Diaqua­bis(5-carb­oxy-1H-pyrazole-3-carboxyl­ato-κ2N2,O3)cobalt(II) dihydrate

Xie, H.-D.; Jin, L.; Xie, C.-Z.

doi:10.1107/S1600536809029456

metal-organic compounds

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ISSN: 2056-9890

Volume 65| Part 8| August 2009| Pages m1009-m1010

doi:10.1107/S1600536809029456

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Diaquabis(5-carboxy-1H-pyrazole-3-carboxylato-κ²N²,O³)cobalt(II) dihydrate

Hui-Dong Xie,^a ^* Li Jin ^a and Cheng-Zhi Xie ^b

^aSchool of Science, Xi'an University of Architecture & Technology, Xi'an 710055, People's Republic of China, and ^bTianjin Medical University, Tianjin 300070, People's Republic of China
^*Correspondence e-mail: xhd02@mails.thu.edu.cn

(Received 18 July 2009; accepted 23 July 2009; online 31 July 2009)

In the title complex, [Co(C₅H₃N₂O₄)₂(H₂O)₂]·2H₂O, the Co^II ion lies on an inversion center and is coordinated in a distorted octahedral environment. In the crystal structure, complex and water molecules are linked into a three-dimensional network by O—H⋯O and N—H⋯O hydrogen bonds.

Related literature

For a mononuclear zinc(II) complex with a pyrazole-3,5-dicarboxylato ligand, see: Xie et al. (2006 ) and for a cobalt(III) complex with a 5-carboxy-1H-pyrazole-3-carboxylato ligand, see: Xie et al. (2007 ). The 3,5-pyrazoledicarboxylic acid ligand is asymmetric and has six potential coordination sites which can act to link together metal centers through a number of bridging modes, see: King et al. (2004 ). A variety of complexes containing this ligand have been reported, see: Frisch & Cahill (2005 ); King et al. (2003 , 2004); Li et al. (2005 ); Pan, Ching et al. (2001 ); Pan, Frydel et al. (2001 ).

Experimental

Crystal data

[Co(C₅H₃N₂O₄)₂(H₂O)₂]·2H₂O
M_r = 441.18
Monoclinic, P 2₁ /c
a = 10.030 (3) Å
b = 12.483 (4) Å
c = 6.827 (2) Å
β = 108.641 (4)°
V = 809.9 (5) Å³
Z = 2
Mo Kα radiation
μ = 1.14 mm⁻¹
T = 291 K
0.32 × 0.27 × 0.14 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.713, T_max = 0.854
5748 measured reflections
1502 independent reflections
1331 reflections with I > 2σ(I)
R_int = 0.036

Refinement

R[F² > 2σ(F²)] = 0.048
wR(F²) = 0.142
S = 1.12
1502 reflections
129 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.84 e Å⁻³
Δρ_min = −0.44 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

Co1—O5	2.065 (3)
Co1—N1	2.108 (3)
Co1—O1	2.120 (3)
O1—C1	1.262 (5)
O2—C1	1.256 (5)

O5ⁱ—Co1—O5	180
O5—Co1—N1	90.84 (12)
O5—Co1—N1ⁱ	89.16 (12)
N1—Co1—N1ⁱ	180
O5—Co1—O1ⁱ	91.18 (12)
N1—Co1—O1ⁱ	103.22 (11)
O5—Co1—O1	88.82 (12)
N1—Co1—O1	76.78 (11)
O1ⁱ—Co1—O1	180
Symmetry code: (i) -x+1, -y+2, -z.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H4⋯O2ⁱⁱ	0.82	1.73	2.535 (4)	169
O5—H1W⋯O3ⁱⁱⁱ	0.83	2.07	2.887 (4)	171
O5—H2W⋯O2^iv	0.83	1.91	2.726 (4)	171
O6—H4W⋯O1^v	0.85 (11)	2.06 (11)	2.828 (5)	149 (10)
O6—H3W⋯O3^vi	0.84	2.30	2.932 (5)	132
N2—H2⋯O6^vii	0.86	1.91	2.714 (5)	155
Symmetry codes: (ii) $[-x+2, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) x-1, y, z; (iv) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (v) -x+1, -y+1, -z; (vi) $[-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (vii) x, y+1, z.

