1,4-Bis[2-(2-pyrid­yl)-1H-imidazol-1-yl]butane

Tan, K.; Li, S.-L.

doi:10.1107/S1600536808036775

organic compounds

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ISSN: 2056-9890

Volume 64| Part 12| December 2008| Page o2360

doi:10.1107/S1600536808036775

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1,4-Bis[2-(2-pyridyl)-1H-imidazol-1-yl]butane

Ke Tan ^a and Shun-Li Li ^b ^*

^aBiological Scientific and Technical College, Changchun University, Changchun 130022, People's Republic of China, and ^bDepartment of Chemistry, Northeast Normal University, Changchun 130024, People's Republic of China
^*Correspondence e-mail: lishunli@yahoo.cn

(Received 22 September 2008; accepted 8 November 2008; online 13 November 2008)

The title compound, C₂₀H₂₀N₆, was isolated from dimethyl sulfoxide solution using 2-(1H-imidazol-2-yl)pyridine and 1,4-dichlorobutane in the presence of NaOH.

Related literature

For the coordination capabilities and catalytic properties of the metal complexes of N-heterocyclic precursors, see: Chiswell et al. (1964 ); Herrmann (2002 ); Herrmann & Kocher (1997 ). For metal complexes with N-donor ligands, see: Carlucci et al. (2005 );

Experimental

Crystal data

C₂₀H₂₀N₆
M_r = 344.42
Monoclinic, P 2₁ /c
a = 11.0426 (10) Å
b = 13.4510 (12) Å
c = 12.7081 (11) Å
β = 111.213 (2)°
V = 1759.7 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 293 (2) K
0.43 × 0.39 × 0.36 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ) T_min = 0.938, T_max = 0.966
10708 measured reflections
4139 independent reflections
1705 reflections with I > 2σ(I)
R_int = 0.031

Refinement

R[F² > 2σ(F²)] = 0.052
wR(F²) = 0.125
S = 1.03
4139 reflections
215 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.48 e Å⁻³
Δρ_min = −0.47 e Å⁻³

Data collection: SMART (Bruker, 1997 ); cell refinement: SAINT (Bruker, 1999 ; data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808036775/wk2095sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808036775/wk2095Isup2.hkl

checkCIF report

Comment top

Numerous flexible or rigid N-heterocyclic precursors have been synthesized and studied because they attract considerable attention because of their diverse coordination capabilities and the important catalytic properties of their metal complexes (Herrmann, 2002; Herrmann & Kocher, 1997). A lot of metal complexes with N-donor ligands, especially ligands with imidazole-type rings separated by an aromatic spacer, have been isolated with various structures (Carlucci et al., 2005). In the present work, the crystal structure of an N-donor ligand, (I), a newspacer for metal organic frameworks, is reported.

In the molecular structure of the title compound, (I), bond lengths and angles are normal. The dihedral angles between the imidazole ring and the pyridine ring in the same 2-(pyridin-2-yl)-1H-imidazol group are 11.6 and 37.8°, respectively. The dihedral angle between two imidazole rings in the same ligand is 13.2°. And the corresponding angle between two pyridine rings in the same ligand is 36.4°.

Related literature top

For the coordination capabilities and catalytic properties of the

metal complexes of N-heterocyclic precursors, see: Chiswell et al. (1964); Herrmann (2002); Herrmann & Kocher (1997). For metal complexes with N-donor ligands, see: Carlucci et al. (2005);

Experimental top

The predecessor 2-(2-pyridyl)imidazole was synthesized according to the literature (Chiswell et al., 1964). A mixture of 2-(2-pyridyl)imidazole (7.25 g, 50 mmol) and NaOH (2.00 g, 50 mmol) in DMSO (20 ml) was stirred at 60°Cfor 1 h, and the 1,4-dichlorobutane(3.18 g, 25 mmol) was added. The mixture was cooled to room temperature after stirring at 60°Cfor 24 h and then poured into 200 ml of water. A yellow solid formed immediately, which was isolated by filtration in 80% yield after drying in air. Crystals suitable for X-ray diffraction were isolated from 65% ethanol.

Computing details top

Data collection: SMART (Bruker, 1997); cell refinement: SMART (Bruker, 1997); data reduction: SAINT (Bruker, 1999); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

Fig. 1. A view of the molecule of (I). Displacement ellipsoids are drawn at the 30% probability level.

