Formation of a macrocycle from di­chloro­dimethyl­silane and a pyridoxalimine Schiff base ligand

Böhme, U.; Schwarzer, A.; Günther, B.

doi:10.1107/S2056989021010185

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Volume 77| Part 11| November 2021| Pages 1099-1102

https://doi.org/10.1107/S2056989021010185

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Formation of a macrocycle from dichlorodimethylsilane and a pyridoxalimine Schiff base ligand

Uwe Böhme,^a ^* Anke Schwarzer ^b and Betty Günther ^a

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

Edited by O. Blacque, University of Zürich, Switzerland (Received 24 September 2021; accepted 1 October 2021; online 13 October 2021)

The reaction of dichlorodimethylsilane with a polydentate Schiff base ligand derived from pyridoxal and 2-ethanolamine yielded the macrocyclic silicon compound (8E,22E)-4,4,12,18,18,26-hexamethyl-3,5,17,19-tetraoxa-8,13,22,27-tetraaza-4,18-disilatricyclo[22.4.0.0^10,15]octacosa-1(24),8,10,12,14,22,25,27-octaene-11,25-diol, C₂₄H₃₆N₄O₆Si₂. The asymmetric unit contains the half macrocycle with an intramolecular O—H⋯N hydrogen bond between the imine nitrogen atom and a neighbouring oxygen atom. The crystal structure is dominated by C—H⋯O and C—H⋯π interactions, which form a high ordered molecular network.

Keywords: crystal structure; organosiloxane; pyridoxal; Schiff base; macrocycle.

CCDC reference: 2113407

1. Chemical context

The heterocyclic aldehyde pyridoxal is one of the active forms of vitamin B₆. This vitamin is an essential cofactor to a large number of enzymes that catalyze many reactions of amino acids (Sykes et al., 1991 ). The coordination chemistry of Schiff bases generated from amino acids and pyridoxal with transition metal ions has been investigated intensive (Christensen, 1957 ; Long et al., 1980 ; Dawes et al., 1982 ; Walz et al., 1983 ; Rao et al., 1985 ; Astheimer et al., 1985 ; Sykes et al., 1991; Costa Pessoa et al., 1999 ). We are working on silicon complexes with tridentate O,N,O-ligands (Böhme & Günther, 2007a ; Böhme et al., 2006 ; Paul et al., 2014 ; Warncke et al., 2012 ; Schwarzer et al., 2018 ). Therefore, we prepared a Schiff base from pyridoxal and 2-aminoethanol as a potential O,N,O-ligand. The crystal structure of this molecule, 4-[(2-hydroxyethyl)iminomethyl]-5- hydroxymethyl-2-methylpyridine-3-ol (I), was published earlier (Böhme & Günther, 2007b ). Compound (I) was used recently as ligand molecule to coordinate copper and silver ions (Annaraj & Neelakantan, 2014 , 2015 ). Herein we report the results of reaction between (I) and dichlorodimethylsilane.

There are several potential coordination sites at the ligand molecule (I): the pyridine and the imino nitrogen atoms, two aliphatic and one phenolic hydroxyl groups. The presence of these functional groups makes it difficult to predict the structure of the reaction product with dichlorodimethylsilane. It was our initial goal to prepare a pentacoordinate silicon complex like (II). Surprisingly the macrocyclic silicon compound (III) was obtained from the reaction of (I) with Me₂SiCl₂. The reaction was performed in tetrahydrofuran in presence of triethylamine as supporting base to remove the hydrogen chloride, which is formed during the reaction. Recrystallization of the raw product from 1,2-dimethoxyethane and diethyl ether gave yellow crystals suitable for structure analysis.

