2]n, but 0° in free bbtz molecule by imposed crystallographic symmetry. The dihedral angles between the benzene plane and triazole planes in (I) are 67.6 (1) and 65.8 (1)°, compared with the values 66.46 (9) and 66.10 (7)° in [Ni(bbtz)2(N3)2]n, 67.26 (9) and 66.96 (7)° in [Co(bbtz)2(N3)2]n, and 77.81 (9)° in the free bbtz molecule.

As illustrated in Fig. 2, each bbtz ligand in (I) coordinates to the NiII atoms through its two triazole nitrogen atoms, thus acting as a bridging bidentate ligand to form a two-dimensional neutral (4,4) network. The networks contain square grids (52-membered ring), with a NiII atom at each corner and a bbtz ligand at each edge connecting two NiII atoms. As a consequence of the symmetry of the crystal structure, the edge lengths are equal, with a value of 14.383 (1) Å, similar to the M···M separations [14.3646 (15) Å] in [Ni(bbtz)2(N3)2]n (Wang et al., 2007), and [14.4156 (18) Å] in [Co(bbtz)2(N3)2]n (Li et al., 2004).

The diagonal lengths of the square grid are 20.191 (1) and 20.489 (1) Å; the square angles are 90.8 (1) and 89.2 (1)°. The square-grid sheets are stacked in an off-set fashion parallel to the c direction. The off-set half-cell superposition of each pair of adjacent networks divides the voids into smaller rectangle. The cyanate anions of one sheet project into the holes of the next sheet. In the superposition structure, the sheets are arranged in the sequence ··· A—B—A—B ···(Fig.3).

Related literature top

The synthesis of the ligand 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (bbtz) is described by Peng et al. (2004). Several bbtz complexes have been synthesized and structurally characterized (Li et al., 2004, 2005; Wang et al., 2007). The complex [Ni(bbtz)2(N3)2]n has a similar two-dimensional (4,4) network (Wang et al., 2007). For flexible bis(triazole) ligands, see: Haasnoot (2000); Albada et al. (2000); Zhao et al. (2002); Meng et al. (2004).

Experimental top

A 25 ml H2O/EtOH solution (v/v, 1:1) of 1,4-bis(1,2,4-triazol-1- ylmethyl)benzene (bbtz) (0.240 g, 1.0 mmol) was added to one leg of a H-shape tube, and 25 ml H2O/EtOH (v/v, 1:1) solution of Ni(NO3)2.6H2O (0.145 g, 0.5 mmol) and NaOCN (0.088 g, 1.4 mmol) was added to the other leg of the tube. The tube was allowed to stand in air at the room temperature for about one month. The light-blue crystals [Ni(bbtz)2(NCO)2]n (I) suitable for X-ray diffraction were obtained. Yield 73%. Elemental analysis confirmed the organic content (Found: C, 49.96; H, 3.82; N, 31.38%. Calcd. for C26H24N14NiO2: C, 50.10; H, 3.88; N, 31.47%).

Refinement top

H atom were placed in idealized positions and refined as riding, with C—H distances of 0.95 (triazole and benzene) and 0.99Å (methyl), and with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear (Rigaku, 2000); data reduction: CrystalClear (Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXTL (Bruker, 1998).

