Hexakis(1H-imidazole-κN3)cobalt(III) tris­(hexa­fluoridophosphate) hexa­hydrate

Surdykowski, A.; Łęczkowska, A.; Dobrzańska, L.; Szłyk, E.

doi:10.1107/S160053680903863X

metal-organic compounds

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ISSN: 2056-9890

Volume 65| Part 10| October 2009| Pages m1256-m1257

doi:10.1107/S160053680903863X

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Hexakis(1H-imidazole-κN³)cobalt(III) tris(hexafluoridophosphate) hexahydrate

Andrzej Surdykowski,^a Anna Łęczkowska,^a Liliana Dobrzańska ^b ^* and Edward Szłyk ^a

^aFaculty of Chemistry, Nicolaus Copernicus University, Gagarina 7, 87-100 Toruń, Poland, and ^bDepartment of Chemistry, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa
^*Correspondence e-mail: lianger@sun.ac.za

(Received 23 September 2009; accepted 24 September 2009; online 30 September 2009)

In the crystal structure of the title compound, [Co(C₃H₄N₂)₆](PF₆)₃·6H₂O, the Co^III atom lies on a special position with site-symmetry $[\overline{3}]$ and the P atom is located on a special position with site symmetry $[\overline{1}]$ . The Co^III atom has an almost ideal octahedral coordination formed by the N atoms of six imidazole ligands. The water molecules form hydrogen-bonded helical chains propagating in [001] by O—H⋯O interactions with a distance of 2.913 (2) Å. They simultaneously interact as hydrogen-bond acceptors and donors with the cations and anions, respectively, resulting in the formation of a three-dimensional assembly. Weak C—H⋯F interactions further stabilize the crystal structure.

Related literature

For Co^III complexes with heterocycles, see: Wojtczak et al. (1990 ); Pazderski et al. (2008 ). For the hexakis(imidazole)-cobalt(III) ion in solution, see: Navon & Panigel (1989 ); Wiśniewska & Kita (2006 ). For Co—N bond distances in hexakis(imidazole)-cobalt(II) complexes, see: Tong et al. (2002 ). For Co^III—N and Co^II—N bond lengths in hexaammine–cobalt complexes, see: Kime & Ibers (1969 ). The water molecules present in the crystal structure form helical chains similar to those observed in a trichlorophloroglucinol structure, see: Saha & Nangia (2005 ).

Experimental

Crystal data

[Co(C₃H₄N₂)₆](PF₆)₃·6H₂O
M_r = 1010.43
Trigonal, $[R \overline 3]$
a = 20.9911 (13) Å
c = 7.0156 (9) Å
V = 2677.1 (4) Å³
Z = 3
Mo Kα radiation
μ = 0.77 mm⁻¹
T = 100 K
0.25 × 0.25 × 0.21 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1997 ) T_min = 0.832, T_max = 0.856
4893 measured reflections
1373 independent reflections
1288 reflections with I > 2σ(I)
R_int = 0.026

Refinement

R[F² > 2σ(F²)] = 0.031
wR(F²) = 0.083
S = 1.08
1373 reflections
98 parameters
3 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.54 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H6⋯O1ⁱ	0.96 (3)	1.98 (3)	2.913 (2)	163 (3)
N3—H3⋯O1	0.88	1.98	2.834 (2)	165
O1—H7⋯F3ⁱⁱ	0.96 (3)	2.10 (3)	2.945 (2)	146 (2)
C2—H2⋯F3ⁱⁱⁱ	0.95	2.34	3.042 (2)	131
C4—H4⋯F1^iv	0.95	2.40	3.303 (2)	158
Symmetry codes: (i) $[-y+{\script{2\over 3}}, x-y+{\script{1\over 3}}, z+{\script{1\over 3}}]$ ; (ii) x-y, x, -z+1; (iii) $[-x+{\script{2\over 3}}, -y+{\script{1\over 3}}, -z+{\script{1\over 3}}]$ ; (iv) $[-x+y+{\script{1\over 3}}, -x+{\script{2\over 3}}, z+{\script{2\over 3}}]$ .

