Di-μ-bromido-bis­({2-[(4,6-dimethyl­pyrimidin-2-yl)disulfan­yl]-4,6-dimethyl­pyrimidine-κ2N1,S2}copper(I))

Nimthong, R.; Pakawatchai, C.; Wattanakanjana, Y.

doi:10.1107/S1600536812016315

metal-organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 68| Part 5| May 2012| Page m645

doi:10.1107/S1600536812016315

Open

access

Di-μ-bromido-bis({2-[(4,6-dimethylpyrimidin-2-yl)disulfanyl]-4,6-dimethylpyrimidine-κ²N¹,S²}copper(I))

Ruthairat Nimthong,^a Chaveng Pakawatchai ^a ^* and Yupa Wattanakanjana ^b

^aDepartment of Chemistry and Center for Innovation in Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand, and ^bDepartment of Chemistry, Faculty of Science, Prince of Songkla University, Hat Yai 90112, Thailand
^*Correspondence e-mail: chaveng.p@psu.ac.th

(Received 30 March 2012; accepted 15 April 2012; online 21 April 2012)

The title dinuclear complex, [Cu₂Br₂(C₁₂H₁₄N₄S₂)₂], is located about an inversion center. The Cu^I ion is coordinated in a distorted tetrahedral geometry by two bridging Br atoms in addition to an N and an S atom from the 2-[(4,6-dimethylpyrimidin-2-yl)disulfanyl]-4,6-dimethylpyrimidine ligand. In the crystal, π–π stacking interactions are observed with a centroid–centroid distance of 3.590 (2) Å.

Related literature

For potential applications of heterocyclic thioamides and their metal complexes, see: Battistuzzi & Peyronel (1981 ); Holm & Solomon (1996 ); Cox et al. (2006 ); Falcomer et al. (2006 ); Sevier & Kaiser (2006 ); Saxena et al. (2009 ). For related structures, see: Lemos et al. (2001 ); Aslanidis et al. (2004 ); Freeman et al. (2008 ).

Experimental

Crystal data

[Cu₂Br₂(C₁₂H₁₄N₄S₂)₂]
M_r = 843.68
Monoclinic, C 2/c
a = 15.3351 (7) Å
b = 15.3898 (7) Å
c = 14.3398 (7) Å
β = 109.178 (1)°
V = 3196.4 (3) Å³
Z = 4
Mo Kα radiation
μ = 4.12 mm⁻¹
T = 293 K
0.21 × 0.18 × 0.10 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: integration (SADABS; Bruker, 2003 ) T_min = 0.425, T_max = 0.662
12339 measured reflections
2732 independent reflections
2344 reflections with I > 2σ(I)
R_int = 0.024

Refinement

R[F² > 2σ(F²)] = 0.028
wR(F²) = 0.077
S = 1.04
2732 reflections
181 parameters
55 restraints
H-atom parameters constrained
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: SMART (Bruker, 1998 ); cell refinement: SAINT (Bruker, 2003); 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: SHELXL97 and publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536812016315/lh5449sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812016315/lh5449Isup2.hkl

checkCIF report

Comment top

The studies of cooordination multidentate ligands such as heterocyclic thioamides, in complexes of closed-shell d¹⁰ metal ions, have been shown attention from a number of researchers (Saxena et al., 2009; Cox et al., 2006; Falcomer et al., 2006) because of their interesting biochemical properties and presence in active sites of many metalloproteins (Holm & Solomon, 1996; Battistuzzi & Peyronel, 1981). Particularly, the formation of disulfide bonds is an essential step in the folding and assembly of the extracellular domains of many membrane and secreted proteins which are important features of the structure of many proteins (Sevier & Kaiser, 2006).

The molecular structure of the title compound is shown in Fig. 1. The complex is dinuclear in which the Cu^I ions adopt distorted tetrahedral geometries. There is a binuclear µ,µ'-dibromobridged CuBr₂Cu core. The Cu—S and Cu—N distances are similar to those reported for other thioamide containing complexes (Aslanidis et al., 2004; Lemos et al., 2001) and the disulfide bond distances is shorter than that reported in a related compound with a disulfide bond (Freeman et al., 2008). The 'bite' angle S—Cu—N angle is 90.77 (7)°. The molecule lies on a crystallographic inversion center which is at the center of the CuBr₂Cu core with a Cu···Cu separation of 2.7802 (7) Å. This value is close the sum of the van der Waals radii for two Cu atoms (2.8 Å). In the crystal π–π stacking interactions with a centroid to centroid distance of 3.590 (2) Å are observed (Fig. 2). In addition, fairly short C(sp³)—H···N intermolecular distances (H···N = 2.67 Å, C(sp³)—N = 3.41 Å and C(sp³)—H···N = 134.2°) are observed (Fig. 3).

