6-[(2-Hy­droxy-5-methyl­anilino)methyl­idene]-4-nitro­cyclo­hexa-2,4-dien-1-one

Böhme, U.; Fels, S.

doi:10.1107/S241431462001384X

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 5| Part 10| October 2020| x201384

https://doi.org/10.1107/S241431462001384X

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6-[(2-Hydroxy-5-methylanilino)methylidene]-4-nitrocyclohexa-2,4-dien-1-one

Uwe Böhme ^a ^* and Sabine Fels ^a

^aInstitut für Anorganische Chemie, Technische Universität Bergakademie Freiberg, Leipziger Str. 29, 09599 Freiberg, Germany
^*Correspondence e-mail: uwe.boehme@chemie.tu-freiberg.de

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 15 October 2020; accepted 16 October 2020; online 23 October 2020)

The title compound, C₁₄H₁₂N₂O₄, is nearly planar with a dihedral angle between the aromatic rings of 1.41 (8)°. The phenolic O atom is deprotonated and the N atom of the azomethine unit carries the proton, thereby forming an intramolecular N—H⋯O hydrogen bond. In the crystal, the molecules form inversion dimers via pairwise O—H⋯O hydrogen bonds.

Keywords: crystal structure; Schiff base; tridentate ligand.

CCDC reference: 2038926

Structure description

Aromatic Schiff bases with ortho-hydroxy groups are useful as acyclic polydentate ligands for the preparation of chelate complexes with a wide variety of metal ions (Freeman & White, 1956 ; Calligaris & Randaccio, 1987 ; Pettinari et al., 2001 ; Hernández-Molina & Mederos, 2004 ). We are working on silicon, tin, and titanium complexes with tridentate O,N,O-ligands (Böhme & Günther, 2006 , 2007 ; Böhme et al., 2006 ; Paul et al., 2014 ; Warncke et al., 2012 , 2016 ; Schwarzer et al., 2018 ).

The title compound was prepared in order to extend the series of available ligands. Its preparation was performed according to methods described in the literature for the parent compound salicyclidene-o-aminophenol (salopH₂; Freeman & White, 1956; Pettinari et al., 2001) by the reaction of 2-hydroxy-5-nitrobenzaldehyde and 2-amino-4-methylphenol in ethanol.

The molecule is nearly planar with a dihedral angle between the aromatic rings of 1.41 (8)°. Atom H2 forms an intramolecular hydrogen bond (Table 1, Fig. 1) between the phenolic oxygen atom O1 and N1 of the azomethine unit: the hydrogen atom is localized at a distance of 0.93 (2) Å from N1, indicating the presence of the keto–amine form. The presence of a quinoidal structure is further supported by the shortening of the bond C3—O1 to 1.2734 (19) Å and the lengthening of the adjacent C—C bonds in the phenyl ring [C2—C3 = 1.446 (2), C3—C4 = 1.420 (2) Å] (Nazır et al., 2000 ; Warncke et al., 2016). There are several structure reports of Schiff bases with an oxygen atom in the ortho-position where the intramolecular bridging hydrogen atom is localized at the nitrogen atom (e.g. Pradeep, 2005 ; Dubs et al., 2000 ; Höpfl et al., 1998 ; Böhme & Fels, 2008a ,b ). The stabilization of salicylidene-imines by `resonance-assisted hydrogen bonding' has been discussed previously (Hökelek et al., 2004 ).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H2⋯O1	0.93 (2)	1.84 (2)	2.6065 (18)	138.1 (17)
O2—H9⋯O1ⁱ	0.79 (3)	1.81 (3)	2.5817 (18)	163 (3)
C1—H1⋯O4ⁱⁱ	0.93	2.32	3.220 (2)	162
Symmetry codes: (i) ; (ii) .

Figure 1
The molecular structure of the title compound, drawn with 50% probability displacement ellipsoids.

In the crystal, the molecule forms dimers via pairwise O2—H9⋯O1 hydrogen bonds. An intermolecular C—H⋯O short contact (H⋯O = 2.32 Å) to one of the O atoms of the nitro group is also present.

