Bis[μ-(E)-N-(pyridin-3-yl­methyl­idene)hy­droxy­amine]-κ2N1:N3;κ2N3:N1-bis­{[(E)-N-(pyridin-3-yl­methyl­idene-κN)hy­droxy­amine]­silver(I)} dinitrate

Gao, S.; Ng, S.W.

doi:10.1107/S1600536812045898

metal-organic compounds

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ISSN: 2056-9890

Volume 68| Part 12| December 2012| Page m1547

doi:10.1107/S1600536812045898

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Bis[μ-(E)-N-(pyridin-3-ylmethylidene)hydroxyamine]-κ²N¹:N³;κ²N³:N¹-bis{[(E)-N-(pyridin-3-ylmethylidene-κN)hydroxyamine]silver(I)} dinitrate

Shan Gao ^a and Seik Weng Ng ^b,^c ^*

^aKey Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, Heilongjiang University, Harbin 150080, People's Republic of China, ^bDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia, and ^cChemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203 Jeddah, Saudi Arabia
^*Correspondence e-mail: seikweng@um.edu.my

(Received 4 November 2012; accepted 6 November 2012; online 28 November 2012)

In the centrosymmetric dinuclear title Ag^I compound, [Ag₂(C₆H₆N₂O)₄](NO₃)₂, the aromatic amine-coordinated Ag^I atom is further bridged by two hydroxylamine molecules that use aromatic and oxime N atoms for bridging, and it exists in a distorted trigonal-planar geometry. In the crystal, the nitrate anions link to the dinuclear compound molecules via O—H⋯O hydrogen bonds, generating a chain running along the a-axis direction.

Related literature

For bis(nicotinylaldehyde oxime)silver perchlorate, see: Xu et al. (2012 ) and for (nitrato)(picolinaldehyde oxime)silver, see: Abu-Youssef et al. (2010 ).

Experimental

Crystal data

[Ag₂(C₆H₆N₂O)₄](NO₃)₂
M_r = 828.27
Triclinic, $[P \overline 1]$
a = 7.2913 (10) Å
b = 8.3395 (10) Å
c = 13.1415 (17) Å
α = 92.934 (4)°
β = 95.008 (4)°
γ = 111.360 (3)°
V = 738.38 (16) Å³
Z = 1
Mo Kα radiation
μ = 1.40 mm⁻¹
T = 293 K
0.24 × 0.21 × 0.17 mm

Data collection

Rigaku R-AXIS RAPID IP diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ) T_min = 0.730, T_max = 0.797
7293 measured reflections
3341 independent reflections
2896 reflections with I > 2σ(I)
R_int = 0.035

Refinement

R[F² > 2σ(F²)] = 0.040
wR(F²) = 0.107
S = 1.11
3341 reflections
210 parameters
H-atom parameters constrained
Δρ_max = 1.71 e Å⁻³
Δρ_min = −0.34 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O3ⁱ	0.84	2.39	3.189 (6)	158
O1—H1⋯O4ⁱ	0.84	2.20	2.925 (5)	145
O2—H2⋯O4ⁱⁱ	0.84	1.92	2.745 (4)	169
Symmetry codes: (i) -x+2, -y+1, -z+1; (ii) -x+2, -y+2, -z.

Data collection: RAPID-AUTO (Rigaku, 1998 ); cell refinement: RAPID-AUTO; data reduction: CrystalClear (Rigaku/MSC, 2002 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536812045898/xu5646sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812045898/xu5646Isup2.hkl

checkCIF report

Comment top

A previous study on the adducts of silver salts with nicotinylaldehyde oxime reported the salt, [Ag(C₆H₆N₂O)₂] ClO₄; the metal atom shows linear coordination (Xu et al., 2012). The aromatic amine-coordinated Ag^I atom in dinuclear [Ag(C₆H₆N₂O)₂]₂ 2NO₃ is bridged by another hydroxylamine molecule that uses its aromatic and oxime N atoms for bridging, and it exists in a trigonal planar geometry (Scheme I, Fig. 1). The hydroxyl OH groups forms H atoms to the nitrate O atoms of adjacent molecules to generate a chain running along the shortest axis of the orthorhombic unit cell (Table 1).

With picolinylaldehyde oxime in place of nicotinylaldehyde oxime, the synthesis yields the monomeric adduct in which the metal atom is chelated by the ligand (Abu-Youssef et al., 2010).

