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Volume 68 
Part 9 
Pages m246-m250  
September 2012  

Received 4 July 2012
Accepted 12 July 2012
Online 1 August 2012

1,1'-Methylenedipyridinium tetrachloridocuprate(II) and bis[tetrachloridoaurate(III)] hybrid salts by X-ray powder diffraction

aDepartment of Chemistry, Atomic Energy Commission of Syria (AECS), PO Box 6091, Damascus, Syrian Arab Republic
Correspondence e-mail: cscientific@aec.org.sy

In order to explore the potential propensity of the 1,1'-methylenedipyridinium dication to form organic-inorganic hybrid ionic compounds by reaction with the appropriate halide metal salt, the organic-inorganic hybrid salts 1,1'-methylenedipyridinium tetrachloridocuprate(II), (C11H12N2)[CuCl4], (I), and 1,1'-methylenedipyridinium bis[tetrachloridoaurate(III)], (C11H12N2)[AuCl4]2, (II), were obtained by treatment of 1,1'-methylenedipyridinium dichloride with CuCl2 and Na[AuCl4], respectively. Both hybrid salts were isolated as pure compounds, fully characterized by multinuclear NMR spectroscopy and their molecular structures confirmed by powder X-ray diffraction studies. The crystal structures consist of discrete 1,1'-methylenedipyridinium dications and [CuCl4]2- and [AuCl4]- anions for (I) and (II), respectively. As expected, the dications form a butterfly shape; the CuII centre of [CuCl4]2- has a distorted tetrahedral configuration and the AuIII centre of [AuCl4]- shows a square-planar coordination. The ionic species of (I) and the dication of (II) each have twofold axial symmetry, while the two [AuCl4]- anions are located on a mirror-plane site. Both crystal structures are stabilized by intermolecular C-H...Cl hydrogen bonds and also by Cl...[pi] interactions. It is noteworthy that, while the average intermolecular centroid-centroid pyridinium ring distance in (I) is 3.643 (8) Å, giving strong evidence for noncovalent [pi]-[pi] ring interactions, for (II), the shortest centroid-centroid distance between pyridinium rings of 5.502 (9) Å is too long for any significant [pi]-[pi] ring interactions, which might be due to the bulk of the two [AuCl4]- anions.

