(S)-Alanine ethyl ester tetra­cyanidoborate, (C5H12NO)[B(CN)4]

Peppel, T.; Köckerling, M.

doi:10.1107/S2414314621005629

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 6| Part 6| June 2021| x210562

https://doi.org/10.1107/S2414314621005629

Open

access

(S)-Alanine ethyl ester tetracyanidoborate, (C₅H₁₂NO)[B(CN)₄]

Tim Peppel ^a ^* and Martin Köckerling ^b

^aLeibniz-Institut für Katalyse e.V. (LIKAT), Heterogene Photokatalyse, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany, and ^bUniversität Rostock, Institut für Chemie, Anorganische Festkörperchemie, Albert-Einstein-Str. 3a, D-18059 Rostock, Germany
^*Correspondence e-mail: tim.peppel@catalysis.de

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 27 May 2021; accepted 1 June 2021; online 4 June 2021)

The title molecular salt, C₅H₁₂NO⁺·C₄BN₄⁻ or (C₅H₁₂NO)[B(CN)₄], was obtained as single crystals by slow evaporation of a solution of the compound in acetonitrile over several weeks. The asymmetric unit contains two (S)-alanine ethyl ester cations and two tetracyanidoborate anions, which are linked by N—H⋯N hydrogen bonds. The compound exhibits a relatively low melting point of 110°C and shows a solid–solid phase transition near room temperature (T_s–s = 29°C) on the basis of DSC measurements.

Keywords: crystal structure; borate; amino acid.

CCDC reference: 2087276

Structure description

For more than 20 years, ionic liquids as salts with low melting points have attracted great interest because of their unique properties and applications. These properties include for instance large liquid ranges, broad electrochemical windows as well as low vapour pressures (Hallett & Welton, 2011 ; Welton, 1999 ). The title compound acts as a first example of a low-melting chiral substance in our ongoing efforts to investigate tetracyanidoborate-based ionic liquids (Bernsdorf et al., 2009 ; Flemming et al., 2010 ; Siegesmund et al., 2017 ).

The asymmetric unit of the title compound consists of two (S)-alanine ethyl ester cations and two tetracyanidoborate anions (Fig. 1). The conformations of the cations about the stereogenic centres (C10 and C15) are almost the same, as indicated by the C9—C10—C11—O2 and C14—C15—C16—O4 torsion angles of −61.9 (3) and −63.0 (3)°, respectively, but the conformations of the ethyl side chains differ substantially: C11—O2—C12—C13 = −86.1 (3) and C16—O4—C17—C18 = 136.5 (3)°. Otherwise, all bond lengths and angles within the cation are in the expected ranges (Dimitrijević et al., 2013 ). The geometry around the B atoms is close to tetrahedral with C—B—C angles ranging from 107.8 (2) to 111.2 (2)°.

Figure 1
The asymmetric unit of (C₅H₁₂NO)[B(CN)₄] with atom labelling.

In the extended structure, the shortest hydrogen-bond contacts are found between the N-bonded H atoms of the cations (N9 and N10) and the N atoms of the tetracyanidoborate anions: the shortest N⋯N donor–acceptor distance is 2.920 (3) Å (Table 1). Fig. 2 shows the packing of the ions within and around the unit cell.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N9—H9F⋯N6ⁱ	0.91	2.16	2.920 (3)	141
N10—H10B⋯N4ⁱⁱ	0.91	2.05	2.953 (3)	174
N10—H10D⋯N1	0.91	2.07	2.961 (3)	166
N9—H9E⋯N8ⁱⁱⁱ	0.91	2.14	3.001 (3)	158
N10—H10C⋯N2^iv	0.91	2.15	3.015 (3)	159
N9—H9D⋯N5^v	0.91	2.14	3.017 (3)	161
N9—H9F⋯N3^vi	0.91	2.64	3.147 (3)	116
Symmetry codes: (i) $[x-{\script{1\over 2}}, y+{\script{1\over 2}}, z-1]$ ; (ii) $[x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]$ ; (iii) ; (iv) x, y+1, z; (v) $[x-{\script{1\over 2}}, y-{\script{1\over 2}}, z-1]$ ; (vi) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z]$ .

Figure 2
A view of the unit-cell contents in projection down the b axis.