Data collection: SMART (Bruker, 2001 ); cell refinement: SAINT (Bruker, 2002 ); data reduction: SAINT; 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: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053680903863X/hg2572sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053680903863X/hg2572Isup2.hkl

checkCIF report

Comment top

During the course of ongoing studies on Co^III complexes with heterocycles (Wojtczak et al., 1990; Pazderski et al., 2008) the title compound (I) was isolated. The crystal structure of (I) is built of mononuclear [Co(imidazole)₆]³⁺ trications with the Co1 atom lying on Wyckoff position 3a (site symmetry 3), PF₆^- anions with P atom lying on Wyckoff position 9 d (site symmetry 1) and lattice water molecules (Fig.1). It is worth mentioning that this is the first structure consisting of a hexakis(imidazole)-cobalt(III) cationic complex, whereas more than 15 structures consisting of a hexakis(imidazole)-cobalt(II) complex ion were reported. Furthermore, there are only two papers on the hexakis(imidazole)-cobalt(III) ion in solution, describing spectroscopic (Navon & Panigel, 1989) and kinetic properties (Wiśniewska & Kita, 2006) respectively. The Co^III ion has an almost ideal octahedral environment formed by six imidazole N atoms, with cis-N—Co—N angles of 88.68 (7)° and 91.32 (7)°. The planes of neighbouring imidazole rings are twisted from their usual perpendicular positions. This is the result of the extensive net of hydrogen bonds in the structure in which imidazole rings are involved (dihedral angle = 72.4 (6)°). The Co—N bond distance is equal to 1.961 (1) Å and as expected is slightly shorter than those reported for hexakis(imidazole)-cobalt(II) complexes with distances of 2.140±2.188 Å (Tong et al., 2002). A similar relation of bond lengths was reported for Co^III—N and Co(II)—N in hexaamminecobalt complexes (Kime & Ibers, 1969) with differences between those distances of 0.18 Å. The water molecules present in the crystal structure form helical chains (helix pitch = 7.016 (2) Å, c axis) similar to those observed in a trichlorophloroglucinol structure (Saha & Nangia, 2005). They are propagated in [001] directions by O1—H6···O1ⁱ interactions (symmetry operation: -y + 2/3, x-y + 1/3, z + 1/3) with a distance of 2.913 (2) Å), which are stabilized by hydrogen bonding with the remaining molecular units (Table 1) giving in turn a three-dimensional assembly. The weak C—H···F interactions (Table 1) further stabilize the packing arrangement (Fig. 2).

Related literature top

For Co^III complexes with heterocycles, see: Wojtczak et al. (1990); Pazderski et al. (2008). For the hexakis(imidazole)-cobalt(III) ion in solution, see: Navon & Panigel (1989); Wiśniewska & Kita (2006). For Co—N bond distances in hexakis(imidazole)-cobalt(II) complexes, see: Tong et al. (2002). For Co^III—N and Co(II)—N bond lengths in hexaammine–cobalt complexes, see: Kime & Ibers (1969). The water molecules present in the crystal structure form helical chains similar to those observed in a trichlorophloroglucinol structure, see: Saha & Nangia (2005).

Experimental top

A mixture of 11.84 g (174 mmol) of imidazole and 2.02 g (5 mmol) of Co(pyridine)₃Cl₃ was grinded for several minutes until the color changed from green to red. The mixture was subsequently dissolved in 100 ml of distilled water and the pH was adjusted to 2–3 by adding 3 M HCl. Then the mixture was diluted with water to a final volume of 2 l and passed through a Sephadex SP C-25 column starting with an aqueous 0.05 M HCl solution as eluent. The fraction obtained by using 0.2 M HCl was evaporated in a stream of cold air and the product [Co(imidazole)₆]Cl₃ was filtrated and washed with ethanol. 10 mg of this compound was placed in a 50 ml beaker and 20 ml of a saturated aqueous solution of NH₄PF₆ was added. Red crystals suitable for single-crystal X-ray analysis were obtained by slow evaporation.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 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: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The molecular structure of (I), with the atom-numbering scheme [symmetry codes:(i) y,-x + y,-z; (ii) -x + y, -x, z; (iii) -x, -y, -z; (iv) -y, x-y, z; (v) x-y, x, -z; (vi) -x + 2/3,-y + 1/3,-z + 1/3]. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The crystal packing of (I) viewed down [001] with the extensive net of hydrogen bonds leading to a three-dimensional arrangement (the red dashed lines indicate strong hydrogen bonding and the blue weak ones).