Figures top
[Figure 1] Fig. 1. The coordination environment of the NiII atom of (I) at the 30% probability level. [Symmetry codes: # −x, −y + 1, −z + 1 $ −x + 1, y − 1/2, −z + 1/2 & x − 1, −y + 3/2, z + 1/2]. The hydrogen atoms have been omitted for clarity.
[Figure 2] Fig. 2. Viewing the two-dimensional (4,4) network of the title compound along the c direction.
[Figure 3] Fig. 3. The cell packing of the title compound
Poly[bis[µ-1,4-bis(1,2,4-triazol-1-ylmethyl)benzene]dicyanatonickel(II)] top
Crystal data top
[Ni(CNO)2(C12H12N6)2]F000 = 644
Mr = 623.30Dx = 1.495 Mg m−3
Monoclinic, P21/cMo Kα radiation
λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 5408 reflections
a = 8.3857 (7) Åθ = 3.0–27.5º
b = 20.1913 (14) ŵ = 0.75 mm−1
c = 8.4229 (7) ÅT = 193 (2) K
β = 103.836 (2)ºPrism, light-blue
V = 1384.77 (19) Å30.50 × 0.20 × 0.20 mm
Z = 2
Data collection top
Rigaku Mercury CCD
diffractometer		3168 independent reflections
Radiation source: fine-focus sealed tube2828 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.027
Detector resolution: 7.31 pixels mm-1θmax = 27.5º
T = 193(2) Kθmin = 3.2º
ω scansh = −10→10
Absorption correction: multi-scan
(Jacobson, 1998)		k = −23→26
Tmin = 0.704, Tmax = 0.864l = −8→10
15292 measured reflections
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)] = 0.035H-atom parameters constrained
wR(F2) = 0.092  w = 1/[σ2(Fo2) + (0.047P)2 + 0.5612P]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max < 0.001
3168 reflectionsΔρmax = 0.28 e Å−3
197 parametersΔρmin = −0.25 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
[Ni(CNO)2(C12H12N6)2]V = 1384.77 (19) Å3
Mr = 623.30Z = 2
Monoclinic, P21/cMo Kα
a = 8.3857 (7) ŵ = 0.75 mm−1
b = 20.1913 (14) ÅT = 193 (2) K
c = 8.4229 (7) Å0.50 × 0.20 × 0.20 mm
β = 103.836 (2)º
Data collection top
Rigaku Mercury CCD
diffractometer		3168 independent reflections
Absorption correction: multi-scan
(Jacobson, 1998)		2828 reflections with I > 2σ(I)
Tmin = 0.704, Tmax = 0.864Rint = 0.027
15292 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.035197 parameters
wR(F2) = 0.092H-atom parameters constrained
S = 1.06Δρmax = 0.28 e Å−3
3168 reflectionsΔρmin = −0.25 e Å−3
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
Ni10.00000.50000.50000.02367 (11)
O10.51308 (17)0.53499 (8)0.77007 (19)0.0498 (4)
N10.14183 (18)0.58347 (7)0.09373 (17)0.0285 (3)
N2−0.0216 (2)0.58482 (9)0.0260 (2)0.0395 (4)
N30.02897 (17)0.54577 (7)0.28271 (17)0.0270 (3)
N40.80765 (18)0.83698 (7)0.20798 (18)0.0302 (3)
N50.9361 (2)0.80325 (8)0.1727 (2)0.0388 (4)
N60.92675 (17)0.90787 (7)0.08018 (17)0.0275 (3)
N70.24273 (19)0.52223 (8)0.60611 (19)0.0337 (3)
C10.3763 (2)0.65567 (9)0.0773 (2)0.0295 (4)
C20.5224 (2)0.64025 (9)0.1849 (3)0.0390 (4)
H2A0.55020.59520.20910.047*