1,4-Bis[2-(2-pyridyl)-1H-imidazol-1-yl]butane top

Crystal data top

C₂₀H₂₀N₆	F(000) = 728
M_r = 344.42	D_x = 1.300 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 795 reflections
a = 11.0426 (10) Å	θ = 2.0–28.3°
b = 13.4510 (12) Å	µ = 0.08 mm⁻¹
c = 12.7081 (11) Å	T = 293 K
β = 111.213 (2)°	Block, colorless
V = 1759.7 (3) Å³	0.43 × 0.39 × 0.36 mm
Z = 4

Data collection top

Bruker SMART APEX CCD area-detector diffractometer	4139 independent reflections
Radiation source: fine-focus sealed tube	1705 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.031
ω scans	θ_max = 28.3°, θ_min = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −14→7
T_min = 0.938, T_max = 0.966	k = −17→17
10708 measured reflections	l = −14→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)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.125	H-atom parameters constrained
S = 1.03	w = 1/[σ²(F_o²) + (0.04P)²] where P = (F_o² + 2F_c²)/3
4139 reflections	(Δ/σ)_max < 0.001
215 parameters	Δρ_max = 0.49 e Å⁻³
1 restraint	Δρ_min = −0.48 e Å⁻³

Crystal data top

C₂₀H₂₀N₆	V = 1759.7 (3) Å³
M_r = 344.42	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 11.0426 (10) Å	µ = 0.08 mm⁻¹
b = 13.4510 (12) Å	T = 293 K
c = 12.7081 (11) Å	0.43 × 0.39 × 0.36 mm
β = 111.213 (2)°