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

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809029456/lh2869sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809029456/lh2869Isup2.hkl

checkCIF report

Comment top

In the past few decades, self-assembly processes involving metal ions and organic ligands directed by either metal coordination or hydrogen bonds have received a great deal of attention in the field of supramolecular chemistry and crystal engineering. The 3,5-pyrazoledicarboxylic acid ligand is asymmetric and has six potential coordination sites which can act to link together metal centers through a number of bridging modes (King et al., 2004). A variety of complexes containing this ligand have been reported (Frisch et al., 2005; King et al., 2003, 2004; Pan, Ching et al., 2001; Pan, Frydel et al., 2001; Li et al., 2005).

The molecular structure of the title complex , (I), is shown in Fig. 1. The Co^II ion is located on an inversion center and is coordinated in a distorted octahedral environment. The axial sites are occupied by water molecules and the equatorial plane is fromed by two oxygen donors and two nitrogen donors from two chelating 5-carboxy-pyrazole-3-carboxylato ligands. In the crystal structure complex and water molecules are linked into a three-dimensional network by O-H···O and N-H···O hydrogen bonds.

Related literature top

For a mononuclear zinc(II) complex with a pyrazole-3,5-dicarboxylato ligand, see: Xie et al. (2006) and for a cobalt(III) complex with a 5-carboxy-1H-pyrazole-3-carboxylato ligand, see: Xie et al. (2007). The 3,5-pyrazoledicarboxylic acid ligand is asymmetric and has six potential coordination sites which can act to link together metal centers through a number of bridging modes, see: King et al. (2004). A variety of complexes containing this ligand have been reported, see: Frisch & Cahill (2005); King et al. (2003, 2004); Li et al. (2005); Pan, Ching et al. (2001); Pan, Frydel et al. (2001).

Experimental top

A mixture of cobalt(II) nitrate (hexhydrate) (0.2 mmol, 58 mg), 3,5-pyrazoledicarboxylic acid (0.4 mmol, 62 mg) and H₂O (18.0 ml) in a 1:2:5000 molar ratio was sealed in a 25 ml stainless steel reactor with a Teflon liner. The autoclave was kept at 423 K for 3 d, then cooled to room temperature at a rate of 4 K/h. Orange block-shaped crystals of the title complex were collected by filtration for the structural analysis.

Computing details top

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

	Fig. 1. The molecular structure of (I), with atom labels and 35% probability displacement ellipsoids for non-H atoms [symmetry code: (A) -x+1, -y+2, -z]. Only the unique solvent water molecule is shown.
	Fig. 2. Part of the crystal structure of (I) showing the donor acceptor distances of hydrogen bonds as dashed lines. H atoms have been omitted for clarity.

Diaquabis(5-carboxy-1H-pyrazole-3-carboxylato- κ²N²,O³)cobalt(II) dihydrate top

Crystal data top

[Co(C₅H₃N₂O₄)₂(H₂O)₂]·2H₂O	F(000) = 450
M_r = 441.18	D_x = 1.809 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2747 reflections
a = 10.030 (3) Å	θ = 2.7–27.9°
b = 12.483 (4) Å	µ = 1.14 mm⁻¹
c = 6.827 (2) Å	T = 291 K
β = 108.641 (4)°	Block, orange
V = 809.9 (5) Å³	0.32 × 0.27 × 0.14 mm
Z = 2

Data collection top

Bruker SMART CCD diffractometer	1502 independent reflections
Radiation source: fine-focus sealed tube	1331 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.036
ϕ and ω scans	θ_max = 25.5°, θ_min = 2.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −12→12
T_min = 0.713, T_max = 0.854	k = −15→15
5748 measured reflections	l = −8→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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.142	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	w = 1/[σ²(F_o²) + (0.0775P)² + 1.4115P] where P = (F_o² + 2F_c²)/3
1502 reflections	(Δ/σ)_max < 0.001
129 parameters	Δρ_max = 0.84 e Å⁻³
0 restraints	Δρ_min = −0.44 e Å⁻³

Crystal data top

[Co(C₅H₃N₂O₄)₂(H₂O)₂]·2H₂O	V = 809.9 (5) Å³
M_r = 441.18	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 10.030 (3) Å	µ = 1.14 mm⁻¹
b = 12.483 (4) Å	T = 291 K
c = 6.827 (2) Å	0.32 × 0.27 × 0.14 mm
β = 108.641 (4)°