Comment

Over the past decade, research activity in the design of organic-inorganic hybrid ionic materials has steadily increased, because of the potential applications particularly in the areas of crystal engineering, supramolecular chemistry and materials science (Kimizuka & Kunitake, 1996[Kimizuka, N. & Kunitake, T. (1996). Adv. Mater. 8, 89-91.]; Mitzi et al., 1999[Mitzi, D. B., Prikas, M. T. & Chondroudis, K. (1999). Chem. Mater. 11, 542-544.]; Bonhomme & Kanatzidis, 1998[Bonhomme, F. & Kanatzidis, M. G. (1998). Chem. Mater. 10, 1153-1159.]; Wachhold & Kanatzidis, 2000[Wachhold, M. & Kanatzidis, M. G. (2000). Chem. Mater. 12, 2914-2923.]); these materials also have applications as optical semiconductors (Kagan et al., 1999[Kagan, C. R., Mitzi, D. B. & Dimitrakopoulos, C. D. (1999). Science, 286, 945-947.]; Li et al., 2008[Li, H., Chen, Z., Cheng, L., Liu, J., Chen, X. & Li, J. (2008). Cryst. Growth Des. 8, 4355-4358.]). Although the first preparation of the 1,1'-methylenedipyridinium dication, [(C5H5N)2CH2]2+, goes back to more than a century ago (Baer & Prescott, 1896[Baer, S. H. & Prescott, A. B. (1896). J. Am. Chem. Soc. 18, 988-989.]), its potential ability to form organic-inorganic hybrid salts has not been well exploited. However, countable organic-inorganic hybrid salts of 1,1'-methylenedipyridinium with mixed halo-osmium(IV) anions have been structurally characterized and reported, motivated by the investigations of octahedrally coordinated complexes, for example, trans-[(C5H5N)2CH2][OsF4Cl2]·H2O (Bruhn & Preetz, 1995a[Bruhn, C. & Preetz, W. (1995a). Acta Cryst. C51, 865-867.]), the isomeric pair fac- and mer-[(C5H5N)2CH2][OsCl3F3] (Bruhn & Preetz, 1995b[Bruhn, C. & Preetz, W. (1995b). Acta Cryst. C51, 1112-1116.]), the two isomers cis- and trans-[(C5H5N)2CH2][OsCl4F2] (Bruhn & Preetz, 1996[Bruhn, C. & Preetz, W. (1996). Acta Cryst. C52, 321-325.]), and cis-[(C5H5N)2CH2][OsBr2F4] (Höhling & Preetz, 1998[Höhling, M. & Preetz, W. (1998). Acta Cryst. C54, 481-483.]). The related complex salt [(C5H5N)2CH2][Cu(NCS)4] has also been described (Niu et al., 2008[Niu, Y.-Y., Wu, B.-L., Guo, X.-L., Song, Y.-L., Liu, X.-C., Zhang, H.-Y., Hou, H.-W., Niu, C.-Y. & Ng, S.-W. (2008). Cryst. Growth Des. 8, 2393-2401.]). This motivated us to synthesize a series of new organic-inorganic hybrid salts based on the 1,1'-methylenedipyridinium dication, which might have some applications in the field of materials science (Bonhomme & Kanatzidis, 1998[Bonhomme, F. & Kanatzidis, M. G. (1998). Chem. Mater. 10, 1153-1159.]; Wachhold & Kanatzidis, 2000[Wachhold, M. & Kanatzidis, M. G. (2000). Chem. Mater. 12, 2914-2923.]). Very recently, we reported the synthesis and molecular structure characterizations of the complex salts [(C5H5N)2CH2][MCl4] (M = Zn or Cd; Al-Ktaifani & Rukiah, 2011[Al-Ktaifani, M. M. & Rukiah, M. K. (2011). Chem. Pap. Chem. Zvesti, 65, 469-476.]) and [(C5H5N)2CH2][PtCln] (n = 4 or 6; Al-Ktaifani & Rukiah, 2012[Al-Ktaifani, M. M. & Rukiah, M. K. (2012). Chem. Pap. Chem. Zvesti, doi:10.2478/s11696-012-0221-8.]). In this article, the synthesis of 1,1'-methylenedipyridinium tetrachloridocuprate(II), [(C5H5N)2CH2][CuCl4], (I)[link], and 1,1'-methylenedipyridinium bis[tetrachloridoaurate(III)], [(C5H5N)2CH2][AuCl4]2, (II)[link], and their structural characterization by powder X-ray diffraction is presented.

[Scheme 1]

Compounds (I)[link] and (II)[link] have a tendency to crystallize in the form of a very fine yellow powder. Since no single crystal of sufficient size and quality could be obtained, a crystal structure determination by powder X-ray diffraction was applied. The crystal and molecular structures of (I)[link] and (II)[link] show discrete organic dications and a [CuCl4]2- anion for (I)[link] and two [AuCl4]- anions for (II)[link]. A view of the molecular structures of the two compounds with the atomic labelling is shown in Fig. 1[link]. The asymmetric unit of (I)[link] contains one half of the 1,1'-methylenedipyridinium dication and one half of a tetrachloridocuprate(II) anion, while the asymmetric unit of (II)[link] contains one half of a 1,1'-methylenedipyridinium dication and two half tetrachloridoaurate anions. In (I)[link], the methylene C atom and the CuII atom are located on a twofold axis. The CuII centre is four-coordinated in a distorted tetrahedral configuration by four Cl atoms [the largest Cl-Cu-Cl angle is 134.26 (18)°, while the smallest is 96.9 (3)°] with almost equal Cu-Cl bond distances [2.249 (5)-2.254 (4) Å] (Table 1[link]), which is comparable to observations for [(C2H5)4N][(CH3)4N][CuCl4] (Mahoui et al., 1996[Mahoui, A., Lapasset, J., Moret, J. & Saint Grégoire, P. (1996). Acta Cryst. C52, 2674-2676.]). For (II)[link], the methylene C atom is also located on a twofold axis, while the two AuIII centres and two Cl atoms of each [AuCl4]- anion are located on a mirror plane. Both AuIII centres have square-planar coordinations and the Au-Cl bond lengths [2.241 (15)-2.285 (9) Å] and angles (90°) are in good agreement with normal values (Table 3[link]) and very close to their corresponding average value in the related salt (C24H18N6)[AuCl4]2 (Abedi et al., 2011[Abedi, A., Dabbaghi, A. & Amani, V. (2011). Acta Cryst. E67, m1375-m1376.]). For both structures, the dication exhibits a butterfly shape, with all bond distances and angles similar and comparable to those in the related hybrid salts [(C5H5N)2CH2][MCl4] (M = Zn, Cd or Pt; Al-Ktaifani & Rukiah, 2011[Al-Ktaifani, M. M. & Rukiah, M. K. (2011). Chem. Pap. Chem. Zvesti, 65, 469-476.], 2012[Al-Ktaifani, M. M. & Rukiah, M. K. (2012). Chem. Pap. Chem. Zvesti, doi:10.2478/s11696-012-0221-8.]).