Synthesis and crystallization

The title compound, (C₅H₁₂NO)[B(CN)₄], was obtained in high purity as a colorless solid on a multi-gram scale from the salt metathesis of (S)-alanine ethyl ester hydrochloride and K[B(CN)₄] in acetonic solution at room temperature. (S)-Alanine ethyl ester hydrochloride (2.0 g, 13.0 mmol) was added in one portion to a vigorously stirred solution of K[B(CN)₄] (2.2 g, 14.3 mmol) in 100 ml acetone at room temperature and was further stirred overnight. The precipitate was filtered off and the solvent of the filtrate was removed in vacuum. The residue was dissolved in a minimum amount of dichloromethane, filtered again and the solvent was removed in vacuum. The final product was obtained as a colourless solid in high yield (2.8 g, 91%); m.p. = 110°C, T_s–s = 29°C. The thermal behaviour was determined by means of differential scanning calorimetry (DSC) in the temperature range from −100 to 200°C with a heating rate of 10 K min⁻¹. Analytical data for C₉H₁₂BN₅O₂ % (calc.): C 46.43 (46.39); H 5.25 (5.19); N 26.53 (30.05).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. Sixteen reflections were omitted from the refinement because their intensities were affected by the beam stop. Details can be found in the refine_ special_details field in the CIF. The refined value of the Flack absolute structure parameter of 0.2 (8) was ambiguous, and the absolute structure was assigned on the basis of the enantiomeric pure (S)-alanine ethyl ester hydrochloride used in the synthesis.

Table 2
Experimental details

Crystal data
Chemical formula	C₅H₁₂NO₂⁺·C₄N₄B⁻
M_r	233.05
Crystal system, space group	Monoclinic, C2
Temperature (K)	173
a, b, c (Å)	17.059 (1), 8.7467 (4), 18.855 (1)
β (°)	111.468 (4)
V (Å³)	2618.2 (3)
Z	8
Radiation type	Mo Kα
μ (mm⁻¹)	0.09
Crystal size (mm)	0.27 × 0.18 × 0.15

Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2017 )
No. of measured, independent and observed [I > 2σ(I)] reflections	11976, 7354, 5158
R_int	0.038
(sin θ/λ)_max (Å⁻¹)	0.725

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.053, 0.133, 1.00
No. of reflections	7354
No. of parameters	307
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.38, −0.24
Absolute structure	Flack x determined using 1751 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )
Absolute structure parameter	0.2 (8)
Computer programs: APEX2 and SAINT (Bruker, 2017), SHELXS (Sheldrick, 2015b ), SHELXT (Sheldrick, 2015a ), DIAMOND (Brandenburg & Putz, 2019 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 2087276

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314621005629/hb4385sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314621005629/hb4385Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314621005629/hb4385Isup3.cml

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2017); cell refinement: SAINT (Bruker, 2017); data reduction: SAINT (Bruker, 2017); program(s) used to solve structure: SHELXS (Sheldrick, 2015b); program(s) used to refine structure: SHELXT (Sheldrick, 2015a); molecular graphics: DIAMOND (Brandenburg & Putz, 2019); software used to prepare material for publication: publCIF (Westrip, 2010).

1-Ethoxy-1-oxopropan-2-aminium tetracyanoborate top

Crystal data top

C₅H₁₂NO₂⁺·C₄N₄B⁻	F(000) = 976
M_r = 233.05	D_x = 1.182 Mg m⁻³
Monoclinic, C2	Mo Kα radiation, λ = 0.71073 Å
a = 17.059 (1) Å	Cell parameters from 2564 reflections
b = 8.7467 (4) Å	θ = 4.3–25.5°
c = 18.855 (1) Å	µ = 0.09 mm⁻¹
β = 111.468 (4)°	T = 173 K
V = 2618.2 (3) Å³	Block, colourless
Z = 8	0.27 × 0.18 × 0.15 mm

Data collection top

Bruker APEXII CCD diffractometer	5158 reflections with I > 2σ(I)
Radiation source: microfocus sealed tube	R_int = 0.038
φ and ω scans	θ_max = 31.0°, θ_min = 4.4°
Absorption correction: multi-scan (SADABS; Bruker, 2017)	h = −24→24
	k = −10→12
11976 measured reflections	l = −25→26
7354 independent reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.053	H-atom parameters constrained
wR(F²) = 0.133	w = 1/[σ²(F_o²) + (0.0649P)²] where P = (F_o² + 2F_c²)/3
S = 1.00	(Δ/σ)_max < 0.001
7354 reflections	Δρ_max = 0.38 e Å⁻³
307 parameters	Δρ_min = −0.24 e Å⁻³
1 restraint	Absolute structure: Flack x determined using 1751 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.2 (8)

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.