Hexakis(1H-imidazole-κN³)cobalt(III) tris(hexafluoridophosphate) hexahydrate top

Crystal data top

[Co(C₃H₄N₂)₆](PF₆)₃·6H₂O	D_x = 1.880 Mg m⁻³
M_r = 1010.43	Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3	Cell parameters from 3782 reflections
Hall symbol: -R 3	θ = 3.1–28.2°
a = 20.9911 (13) Å	µ = 0.77 mm⁻¹
c = 7.0156 (9) Å	T = 100 K
V = 2677.1 (4) Å³	Block, red
Z = 3	0.25 × 0.25 × 0.21 mm
F(000) = 1530

Data collection top

Bruker SMART APEX CCD area-detector diffractometer	1373 independent reflections
Radiation source: fine-focus sealed tube	1288 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.026
ω scans	θ_max = 28.2°, θ_min = 3.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −22→27
T_min = 0.832, T_max = 0.856	k = −26→26
4893 measured reflections	l = −9→8

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.083	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ²(F_o²) + (0.0444P)² + 4.9022P] where P = (F_o² + 2F_c²)/3
1373 reflections	(Δ/σ)_max < 0.001
98 parameters	Δρ_max = 0.54 e Å⁻³
3 restraints	Δρ_min = −0.31 e Å⁻³

Crystal data top

[Co(C₃H₄N₂)₆](PF₆)₃·6H₂O	Z = 3
M_r = 1010.43	Mo Kα radiation
Trigonal, R3	µ = 0.77 mm⁻¹
a = 20.9911 (13) Å	T = 100 K
c = 7.0156 (9) Å	0.25 × 0.25 × 0.21 mm
V = 2677.1 (4) Å³

Data collection top

Bruker SMART APEX CCD area-detector diffractometer	1373 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	1288 reflections with I > 2σ(I)
T_min = 0.832, T_max = 0.856	R_int = 0.026
4893 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.031	3 restraints
wR(F²) = 0.083	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	Δρ_max = 0.54 e Å⁻³
1373 reflections	Δρ_min = −0.31 e Å⁻³
98 parameters

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

	x	y	z	U_iso*/U_eq
Co1	0.0000	0.0000	0.0000	0.01001 (15)
F2	0.25776 (5)	0.09189 (5)	0.20301 (16)	0.0242 (3)
N1	0.05651 (7)	0.08788 (7)	0.15758 (19)	0.0126 (3)
N3	0.14686 (7)	0.19255 (7)	0.2646 (2)	0.0161 (3)
H3	0.1914	0.2302	0.2812	0.019*
C5	0.02873 (8)	0.11667 (8)	0.2899 (2)	0.0155 (3)
H5	−0.0213	0.0945	0.3285	0.019*
C2	0.12841 (8)	0.13594 (8)	0.1462 (2)	0.0150 (3)
H2	0.1618	0.1307	0.0653	0.018*
C4	0.08453 (9)	0.18177 (8)	0.3556 (2)	0.0171 (3)
H4	0.0810	0.2134	0.4464	0.020*
P1	0.3333	0.1667	0.1667	0.01496 (16)
F1	0.34563 (7)	0.13360 (7)	−0.02524 (19)	0.0421 (4)
F3	0.37650 (6)	0.13458 (7)	0.2841 (2)	0.0402 (4)
O1	0.27980 (6)	0.31811 (6)	0.37976 (18)	0.0203 (3)
H6	0.3046 (15)	0.3048 (15)	0.473 (4)	0.052 (8)*
H7	0.2625 (15)	0.3462 (14)	0.447 (4)	0.051 (8)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Co1	0.00877 (17)	0.00877 (17)	0.0125 (3)	0.00438 (9)	0.000	0.000
F2	0.0135 (4)	0.0191 (5)	0.0324 (6)	0.0026 (4)	0.0030 (4)	0.0038 (4)
N1	0.0126 (6)	0.0113 (6)	0.0144 (6)	0.0063 (5)	−0.0004 (5)	0.0004 (5)
N3	0.0148 (6)	0.0122 (6)	0.0179 (7)	0.0041 (5)	−0.0023 (5)	−0.0005 (5)
C5	0.0158 (7)	0.0158 (7)	0.0158 (8)	0.0085 (6)	−0.0001 (5)	−0.0015 (6)
C2	0.0137 (7)	0.0137 (7)	0.0171 (7)	0.0063 (6)	−0.0016 (5)	−0.0009 (5)
C4	0.0205 (8)	0.0153 (7)	0.0161 (8)	0.0095 (6)	−0.0020 (6)	−0.0023 (6)
P1	0.0104 (3)	0.0156 (3)	0.0172 (3)	0.0052 (2)	0.00177 (19)	0.0010 (2)
F1	0.0372 (7)	0.0354 (7)	0.0378 (7)	0.0062 (5)	0.0167 (5)	−0.0130 (5)
F3	0.0160 (5)	0.0422 (7)	0.0588 (9)	0.0118 (5)	0.0027 (5)	0.0283 (6)
O1	0.0192 (6)	0.0197 (6)	0.0207 (6)	0.0086 (5)	−0.0039 (5)	−0.0035 (5)