In the crystal structures of (I)[link] and (II)[link], weak intermolecular C-H...Cl hydrogen bonds (Tables 2[link] and 4[link]) link the molecules to form a one-dimensional chain along the a axis (Fig. 2[link]). These hydrogen bonds may be effective in the stabilization of the structures of (I)[link] and (II)[link]. The crystal packing of (I)[link] is also further stabilized by noncovalent [pi]-[pi] interactions (Hunter & Sanders, 1990[Hunter, C. A. & Sanders, J. K. M. (1990). J. Am. Chem. Soc. 112, 5525-5534.]; Janiak, 2000[Janiak, C. (2000). J. Chem. Soc. Dalton Trans. pp. 3885-3896.]) between pyridinium rings of adjacent dications [Cg1...Cg1(-x, -y, -z + 1) = 3.643 (8) Å, where Cg1 is the centroid of the N1/C2-C6 ring]. In a similar manner, the relatively short Cu1-Cl1...Cg1(x, y, z) distances [3.515 (7) Å] are also strong evidence for noncovalent Cl-[pi] interaction (Imai et al., 2008[Imai, Y. N., Inoue, Y., Nakanishi, I. & Kitaura, K. (2008). Protein Sci. 17, 1129-1137.]). In contrast to (I)[link], for (II)[link], the shortest intermolecular centroid-centroid distance between pyridinium rings [5.502 (9) Å] is too long for any significant [pi]-[pi] ring interactions (Janiak, 2000[Janiak, C. (2000). J. Chem. Soc. Dalton Trans. pp. 3885-3896.]), which might be attributed to the bulk of the two [AuCl4]- anions. However, the Au1-Cl2...Cg1(x, y, z + 1) and Au2-Cl6...Cg1(-x, -y + 1, z) distances [3.87 (2) and 3.57 (2) Å, respectively] also suggest Cl-[pi] interactions (Imai et al., 2008[Imai, Y. N., Inoue, Y., Nakanishi, I. & Kitaura, K. (2008). Protein Sci. 17, 1129-1137.]), which might play a role in controlling crystal packing. The AuIII...AuIII distance [4.245 (6) Å] in (II)[link] is longer than the sum of the van der Waals radii for gold (3.4 Å; Bondi, 1964[Bondi, A. (1964). J. Phys. Chem. 68, 441-451.]), suggesting there is no significant Au...Au interaction.

[Figure 1]
Figure 1
The molecular structures of (a) (I)[link] and (b) (II)[link], showing the atom-labelling schemes. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii. [Symmetry codes: (i) -x, y, -z + [{3\over 2}]; (ii) -x, -y + 1, z; (iii) -x + [{1\over 2}], y, z.]
[Figure 2]
Figure 2
Portions of the packing diagrams of (a) (I)[link] and (b) (II)[link]. Hydrogen bonds between molecules are indicated by dashed lines. [Symmetry codes: (i) -x - [{1\over 2}], y - [{1\over 2}], -z + [{3\over 2}]; (ii) -x, -y + 1, z - 1.]
[Figure 3]
Figure 3
The final Rietveld plots for (a) (I)[link] and (b) (II)[link]. Observed data points are indicated by dots and the best-fit profile (upper trace) and difference pattern (lower trace) are solid lines. The vertical bars indicate the positions of Bragg peaks.