Related literature top

For potential applications of heterocyclic thioamides and their metal complexes, see: Battistuzzi & Peyronel (1981); Holm & Solomon (1996); Cox et al. (2006); Falcomer et al. (2006); Sevier & Kaiser (2006); Saxena et al. (2009). For related structures, see: Lemos et al. (2001); Aslanidis et al. (2004); Freeman et al. (2008).

Experimental top

4,6-Dimethyl-2-pyrimidinethiol, dmpymtH, (0.07 g, 0.50 mmol) was dissolved in 30 cm³ of methanol at 343-348K. CuBr (0.1 g, 0.70 mmol) was added and the mixture was stirred for 5 h. The resulting clear solution was filtered off and left to evaporate at room temperature. The crystalline complex, which was deposited upon standing for several days, was filtered off and dried in vacuo (yield 75%).

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 2003); data reduction: SAINT (Bruker, 2003); 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: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).

Figures top

	Fig. 1. The molecular structure with displacement ellipsoids drawn at the 50% probability level. Unlabeled atoms are related by (-x+1/2, -y+1/2, -z+1).
	Fig. 2. Part of the crystal structure with π–π stacking interactions shown as dashed lines.
	Fig. 3. Part of the crystal structure with weak C—H···N hydrogen bonds shown as dashed lines.

Di-µ-bromido-bis({2-[(4,6-dimethylpyrimidin-2-yl)disulfanyl]-4,6- dimethylpyrimidine-κ²N¹,S²}copper(I)) top

Crystal data top

[Cu₂Br₂(C₁₂H₁₄N₄S₂)₂]	F(000) = 1680
M_r = 843.68	D_x = 1.753 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 16645 reflections
a = 15.3351 (7) Å	θ = 1.9–24.7°
b = 15.3898 (7) Å	µ = 4.12 mm⁻¹
c = 14.3398 (7) Å	T = 293 K
β = 109.178 (1)°	Plate, colorless
V = 3196.4 (3) Å³	0.21 × 0.18 × 0.10 mm
Z = 4

Data collection top

Bruker SMART CCD diffractometer	2732 independent reflections
Radiation source: fine-focus sealed tube	2344 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.024
ϕ and ω scans	θ_max = 24.7°, θ_min = 1.9°
Absorption correction: integration (SADABS; Bruker, 2003)	h = −18→18
T_min = 0.425, T_max = 0.662	k = −18→17
12339 measured reflections	l = −16→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)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.077	H-atom parameters constrained
S = 1.04	w = 1/[σ²(F_o²) + (0.0412P)² + 3.1838P] where P = (F_o² + 2F_c²)/3
2732 reflections	(Δ/σ)_max = 0.001
181 parameters	Δρ_max = 0.37 e Å⁻³
55 restraints	Δρ_min = −0.31 e Å⁻³

Crystal data top

[Cu₂Br₂(C₁₂H₁₄N₄S₂)₂]	V = 3196.4 (3) Å³
M_r = 843.68	Z = 4
Monoclinic, C2/c	Mo Kα radiation
a = 15.3351 (7) Å	µ = 4.12 mm⁻¹
b = 15.3898 (7) Å	T = 293 K
c = 14.3398 (7) Å	0.21 × 0.18 × 0.10 mm
β = 109.178 (1)°