Geometric parameters (Å, º) top

Co1—N1	1.9605 (13)	C5—C4	1.361 (2)
Co1—N1ⁱ	1.9605 (13)	C5—H5	0.9500
Co1—N1ⁱⁱ	1.9605 (13)	C2—H2	0.9500
Co1—N1ⁱⁱⁱ	1.9605 (13)	C4—H4	0.9500
Co1—N1^iv	1.9605 (13)	P1—F1^vi	1.5939 (12)
Co1—N1^v	1.9605 (13)	P1—F1	1.5938 (12)
F2—P1	1.5985 (9)	P1—F2^vi	1.5985 (9)
N1—C2	1.3340 (19)	P1—F3^vi	1.6012 (11)
N1—C5	1.3854 (19)	P1—F3	1.6012 (11)
N3—C2	1.339 (2)	O1—H6	0.96 (3)
N3—C4	1.369 (2)	O1—H7	0.96 (3)
N3—H3	0.8800

N1—Co1—N1ⁱ	88.68 (5)	N1—C5—H5	125.5
N1—Co1—N1ⁱⁱ	91.32 (5)	N1—C2—N3	110.48 (14)
N1—Co1—N1^v	88.68 (5)	N1—C2—H2	124.8
N1—Co1—N1ⁱⁱⁱ	180.00 (9)	N3—C2—H2	124.8
N1^v—Co1—N1ⁱⁱⁱ	91.32 (5)	C5—C4—N3	106.26 (14)
N1^v—Co1—N1ⁱ	91.32 (5)	C5—C4—H4	126.9
N1ⁱⁱⁱ—Co1—N1ⁱ	91.32 (5)	N3—C4—H4	126.9
N1^v—Co1—N1ⁱⁱ	180.00 (9)	F1^vi—P1—F1	180.0
N1ⁱⁱⁱ—Co1—N1ⁱⁱ	88.68 (5)	F1^vi—P1—F2	89.75 (6)
N1ⁱ—Co1—N1ⁱⁱ	88.68 (5)	F1—P1—F2	90.25 (6)
N1—Co1—N1^iv	91.32 (5)	F1^vi—P1—F2^vi	90.25 (6)
N1^v—Co1—N1^iv	88.68 (5)	F1—P1—F2^vi	89.75 (6)
N1ⁱⁱⁱ—Co1—N1^iv	88.68 (5)	F2—P1—F2^vi	179.997 (1)
N1ⁱ—Co1—N1^iv	180.00 (5)	F1^vi—P1—F3^vi	90.13 (8)
N1ⁱⁱ—Co1—N1^iv	91.32 (5)	F1—P1—F3^vi	89.86 (8)
C2—N1—C5	105.91 (12)	F2—P1—F3^vi	90.15 (6)
C2—N1—Co1	126.96 (11)	F2^vi—P1—F3^vi	89.85 (6)
C5—N1—Co1	126.84 (10)	F1^vi—P1—F3	89.86 (8)
C2—N3—C4	108.30 (13)	F1—P1—F3	90.14 (8)
C2—N3—H3	125.8	F2—P1—F3	89.85 (6)
C4—N3—H3	125.8	F2^vi—P1—F3	90.15 (6)
C4—C5—N1	109.04 (14)	F3^vi—P1—F3	180.0
C4—C5—H5	125.5	H6—O1—H7	105.7 (19)

N1^v—Co1—N1—C2	−98.46 (15)	C2—N1—C5—C4	0.10 (17)
N1ⁱ—Co1—N1—C2	−7.11 (13)	Co1—N1—C5—C4	−174.02 (11)
N1ⁱⁱ—Co1—N1—C2	81.54 (15)	C5—N1—C2—N3	0.45 (17)
N1^iv—Co1—N1—C2	172.89 (13)	Co1—N1—C2—N3	174.56 (10)
N1^v—Co1—N1—C5	74.46 (10)	C4—N3—C2—N1	−0.82 (18)
N1ⁱ—Co1—N1—C5	165.81 (14)	N1—C5—C4—N3	−0.58 (18)
N1ⁱⁱ—Co1—N1—C5	−105.54 (10)	C2—N3—C4—C5	0.85 (18)
N1^iv—Co1—N1—C5	−14.19 (14)