Data collection top

Bruker SMART CCD diffractometer	1502 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	1331 reflections with I > 2σ(I)
T_min = 0.713, T_max = 0.854	R_int = 0.036
5748 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.048	0 restraints
wR(F²) = 0.142	H atoms treated by a mixture of independent and constrained refinement
S = 1.12	Δρ_max = 0.84 e Å⁻³
1502 reflections	Δρ_min = −0.44 e Å⁻³
129 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	0.5000	1.0000	0.0000	0.0227 (3)
O1	0.5183 (3)	0.8358 (2)	−0.0667 (5)	0.0308 (6)
O2	0.6657 (3)	0.6977 (2)	−0.0142 (5)	0.0337 (7)
O3	1.1998 (3)	0.9569 (3)	0.3134 (5)	0.0408 (8)
O4	1.0960 (3)	1.1105 (2)	0.3529 (5)	0.0366 (7)
H4	1.1772	1.1324	0.3977	0.055*
O5	0.4797 (3)	0.9554 (3)	0.2803 (5)	0.0378 (7)
H1W	0.4031	0.9594	0.3020	0.045*
H2W	0.5296	0.9069	0.3484	0.045*
O6	0.7621 (4)	0.2301 (3)	0.2670 (8)	0.0684 (13)
H3W	0.7617	0.2926	0.3116	0.082*
N1	0.7187 (3)	0.9727 (3)	0.1137 (5)	0.0238 (7)
N2	0.8371 (3)	1.0290 (2)	0.1925 (5)	0.0237 (7)
H2	0.8402	1.0958	0.2251	0.028*
C1	0.6402 (4)	0.7957 (3)	−0.0049 (6)	0.0239 (8)
C2	0.7586 (4)	0.8723 (3)	0.0850 (6)	0.0232 (7)
C3	0.9054 (4)	0.8646 (3)	0.1462 (6)	0.0255 (8)
H3	0.9595	0.8047	0.1422	0.031*
C4	0.9519 (4)	0.9668 (3)	0.2143 (6)	0.0246 (8)
C5	1.0964 (4)	1.0103 (3)	0.2981 (6)	0.0264 (8)
H4W	0.678 (12)	0.232 (9)	0.182 (18)	0.19 (4)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Co1	0.0135 (4)	0.0169 (4)	0.0356 (4)	0.0024 (2)	0.0049 (3)	0.0001 (3)
O1	0.0156 (13)	0.0203 (13)	0.0522 (17)	0.0011 (10)	0.0046 (11)	−0.0035 (12)
O2	0.0203 (14)	0.0210 (14)	0.0535 (18)	0.0006 (10)	0.0031 (12)	−0.0062 (12)
O3	0.0198 (15)	0.0342 (16)	0.066 (2)	0.0006 (12)	0.0106 (14)	−0.0041 (15)
O4	0.0207 (14)	0.0269 (15)	0.0568 (19)	−0.0042 (11)	0.0048 (13)	−0.0063 (13)
O5	0.0292 (16)	0.0418 (17)	0.0443 (16)	0.0129 (13)	0.0143 (13)	0.0130 (14)
O6	0.041 (2)	0.0318 (19)	0.124 (4)	0.0026 (15)	0.014 (2)	−0.010 (2)
N1	0.0136 (15)	0.0210 (15)	0.0344 (17)	0.0010 (12)	0.0041 (12)	−0.0024 (12)
N2	0.0159 (15)	0.0154 (14)	0.0379 (17)	−0.0022 (12)	0.0059 (13)	−0.0025 (13)
C1	0.0170 (17)	0.0197 (18)	0.0327 (19)	−0.0005 (14)	0.0047 (15)	−0.0014 (14)
C2	0.0167 (17)	0.0185 (17)	0.0329 (19)	−0.0012 (14)	0.0056 (15)	−0.0014 (14)
C3	0.0171 (17)	0.0183 (18)	0.039 (2)	0.0018 (13)	0.0066 (15)	−0.0005 (15)
C4	0.0154 (17)	0.0236 (18)	0.0336 (19)	0.0010 (14)	0.0064 (14)	0.0008 (15)
C5	0.0205 (19)	0.0238 (19)	0.033 (2)	−0.0021 (14)	0.0065 (16)	0.0010 (15)