Data collection top

Bruker SMART CCD diffractometer	2732 independent reflections
Absorption correction: integration (SADABS; Bruker, 2003)	2344 reflections with I > 2σ(I)
T_min = 0.425, T_max = 0.662	R_int = 0.024
12339 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.028	55 restraints
wR(F²) = 0.077	H-atom parameters constrained
S = 1.04	Δρ_max = 0.37 e Å⁻³
2732 reflections	Δρ_min = −0.31 e Å⁻³
181 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
C1A	0.12116 (19)	0.06625 (19)	0.6388 (2)	0.0437 (7)
C2A	0.0939 (2)	−0.0746 (2)	0.5935 (3)	0.0541 (8)
C3A	0.1153 (2)	−0.0561 (2)	0.5100 (3)	0.0559 (8)
H1A	0.1118	−0.0994	0.4637	0.067*
C4A	0.1417 (2)	0.0265 (2)	0.4949 (2)	0.0491 (7)
C5A	0.0690 (3)	−0.1640 (2)	0.6172 (4)	0.0806 (12)
H2A	0.0531	−0.1622	0.6766	0.097*
H4A	0.1206	−0.2022	0.6264	0.097*
H3A	0.0172	−0.1849	0.5637	0.097*
C6A	0.1667 (3)	0.0518 (3)	0.4062 (3)	0.0738 (11)
H7A	0.1835	0.1121	0.4107	0.089*
H5A	0.1147	0.0423	0.3477	0.089*
H6A	0.2178	0.0173	0.4033	0.089*
C1B	0.0927 (2)	0.3281 (2)	0.6662 (2)	0.0444 (7)
C2B	0.0657 (2)	0.4721 (2)	0.6545 (2)	0.0535 (8)
C3B	−0.0270 (2)	0.4533 (2)	0.6114 (2)	0.0572 (8)
H1B	−0.0700	0.4979	0.5910	0.069*
C4B	−0.0549 (2)	0.3680 (2)	0.5989 (2)	0.0534 (8)
C5B	0.1020 (3)	0.5630 (2)	0.6741 (3)	0.0741 (11)
H2B	0.1679	0.5614	0.7044	0.089*
H4B	0.0749	0.5914	0.7174	0.089*
H3B	0.0866	0.5943	0.6129	0.089*
C6B	−0.1546 (2)	0.3429 (3)	0.5541 (3)	0.0743 (11)
H5B	−0.1599	0.2807	0.5516	0.089*
H6B	−0.1787	0.3661	0.4885	0.089*
H7B	−0.1890	0.3658	0.5937	0.089*
Cu1	0.20241 (3)	0.20852 (2)	0.55473 (3)	0.05128 (14)
N1A	0.09541 (17)	−0.01146 (17)	0.65843 (19)	0.0522 (6)
N2A	0.14596 (16)	0.09016 (15)	0.56177 (17)	0.0420 (5)
N1B	0.12747 (18)	0.40741 (17)	0.68337 (19)	0.0515 (6)
N2B	0.00657 (18)	0.30262 (16)	0.62617 (19)	0.0491 (6)
S1A	0.12183 (7)	0.14055 (6)	0.73360 (6)	0.0591 (2)
S1B	0.18435 (6)	0.24973 (5)	0.70698 (6)	0.0506 (2)
Br1	0.13259 (2)	0.31106 (2)	0.42440 (3)	0.05795 (13)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1A	0.0383 (15)	0.0440 (16)	0.0466 (16)	0.0048 (12)	0.0110 (13)	0.0077 (13)
C2A	0.0375 (17)	0.0438 (17)	0.072 (2)	−0.0002 (13)	0.0056 (15)	0.0108 (16)
C3A	0.0514 (19)	0.0434 (17)	0.066 (2)	−0.0011 (14)	0.0099 (16)	−0.0083 (15)
C4A	0.0506 (18)	0.0460 (17)	0.0482 (17)	0.0027 (14)	0.0127 (14)	−0.0042 (14)
C5A	0.070 (3)	0.049 (2)	0.113 (3)	−0.0075 (18)	0.017 (2)	0.017 (2)
C6A	0.107 (3)	0.062 (2)	0.063 (2)	−0.011 (2)	0.042 (2)	−0.0166 (18)
C1B	0.0487 (17)	0.0486 (17)	0.0411 (16)	0.0076 (13)	0.0216 (13)	−0.0017 (13)
C2B	0.070 (2)	0.0468 (18)	0.0517 (18)	0.0055 (15)	0.0303 (16)	−0.0021 (14)
C3B	0.060 (2)	0.0566 (19)	0.059 (2)	0.0166 (15)	0.0256 (16)	0.0068 (16)
C4B	0.0501 (18)	0.063 (2)	0.0504 (18)	0.0081 (15)	0.0211 (14)	0.0066 (15)
C5B	0.092 (3)	0.051 (2)	0.083 (3)	0.0023 (19)	0.034 (2)	−0.0080 (19)
C6B	0.051 (2)	0.090 (3)	0.082 (3)	0.0056 (19)	0.0231 (18)	0.018 (2)
Cu1	0.0570 (3)	0.0424 (2)	0.0616 (3)	0.00037 (16)	0.0292 (2)	0.00422 (17)
N1A	0.0473 (14)	0.0483 (15)	0.0595 (16)	−0.0005 (12)	0.0157 (12)	0.0126 (13)
N2A	0.0429 (13)	0.0409 (13)	0.0426 (13)	−0.0011 (10)	0.0146 (10)	0.0018 (10)
N1B	0.0565 (16)	0.0476 (15)	0.0552 (15)	0.0014 (12)	0.0249 (12)	−0.0074 (12)
N2B	0.0477 (15)	0.0521 (15)	0.0501 (15)	0.0017 (12)	0.0197 (12)	0.0034 (12)
S1A	0.0828 (6)	0.0531 (5)	0.0510 (5)	0.0106 (4)	0.0351 (4)	0.0078 (4)
S1B	0.0495 (4)	0.0485 (5)	0.0521 (4)	0.0070 (3)	0.0142 (3)	−0.0062 (4)
Br1	0.0467 (2)	0.0548 (2)	0.0746 (3)	0.01020 (14)	0.02299 (17)	0.02122 (16)