Synthesis and crystallization

To 2-amino-4-methylphenol (1.13 g, 9.18 mmol) dissolved in ethanol (80 ml) was added 2-hydroxy-5-nitrobenzaldehyde (1.53 g, 9.18 mmol) in ethanol (20 ml). An orange precipitate appeared after addition. The resulting suspension was heated at reflux temperature for 2 h. The precipitate was filtered off and washed with ethanol. After drying, the product was purified by recrystallization from ethanol solution. Yellow solid (2.21 g, 88.4%, m.p. 536 K). NMR (DMSO, 300 K, TMS): ¹H: δ = 15.76, 10.17 (s, OH, NH, 2H), 9.31 (s, CH—N, 1H), 8.59–6.86 (m, CH_ar (ar = aromatic) 6H), 2.28 (s, Ar—CH₃, 3H); ¹³C: 172.8 (C3), 158.9 (C1), 148.1 (C9), 136.6 (C6), 130.4, 129.8, 129.1, 128.7, 128.6, 120.6, 118.8, 116.4, 116.3 (9 signals for aromatic C), 20.1 (C14).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The methyl group at C14 is rotationally disordered over two orientations in a 0.59 (5):0.41 (5) ratio.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₄H₁₂N₂O₄
M_r	272.26
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	303
a, b, c (Å)	6.5499 (3), 7.6232 (3), 25.6211 (11)
β (°)	96.216 (1)
V (Å³)	1271.77 (9)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.11
Crystal size (mm)	0.47 × 0.38 × 0.12

Data collection
Diffractometer	Bruker SMART CCD
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	11875, 2504, 1776
R_int	0.023
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.041, 0.114, 1.04
No. of reflections	2504
No. of parameters	191
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.16, −0.17
Computer programs: SMART and SAINT (Bruker, 2004 ), SHELXS (Sheldrick, 2008 ), SHELXL2017/1 (Sheldrick, 2015 ) and ORTEP-3 for Windows (Farrugia, 2012 ).

Structural data

CCDC reference: 2038926

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S241431462001384X/hb4367sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S241431462001384X/hb4367Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S241431462001384X/hb4367Isup3.cml

checkCIF report

Computing details top

Data collection: SMART (Bruker, 2004); cell refinement: SMART (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL2017/1 (Sheldrick, 2015); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: SHELXL2017/1 (Sheldrick, 2015).

6-[(2-Hydroxy-5-methylanilino)methylidene]-4-nitrocyclohexa-2,4-dien-1-one top

Crystal data top

C₁₄H₁₂N₂O₄	D_x = 1.422 Mg m⁻³
M_r = 272.26	Melting point: 536 K
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 6.5499 (3) Å	Cell parameters from 5292 reflections
b = 7.6232 (3) Å	θ = 2.7–30.2°
c = 25.6211 (11) Å	µ = 0.11 mm⁻¹
β = 96.216 (1)°	T = 303 K
V = 1271.77 (9) Å³	Prism, yellow
Z = 4	0.47 × 0.38 × 0.12 mm
F(000) = 568

Data collection top

Bruker SMART CCD diffractometer	1776 reflections with I > 2σ(I)
Radiation source: sealed tube	R_int = 0.023
Graphite monochromator	θ_max = 26.0°, θ_min = 2.8°
phi and ω scans	h = −5→8
11875 measured reflections	k = −9→9
2504 independent reflections	l = −31→27

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)] = 0.041	Hydrogen site location: mixed
wR(F²) = 0.114	H atoms treated by a mixture of independent and constrained refinement
S = 1.04	w = 1/[σ²(F_o²) + (0.0502P)² + 0.2714P] where P = (F_o² + 2F_c²)/3
2504 reflections	(Δ/σ)_max < 0.001
191 parameters	Δρ_max = 0.16 e Å⁻³
0 restraints	Δρ_min = −0.17 e Å⁻³

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Hydrogen atoms bonded to C were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.93 Å for Csp², and 0.96 Å for CH₃. U_iso(H) = xU_eq(C), where x = 1.2 for Csp² and 1.5 for CH₃. The hydrogen atoms at N1 and O2 (H2 and H9) were located by difference Fourier synthesis and freely refined.