C30.6300 (2)0.68970 (10)0.2586 (2)0.0388 (4)
H3A0.73060.67810.33240.047*
C40.5919 (2)0.75545 (9)0.2256 (2)0.0312 (4)
C50.4459 (3)0.77098 (10)0.1158 (3)0.0435 (5)
H5A0.41850.81610.09110.052*
C60.3389 (3)0.72163 (10)0.0412 (3)0.0435 (5)
H6A0.23960.7331−0.03480.052*
C70.2624 (2)0.60073 (10)−0.0015 (2)0.0370 (4)
H7A0.20330.6147−0.11270.044*
H7B0.32820.5610−0.01230.044*
C8−0.0831 (2)0.56153 (10)0.1443 (2)0.0347 (4)
H8A−0.19780.55620.13330.042*
C90.1696 (2)0.56019 (9)0.2452 (2)0.0311 (4)
H9A0.27520.55470.31640.037*
C100.7068 (3)0.80889 (10)0.3107 (2)0.0382 (4)
H10A0.64150.84470.34450.046*
H10B0.77970.79020.41070.046*
C111.0026 (2)0.84856 (9)0.0954 (2)0.0349 (4)
H11A1.09640.84000.05390.042*
C120.8044 (2)0.89849 (9)0.1525 (2)0.0288 (4)
H12A0.72600.93110.16300.035*
C130.3752 (2)0.52878 (8)0.6844 (2)0.0275 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ni10.02108 (17)0.02854 (18)0.02304 (17)0.00161 (11)0.00850 (12)0.00138 (11)
O10.0248 (7)0.0645 (10)0.0567 (9)−0.0067 (7)0.0029 (6)0.0001 (8)
N10.0284 (7)0.0334 (8)0.0251 (7)−0.0067 (6)0.0090 (6)0.0005 (6)
N20.0329 (9)0.0497 (10)0.0341 (8)−0.0023 (7)0.0045 (7)0.0115 (7)
N30.0267 (7)0.0296 (7)0.0265 (7)0.0014 (6)0.0099 (6)0.0027 (6)
N40.0312 (8)0.0307 (8)0.0299 (7)−0.0074 (6)0.0097 (6)−0.0030 (6)
N50.0357 (9)0.0328 (8)0.0495 (10)−0.0002 (7)0.0133 (8)−0.0016 (7)
N60.0253 (7)0.0305 (7)0.0283 (7)−0.0027 (6)0.0094 (6)−0.0013 (6)
N70.0260 (8)0.0438 (9)0.0318 (8)−0.0009 (7)0.0080 (6)0.0012 (7)
C10.0314 (9)0.0327 (9)0.0272 (8)−0.0065 (7)0.0127 (7)0.0027 (7)
C20.0404 (11)0.0285 (9)0.0472 (11)−0.0008 (8)0.0089 (9)0.0058 (8)
C30.0333 (10)0.0380 (10)0.0411 (10)−0.0027 (8)0.0007 (8)0.0089 (8)
C40.0343 (9)0.0333 (9)0.0288 (8)−0.0070 (7)0.0132 (7)0.0011 (7)
C50.0406 (11)0.0298 (10)0.0576 (13)0.0006 (8)0.0071 (10)0.0090 (9)
C60.0329 (10)0.0426 (11)0.0503 (12)−0.0016 (8)0.0010 (9)0.0096 (9)
C70.0396 (10)0.0469 (11)0.0289 (9)−0.0135 (9)0.0168 (8)−0.0041 (8)
C80.0263 (9)0.0429 (10)0.0352 (9)0.0020 (8)0.0080 (7)0.0089 (8)
C90.0254 (8)0.0418 (10)0.0268 (8)−0.0027 (7)0.0079 (7)0.0029 (7)
C100.0481 (11)0.0390 (10)0.0310 (9)−0.0141 (9)0.0164 (8)−0.0021 (8)
C110.0294 (9)0.0347 (10)0.0427 (10)−0.0022 (7)0.0128 (8)−0.0038 (8)
C120.0269 (8)0.0305 (9)0.0301 (9)−0.0031 (7)0.0092 (7)−0.0028 (7)
C130.0277 (9)0.0258 (9)0.0322 (9)−0.0004 (7)0.0134 (7)0.0025 (7)
Geometric parameters (Å, °) top
Ni1—N7i2.0672 (15)C1—C21.374 (3)
Ni1—N72.0672 (16)C1—C61.385 (3)
Ni1—N3i2.1156 (13)C1—C71.510 (3)
Ni1—N32.1156 (13)C2—C31.388 (3)
Ni1—N6ii2.1195 (14)C2—H2A0.9500
Ni1—N6iii2.1195 (14)C3—C41.378 (3)
O1—C131.214 (2)C3—H3A0.9500
N1—C91.327 (2)C4—C51.382 (3)
N1—N21.353 (2)C4—C101.509 (3)
N1—C71.475 (2)C5—C61.387 (3)
N2—C81.314 (2)C5—H5A0.9500
N3—C91.325 (2)C6—H6A0.9500
N3—C81.349 (2)C7—H7A0.9900
N4—C121.325 (2)C7—H7B0.9900