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

	x	y	z	U_iso*/U_eq
B1	0.4401 (2)	0.0236 (3)	0.3575 (2)	0.0267 (6)
C1	0.4986 (2)	0.1670 (3)	0.3916 (2)	0.0327 (6)
N1	0.5418 (2)	0.2686 (3)	0.4167 (2)	0.0494 (7)
C2	0.4971 (2)	−0.1273 (3)	0.3745 (2)	0.0281 (5)
N2	0.5371 (2)	−0.2346 (3)	0.3855 (1)	0.0405 (6)
C3	0.3940 (2)	0.0381 (3)	0.2677 (2)	0.0326 (6)
N3	0.3621 (2)	0.0434 (3)	0.2032 (2)	0.0505 (7)
C4	0.3729 (2)	0.0061 (3)	0.3968 (2)	0.0343 (6)
N4	0.3242 (2)	−0.0082 (4)	0.4246 (2)	0.0524 (7)
B2	0.4421 (2)	0.4179 (3)	0.8626 (2)	0.0288 (6)
C5	0.4893 (2)	0.5759 (3)	0.8893 (2)	0.0378 (6)
N5	0.5235 (2)	0.6898 (3)	0.9064 (2)	0.0574 (8)
C6	0.5081 (2)	0.2830 (3)	0.8927 (2)	0.0345 (6)
N6	0.5555 (2)	0.1866 (3)	0.9158 (2)	0.0505 (7)
C7	0.4013 (2)	0.4174 (4)	0.7723 (2)	0.0396 (7)
N7	0.3728 (2)	0.4224 (4)	0.7078 (2)	0.068 (1)
C8	0.3709 (2)	0.3968 (3)	0.8974 (2)	0.0304 (5)
N8	0.3198 (2)	0.3818 (3)	0.9222 (2)	0.0423 (6)
C9	0.1899 (2)	0.2660 (3)	0.0774 (2)	0.0485 (8)
H9A	0.1933	0.2721	0.1304	0.073*
H9B	0.2436	0.2290	0.0762	0.073*
H9C	0.1447	0.1952	0.0491	0.073*
C10	0.1714 (2)	0.4213 (3)	0.0417 (1)	0.0284 (5)
H10A	0.1168	0.4582	0.0436	0.034*
N9	0.1651 (1)	0.4193 (2)	−0.0392 (1)	0.0251 (4)
H9D	0.1236	0.3536	−0.0663	0.038*
H9E	0.2150	0.3881	−0.0414	0.038*
H9F	0.1529	0.5149	−0.0592	0.038*
C11	0.2398 (2)	0.5319 (3)	0.0848 (1)	0.0290 (5)
O1	0.2858 (1)	0.5932 (2)	0.0589 (1)	0.0390 (5)
O2	0.2429 (1)	0.5455 (2)	0.1560 (1)	0.0417 (5)
C12	0.3156 (2)	0.6236 (4)	0.2100 (2)	0.0534 (9)
H12A	0.3004	0.6699	0.2511	0.064*
H12B	0.3340	0.7064	0.1838	0.064*
C13	0.3855 (2)	0.5119 (6)	0.2431 (2)	0.069 (1)
H13A	0.4347	0.5646	0.2791	0.103*
H13B	0.4003	0.4663	0.2022	0.103*
H13C	0.3674	0.4313	0.2699	0.103*
C14	0.6152 (2)	0.5843 (4)	0.5570 (2)	0.0447 (7)
H14A	0.6329	0.6107	0.6111	0.067*
H14B	0.5816	0.4904	0.5470	0.067*
H14C	0.5813	0.6678	0.5261	0.067*
C15	0.6923 (2)	0.5598 (3)	0.5365 (1)	0.0262 (5)
H15A	0.7255	0.6569	0.5462	0.031*
N10	0.6667 (1)	0.5199 (2)	0.4547 (1)	0.0228 (4)
H10B	0.7135	0.5058	0.4430	0.034*
H10C	0.6352	0.5971	0.4258	0.034*
H10D	0.6358	0.4323	0.4451	0.034*
C16	0.7477 (2)	0.4339 (3)	0.5836 (1)	0.0246 (5)
O3	0.7610 (1)	0.3169 (2)	0.5581 (1)	0.0429 (5)
O4	0.7763 (2)	0.4724 (3)	0.6559 (1)	0.0500 (6)
C17	0.8324 (2)	0.3692 (4)	0.7118 (2)	0.0477 (8)
H17A	0.8557	0.2922	0.6864	0.057*
H17B	0.8015	0.3151	0.7397	0.057*
C18	0.9012 (2)	0.4620 (6)	0.7653 (2)	0.065 (1)