Experimental

All reactions and manipulations were carried out in air with reagent-grade solvents. [(C5H5N)2CH2]Cl2·H2O was prepared according to the literature method of Almarzoqi et al. (1986[Almarzoqi, B., George, A. V. & Isaacs, N. S. (1986). Tetrahedron, 42, 601-607.]). CuCl2 (BDH, Germany) and Na[AuCl4] (Merck, Germany) were commercial samples and were used as received. 1H and 13C{1H} NMR spectra were recorded on a Bruker Bio spin 400 spectrometer. Microanalysis was performed using EURO EA.

For the synthesis of (I)[link], a solution of [(C5H5N)2CH2]Cl2·H2O (0.22 g, 0.82 mmol) in H2O (3 ml) was added to a solution of CuCl2 (0.114 g, 0.82 mmol) in H2O (3 ml) at room temperature and the mixture stirred overnight. The solvent was then removed in vacuo to afford (I)[link] quantitatively, which was washed with EtOH to afford a yellow powder [yield: 237 mg, 75%; m.p. 493 K (with decomposition)]. For the synthesis of (II)[link], a solution of [(C5H5N)2CH2]Cl2·H2O (0.05 g, 0.19 mmol) in H2O (3 ml) was added to a solution of Na[AuCl4] (0.130 g, 0.38 mmol) in H2O (3 ml) with rapid stirring at ambient temperature. The resulting solution was stirred for 18 h to give an orange-yellow precipitate. The obtained product was filtered off and washed with EtOH to give an orange-yellow powder (yield 115 mg, 71%; m.p. 561 K).

Both salts were obtained as air-stable yellow powdery products and were highly insoluble in common organic solvents. However, although (I)[link] is water soluble, (II)[link] is not, but each has a good solubility in dimethyl sulfoxide (DMSO). The obtained organic-inorganic hybrid salts (I)[link] and (II)[link] were isolated as pure products and fully characterized by multinuclear NMR and elemental analyses, and their molecular structures were confirmed by powder X-ray diffraction studies. Analytical data for C11H12Cl4CuN2, (I)[link]: found C 35.54, H 3.20, N 7.39%; required C 34.99, H 3.21, N 7.41%. 1H NMR (DMSO-d6): [delta] 7.46 (s, 2H, CH2), 8.33 (m, 4H, py), 8.80 (m, 2H, py), 9.72 (m, 4H, py); 13C{1H} NMR (DMSO-d6): [delta] 76.81 (CH2), 129.23 (py), 146.48 (py), 149.20 (py). Analytical data for C11H12Au2Cl8N2, (II)[link]: found C 15.05, H 1.32, N 2.94%; required C 15.45, H 1.42, N 3.29%. 1H NMR (DMSO-d6): [delta] 7.26 (s, 2H, CH2), 8.33 (m, 4H, py), 8.80 (m, 2H, py), 9.45 (m, 4H, py). 13C{1H} NMR (DMSO-d6): [delta] 77.53 (CH2), 129.21 (py), 146.32 (py), 149.27 (py).

Compound (I)[link]

Crystal data
  • (C11H12N2)[CuCl4]

  • Mr = 377.59

  • Monoclinic, C 2/c

  • a = 9.90009 (11) Å

  • b = 9.94558 (11) Å

  • c = 15.0359 (2) Å

  • [beta] = 102.4903 (8)°

  • V = 1445.43 (4) Å3

  • Z = 4

  • Cu K[alpha]1 radiation

  • [lambda] = 1.5406 Å

  • [mu] = 8.79 mm-1

  • T = 298 K

  • flat sheet, 8 × 8 mm

Data collection
  • Stoe Stadi-P transmission diffractometer

  • Specimen mounting: powder loaded between two Mylar foils

  • Data collection mode: transmission

  • Scan method: step

  • Absorption correction: for a cylinder mounted on the [varphi] axis (GSAS; Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). GSAS Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.]) Tmin = 0.125, Tmax = 0.230

  • 2[theta]min = 8.005°, 2[theta]max = 89.985°, 2[theta]step = 0.02°

Refinement
  • Rp = 0.036

  • Rwp = 0.050

  • Rexp = 0.028

  • R(F2) = 0.02794

  • [chi]2 = 3.497

  • 4100 data points

  • 204 parameters

  • 24 restraints

  • H-atom parameters not refined

Table 1
Selected geometric parameters (Å, °) for (I)[link]