Geometric parameters (Å, º) top

C1A—N1A	1.319 (4)	C2B—C3B	1.381 (5)
C1A—N2A	1.332 (4)	C2B—C5B	1.498 (5)
C1A—S1A	1.774 (3)	C3B—C4B	1.375 (5)
C2A—N1A	1.341 (4)	C3B—H1B	0.9300
C2A—C3A	1.371 (5)	C4B—N2B	1.346 (4)
C2A—C5A	1.496 (4)	C4B—C6B	1.501 (5)
C3A—C4A	1.372 (4)	C5B—H2B	0.9600
C3A—H1A	0.9300	C5B—H4B	0.9600
C4A—N2A	1.358 (4)	C5B—H3B	0.9600
C4A—C6A	1.495 (5)	C6B—H5B	0.9600
C5A—H2A	0.9600	C6B—H6B	0.9600
C5A—H4A	0.9600	C6B—H7B	0.9600
C5A—H3A	0.9600	Cu1—N2A	2.033 (2)
C6A—H7A	0.9600	Cu1—S1B	2.3754 (9)
C6A—H5A	0.9600	Cu1—Br1	2.4114 (5)
C6A—H6A	0.9600	Cu1—Br1ⁱ	2.4669 (5)
C1B—N2B	1.315 (4)	Cu1—Cu1ⁱ	2.7801 (7)
C1B—N1B	1.323 (4)	S1A—S1B	2.0318 (13)
C1B—S1B	1.798 (3)	Br1—Cu1ⁱ	2.4668 (5)
C2B—N1B	1.342 (4)

N1A—C1A—N2A	127.9 (3)	C3B—C4B—C6B	122.1 (3)
N1A—C1A—S1A	110.3 (2)	C2B—C5B—H2B	109.5
N2A—C1A—S1A	121.7 (2)	C2B—C5B—H4B	109.5
N1A—C2A—C3A	120.0 (3)	H2B—C5B—H4B	109.5
N1A—C2A—C5A	117.2 (3)	C2B—C5B—H3B	109.5
C3A—C2A—C5A	122.8 (3)	H2B—C5B—H3B	109.5
C2A—C3A—C4A	119.9 (3)	H4B—C5B—H3B	109.5
C2A—C3A—H1A	120.0	C4B—C6B—H5B	109.5
C4A—C3A—H1A	120.0	C4B—C6B—H6B	109.5
N2A—C4A—C3A	120.3 (3)	H5B—C6B—H6B	109.5
N2A—C4A—C6A	116.5 (3)	C4B—C6B—H7B	109.5
C3A—C4A—C6A	123.2 (3)	H5B—C6B—H7B	109.5
C2A—C5A—H2A	109.5	H6B—C6B—H7B	109.5
C2A—C5A—H4A	109.5	N2A—Cu1—S1B	90.77 (7)
H2A—C5A—H4A	109.5	N2A—Cu1—Br1	122.47 (7)
C2A—C5A—H3A	109.5	S1B—Cu1—Br1	112.43 (3)
H2A—C5A—H3A	109.5	N2A—Cu1—Br1ⁱ	108.72 (7)
H4A—C5A—H3A	109.5	S1B—Cu1—Br1ⁱ	110.22 (3)
C4A—C6A—H7A	109.5	Br1—Cu1—Br1ⁱ	110.523 (16)
C4A—C6A—H5A	109.5	N2A—Cu1—Cu1ⁱ	138.63 (7)
H7A—C6A—H5A	109.5	S1B—Cu1—Cu1ⁱ	129.62 (3)
C4A—C6A—H6A	109.5	Br1—Cu1—Cu1ⁱ	56.200 (16)
H7A—C6A—H6A	109.5	Br1ⁱ—Cu1—Cu1ⁱ	54.323 (15)
H5A—C6A—H6A	109.5	C1A—N1A—C2A	116.6 (3)
N2B—C1B—N1B	129.9 (3)	C1A—N2A—C4A	115.2 (3)
N2B—C1B—S1B	120.5 (2)	C1A—N2A—Cu1	122.05 (19)
N1B—C1B—S1B	109.5 (2)	C4A—N2A—Cu1	122.3 (2)
N1B—C2B—C3B	120.1 (3)	C1B—N1B—C2B	115.2 (3)
N1B—C2B—C5B	116.9 (3)	C1B—N2B—C4B	114.3 (3)
C3B—C2B—C5B	123.0 (3)	C1A—S1A—S1B	105.86 (11)
C4B—C3B—C2B	119.3 (3)	C1B—S1B—S1A	104.42 (11)
C4B—C3B—H1B	120.4	C1B—S1B—Cu1	101.24 (10)
C2B—C3B—H1B	120.4	S1A—S1B—Cu1	99.01 (4)
N2B—C4B—C3B	121.2 (3)	Cu1—Br1—Cu1ⁱ	69.476 (16)
N2B—C4B—C6B	116.7 (3)