Symmetry codes: (i) y, −x+y, −z; (ii) −x+y, −x, z; (iii) −x, −y, −z; (iv) −y, x−y, z; (v) x−y, x, −z; (vi) −x+2/3, −y+1/3, −z+1/3.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H6···O1^vii	0.96 (3)	1.98 (3)	2.913 (2)	163 (3)
N3—H3···O1	0.88	1.98	2.834 (2)	165
O1—H7···F3^viii	0.96 (3)	2.10 (3)	2.945 (2)	146 (2)
C2—H2···F3^vi	0.95	2.34	3.042 (2)	131
C4—H4···F1^ix	0.95	2.40	3.303 (2)	158

Symmetry codes: (vi) −x+2/3, −y+1/3, −z+1/3; (vii) −y+2/3, x−y+1/3, z+1/3; (viii) x−y, x, −z+1; (ix) −x+y+1/3, −x+2/3, z+2/3.

Experimental details

Crystal data
Chemical formula	[Co(C₃H₄N₂)₆](PF₆)₃·6H₂O
M_r	1010.43
Crystal system, space group	Trigonal, R3
Temperature (K)	100
a, c (Å)	20.9911 (13), 7.0156 (9)
V (Å³)	2677.1 (4)
Z	3
Radiation type	Mo Kα
µ (mm⁻¹)	0.77
Crystal size (mm)	0.25 × 0.25 × 0.21

Data collection
Diffractometer	Bruker SMART APEX CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1997)
T_min, T_max	0.832, 0.856
No. of measured, independent and observed [I > 2σ(I)] reflections	4893, 1373, 1288
R_int	0.026
(sin θ/λ)_max (Å⁻¹)	0.666

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.031, 0.083, 1.08
No. of reflections	1373
No. of parameters	98
No. of restraints	3
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.54, −0.31

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour 2001).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H6···O1ⁱ	0.96 (3)	1.98 (3)	2.913 (2)	163 (3)
N3—H3···O1	0.88	1.975	2.834 (2)	165
O1—H7···F3ⁱⁱ	0.96 (3)	2.10 (3)	2.945 (2)	146 (2)
C2—H2···F3ⁱⁱⁱ	0.95	2.34	3.042 (2)	131
C4—H4···F1^iv	0.95	2.40	3.303 (2)	158

Symmetry codes: (i) −y+2/3, x−y+1/3, z+1/3; (ii) x−y, x, −z+1; (iii) −x+2/3, −y+1/3, −z+1/3; (iv) −x+y+1/3, −x+2/3, z+2/3.

Acknowledgements

The authors wish to thank the Nicolaus Copernicus University and the National Research Foundation of South Africa for financial support.

References

Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. CrossRef CAS Google Scholar
Bruker (2001). SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2002). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Kime, N. E. & Ibers, J. A. (1969). Acta Cryst. B25, 168–169. CrossRef CAS IUCr Journals Web of Science Google Scholar
Navon, G. & Panigel, R. (1989). Inorg. Chem. 28, 1405–1407. CrossRef CAS Web of Science Google Scholar
Pazderski, L., Surdykowski, A., Pazderska-Szablowicz, M., Sitkowski, J., Kozerski, L., Kamieński, B. & Szłyk, E. (2008). Cent. Eur. J. Chem. 6, 55–64. Web of Science CrossRef CAS Google Scholar
Saha, B. K. & Nangia, A. (2005). Chem. Commun. 24, 3024–3026. Web of Science CSD CrossRef Google Scholar
Sheldrick, G. M. (1997). SADABS. University of Göttingen, Germany. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Tong, M.-L., Li, W., Chen, X.-M. & Ng, S. W. (2002). Acta Cryst. E58, m186–m188. Web of Science CSD CrossRef IUCr Journals Google Scholar
Wiśniewska, J. & Kita, P. (2006). Transition Met. Chem. 31, 232–236. Google Scholar
Wojtczak, A., Kosturkiewicz, Z. & Surdykowski, A. (1990). Acta Cryst. C46, 578–581. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar

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