N4—N51.366 (2)C8—H8A0.9500
N4—C101.461 (2)C9—H9A0.9500
N5—C111.321 (2)C10—H10A0.9900
N6—C121.326 (2)C10—H10B0.9900
N6—C111.347 (2)C11—H11A0.9500
N6—Ni1iv2.1195 (14)C12—H12A0.9500
N7—C131.156 (2)
N7i—Ni1—N7180.0C4—C3—H3A119.7
N7i—Ni1—N3i88.53 (6)C2—C3—H3A119.7
N7—Ni1—N3i91.47 (6)C3—C4—C5118.61 (17)
N7i—Ni1—N391.47 (6)C3—C4—C10120.15 (18)
N7—Ni1—N388.53 (6)C5—C4—C10121.23 (18)
N3i—Ni1—N3180.0C4—C5—C6120.90 (18)
N7i—Ni1—N6ii90.12 (6)C4—C5—H5A119.5
N7—Ni1—N6ii89.88 (6)C6—C5—H5A119.5
N3i—Ni1—N6ii89.67 (5)C1—C6—C5120.22 (19)
N3—Ni1—N6ii90.33 (5)C1—C6—H6A119.9
N7i—Ni1—N6iii89.88 (6)C5—C6—H6A119.9
N7—Ni1—N6iii90.12 (6)N1—C7—C1112.26 (14)
N3i—Ni1—N6iii90.33 (5)N1—C7—H7A109.2
N3—Ni1—N6iii89.67 (5)C1—C7—H7A109.2
N6ii—Ni1—N6iii180.0N1—C7—H7B109.2
C9—N1—N2109.87 (14)C1—C7—H7B109.2
C9—N1—C7128.37 (16)H7A—C7—H7B107.9
N2—N1—C7121.56 (15)N2—C8—N3114.90 (16)
C8—N2—N1102.41 (14)N2—C8—H8A122.6
C9—N3—C8102.61 (14)N3—C8—H8A122.6
C9—N3—Ni1126.55 (12)N3—C9—N1110.21 (16)
C8—N3—Ni1130.56 (12)N3—C9—H9A124.9
C12—N4—N5109.95 (14)N1—C9—H9A124.9
C12—N4—C10127.36 (16)N4—C10—C4113.01 (15)
N5—N4—C10122.24 (16)N4—C10—H10A109.0
C11—N5—N4102.10 (15)C4—C10—H10A109.0
C12—N6—C11103.21 (15)N4—C10—H10B109.0
C12—N6—Ni1iv125.93 (12)C4—C10—H10B109.0
C11—N6—Ni1iv130.10 (12)H10A—C10—H10B107.8
C13—N7—Ni1169.80 (15)N5—C11—N6114.67 (16)
C2—C1—C6118.82 (17)N5—C11—H11A122.7
C2—C1—C7119.59 (17)N6—C11—H11A122.7
C6—C1—C7121.57 (18)N6—C12—N4110.07 (16)
C1—C2—C3120.89 (18)N6—C12—H12A125.0
C1—C2—H2A119.6N4—C12—H12A125.0
C3—C2—H2A119.6N7—C13—O1178.3 (2)
C4—C3—C2120.54 (18)
C9—N1—N2—C8−0.1 (2)C7—C1—C6—C5179.90 (19)
C7—N1—N2—C8175.07 (17)C4—C5—C6—C10.7 (3)
N7i—Ni1—N3—C9−163.56 (15)C9—N1—C7—C1−61.6 (3)
N7—Ni1—N3—C916.44 (15)N2—N1—C7—C1124.14 (19)
N6ii—Ni1—N3—C9−73.44 (15)C2—C1—C7—N191.4 (2)
N6iii—Ni1—N3—C9106.56 (15)C6—C1—C7—N1−89.9 (2)
N7i—Ni1—N3—C89.20 (17)N1—N2—C8—N30.3 (2)
N7—Ni1—N3—C8−170.80 (17)C9—N3—C8—N2−0.4 (2)
N6ii—Ni1—N3—C899.33 (17)Ni1—N3—C8—N2−174.48 (13)
N6iii—Ni1—N3—C8−80.67 (17)C8—N3—C9—N10.3 (2)
C12—N4—N5—C11−0.2 (2)Ni1—N3—C9—N1174.71 (11)
C10—N4—N5—C11−173.03 (16)N2—N1—C9—N3−0.2 (2)
N3i—Ni1—N7—C138.8 (9)C7—N1—C9—N3−174.92 (16)
N3—Ni1—N7—C13−171.2 (9)C12—N4—C10—C4115.0 (2)
N6ii—Ni1—N7—C13−80.8 (9)N5—N4—C10—C4−73.5 (2)
N6iii—Ni1—N7—C1399.2 (9)C3—C4—C10—N4101.5 (2)
C6—C1—C2—C31.0 (3)C5—C4—C10—N4−79.7 (2)
C7—C1—C2—C3179.69 (18)N4—N5—C11—N60.3 (2)
C1—C2—C3—C40.2 (3)C12—N6—C11—N5−0.2 (2)
C2—C3—C4—C5−1.0 (3)Ni1iv—N6—C11—N5170.08 (13)
C2—C3—C4—C10177.90 (18)C11—N6—C12—N40.11 (19)
C3—C4—C5—C60.6 (3)Ni1iv—N6—C12—N4−170.75 (11)
C10—C4—C5—C6−178.32 (19)N5—N4—C12—N60.0 (2)
C2—C1—C6—C5−1.5 (3)C10—N4—C12—N6172.43 (16)
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x+1, y−1/2, −z+1/2; (iii) x−1, −y+3/2, z+1/2; (iv) −x+1, y+1/2, −z+1/2.
Acknowledgements top