H18A	0.9405	0.3952	0.8037	0.097*
H18B	0.8776	0.5372	0.7904	0.097*
H18C	0.9313	0.5153	0.7371	0.097*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
B1	0.024 (1)	0.028 (1)	0.028 (2)	−0.001 (1)	0.010 (1)	0.001 (1)
C1	0.035 (1)	0.033 (1)	0.030 (1)	−0.001 (1)	0.012 (1)	0.001 (1)
N1	0.057 (2)	0.042 (1)	0.045 (2)	−0.017 (1)	0.014 (1)	−0.006 (1)
C2	0.027 (1)	0.031 (1)	0.029 (1)	−0.001 (1)	0.013 (1)	0.004 (1)
N2	0.038 (1)	0.041 (1)	0.045 (2)	0.007 (1)	0.018 (1)	0.009 (1)
C3	0.032 (1)	0.031 (1)	0.033 (2)	−0.001 (1)	0.010 (1)	0.002 (1)
N3	0.051 (2)	0.060 (2)	0.033 (1)	−0.004 (1)	0.006 (1)	0.003 (1)
C4	0.029 (1)	0.038 (1)	0.037 (2)	0.001 (1)	0.014 (1)	0.000 (1)
N4	0.041 (1)	0.070 (2)	0.055 (2)	0.002 (1)	0.028 (1)	−0.001 (2)
B2	0.028 (1)	0.028 (1)	0.029 (2)	0.004 (1)	0.009 (1)	0.001 (1)
C5	0.027 (1)	0.036 (1)	0.048 (2)	0.002 (1)	0.011 (1)	0.006 (1)
N5	0.039 (1)	0.041 (2)	0.081 (2)	−0.006 (1)	0.009 (1)	0.003 (2)
C6	0.037 (1)	0.035 (1)	0.029 (2)	0.006 (1)	0.010 (1)	−0.002 (1)
N6	0.053 (2)	0.046 (2)	0.043 (2)	0.019 (1)	0.007 (1)	−0.003 (1)
C7	0.040 (2)	0.045 (2)	0.035 (2)	0.010 (1)	0.014 (1)	0.007 (1)
N7	0.070 (2)	0.098 (3)	0.034 (2)	0.023 (2)	0.015 (1)	0.012 (2)
C8	0.029 (1)	0.028 (1)	0.030 (1)	0.002 (1)	0.006 (1)	−0.002 (1)
N8	0.036 (1)	0.047 (1)	0.046 (2)	0.001 (1)	0.019 (1)	0.001 (1)
C9	0.077 (2)	0.033 (2)	0.034 (2)	−0.009 (2)	0.018 (2)	0.002 (1)
C10	0.028 (1)	0.032 (1)	0.026 (1)	−0.002 (1)	0.012 (1)	0.002 (1)
N9	0.026 (1)	0.0231 (9)	0.025 (1)	−0.0002 (8)	0.0083 (8)	−0.0007 (8)
C11	0.035 (1)	0.028 (1)	0.024 (1)	−0.001 (1)	0.011 (1)	0.002 (1)
O1	0.047 (1)	0.041 (1)	0.033 (1)	−0.0185 (9)	0.0192 (9)	−0.0055 (8)
O2	0.054 (1)	0.047 (1)	0.026 (1)	−0.016 (1)	0.0161 (8)	−0.0048 (8)
C12	0.073 (2)	0.056 (2)	0.026 (2)	−0.030 (2)	0.012 (2)	−0.010 (1)
C13	0.054 (2)	0.100 (3)	0.046 (2)	−0.014 (2)	0.010 (2)	−0.022 (2)
C14	0.049 (2)	0.060 (2)	0.030 (1)	0.027 (2)	0.020 (1)	0.009 (1)
C15	0.035 (1)	0.022 (1)	0.021 (1)	0.004 (1)	0.0097 (9)	0.0004 (9)
N10	0.0255 (9)	0.0230 (9)	0.021 (1)	0.0000 (8)	0.0092 (7)	0.0005 (7)
C16	0.025 (1)	0.027 (1)	0.022 (1)	0.0028 (9)	0.0096 (9)	0.0022 (9)
O3	0.059 (1)	0.032 (1)	0.032 (1)	0.0192 (9)	0.0095 (9)	−0.0016 (8)
O4	0.068 (1)	0.049 (1)	0.023 (1)	0.026 (1)	0.0046 (9)	0.0007 (9)
C17	0.052 (2)	0.062 (2)	0.026 (2)	0.027 (2)	0.010 (1)	0.013 (1)
C18	0.041 (2)	0.104 (3)	0.048 (2)	0.015 (2)	0.014 (2)	0.014 (2)