Data collection top

Bruker SMART APEX CCD area-detector diffractometer	4139 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	1705 reflections with I > 2σ(I)
T_min = 0.938, T_max = 0.966	R_int = 0.031
10708 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.053	1 restraint
wR(F²) = 0.125	H-atom parameters constrained
S = 1.03	Δρ_max = 0.49 e Å⁻³
4139 reflections	Δρ_min = −0.48 e Å⁻³
215 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
N1	0.34332 (12)	0.07519 (9)	0.63433 (12)	0.0497 (5)
C1	0.39593 (14)	0.06046 (10)	0.75039 (11)	0.0417 (6)
C2	0.46903 (15)	−0.02419 (12)	0.79408 (9)	0.0518 (7)
H2	0.5042	−0.0341	0.8717	0.062*
C3	0.48952 (15)	−0.09411 (9)	0.72171 (14)	0.0624 (8)
H3	0.5384	−0.1508	0.7509	0.075*
C4	0.43691 (16)	−0.07938 (11)	0.60565 (13)	0.0589 (7)
H4	0.4506	−0.1262	0.5572	0.071*
C5	0.36382 (15)	0.00527 (12)	0.56196 (8)	0.0590 (7)
H5	0.3286	0.0151	0.4843	0.071*
C6	0.37230 (15)	0.13348 (10)	0.81951 (12)	0.0395 (6)
N3	0.43588 (14)	0.13294 (11)	0.93287 (12)	0.0502 (5)
C7	0.39003 (16)	0.20944 (13)	0.97707 (11)	0.0534 (7)
H7	0.4169	0.2262	1.0531	0.064*
C8	0.29810 (15)	0.25725 (11)	0.89103 (13)	0.0488 (6)
H8	0.2508	0.3126	0.8976	0.059*
N4	0.28714 (14)	0.21030 (11)	0.79365 (11)	0.0413 (5)
C9	−0.1363 (2)	0.11723 (18)	0.21435 (19)	0.0467 (6)
C10	−0.1977 (3)	0.0643 (2)	0.1161 (2)	0.0572 (7)
H10	−0.2821	0.0804	0.0697	0.069*
C11	−0.1323 (3)	−0.0127 (2)	0.0876 (2)	0.0694 (8)
H11	−0.1715	−0.0488	0.0215	0.083*
C12	−0.0090 (3)	−0.03454 (19)	0.1584 (2)	0.0656 (8)
H12	0.0381	−0.0852	0.1411	0.079*
C13	0.0436 (3)	0.0197 (2)	0.2550 (2)	0.0633 (7)
H13	0.1268	0.0030	0.3036	0.076*
C14	−0.2034 (2)	0.20182 (19)	0.24123 (19)	0.0474 (6)
C15	−0.2823 (2)	0.3070 (2)	0.3309 (2)	0.0606 (7)
H15	−0.3017	0.3407	0.3868	0.073*
C16	−0.3281 (3)	0.3272 (2)	0.2197 (2)	0.0679 (8)
H16	−0.3850	0.3789	0.1863	0.081*
C17	0.2028 (2)	0.24607 (16)	0.68080 (17)	0.0451 (6)
H17A	0.2504	0.2412	0.6302	0.054*
H17B	0.1837	0.3158	0.6866	0.054*
C18	0.0760 (2)	0.19055 (17)	0.62919 (17)	0.0458 (6)
H18A	0.0266	0.1950	0.6785	0.055*
H18B	0.0932	0.1209	0.6205	0.055*
C19	−0.0021 (2)	0.23502 (17)	0.51472 (17)	0.0463 (6)
H19A	−0.0206	0.3041	0.5247	0.056*
H19B	0.0499	0.2332	0.4674	0.056*
C20	−0.1283 (2)	0.18114 (18)	0.45550 (17)	0.0521 (7)
H20A	−0.1103	0.1121	0.4445	0.062*
H20B	−0.1807	0.1827	0.5025	0.062*
N2	−0.0161 (2)	0.09507 (15)	0.28481 (16)	0.0547 (6)
N5	−0.20146 (18)	0.22651 (15)	0.34553 (15)	0.0499 (5)
N6	−0.2800 (2)	0.26188 (17)	0.16254 (16)	0.0592 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0433 (12)	0.0591 (14)	0.0435 (11)	0.0011 (11)	0.0120 (10)	0.0039 (10)
C1	0.0336 (14)	0.0477 (16)	0.0433 (14)	−0.0021 (12)	0.0134 (11)	0.0033 (12)
C2	0.0542 (17)	0.0541 (17)	0.0480 (15)	0.0130 (14)	0.0197 (13)	0.0063 (13)
C3	0.0624 (19)	0.0572 (18)	0.0724 (19)	0.0184 (15)	0.0300 (16)	0.0105 (15)
C4	0.0576 (18)	0.0644 (19)	0.0600 (18)	0.0036 (15)	0.0275 (15)	−0.0020 (14)
C5	0.0577 (18)	0.072 (2)	0.0489 (15)	−0.0003 (16)	0.0212 (14)	−0.0070 (15)
C6	0.0390 (14)	0.0402 (15)	0.0386 (14)	0.0023 (12)	0.0132 (12)	−0.0029 (11)
N3	0.0484 (13)	0.0572 (14)	0.0408 (12)	0.0002 (11)	0.0113 (10)	0.0023 (10)
C7	0.0606 (18)	0.0584 (17)	0.0407 (14)	−0.0019 (15)	0.0179 (14)	−0.0079 (13)
C8	0.0547 (17)	0.0471 (16)	0.0462 (15)	0.0000 (13)	0.0202 (13)	−0.0054 (13)
N4	0.0409 (12)	0.0417 (12)	0.0396 (11)	0.0002 (10)	0.0122 (10)	−0.0003 (9)
C9	0.0460 (17)	0.0529 (17)	0.0424 (14)	−0.0080 (14)	0.0174 (14)	0.0021 (12)
C10	0.0557 (18)	0.0694 (19)	0.0465 (16)	−0.0118 (16)	0.0184 (14)	−0.0005 (14)
C11	0.084 (2)	0.067 (2)	0.0632 (19)	−0.0193 (19)	0.0340 (19)	−0.0153 (16)
C12	0.077 (2)	0.0563 (19)	0.0702 (19)	−0.0037 (17)	0.0342 (18)	−0.0105 (16)
C13	0.0542 (18)	0.0583 (18)	0.0733 (19)	0.0057 (16)	0.0181 (16)	−0.0025 (15)
C14	0.0381 (15)	0.0605 (18)	0.0423 (15)	−0.0038 (14)	0.0128 (13)	−0.0029 (13)
C15	0.0445 (16)	0.077 (2)	0.0548 (17)	0.0102 (16)	0.0115 (14)	−0.0114 (15)
C16	0.0498 (18)	0.081 (2)	0.0626 (18)	0.0179 (16)	0.0081 (16)	0.0013 (16)
C17	0.0429 (15)	0.0441 (15)	0.0433 (13)	0.0031 (13)	0.0096 (12)	0.0067 (11)
C18	0.0421 (15)	0.0497 (15)	0.0438 (14)	0.0013 (13)	0.0132 (12)	0.0046 (11)
C19	0.0407 (14)	0.0539 (16)	0.0398 (13)	0.0023 (13)	0.0091 (12)	0.0027 (12)
C20	0.0454 (16)	0.0670 (18)	0.0435 (15)	−0.0044 (14)	0.0157 (13)	−0.0002 (12)
N2	0.0478 (14)	0.0564 (14)	0.0553 (13)	0.0004 (12)	0.0132 (12)	−0.0049 (11)
N5	0.0387 (12)	0.0689 (15)	0.0376 (12)	0.0013 (11)	0.0085 (10)	−0.0021 (11)
N6	0.0482 (14)	0.0759 (17)	0.0483 (13)	0.0105 (13)	0.0112 (12)	0.0039 (12)