2. Structural commentary

Compound (III) crystallizes in the monoclinic space group I2/c with the half macrocycle in the asymmetric unit. Fig. 1 shows the asymmetric unit and the atomic labelling scheme. The macrocycle is generated by a crystallographic C2 axis through the centre of the macrocycle (Fig. 2). The silicon atom is bound to the two methyl groups and to the aliphatic oxygen atoms O2 and O3, thus forming a macrocycle (Fig. 2). A quite similar macrocycle has been obtained from the reaction of a related pyridoxal-derived Schiff base and dichlorodiphenylsilane (Böhme et al., 2008 ). The short Si—O bonds (see Table 1) are in the range for comparable Si—O bonds (Wagler et al., 2005 ; Böhme et al., 2006, 2008; Böhme & Günther, 2007a; Böhme & Foehn, 2007 ). The silicon atom is distorted tetrahedral with bond angles between 103.40 (5) and 113.16 (7)° (Table 1). The rather large bond angles at the oxygen atoms (see Table 1) have been explained by the ionic character of the Si—O bonds (Gillespie & Johnson, 1997 ). There is a strong intramolecular O—H⋯N interaction (entry 1, Table 2) between the imine nitrogen atom N2 and the O1—H1 group in the neighbouring position at the pyridoxal ring. The formation of hydrogen bridges between the imine nitrogen atom and an ortho-hydroxyl group is a feature that is often observed in Schiff bases with o-hydroxy groups (Hökelek et al., 2004 ; Filarowski et al., 1999 ). This strong intramolecular O—H⋯N interaction leads to a six-membered pseudo ring consisting of H1—O1—C2—C3—C7—N2. This pseudo ring is planar with an r.m.s. deviation of 0.009 Å from the ring plane. According to the graph-set notation proposed by Etter et al. (1990 ), these hydrogen bonds form motifs with an S₁¹(6) graph-set descriptor. The hydrogen bonds C7—H7⋯O3 link different parts within one macrocycle via intra-annular hydrogen bonds (Fig. 2).

Table 1
Selected geometric parameters (Å, °)

Si1—O2	1.6435 (9)	Si1—C12	1.8443 (14)
Si1—O3ⁱ	1.6487 (9)	Si1—C11	1.8589 (15)

O2—Si1—O3ⁱ	103.40 (5)	O3ⁱ—Si1—C11	109.52 (6)
O2—Si1—C12	106.94 (6)	C12—Si1—C11	113.16 (7)
O3ⁱ—Si1—C12	112.06 (6)	C8—O2—Si1	123.61 (8)
O2—Si1—C11	111.33 (7)	C10—O3—Si1ⁱ	123.50 (8)
Symmetry code: (i) $[-x+2, y, -z+{\script{1\over 2}}]$ .

Table 2
Hydrogen-bond geometry (Å, °)

Cg1 is the centroid of the N1/C1–C5 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N2	0.90 (2)	1.76 (2)	2.5923 (15)	153.2 (18)
C5—H5⋯O1ⁱⁱ	0.95	2.69	3.5451 (16)	151
C6—H6A⋯O2ⁱⁱⁱ	0.98	2.59	3.3464 (17)	134
C7—H7⋯O3ⁱ	0.95	2.57	3.4882 (15)	162
C9—H9B⋯O2^iv	0.99	2.60	3.5087 (16)	153
C9—H9B⋯Cg1^iv	0.99	3.31	4.039 (2)	131
C11—H11A⋯Cg1ⁱⁱ	0.98	2.85	3.7880 (2)	160
Symmetry codes: (i) $[-x+2, y, -z+{\script{1\over 2}}]$ ; (ii) $[x, -y+1, z-{\script{1\over 2}}]$ ; (iii) $[x, -y+1, z+{\script{1\over 2}}]$ ; (iv) $[-x+{\script{3\over 2}}, -y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 1
The asymmetric unit of (III), drawn with 50% probability displacement ellipsoids. The dashed line shows the intramolecular O1—H1⋯N2 hydrogen bond.

Figure 2
The molecular structure of (III), drawn with 50% probability displacement ellipsoids.

3. Supramolecular features

A bifurcated intermolecular C—H⋯O interaction is observed at O2 (Table 2). The interaction of C6—H6A⋯O2 and C5—H5⋯O1 results in a chain along the crystallographic b-axis. The C—H⋯O interaction of C9—H9B with O2 connects adjacent chains (Fig. 3).

Figure 3
Packing excerpt of (III) showing C—H⋯O hydrogen bonds (dashed lines).

Apart from the relevant C—H⋯O interaction, two C—H⋯π contacts with the pyridine moiety (Cg1) are observed. First, a bifurcation at H9B (d = 3.31 Å) shows up within the C—H⋯O chains along the c axis. Furthermore, C11—H11A⋯Cg1 (d = 2.85 Å) supports the C—H⋯O interactions of H5 and H6A.