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
O1	0.19636 (18)	0.85732 (19)	−0.05759 (5)	0.0666 (4)
O2	0.5013 (2)	0.9258 (2)	0.05845 (5)	0.0669 (4)
H9	0.596 (4)	0.991 (3)	0.0647 (10)	0.093 (9)*
N1	0.1333 (2)	0.79690 (18)	0.03950 (5)	0.0468 (4)
H2	0.215 (3)	0.835 (3)	0.0143 (8)	0.077 (6)*
N2	−0.5557 (2)	0.5515 (2)	−0.11991 (6)	0.0576 (4)
O3	−0.6215 (2)	0.5556 (2)	−0.16650 (6)	0.0845 (5)
O4	−0.6495 (2)	0.48027 (19)	−0.08672 (6)	0.0740 (4)
C1	−0.0438 (2)	0.7351 (2)	0.02029 (6)	0.0481 (4)
H1	−0.133979	0.696628	0.043493	0.058*
C2	−0.1063 (2)	0.7235 (2)	−0.03427 (6)	0.0447 (4)
C3	0.0234 (2)	0.7870 (2)	−0.07240 (6)	0.0479 (4)
C4	−0.0523 (3)	0.7664 (3)	−0.12613 (7)	0.0563 (5)
H4	0.027853	0.804716	−0.151711	0.068*
C5	−0.2369 (3)	0.6928 (2)	−0.14126 (7)	0.0541 (5)
H5	−0.282485	0.681930	−0.176767	0.065*
C6	−0.3600 (2)	0.6328 (2)	−0.10331 (7)	0.0471 (4)
C7	−0.2971 (2)	0.6483 (2)	−0.05097 (7)	0.0478 (4)
H7	−0.381007	0.608690	−0.026386	0.057*
C8	0.2130 (2)	0.8135 (2)	0.09270 (6)	0.0456 (4)
C9	0.4090 (3)	0.8863 (2)	0.10173 (7)	0.0510 (4)
C10	0.4949 (3)	0.9106 (3)	0.15292 (7)	0.0634 (5)
H10	0.624875	0.960150	0.159624	0.076*
C11	0.3879 (3)	0.8614 (3)	0.19404 (7)	0.0684 (6)
H11	0.446815	0.879703	0.228288	0.082*
C12	0.1941 (3)	0.7851 (3)	0.18568 (7)	0.0599 (5)
C13	0.1080 (3)	0.7624 (2)	0.13445 (6)	0.0526 (4)
H13	−0.021705	0.712381	0.127863	0.063*
C14	0.0811 (4)	0.7261 (4)	0.23108 (8)	0.0869 (7)
H14A	0.169804	0.653676	0.254283	0.130*	0.59 (5)
H14B	−0.038512	0.660356	0.217905	0.130*	0.59 (5)
H14C	0.040213	0.826966	0.249852	0.130*	0.59 (5)
H14D	0.141816	0.780054	0.262897	0.130*	0.41 (5)