Related literature top

For bis(nicotinylaldehyde oxime)silver perchlorate, see: Xu et al. (2012) and for (nitrato)(picolinaldehyde oxime)silver, see: Abu-Youssef et al. (2010).

Experimental top

Nicotinyladehyde oxime was synthesized from the reaction of nicotinylaldehyde and hydroxylamine. Silver nitrate (1 mmol) dissolved in water (5 ml) was added to nicotinylaldehyde oxime (1 mmol) dissolved in ethanol (5 ml). The solution was filtered and set aside, away from light, for the growth of colorless crystals.

Computing details top

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalClear (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of [Ag(C₆H₆N₂O)₂]₂ 2NO₃ at the 50% probability level; hydrogen atoms are drawn as spheres of arbitrary radius.

Bis[µ-(E)-N-(pyridin-3-ylmethylidene)hydroxyamine]- κ²N¹:N³;κ²N³:N¹-bis{[(E)- N-(pyridin-3-ylmethylidene-κN)hydroxyamine]silver(I)} dinitrate top

Crystal data top

[Ag₂(C₆H₆N₂O)₄](NO₃)₂	Z = 1
M_r = 828.27	F(000) = 412
Triclinic, P1	D_x = 1.863 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.2913 (10) Å	Cell parameters from 6130 reflections
b = 8.3395 (10) Å	θ = 3.0–27.4°
c = 13.1415 (17) Å	µ = 1.40 mm⁻¹
α = 92.934 (4)°	T = 293 K
β = 95.008 (4)°	Prism, colorless
γ = 111.360 (3)°	0.24 × 0.21 × 0.17 mm
V = 738.38 (16) Å³

Data collection top

Rigaku R-AXIS RAPID IP diffractometer	3341 independent reflections
Radiation source: fine-focus sealed tube	2896 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.035
ω scan	θ_max = 27.4°, θ_min = 3.0°
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	h = −9→9
T_min = 0.730, T_max = 0.797	k = −10→10
7293 measured reflections	l = −17→16

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.107	H-atom parameters constrained
S = 1.11	w = 1/[σ²(F_o²) + (0.056P)² + 0.3361P] where P = (F_o² + 2F_c²)/3
3341 reflections	(Δ/σ)_max = 0.001
210 parameters	Δρ_max = 1.71 e Å⁻³
0 restraints	Δρ_min = −0.34 e Å⁻³

Crystal data top

[Ag₂(C₆H₆N₂O)₄](NO₃)₂	γ = 111.360 (3)°
M_r = 828.27	V = 738.38 (16) Å³
Triclinic, P1	Z = 1
a = 7.2913 (10) Å	Mo Kα radiation
b = 8.3395 (10) Å	µ = 1.40 mm⁻¹
c = 13.1415 (17) Å	T = 293 K
α = 92.934 (4)°	0.24 × 0.21 × 0.17 mm
β = 95.008 (4)°

Data collection top

Rigaku R-AXIS RAPID IP diffractometer	3341 independent reflections
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	2896 reflections with I > 2σ(I)
T_min = 0.730, T_max = 0.797	R_int = 0.035
7293 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	0 restraints
wR(F²) = 0.107	H-atom parameters constrained
S = 1.11	Δρ_max = 1.71 e Å⁻³
3341 reflections	Δρ_min = −0.34 e Å⁻³
210 parameters