In summary, the crystal structure is dominated by C—H⋯O and C—H⋯π interactions, forming a highly ordered molecular network.

The potential bonding sites in combination with the cavity of the macrocycle makes (III) a suitable candidate for supramolecular recognition processes. The available pyridine N, azomethine N, and OH groups could be useful for the generation of nanostructures via complexation with transition metals (Leininger et al., 2000 ).

4. Database survey

A CSD search with ConQuest (Bruno et al., 2002 ) for macrocycles containing Schiff bases from pyridoxal and 2-aminoalcohols showed that only one comparable silicon compound exists (Böhme et al., 2008, refcode MOKVEO). The main differences between these two structures of silicon-containing macrocycles are as follows. First, (III) was found to crystallize without solvent while MOKVEO encloses chlorofom molecules. Probably as a result, the symmetry is lower in MOKVEO (triclinic, P $[\overline{1}]$ ) than in (III) showing the monoclinic I2/c symmetry. On the basis of the structure of (III) presented here and the former investigation (Böhme et al., 2008), it can be assumed that pyridoxalimine-derived Schiff bases prefer the formation of macrocycles with diorganosilane units. However, it seems to be possible that compound (I) can also act as a tridentate O,N,O-ligand, as was shown recently with a hexacoordinate titanium complex (Böhme & Günther, 2020 ).

5. Synthesis and crystallization

The preparation of (III) was performed in Schlenk tubes under argon with dry and air-free solvents.

Compound (III) was prepared by reaction of 4-[(2-hydroxyethyl)iminomethyl]-5-hydroxymethyl-2-methylpyridine-3-ol (I) (1.7 g, 8 mmol) with dichlorodimethylsilane (1.03 g, 8 mmol) in the presence of triethylamine (2.02 g, 20 mmol). The reaction was performed in dry tetrahydrofuran at room temperature. A white precipitate of triethylamine hydrochloride formed upon stirring of the mixture for five days. After this period, the triethylamine hydrochloride was filtered off and washed with tetrahydrofuran. The solvent was removed in vacuo from the resulting clear yellow solution. The remaining solid was extracted with 1,2-dimethoxyethane. Addition of diethyl ether and cooling to 278 K yielded yellow crystals of (III) (1.66 g, 78%, m.p. 390 K).

NMR (CDCl₃, 300 K, TMS, in p.p.m.): ²⁹Si: −0.1. ¹H: δ = 0.14 (_s, Me₂Si, 6H), 2.50 (s, CH₃ pyridoxal, 3H), 3.71, 3.90 (t, N—CH₂—CH₂—O, 4H), 4.78 (s, CH₂—O pyridoxal, 2H), 7.89 (s, CH pyridoxal, 1H), 8.84 (s, HC=N, 1H), 14.05 (s, OH pyridoxal, 1H). ¹³C: 3.0 (Me₂Si), 22.0 (CH₃ pyridoxal), 63.3, 64.6 (N—CH₂—CH₂—O), 66.4 (CH₂—O pyridoxal), 122.6, 133.4, 140.8, 153.8, 157.8 (five C pyridoxal), 167.5 (HC=N).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. The hydrogen atom at O1 was refined freely. The methyl groups were refined as idealized rigid groups allowed to rotate but not tip (AFIX 137; C—H = 0.98 Å, H—C—H = 109.5°). Other hydrogens were included using a riding model starting from calculated positions (C—H_aromatic = 0.95, C—H_methylene = 0.99 Å). The U_iso(H) values were fixed at 1.5 (for the methyl H) or 1.2 times the equivalent U_eq value of the parent carbon atoms.

Table 3
Experimental details

Crystal data
Chemical formula	C₂₄H₃₆N₄O₆Si₂
M_r	532.75
Crystal system, space group	Monoclinic, I2/c
Temperature (K)	153
a, b, c (Å)	12.9641 (8), 16.8966 (7), 13.1085 (8)
β (°)	101.198 (5)
V (Å³)	2816.7 (3)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	0.17
Crystal size (mm)	0.40 × 0.33 × 0.15

Data collection
Diffractometer	Stoe IPDS 2T
Absorption correction	Integration (X-RED; Stoe, 2009 )
T_min, T_max	0.907, 0.993
No. of measured, independent and observed [I > 2σ(I)] reflections	19293, 3242, 2833
R_int	0.039
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.032, 0.082, 1.08
No. of reflections	3242
No. of parameters	169
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.32, −0.23
Computer programs: X-AREA and X-RED (Stoe, 2009), SHELXS (Sheldrick, 2008 ), SHELXL2017/1 (Sheldrick, 2015 ) and ORTEP-3 for Windows (Farrugia, 2012 ).