H14E	0.090280	0.600890	0.234441	0.130*	0.41 (5)
H14F	−0.060592	0.760054	0.224701	0.130*	0.41 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0548 (7)	0.0944 (10)	0.0521 (8)	−0.0311 (7)	0.0125 (6)	−0.0061 (7)
O2	0.0594 (8)	0.0874 (10)	0.0547 (8)	−0.0275 (8)	0.0103 (6)	0.0008 (7)
N1	0.0490 (8)	0.0530 (9)	0.0390 (8)	−0.0094 (7)	0.0082 (6)	−0.0016 (6)
N2	0.0509 (8)	0.0630 (10)	0.0572 (10)	−0.0064 (7)	−0.0016 (7)	−0.0013 (8)
O3	0.0695 (9)	0.1175 (13)	0.0616 (10)	−0.0193 (8)	−0.0147 (7)	0.0000 (8)
O4	0.0583 (8)	0.0872 (10)	0.0757 (10)	−0.0265 (7)	0.0040 (7)	0.0075 (8)
C1	0.0475 (9)	0.0534 (10)	0.0446 (10)	−0.0096 (8)	0.0108 (7)	−0.0013 (8)
C2	0.0462 (9)	0.0476 (10)	0.0411 (9)	−0.0056 (7)	0.0074 (7)	−0.0032 (7)
C3	0.0466 (9)	0.0539 (10)	0.0446 (9)	−0.0076 (8)	0.0107 (7)	−0.0055 (8)
C4	0.0561 (10)	0.0722 (12)	0.0427 (10)	−0.0119 (9)	0.0145 (8)	−0.0019 (9)
C5	0.0567 (10)	0.0636 (12)	0.0414 (10)	−0.0032 (9)	0.0036 (8)	−0.0037 (8)
C6	0.0439 (8)	0.0481 (10)	0.0487 (10)	−0.0033 (7)	0.0021 (7)	−0.0025 (8)
C7	0.0453 (9)	0.0518 (10)	0.0476 (10)	−0.0073 (7)	0.0111 (7)	0.0024 (8)
C8	0.0514 (9)	0.0459 (9)	0.0393 (9)	−0.0042 (7)	0.0044 (7)	−0.0007 (7)
C9	0.0520 (9)	0.0543 (11)	0.0470 (10)	−0.0077 (8)	0.0064 (8)	0.0025 (8)
C10	0.0543 (10)	0.0788 (14)	0.0546 (12)	−0.0118 (10)	−0.0058 (8)	0.0012 (10)
C11	0.0759 (13)	0.0842 (15)	0.0423 (11)	−0.0087 (11)	−0.0059 (9)	0.0016 (10)
C12	0.0717 (12)	0.0652 (12)	0.0428 (10)	−0.0087 (10)	0.0062 (8)	0.0012 (9)
C13	0.0566 (10)	0.0566 (11)	0.0452 (10)	−0.0116 (8)	0.0081 (8)	−0.0013 (8)
C14	0.1101 (18)	0.1055 (18)	0.0469 (12)	−0.0257 (15)	0.0171 (12)	0.0029 (12)