Geometric parameters (Å, º) top

N1—C1	1.3900	C11—H11	0.9300
N1—C5	1.3900	C12—C13	1.365 (3)
C1—C2	1.3900	C12—H12	0.9300
C1—C6	1.4036	C13—N2	1.337 (3)
C2—C3	1.3900	C13—H13	0.9300
C2—H2	0.9300	C14—N6	1.325 (3)
C3—C4	1.3900	C14—N5	1.359 (3)
C3—H3	0.9300	C15—C16	1.345 (3)
C4—C5	1.3900	C15—N5	1.372 (3)
C4—H4	0.9300	C15—H15	0.9300
C5—H5	0.9300	C16—N6	1.364 (3)
C6—N3	1.3551	C16—H16	0.9300
C6—N4	1.3551	C17—C18	1.511 (3)
N3—C7	1.3551	C17—H17A	0.9700
C7—C8	1.3551	C17—H17B	0.9700
C7—H7	0.9300	C18—C19	1.520 (3)
C8—N4	1.3551	C18—H18A	0.9700
C8—H8	0.9300	C18—H18B	0.9700
N4—C17	1.480 (2)	C19—C20	1.509 (3)
C9—N2	1.338 (3)	C19—H19A	0.9700
C9—C10	1.383 (3)	C19—H19B	0.9700
C9—C14	1.464 (3)	C20—N5	1.470 (3)
C10—C11	1.385 (3)	C20—H20A	0.9700
C10—H10	0.9300	C20—H20B	0.9700
C11—C12	1.365 (3)

C1—N1—C5	120.0	N2—C13—C12	124.6 (2)
N1—C1—C2	120.0	N2—C13—H13	117.7
N1—C1—C6	117.60	C12—C13—H13	117.7
C2—C1—C6	122.40	N6—C14—N5	111.6 (2)
C1—C2—C3	120.0	N6—C14—C9	122.5 (2)
C1—C2—H2	120.0	N5—C14—C9	125.9 (2)
C3—C2—H2	120.0	C16—C15—N5	106.3 (2)
C4—C3—C2	120.0	C16—C15—H15	126.9
C4—C3—H3	120.0	N5—C15—H15	126.9
C2—C3—H3	120.0	C15—C16—N6	111.0 (2)
C3—C4—C5	120.0	C15—C16—H16	124.5
C3—C4—H4	120.0	N6—C16—H16	124.5
C5—C4—H4	120.0	N4—C17—C18	114.81 (17)
C4—C5—N1	120.0	N4—C17—H17A	108.6
C4—C5—H5	120.0	C18—C17—H17A	108.6
N1—C5—H5	120.0	N4—C17—H17B	108.6
N3—C6—N4	108.0	C18—C17—H17B	108.6
N3—C6—C1	121.29	H17A—C17—H17B	107.5
N4—C6—C1	130.66	C17—C18—C19	109.66 (18)
C6—N3—C7	108.0	C17—C18—H18A	109.7
N3—C7—C8	108.0	C19—C18—H18A	109.7
N3—C7—H7	126.0	C17—C18—H18B	109.7
C8—C7—H7	126.0	C19—C18—H18B	109.7
C7—C8—N4	108.0	H18A—C18—H18B	108.2
C7—C8—H8	126.0	C20—C19—C18	112.96 (19)
N4—C8—H8	126.0	C20—C19—H19A	109.0
C6—N4—C8	108.0	C18—C19—H19A	109.0
C6—N4—C17	128.42 (14)	C20—C19—H19B	109.0
C8—N4—C17	123.39 (14)	C18—C19—H19B	109.0
N2—C9—C10	122.2 (2)	H19A—C19—H19B	107.8
N2—C9—C14	118.7 (2)	N5—C20—C19	111.43 (19)
C10—C9—C14	119.1 (2)	N5—C20—H20A	109.3
C9—C10—C11	119.3 (3)	C19—C20—H20A	109.3
C9—C10—H10	120.4	N5—C20—H20B	109.3
C11—C10—H10	120.4	C19—C20—H20B	109.3
C12—C11—C10	118.6 (3)	H20A—C20—H20B	108.0
C12—C11—H11	120.7	C13—N2—C9	116.8 (2)
C10—C11—H11	120.7	C14—N5—C15	106.33 (19)
C13—C12—C11	118.5 (3)	C14—N5—C20	129.4 (2)
C13—C12—H12	120.8	C15—N5—C20	124.2 (2)
C11—C12—H12	120.8	C14—N6—C16	104.8 (2)