Symmetry code: (i) −x+1/2, −y+1/2, −z+1.

Experimental details

Crystal data
Chemical formula	[Cu₂Br₂(C₁₂H₁₄N₄S₂)₂]
M_r	843.68
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	293
a, b, c (Å)	15.3351 (7), 15.3898 (7), 14.3398 (7)
β (°)	109.178 (1)
V (Å³)	3196.4 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	4.12
Crystal size (mm)	0.21 × 0.18 × 0.10

Data collection
Diffractometer	Bruker SMART CCD diffractometer
Absorption correction	Integration (SADABS; Bruker, 2003)
T_min, T_max	0.425, 0.662
No. of measured, independent and observed [I > 2σ(I)] reflections	12339, 2732, 2344
R_int	0.024
(sin θ/λ)_max (Å⁻¹)	0.588

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.077, 1.04
No. of reflections	2732
No. of parameters	181
No. of restraints	55
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.37, −0.31

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 2003), SHELXS97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).

Acknowledgements

We gratefully acknowledge financial support from the Center for Innovation in Chemistry (PERCH–CIC), the Commission on Higher Education, Ministry of Education, the Department of Chemistry and the Graduate School, Prince of Songkla University.

References

Aslanidis, P., Cox, P. J., Divanidis, S. & Karagiannidis, P. (2004). Inorg. Chim. Acta, 357, 4231–4239. Web of Science CSD CrossRef CAS Google Scholar
Battistuzzi, R. & Peyronel, G. (1981). Can. J. Chem. 59, 591–596. CrossRef CAS Web of Science Google Scholar
Bruker (1998). SMART. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2003). SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cox, P. J., Kaltzoglou, A. & Aslanidis, P. (2006). Inorg. Chim. Acta, 359, 3183–3190. Web of Science CSD CrossRef CAS Google Scholar
Falcomer, V. A. S., Lemos, S. S., Batista, A. A., Ellena, A. & Castellano, E. E. (2006). Inorg. Chim. Acta, 359, 1064–1070. Web of Science CSD CrossRef CAS Google Scholar
Freeman, F., Po, H. N., Ho, T. S. & Wang, X. (2008). J. Phys. Chem. A, 112, 1643–1655. Web of Science CrossRef PubMed CAS Google Scholar
Holm, R. H. & Solomon, E. J. (1996). Chem. Rev. 96, 2239–2341. CrossRef PubMed CAS Web of Science Google Scholar
Lemos, S. S., Camargo, M. A., Cadoso, Z. Z., Deflon, V. M., Försterling, F. H. & Hagenbach, A. (2001). Polyhedron, 20, 849–854. Web of Science CSD CrossRef CAS Google Scholar
Saxena, A., Dugan, E. C., Liaw, J., Dembo, M. D. & Pike, R. D. (2009). Polyhedron, 28, 4017–4031. Web of Science CSD CrossRef CAS Google Scholar
Sevier, C. S. & Kaiser, C. A. (2006). Antioxid. Redox Signal. 8, 797–811. Web of Science CrossRef PubMed CAS 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

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.