Geometric parameters (Å, º) top

O1—C3	1.2734 (19)	C6—C7	1.365 (2)
O2—C9	1.353 (2)	C7—H7	0.9300
O2—H9	0.79 (3)	C8—C13	1.389 (2)
N1—C1	1.298 (2)	C8—C9	1.394 (2)
N1—C8	1.411 (2)	C9—C10	1.383 (3)
N1—H2	0.93 (2)	C10—C11	1.379 (3)
N2—O3	1.225 (2)	C10—H10	0.9300
N2—O4	1.2280 (18)	C11—C12	1.392 (3)
N2—C6	1.446 (2)	C11—H11	0.9300
C1—C2	1.416 (2)	C12—C13	1.382 (2)
C1—H1	0.9300	C12—C14	1.513 (3)
C2—C7	1.399 (2)	C13—H13	0.9300
C2—C3	1.446 (2)	C14—H14A	0.9600
C3—C4	1.420 (2)	C14—H14B	0.9600
C4—C5	1.351 (2)	C14—H14C	0.9600
C4—H4	0.9300	C14—H14D	0.9600
C5—C6	1.405 (2)	C14—H14E	0.9600
C5—H5	0.9300	C14—H14F	0.9600

C9—O2—H9	112.4 (18)	C13—C8—N1	123.79 (15)
C1—N1—C8	128.37 (14)	C9—C8—N1	115.70 (14)
C1—N1—H2	114.1 (13)	O2—C9—C10	125.12 (16)
C8—N1—H2	117.6 (13)	O2—C9—C8	115.95 (15)
O3—N2—O4	122.47 (16)	C10—C9—C8	118.92 (15)
O3—N2—C6	118.86 (15)	C11—C10—C9	119.98 (17)
O4—N2—C6	118.67 (15)	C11—C10—H10	120.0
N1—C1—C2	123.24 (14)	C9—C10—H10	120.0
N1—C1—H1	118.4	C10—C11—C12	121.78 (18)
C2—C1—H1	118.4	C10—C11—H11	119.1
C7—C2—C1	118.74 (14)	C12—C11—H11	119.1
C7—C2—C3	120.10 (14)	C13—C12—C11	118.04 (17)
C1—C2—C3	121.17 (14)	C13—C12—C14	120.65 (18)
O1—C3—C4	122.77 (14)	C11—C12—C14	121.31 (18)
O1—C3—C2	120.57 (15)	C12—C13—C8	120.75 (16)
C4—C3—C2	116.67 (14)	C12—C13—H13	119.6
C5—C4—C3	122.11 (15)	C8—C13—H13	119.6
C5—C4—H4	118.9	C12—C14—H14A	109.5
C3—C4—H4	118.9	C12—C14—H14B	109.5
C4—C5—C6	119.96 (16)	H14A—C14—H14B	109.5
C4—C5—H5	120.0	C12—C14—H14C	109.5
C6—C5—H5	120.0	H14A—C14—H14C	109.5
C7—C6—C5	121.13 (15)	H14B—C14—H14C	109.5
C7—C6—N2	119.33 (15)	C12—C14—H14D	109.5
C5—C6—N2	119.53 (15)	C12—C14—H14E	109.5
C6—C7—C2	120.03 (14)	H14D—C14—H14E	109.5
C6—C7—H7	120.0	C12—C14—H14F	109.5
C2—C7—H7	120.0	H14D—C14—H14F	109.5
C13—C8—C9	120.51 (15)	H14E—C14—H14F	109.5

C8—N1—C1—C2	−179.40 (16)	C1—C2—C7—C6	−178.99 (16)
N1—C1—C2—C7	177.42 (16)	C3—C2—C7—C6	0.7 (3)
N1—C1—C2—C3	−2.3 (3)	C1—N1—C8—C13	0.4 (3)
C7—C2—C3—O1	179.29 (16)	C1—N1—C8—C9	−179.56 (17)
C1—C2—C3—O1	−1.0 (3)	C13—C8—C9—O2	177.63 (16)
C7—C2—C3—C4	−0.8 (2)	N1—C8—C9—O2	−2.4 (2)
C1—C2—C3—C4	178.95 (16)	C13—C8—C9—C10	−1.5 (3)
O1—C3—C4—C5	−179.43 (18)	N1—C8—C9—C10	178.44 (16)
C2—C3—C4—C5	0.6 (3)	O2—C9—C10—C11	−178.40 (19)
C3—C4—C5—C6	−0.4 (3)	C8—C9—C10—C11	0.7 (3)
C4—C5—C6—C7	0.4 (3)	C9—C10—C11—C12	0.7 (3)
C4—C5—C6—N2	−178.90 (16)	C10—C11—C12—C13	−1.2 (3)
O3—N2—C6—C7	171.96 (17)	C10—C11—C12—C14	177.9 (2)
O4—N2—C6—C7	−8.3 (2)	C11—C12—C13—C8	0.4 (3)
O3—N2—C6—C5	−8.8 (3)	C14—C12—C13—C8	−178.81 (19)
O4—N2—C6—C5	170.98 (16)	C9—C8—C13—C12	1.0 (3)
C5—C6—C7—C2	−0.5 (3)	N1—C8—C13—C12	−178.96 (17)
N2—C6—C7—C2	178.75 (15)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H2···O1	0.93 (2)	1.84 (2)	2.6065 (18)	138.1 (17)
O2—H9···O1ⁱ	0.79 (3)	1.81 (3)	2.5817 (18)	163 (3)
C1—H1···O4ⁱⁱ	0.93	2.32	3.220 (2)	162

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

Funding information

Funding for this research was provided by: Open Access Funding by the Publication Fund of the TU Bergakademie Freiberg.

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