C5—N1—C1—C2	0.0	C10—C9—C14—N5	141.1 (2)
N1—C1—C2—C3	0.0	N5—C15—C16—N6	0.5 (3)
C1—C2—C3—C4	0.0	C6—N4—C17—C18	83.6 (2)
C2—C3—C4—C5	0.0	C8—N4—C17—C18	−102.05 (19)
C3—C4—C5—N1	0.0	N4—C17—C18—C19	179.30 (18)
C1—N1—C5—C4	0.0	C17—C18—C19—C20	177.87 (19)
N4—C6—N3—C7	0.0	C18—C19—C20—N5	179.65 (19)
C6—N3—C7—C8	0.0	C12—C13—N2—C9	0.7 (4)
N3—C7—C8—N4	0.0	C10—C9—N2—C13	1.0 (3)
N3—C6—N4—C8	0.0	C14—C9—N2—C13	−177.6 (2)
N3—C6—N4—C17	175.07 (18)	N6—C14—N5—C15	0.2 (3)
C1—C6—N4—C17	−7.4 (2)	C9—C14—N5—C15	−176.9 (2)
C7—C8—N4—C6	0.0	N6—C14—N5—C20	−178.8 (2)
C7—C8—N4—C17	−175.38 (17)	C9—C14—N5—C20	4.2 (4)
N2—C9—C10—C11	−1.6 (3)	C16—C15—N5—C14	−0.4 (3)
C14—C9—C10—C11	176.9 (2)	C16—C15—N5—C20	178.6 (2)
C9—C10—C11—C12	0.6 (4)	C19—C20—N5—C14	94.6 (3)
C10—C11—C12—C13	1.0 (4)	C19—C20—N5—C15	−84.2 (3)
C11—C12—C13—N2	−1.7 (4)	N5—C14—N6—C16	0.1 (3)
N2—C9—C14—N6	142.9 (2)	C9—C14—N6—C16	177.3 (2)
C10—C9—C14—N6	−35.7 (3)	C15—C16—N6—C14	−0.4 (3)
N2—C9—C14—N5	−40.3 (3)

Experimental details

Crystal data
Chemical formula	C₂₀H₂₀N₆
M_r	344.42
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	11.0426 (10), 13.4510 (12), 12.7081 (11)
β (°)	111.213 (2)
V (Å³)	1759.7 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.43 × 0.39 × 0.36

Data collection
Diffractometer	Bruker SMART APEX CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996)
T_min, T_max	0.938, 0.966
No. of measured, independent and observed [I > 2σ(I)] reflections	10708, 4139, 1705
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.666

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.053, 0.125, 1.03
No. of reflections	4139
No. of parameters	215
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.49, −0.48

Computer programs: SMART (Bruker, 1997), SAINT (Bruker, 1999), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL-Plus (Sheldrick, 2008).

References

Bruker (1997). SMART. Bruker AXS Inc., Madison,Wisconsin, USA. Google Scholar
Bruker (1999). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Carlucci, L., Ciani, G. & Proserpio, D. M. (2005). Cryst. Growth Des. 5, 37–39. Web of Science CSD CrossRef CAS Google Scholar
Chiswell, B., Lioss, F. & Morris, B. S. (1964). Inorg. Chem. 3, 110–114. CrossRef CAS Web of Science Google Scholar
Herrmann, W. A. (2002). Angew. Chem. Int. Ed. 41, 1290–1309. Web of Science CrossRef CAS Google Scholar
Herrmann, W. A. & Kocher, C. (1997). Angew. Chem. Int. Ed. Engl. 36, 2162–2187. CrossRef CAS Web of Science 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