Cu1-Cl1 2.254 (4)
Cu1-Cl2 2.249 (5)
Cl1-Cu1-Cl1i 96.9 (3)
Cl1-Cu1-Cl2 98.20 (17)
Cl1-Cu1-Cl2i 134.26 (18)
Cl2-Cu1-Cl2i 101.4 (3)
C2-N1-C1-N1i 63.2 (13)
C6-N1-C1-N1i -116.8 (12)
Symmetry code: (i) [-x, y, -z+{\script{3\over 2}}].

Table 2
Hydrogen-bond geometry (Å, °) for (I)[link]

D-H...A D-H H...A D...A D-H...A
C1-H1a...Cl1ii 0.98 2.67 3.518 (9) 145
Symmetry code: (ii) [-x-{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}].

Compound (II)[link]

Crystal data
  • (C11H12N2)[AuCl4]2

  • Mr = 849.79

  • Orthorhombic, I m a 2

  • a = 15.61545 (11) Å

  • b = 17.6525 (3) Å

  • c = 7.56300 (6) Å

  • V = 2084.76 (4) Å3

  • Z = 4

  • Cu K[alpha]1 radiation

  • [lambda] = 1.5406 Å

  • [mu] = 35.51 mm-1

  • T = 298 K

  • flat sheet, 8 × 8 mm

Data collection
  • Stoe Stadi-P transmission diffractometer

  • Specimen mounting: powder loaded between two Mylar foils

  • Data collection mode: transmission

  • Scan method: step

  • Absorption correction: for a cylinder mounted on the [varphi] axis (GSAS; Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). GSAS Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.]) Tmin = 0.181, Tmax = 0.307

  • 2[theta]min = 5.009°, 2[theta]max = 91.989°, 2[theta]step = 0.02°

Refinement
  • Rp = 0.032

  • Rwp = 0.043

  • Rexp = 0.017

  • R(F2) = 0.02683

  • [chi]2 = 6.760

  • 4350 data points

  • 106 parameters

  • 26 restraints

  • H-atom parameters not refined

Table 3
Selected geometric parameters (Å, °) for (II)[link]

Au1-Cl1 2.272 (17)
Au1-Cl2 2.285 (9)
Au1-Cl3 2.241 (15)
Au2-Cl4 2.255 (18)
Au2-Cl5 2.299 (15)
Au2-Cl6 2.272 (9)
Cl1-Au1-Cl2 92.2 (3)
Cl2-Au1-Cl3 87.9 (3)
Cl4-Au2-Cl6 87.5 (3)
Cl5-Au2-Cl6 92.5 (3)
C2-N1-C1-N1i -70.4 (16)
C6-N1-C1-N1i 118.2 (14)
Symmetry code: (i) -x, -y+1, z.

Table 4
Hydrogen-bond geometry (Å, °) for (II)[link]

D-H...A D-H H...A D...A D-H...A
C1-H1C1...Cl2ii 0.98 2.79 3.456 (18) 126
C6-H1C6...Cl5ii 0.99 2.81 3.492 (19) 127
Symmetry code: (ii) -x, -y+1, z-1.

Pattern indexing was performed with the program DICVOL6.0 (Boultif & Louër, 2004[Boultif, A. & Louër, D. (2004). J. Appl. Cryst. 37, 724-731.]). The first 20 lines of the powder pattern were completely indexed on the basis of a monoclinic cell for (I)[link] and an orthorhombic cell for (II)[link]. The figures of merit are sufficiently acceptable to support the obtained indexing results [M(20) = 16.5, F(20) = 34.2(0.0072, 81)] for (I)[link] and [M(20) = 20.4, F(20) = 30.7(0.0085, 77)] for (II)[link]. The best estimated space groups were C2/c in the monoclinic system for (I)[link] and Ima2 in the orthorhombic system for (II)[link].