Geometric parameters (Å, º) top

B1—C4	1.585 (4)	C11—O2	1.330 (3)
B1—C1	1.585 (4)	O2—C12	1.455 (3)
B1—C3	1.591 (4)	C12—C13	1.490 (6)
B1—C2	1.600 (4)	C12—H12A	0.9900
C1—N1	1.142 (4)	C12—H12B	0.9900
C2—N2	1.135 (3)	C13—H13A	0.9800
C3—N3	1.137 (3)	C13—H13B	0.9800
C4—N4	1.138 (4)	C13—H13C	0.9800
B2—C7	1.585 (4)	C14—C15	1.514 (4)
B2—C6	1.586 (4)	C14—H14A	0.9800
B2—C5	1.586 (4)	C14—H14B	0.9800
B2—C8	1.590 (4)	C14—H14C	0.9800
C5—N5	1.140 (4)	C15—N10	1.482 (3)
C6—N6	1.139 (4)	C15—C16	1.510 (3)
C7—N7	1.134 (4)	C15—H15A	1.0000
C8—N8	1.138 (3)	N10—H10B	0.9100
C9—C10	1.497 (4)	N10—H10C	0.9100
C9—H9A	0.9800	N10—H10D	0.9100
C9—H9B	0.9800	C16—O3	1.188 (3)
C9—H9C	0.9800	C16—O4	1.312 (3)
C10—N9	1.489 (3)	O4—C17	1.451 (3)
C10—C11	1.505 (4)	C17—C18	1.479 (5)
C10—H10A	1.0000	C17—H17A	0.9900
N9—H9D	0.9100	C17—H17B	0.9900
N9—H9E	0.9100	C18—H18A	0.9800
N9—H9F	0.9100	C18—H18B	0.9800
C11—O1	1.192 (3)	C18—H18C	0.9800

C4—B1—C1	110.0 (2)	C13—C12—H12A	109.8
C4—B1—C3	110.2 (2)	O2—C12—H12B	109.8
C1—B1—C3	111.2 (2)	C13—C12—H12B	109.8
C4—B1—C2	108.5 (2)	H12A—C12—H12B	108.2
C1—B1—C2	109.0 (2)	C12—C13—H13A	109.5
C3—B1—C2	107.8 (2)	C12—C13—H13B	109.5
N1—C1—B1	178.8 (3)	H13A—C13—H13B	109.5
N2—C2—B1	179.0 (3)	C12—C13—H13C	109.5
N3—C3—B1	177.5 (3)	H13A—C13—H13C	109.5
N4—C4—B1	179.1 (3)	H13B—C13—H13C	109.5
C7—B2—C6	111.0 (2)	C15—C14—H14A	109.5
C7—B2—C5	108.4 (2)	C15—C14—H14B	109.5
C6—B2—C5	108.9 (2)	H14A—C14—H14B	109.5
C7—B2—C8	110.0 (2)	C15—C14—H14C	109.5
C6—B2—C8	108.3 (2)	H14A—C14—H14C	109.5
C5—B2—C8	110.2 (2)	H14B—C14—H14C	109.5
N5—C5—B2	177.8 (3)	N10—C15—C16	108.8 (2)
N6—C6—B2	178.7 (3)	N10—C15—C14	110.3 (2)
N7—C7—B2	177.6 (4)	C16—C15—C14	111.6 (2)
N8—C8—B2	179.8 (3)	N10—C15—H15A	108.7
C10—C9—H9A	109.5	C16—C15—H15A	108.7
C10—C9—H9B	109.5	C14—C15—H15A	108.7
H9A—C9—H9B	109.5	C15—N10—H10B	109.5
C10—C9—H9C	109.5	C15—N10—H10C	109.5
H9A—C9—H9C	109.5	H10B—N10—H10C	109.5
H9B—C9—H9C	109.5	C15—N10—H10D	109.5
N9—C10—C9	112.0 (2)	H10B—N10—H10D	109.5
N9—C10—C11	108.2 (2)	H10C—N10—H10D	109.5
C9—C10—C11	110.3 (2)	O3—C16—O4	126.0 (2)
N9—C10—H10A	108.8	O3—C16—C15	124.2 (2)
C9—C10—H10A	108.8	O4—C16—C15	109.8 (2)
C11—C10—H10A	108.8	C16—O4—C17	119.4 (2)
C10—N9—H9D	109.5	O4—C17—C18	107.6 (3)
C10—N9—H9E	109.5	O4—C17—H17A	110.2
H9D—N9—H9E	109.5	C18—C17—H17A	110.2
C10—N9—H9F	109.5	O4—C17—H17B	110.2
H9D—N9—H9F	109.5	C18—C17—H17B	110.2
H9E—N9—H9F	109.5	H17A—C17—H17B	108.5
O1—C11—O2	125.8 (2)	C17—C18—H18A	109.5
O1—C11—C10	124.3 (2)	C17—C18—H18B	109.5
O2—C11—C10	109.8 (2)	H18A—C18—H18B	109.5
C11—O2—C12	117.2 (2)	C17—C18—H18C	109.5
O2—C12—C13	109.4 (3)	H18A—C18—H18C	109.5
O2—C12—H12A	109.8	H18B—C18—H18C	109.5