Geometric parameters (Å, º) top

Co1—O5ⁱ	2.065 (3)	O5—H2W	0.8277
Co1—O5	2.065 (3)	O6—H3W	0.8380
Co1—N1	2.108 (3)	O6—H4W	0.85 (11)
Co1—N1ⁱ	2.108 (3)	N1—N2	1.336 (4)
Co1—O1ⁱ	2.120 (3)	N1—C2	1.349 (5)
Co1—O1	2.120 (3)	N2—C4	1.358 (5)
O1—C1	1.262 (5)	N2—H2	0.8600
O2—C1	1.256 (5)	C1—C2	1.495 (5)
O3—C5	1.209 (5)	C2—C3	1.400 (5)
O4—C5	1.306 (5)	C3—C4	1.386 (5)
O4—H4	0.8200	C3—H3	0.9300
O5—H1W	0.8288	C4—C5	1.481 (5)

O5ⁱ—Co1—O5	180	N2—N1—C2	106.3 (3)
O5ⁱ—Co1—N1	89.16 (12)	N2—N1—Co1	138.6 (3)
O5—Co1—N1	90.84 (12)	C2—N1—Co1	114.8 (2)
O5ⁱ—Co1—N1ⁱ	90.84 (12)	N1—N2—C4	110.9 (3)
O5—Co1—N1ⁱ	89.16 (12)	N1—N2—H2	124.6
N1—Co1—N1ⁱ	180	C4—N2—H2	124.6
O5ⁱ—Co1—O1ⁱ	88.82 (12)	O2—C1—O1	124.1 (3)
O5—Co1—O1ⁱ	91.18 (12)	O2—C1—C2	119.7 (3)
N1—Co1—O1ⁱ	103.22 (11)	O1—C1—C2	116.2 (3)
N1ⁱ—Co1—O1ⁱ	76.78 (11)	N1—C2—C3	110.7 (3)
O5ⁱ—Co1—O1	91.18 (12)	N1—C2—C1	114.8 (3)
O5—Co1—O1	88.82 (12)	C3—C2—C1	134.5 (3)
N1—Co1—O1	76.78 (11)	C4—C3—C2	104.3 (3)
N1ⁱ—Co1—O1	103.22 (11)	C4—C3—H3	127.9
O1ⁱ—Co1—O1	180	C2—C3—H3	127.9
C1—O1—Co1	116.9 (2)	N2—C4—C3	107.9 (3)
C5—O4—H4	109.5	N2—C4—C5	121.6 (3)
Co1—O5—H1W	121.4	C3—C4—C5	130.6 (3)
Co1—O5—H2W	119.8	O3—C5—O4	125.8 (4)
H1W—O5—H2W	111.9	O3—C5—C4	122.5 (3)
H3W—O6—H4W	95.7	O4—C5—C4	111.7 (3)

O5ⁱ—Co1—O1—C1	92.3 (3)	Co1—N1—C2—C3	174.1 (3)
O5—Co1—O1—C1	−87.7 (3)	N2—N1—C2—C1	−179.5 (3)
N1—Co1—O1—C1	3.4 (3)	Co1—N1—C2—C1	−5.3 (4)
N1ⁱ—Co1—O1—C1	−176.6 (3)	O2—C1—C2—N1	−171.3 (4)
O5ⁱ—Co1—N1—N2	81.6 (4)	O1—C1—C2—N1	8.3 (5)
O5—Co1—N1—N2	−98.4 (4)	O2—C1—C2—C3	9.5 (7)
O1ⁱ—Co1—N1—N2	−6.9 (4)	O1—C1—C2—C3	−170.8 (4)
O1—Co1—N1—N2	173.1 (4)	N1—C2—C3—C4	0.1 (4)
O5ⁱ—Co1—N1—C2	−90.0 (3)	C1—C2—C3—C4	179.3 (4)
O5—Co1—N1—C2	90.0 (3)	N1—N2—C4—C3	−0.1 (4)
O1ⁱ—Co1—N1—C2	−178.6 (3)	N1—N2—C4—C5	179.8 (3)
O1—Co1—N1—C2	1.4 (3)	C2—C3—C4—N2	0.0 (4)
C2—N1—N2—C4	0.2 (4)	C2—C3—C4—C5	−179.9 (4)
Co1—N1—N2—C4	−171.9 (3)	N2—C4—C5—O3	−178.0 (4)
Co1—O1—C1—O2	172.5 (3)	C3—C4—C5—O3	1.9 (7)
Co1—O1—C1—C2	−7.2 (4)	N2—C4—C5—O4	2.7 (5)
N2—N1—C2—C3	−0.2 (4)	C3—C4—C5—O4	−177.4 (4)