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Ag1	0.38614 (4)	0.61092 (3)	0.314850 (18)	0.04700 (13)
O1	1.0366 (4)	0.7195 (3)	0.7651 (2)	0.0501 (6)
H1	1.0758	0.6378	0.7541	0.075*
O2	0.9485 (4)	1.1845 (3)	−0.0856 (2)	0.0522 (6)
H2	0.9451	1.2272	−0.1419	0.078*
O3	0.7359 (7)	0.5156 (5)	0.3151 (4)	0.1102 (16)
O4	1.0106 (5)	0.6444 (5)	0.2602 (3)	0.0751 (10)
O5	0.8581 (6)	0.7867 (4)	0.3354 (3)	0.0792 (10)
N1	0.4261 (4)	0.7161 (4)	0.4767 (2)	0.0393 (6)
N2	0.8633 (4)	0.6911 (4)	0.7003 (2)	0.0426 (6)
N3	0.4227 (4)	0.6552 (4)	0.1507 (2)	0.0393 (6)
N4	0.7795 (4)	1.0353 (4)	−0.0856 (2)	0.0411 (6)
N5	0.8690 (4)	0.6504 (4)	0.3059 (2)	0.0436 (7)
C1	0.2918 (5)	0.5528 (4)	0.0748 (3)	0.0420 (7)
H1A	0.1875	0.4574	0.0915	0.050*
C2	0.3047 (5)	0.5827 (4)	−0.0277 (3)	0.0438 (7)
H2A	0.2104	0.5087	−0.0783	0.053*
C3	0.4576 (5)	0.7221 (4)	−0.0537 (3)	0.0410 (7)
H3	0.4689	0.7437	−0.1220	0.049*
C4	0.5962 (5)	0.8315 (4)	0.0240 (2)	0.0354 (6)
C5	0.5728 (5)	0.7911 (4)	0.1242 (2)	0.0366 (6)
H5	0.6663	0.8621	0.1762	0.044*
C6	0.7622 (5)	0.9865 (4)	0.0046 (3)	0.0375 (7)
H6	0.8559	1.0499	0.0586	0.045*
C7	0.3097 (5)	0.7957 (4)	0.5116 (3)	0.0430 (7)
H7	0.1944	0.7853	0.4708	0.052*
C8	0.3541 (5)	0.8913 (4)	0.6046 (3)	0.0429 (7)
H8	0.2721	0.9467	0.6256	0.051*
C9	0.5228 (5)	0.9041 (4)	0.6669 (3)	0.0407 (7)
H9	0.5570	0.9704	0.7296	0.049*
C10	0.6402 (5)	0.8177 (4)	0.6350 (2)	0.0361 (6)
C11	0.5871 (5)	0.7270 (4)	0.5384 (2)	0.0369 (6)
H11	0.6675	0.6713	0.5156	0.044*
C12	0.8170 (5)	0.8228 (4)	0.6996 (2)	0.0396 (7)
H12	0.8952	0.9234	0.7401	0.048*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ag1	0.05390 (19)	0.0543 (2)	0.03057 (17)	0.01848 (14)	0.00080 (12)	0.00222 (11)
O1	0.0459 (13)	0.0570 (15)	0.0475 (15)	0.0220 (12)	−0.0050 (11)	0.0026 (11)
O2	0.0459 (13)	0.0490 (14)	0.0565 (16)	0.0103 (11)	0.0045 (12)	0.0153 (12)
O3	0.101 (3)	0.062 (2)	0.155 (5)	0.007 (2)	0.035 (3)	0.043 (3)
O4	0.0682 (19)	0.124 (3)	0.062 (2)	0.064 (2)	0.0219 (16)	0.034 (2)
O5	0.100 (3)	0.0675 (19)	0.079 (2)	0.0441 (19)	0.009 (2)	−0.0041 (16)
N1	0.0458 (14)	0.0412 (14)	0.0277 (13)	0.0131 (12)	0.0010 (11)	0.0040 (10)
N2	0.0430 (14)	0.0408 (14)	0.0401 (15)	0.0129 (12)	−0.0037 (12)	0.0043 (11)
N3	0.0400 (14)	0.0462 (15)	0.0333 (14)	0.0179 (12)	0.0039 (11)	0.0034 (11)
N4	0.0401 (14)	0.0401 (14)	0.0439 (16)	0.0154 (12)	0.0063 (12)	0.0039 (12)
N5	0.0483 (16)	0.0521 (17)	0.0383 (15)	0.0257 (15)	0.0081 (13)	0.0138 (13)
C1	0.0393 (16)	0.0407 (17)	0.0425 (18)	0.0106 (14)	0.0054 (14)	0.0021 (13)
C2	0.0442 (17)	0.0446 (17)	0.0386 (18)	0.0150 (15)	−0.0037 (14)	−0.0056 (14)
C3	0.0471 (18)	0.0475 (18)	0.0297 (15)	0.0197 (15)	0.0012 (14)	0.0024 (13)
C4	0.0349 (14)	0.0415 (16)	0.0328 (15)	0.0178 (13)	0.0035 (12)	0.0027 (12)
C5	0.0352 (15)	0.0437 (16)	0.0310 (15)	0.0163 (13)	−0.0002 (12)	−0.0023 (12)
C6	0.0367 (15)	0.0424 (16)	0.0373 (17)	0.0203 (14)	0.0013 (13)	0.0012 (13)
C7	0.0394 (16)	0.0468 (17)	0.0443 (19)	0.0166 (15)	0.0061 (14)	0.0098 (14)
C8	0.0470 (17)	0.0457 (18)	0.0413 (18)	0.0210 (15)	0.0138 (15)	0.0082 (14)
C9	0.0530 (19)	0.0390 (16)	0.0322 (16)	0.0188 (15)	0.0093 (14)	0.0022 (12)
C10	0.0424 (16)	0.0309 (14)	0.0319 (15)	0.0097 (13)	0.0039 (13)	0.0057 (11)
C11	0.0439 (16)	0.0315 (14)	0.0356 (16)	0.0141 (13)	0.0066 (13)	0.0021 (12)
C12	0.0455 (17)	0.0385 (16)	0.0315 (16)	0.0129 (14)	0.0015 (13)	−0.0022 (12)