This work was supported by the Natural Science Foundation of Jiangsu Province (No. BK2006049) and the Funds of the Key Laboratory of Organic Synthesis Chemistry, Jiangsu Province, People's Republic of China.

references
References top

Albada, G. A. V., Guijt, R. C., Haasnoot, J. G., Lutz, M., Spek, A. L. & Reedijk, J. (2000). Eur. J. Inorg. Chem. pp. 121–126.

Bruker (1998). SHELXTL. Version 5.10. Bruker AXS Inc., Madison, Wisconsin, USA.

Haasnoot, J. G. (2000). Coord. Chem. Rev. 200–202, 131–185.

Jacobson, R. (1998). Private communication to Rigaku Corporation, Tokyo, Japan.

Li, B. L., Peng, Y. F., Li, B. Z. & Zhang, Y. (2005). Chem. Commun. pp. 2333–2335.

Li, B.-Z., Peng, Y.-F., Zhang, Y.-P., Li, B.-L. & Zhang, Y. (2004). Acta Cryst. C60, m560–m562.

Meng, X. R., Song, Y. L., Hou, H. W., Han, H. Y., Xiao, B., Fan, Y. T. & Zhu, Y. (2004). Inorg. Chem. 43, 3528–3536.

Peng, Y. F., Li, B. Z., Zhou, J. H., Li, B. L. & Zhang, Y. (2004). Chin. J. Struct. Chem. 23, 985–988.

Rigaku (2000). CrystalClear. Version 1.3. Rigaku Corporation, Tokyo, Japan.

Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.

Wang, L.-Y., Peng, Y.-F., Zhang, Y.-P., Li, B.-L. & Zhang, Y. (2007). Acta Cryst. C63, m297–m299.

Zhao, Q. H., Li, H. F., Wang, X. F. & Chen, Z. D. (2002). New J. Chem. 26, 1709–1710.