Symmetry code: (i) −x+1, −y+2, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4···O2ⁱⁱ	0.82	1.73	2.535 (4)	169
O5—H1W···O3ⁱⁱⁱ	0.83	2.07	2.887 (4)	171
O5—H2W···O2^iv	0.83	1.91	2.726 (4)	171
O6—H4W···O1^v	0.85 (11)	2.06 (11)	2.828 (5)	149 (10)
O6—H3W···O3^vi	0.84	2.30	2.932 (5)	132
N2—H2···O6^vii	0.86	1.91	2.714 (5)	155

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

Experimental details

Crystal data
Chemical formula	[Co(C₅H₃N₂O₄)₂(H₂O)₂]·2H₂O
M_r	441.18
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	291
a, b, c (Å)	10.030 (3), 12.483 (4), 6.827 (2)
β (°)	108.641 (4)
V (Å³)	809.9 (5)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	1.14
Crystal size (mm)	0.32 × 0.27 × 0.14

Data collection
Diffractometer	Bruker SMART CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.713, 0.854
No. of measured, independent and observed [I > 2σ(I)] reflections	5748, 1502, 1331
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.606

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.048, 0.142, 1.12
No. of reflections	1502
No. of parameters	129
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.84, −0.44

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top

Co1—O5	2.065 (3)	O1—C1	1.262 (5)
Co1—N1	2.108 (3)	O2—C1	1.256 (5)
Co1—O1	2.120 (3)

O5ⁱ—Co1—O5	180	N1—Co1—O1ⁱ	103.22 (11)
O5—Co1—N1	90.84 (12)	O5—Co1—O1	88.82 (12)
O5—Co1—N1ⁱ	89.16 (12)	N1—Co1—O1	76.78 (11)
N1—Co1—N1ⁱ	180	O1ⁱ—Co1—O1	180
O5—Co1—O1ⁱ	91.18 (12)

Symmetry code: (i) −x+1, −y+2, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O4—H4···O2ⁱⁱ	0.82	1.73	2.535 (4)	168.9
O5—H1W···O3ⁱⁱⁱ	0.83	2.07	2.887 (4)	171.1
O5—H2W···O2^iv	0.83	1.91	2.726 (4)	171.0
O6—H4W···O1^v	0.85 (11)	2.06 (11)	2.828 (5)	149 (10)
O6—H3W···O3^vi	0.84	2.30	2.932 (5)	132.4
N2—H2···O6^vii	0.86	1.91	2.714 (5)	155.0

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

Acknowledgements

The authors thank the University Youth Fund (grant No. RC0735) for financial support.

References

Bruker (2001). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Frisch, M. & Cahill, C. L. (2005). Dalton Trans. pp. 1518–1523. Web of Science CSD CrossRef Google Scholar
King, P., Clerac, R., Anson, C. E., Coulon, C. & Powell, A. K. (2003). Inorg. Chem. 42, 3492–3500. Web of Science CSD CrossRef PubMed CAS Google Scholar
King, P., Clerac, R., Anson, C. E. & Powell, A. K. (2004). Dalton Trans. pp. 852–861. Web of Science CSD CrossRef Google Scholar
Li, X.-H., Lei, X.-X., Tian, Y.-G. & Wang, S. (2005). Acta Cryst. E61, m702–m704. Web of Science CSD CrossRef IUCr Journals Google Scholar
Pan, L., Ching, N., Huang, X.-Y. & Li, J. (2001). Chem. Eur. J. 7, 4431–4437. CrossRef PubMed CAS Google Scholar
Pan, L., Frydel, T., Sander, M. B., Huang, X.-Y. & Li, J. (2001). Inorg. Chem. 40, 1271–1283. Web of Science CSD CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (1996). 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
Xie, H.-D., Xie, C.-Z., Wang, X.-Q., Shen, G.-Q. & Shen, D.-Z. (2006). Acta Cryst. E62, m3119–m3121. Web of Science CSD CrossRef IUCr Journals Google Scholar
Xie, H.-D., Xie, C.-Z., Wang, X.-Q., Shen, G.-Q. & Shen, D.-Z. (2007). Acta Cryst. E63, m1477–m1479. Web of Science CSD CrossRef IUCr Journals Google Scholar

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