Geometric parameters (Å, º) top

Ag1—N1	2.212 (3)	C2—C3	1.369 (5)
Ag1—N3	2.229 (3)	C2—H2A	0.9300
Ag1—N2ⁱ	2.498 (3)	C3—C4	1.396 (5)
O1—N2	1.397 (4)	C3—H3	0.9300
O1—H1	0.8400	C4—C5	1.385 (4)
O2—N4	1.396 (4)	C4—C6	1.466 (5)
O2—H2	0.8400	C5—H5	0.9300
O3—N5	1.208 (5)	C6—H6	0.9300
O4—N5	1.255 (4)	C7—C8	1.370 (5)
O5—N5	1.214 (4)	C7—H7	0.9300
N1—C11	1.339 (4)	C8—C9	1.383 (5)
N1—C7	1.349 (5)	C8—H8	0.9300
N2—C12	1.262 (4)	C9—C10	1.381 (5)
N2—Ag1ⁱ	2.498 (3)	C9—H9	0.9300
N3—C1	1.337 (5)	C10—C11	1.392 (4)
N3—C5	1.344 (4)	C10—C12	1.466 (5)
N4—C6	1.274 (4)	C11—H11	0.9300
C1—C2	1.387 (5)	C12—H12	0.9300
C1—H1A	0.9300

N1—Ag1—N3	149.49 (11)	C5—C4—C3	117.7 (3)
N1—Ag1—N2ⁱ	107.79 (10)	C5—C4—C6	119.0 (3)
N3—Ag1—N2ⁱ	101.48 (10)	C3—C4—C6	123.3 (3)
N2—O1—H1	109.5	N3—C5—C4	123.8 (3)
N4—O2—H2	109.5	N3—C5—H5	118.1
C11—N1—C7	117.6 (3)	C4—C5—H5	118.1
C11—N1—Ag1	119.9 (2)	N4—C6—C4	120.7 (3)
C7—N1—Ag1	121.6 (2)	N4—C6—H6	119.6
C12—N2—O1	112.4 (3)	C4—C6—H6	119.6
C12—N2—Ag1ⁱ	123.3 (2)	N1—C7—C8	122.8 (3)
O1—N2—Ag1ⁱ	115.10 (18)	N1—C7—H7	118.6
C1—N3—C5	117.2 (3)	C8—C7—H7	118.6
C1—N3—Ag1	121.6 (2)	C7—C8—C9	119.0 (3)
C5—N3—Ag1	121.1 (2)	C7—C8—H8	120.5
C6—N4—O2	110.6 (3)	C9—C8—H8	120.5
O3—N5—O5	120.1 (4)	C10—C9—C8	119.5 (3)
O3—N5—O4	117.9 (4)	C10—C9—H9	120.3
O5—N5—O4	121.9 (4)	C8—C9—H9	120.3
N3—C1—C2	122.8 (3)	C9—C10—C11	117.8 (3)
N3—C1—H1A	118.6	C9—C10—C12	121.5 (3)
C2—C1—H1A	118.6	C11—C10—C12	120.6 (3)
C3—C2—C1	119.4 (3)	N1—C11—C10	123.3 (3)
C3—C2—H2A	120.3	N1—C11—H11	118.4
C1—C2—H2A	120.3	C10—C11—H11	118.4
C2—C3—C4	119.0 (3)	N2—C12—C10	120.1 (3)
C2—C3—H3	120.5	N2—C12—H12	119.9
C4—C3—H3	120.5	C10—C12—H12	119.9