The initial structure of (I)[link] was solved ab initio by direct methods using the program EXPO2009 (Altomare et al., 2009[Altomare, A., Camalli, M., Cuocci, C., Giacovazzo, C., Moliterni, A. & Rizzi, R. (2009). J. Appl. Cryst. 42, 1197-1202.]), while the direct space method was used by the program FOX (Favre-Nicolin & Cerný, 2002[Favre-Nicolin, V. & Cerný, R. (2002). J. Appl. Cryst. 35, 734-743.]) for determination of the initial structure of (II)[link]. The models found by these programs were introduced in the program GSAS (Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). GSAS Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.]) implemented in EXPGUI (Toby, 2001[Toby, B. H. (2001). J. Appl. Cryst. 34, 210-213.]) for Rietveld refinements. The background was refined using a shifted Chebyshev polynomial with 20 coefficients. The Thompson-Cox-Hastings (Thompson et al., 1987[Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79-83.]) pseudo-Voigt profile function was used with corrections for axial divergence peak asymmetry (Finger et al., 1994[Finger, L. W., Cox, D. E. & Jephcoat, A. P. (1994). J. Appl. Cryst. 27, 892-900.]) and microstrain broadening, as described by Stephens (1999[Stephens, P. W. (1999). J. Appl. Cryst. 32, 281-289.]). The two asymmetry parameters of this function, S/L and D/L, were both fixed at 0.022 during the Rietveld refinement. Intensities were corrected from absorption effects with a [mu]d value of 0.9500 for (I)[link] and 0.7646 for (II)[link] ([mu] is the absorption coefficient and d is the sample thickness; these values were determined experimentally). A spherical harmonics correction (Von Dreele, 1997[Von Dreele, R. B. (1997). J. Appl. Cryst. 30, 517-525.]) of intensities for preferred orientation was applied in the final refinement with 18 coefficients for (I)[link] and eight coefficients for (II)[link]. The use of the preferred orientation correction leads to better molecular geometry with better agreement factors. Planar group restraints to the pyridinium ring including their H atoms were applied for both structures. Non-H atoms were not restrained for (I)[link], but for (II)[link] a restraint on bond length for the distance between the methylene C and pyridinium N atoms was applied to a normal value for this bond [1.484 (9) Å]. Before the final refinement, H atoms were introduced from geometrical arguments. The coordinates of these H atoms were not refined for both structures. The final refinement cycles were performed using anisotropic atomic displacement parameters for the Cu and Cl atoms of (I)[link] and for the Au atoms only of (II)[link]. Isotropic atomic displacement parameters for C and N atoms were used for both (I)[link] and (II)[link], while fixed global isotropic atomic displacement parameters [0.050 Å2 for (I)[link] and 0.075 Å2 for (II)] were introduced for H atoms. The final Rietveld plots of the X-ray diffraction patterns for both (I)[link] and (II)[link] are given in Fig. 3[link].

For both compounds, data collection: WinXPOW (Stoe & Cie, 1999[Stoe & Cie (1999). WinXPOW. Stoe & Cie, Darmstadt, Germany.]); cell refinement: GSAS (Larson & Von Dreele, 2004[Larson, A. C. & Von Dreele, R. B. (2004). GSAS Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.]); data reduction: WinXPOW. Program(s) used to solve structure: EXPO2009 (Altomare et al., 2009[Altomare, A., Camalli, M., Cuocci, C., Giacovazzo, C., Moliterni, A. & Rizzi, R. (2009). J. Appl. Cryst. 42, 1197-1202.]) for (I); FOX (Favre-Nicolin & Cerný, 2002[Favre-Nicolin, V. & Cerný, R. (2002). J. Appl. Cryst. 35, 734-743.]) for (II). For both compounds, program(s) used to refine structure: GSAS; molecular graphics: ORTEP-3 (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).


Supplementary data for this paper are available from the IUCr electronic archives (Reference: SK3441 ). Services for accessing these data are described at the back of the journal.


Acknowledgements

We thank Professor I. Othman, Director General, and Professor T. Yassine, Head of the Chemistry Department, for their support of this work. We also thank Chem. R. Al Sabeq, A. Habeb, Waleed Alkalaf and Marouf Mamouli for their assistance with some of the laboratory work. Finally, many thanks are due to Professor John F. Nixon (Sussex University, England) for kindly providing a gift of sodium tetrachloridoaurate(III).

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Acta Cryst (2012). C68, m246-m250   [ doi:10.1107/S0108270112031885 ]