N9—C10—C11—O1	−7.2 (3)	N10—C15—C16—O3	−6.3 (3)
C9—C10—C11—O1	115.7 (3)	C14—C15—C16—O3	115.6 (3)
N9—C10—C11—O2	175.3 (2)	N10—C15—C16—O4	175.1 (2)
C9—C10—C11—O2	−61.9 (3)	C14—C15—C16—O4	−63.0 (3)
O1—C11—O2—C12	−9.5 (4)	O3—C16—O4—C17	2.5 (4)
C10—C11—O2—C12	168.1 (2)	C15—C16—O4—C17	−178.9 (3)
C11—O2—C12—C13	−86.1 (3)	C16—O4—C17—C18	136.5 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N9—H9F···N6ⁱ	0.91	2.16	2.920 (3)	141
N10—H10B···N4ⁱⁱ	0.91	2.05	2.953 (3)	174
N10—H10D···N1	0.91	2.07	2.961 (3)	166
N9—H9E···N8ⁱⁱⁱ	0.91	2.14	3.001 (3)	158
N10—H10C···N2^iv	0.91	2.15	3.015 (3)	159
N9—H9D···N5^v	0.91	2.14	3.017 (3)	161
N9—H9F···N3^vi	0.91	2.64	3.147 (3)	116

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

Acknowledgements

The authors thank Dr A. Villinger (Universität Rostock) for maintaining the functionality of the X-ray facilities. The publication of this article was funded by the Open Access Fund of the Leibniz Association.

Funding information

Funding for this research was provided by: Deutsche Forschungsgemeinschaft (grant No. KO-1616-4 to MK).

References

Bernsdorf, A., Brand, H., Hellmann, R., Köckerling, M., Schulz, A., Villinger, A. & Voss, K. (2009). J. Am. Chem. Soc. 131, 8958–8970. CSD CrossRef PubMed CAS Google Scholar
Brandenburg, K. & Putz, H. (2019). Diamond. Crystal Impact GbR, Bonn, Germany. Google Scholar
Bruker (2017). APEX2, SADABS and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Dimitrijević, D. P., Novaković, S. B., Radić, G. R., Jevtić, V. V., Menéndez-Taboada, L., García-Granda, S. & Trifunović, S. R. (2013). J. Serb. Chem. Soc. 78, 1531–1537. Google Scholar
Flemming, A., Hoffmann, M. & Köckerling, M. (2010). Z. Anorg. Allg. Chem. 636, 562–568. CSD CrossRef CAS Google Scholar
Hallett, J. P. & Welton, T. (2011). Chem. Rev. 111, 3508–3576. Web of Science CrossRef CAS PubMed Google Scholar
Parsons, S., Flack, H. D. & Wagner, T. (2013). Acta Cryst. B69, 249–259. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Siegesmund, A., Topp, A., Nitschke, C. & Köckerling, M. (2017). ChemistrySelect, 2, 11328–11335. CSD CrossRef CAS Google Scholar
Welton, T. (1999). Chem. Rev. 99, 2071–2084. Web of Science CrossRef PubMed CAS Google Scholar
Westrip, S. P. (2010). J. Appl. Cryst. 43, 920–925. Web of Science CrossRef CAS IUCr Journals Google Scholar