N3—Ag1—N1—C11	−93.9 (3)	O2—N4—C6—C4	−179.6 (3)
N2ⁱ—Ag1—N1—C11	103.1 (2)	C5—C4—C6—N4	−174.4 (3)
N3—Ag1—N1—C7	75.2 (3)	C3—C4—C6—N4	4.9 (5)
N2ⁱ—Ag1—N1—C7	−87.8 (3)	C11—N1—C7—C8	2.6 (5)
N1—Ag1—N3—C1	−147.5 (3)	Ag1—N1—C7—C8	−166.8 (2)
N2ⁱ—Ag1—N3—C1	16.0 (3)	N1—C7—C8—C9	−1.5 (5)
N1—Ag1—N3—C5	29.4 (4)	C7—C8—C9—C10	−1.4 (5)
N2ⁱ—Ag1—N3—C5	−167.1 (2)	C8—C9—C10—C11	2.9 (4)
C5—N3—C1—C2	−0.6 (5)	C8—C9—C10—C12	−178.1 (3)
Ag1—N3—C1—C2	176.4 (3)	C7—N1—C11—C10	−0.9 (5)
N3—C1—C2—C3	0.2 (5)	Ag1—N1—C11—C10	168.7 (2)
C1—C2—C3—C4	−0.4 (5)	C9—C10—C11—N1	−1.8 (5)
C2—C3—C4—C5	0.9 (5)	C12—C10—C11—N1	179.2 (3)
C2—C3—C4—C6	−178.4 (3)	O1—N2—C12—C10	179.4 (3)
C1—N3—C5—C4	1.2 (5)	Ag1ⁱ—N2—C12—C10	−35.6 (4)
Ag1—N3—C5—C4	−175.8 (2)	C9—C10—C12—N2	144.0 (3)
C3—C4—C5—N3	−1.4 (5)	C11—C10—C12—N2	−37.1 (5)
C6—C4—C5—N3	178.0 (3)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3ⁱⁱ	0.84	2.39	3.189 (6)	158
O1—H1···O4ⁱⁱ	0.84	2.20	2.925 (5)	145
O2—H2···O4ⁱⁱⁱ	0.84	1.92	2.745 (4)	169

Symmetry codes: (ii) −x+2, −y+1, −z+1; (iii) −x+2, −y+2, −z.

Experimental details

Crystal data
Chemical formula	[Ag₂(C₆H₆N₂O)₄](NO₃)₂
M_r	828.27
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	7.2913 (10), 8.3395 (10), 13.1415 (17)
α, β, γ (°)	92.934 (4), 95.008 (4), 111.360 (3)
V (Å³)	738.38 (16)
Z	1
Radiation type	Mo Kα
µ (mm⁻¹)	1.40
Crystal size (mm)	0.24 × 0.21 × 0.17

Data collection
Diffractometer	Rigaku R-AXIS RAPID IP diffractometer
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995)
T_min, T_max	0.730, 0.797
No. of measured, independent and observed [I > 2σ(I)] reflections	7293, 3341, 2896
R_int	0.035
(sin θ/λ)_max (Å⁻¹)	0.648

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.107, 1.11
No. of reflections	3341
No. of parameters	210
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.71, −0.34

Computer programs: RAPID-AUTO (Rigaku, 1998), CrystalClear (Rigaku/MSC, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O3ⁱ	0.84	2.39	3.189 (6)	158.3
O1—H1···O4ⁱ	0.84	2.20	2.925 (5)	145.0
O2—H2···O4ⁱⁱ	0.84	1.92	2.745 (4)	168.6

Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+2, −y+2, −z.

Acknowledgements

We thank the Key Project of the Natural Science Foundation of Heilongjiang Province (No. ZD200903), the Key Project of the Education Bureau of Heilongjiang Province (Nos. 12511z023 and 2011CJHB006), the Innovation Team of the Education Bureau of Heilongjiang Province (No. 2010 t d03), Heilongjiang University (Hdtd2010–04) and the Ministry of Higher Education of Malaysia (grant No. UM.C/HIR/MOHE/SC/12) for supporting this study.

References

Abu-Youssef, M. A., Soliman, S. V., Langer, V., Gohar, Y. M., Hasanen, A. A., Makhyoun, M. A., Zaky, A. H. & Öhrström, L. R. (2010). Inorg. Chem. 49, 9788–9797. Web of Science CAS PubMed Google Scholar
Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. CrossRef CAS Google Scholar
Higashi, T. (1995). ABSCOR. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku (1998). RAPID-AUTO. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku/MSC (2002). CrystalClear. Rigaku/MSC Inc., The Woodlands, Texas, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar
Xu, J., Gao, S., Ng, S. W. & Tiekink, E. R. T. (2012). Acta Cryst. E68, m735–m736. CSD CrossRef IUCr Journals Google Scholar

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