Supporting information

CCDC reference: 2113407

Crystal structure: contains datablocks I, I_7. DOI: https://doi.org/10.1107/S2056989021010185/zq2266sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989021010185/zq2266Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989021010185/zq2266Isup3.cml

checkCIF report

Computing details top

Data collection: X-AREA (Stoe, 2009); cell refinement: X-AREA (Stoe, 2009); data reduction: X-RED (Stoe, 2009); 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).

(8E,22E)-4,4,12,18,18,26-Hexamethyl-3,5,17,19-tetraoxa-8,13,22,27-tetraaza-4,18-disilatricyclo[22.4.0.0^10,15]octacosa-1(24),8,10,12,14,22,25,27-octaene-11,25-diol top

Crystal data top

C₂₄H₃₆N₄O₆Si₂	F(000) = 1136
M_r = 532.75	D_x = 1.256 Mg m⁻³
Monoclinic, I2/c	Mo Kα radiation, λ = 0.71073 Å
a = 12.9641 (8) Å	Cell parameters from 19293 reflections
b = 16.8966 (7) Å	θ = 3.2–28.8°
c = 13.1085 (8) Å	µ = 0.17 mm⁻¹
β = 101.198 (5)°	T = 153 K
V = 2816.7 (3) Å³	Prism, yellow
Z = 4	0.40 × 0.33 × 0.15 mm

Data collection top

Stoe IPDS 2T diffractometer	3242 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	2833 reflections with I > 2σ(I)
Plane graphite monochromator	R_int = 0.039
Detector resolution: 6.67 pixels mm^-1	θ_max = 27.5°, θ_min = 2.0°
rotation method scans	h = −16→16
Absorption correction: integration (X-RED; Stoe, 2009)	k = −21→21
T_min = 0.907, T_max = 0.993	l = −16→16
19293 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.032	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.082	w = 1/[σ²(F_o²) + (0.0343P)² + 2.1897P] where P = (F_o² + 2F_c²)/3
S = 1.08	(Δ/σ)_max = 0.001
3242 reflections	Δρ_max = 0.32 e Å⁻³
169 parameters	Δρ_min = −0.23 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.

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

	x	y	z	U_iso*/U_eq
Si1	0.86455 (3)	0.32645 (2)	−0.02263 (2)	0.02075 (10)
O1	0.71097 (8)	0.39251 (6)	0.42399 (7)	0.0296 (2)
H1	0.7514 (16)	0.3499 (12)	0.4190 (14)	0.044*
O2	0.80401 (7)	0.38781 (5)	0.04330 (7)	0.02281 (19)
O3	1.06149 (7)	0.27321 (5)	0.43122 (7)	0.02520 (19)
N1	0.67254 (9)	0.55915 (7)	0.24920 (9)	0.0294 (2)
N2	0.83696 (8)	0.29351 (6)	0.35941 (8)	0.0230 (2)
C1	0.66458 (10)	0.51009 (8)	0.32707 (10)	0.0259 (3)
C2	0.72289 (10)	0.43890 (7)	0.34287 (9)	0.0233 (2)
C3	0.78833 (9)	0.41735 (7)	0.27376 (9)	0.0209 (2)
C4	0.79399 (10)	0.46943 (7)	0.19053 (9)	0.0229 (2)
C5	0.73609 (11)	0.53867 (8)	0.18313 (10)	0.0282 (3)
H5	0.741329	0.574080	0.128082	0.034*
C6	0.58959 (11)	0.53139 (9)	0.39701 (11)	0.0338 (3)
H6A	0.629045	0.540267	0.467780	0.051*
H6B	0.539444	0.488047	0.397491	0.051*
H6C	0.551402	0.579715	0.371352	0.051*
C7	0.84345 (9)	0.34072 (7)	0.28447 (9)	0.0206 (2)
H7	0.884566	0.326031	0.234897	0.025*
C8	0.85625 (10)	0.45009 (7)	0.10775 (10)	0.0252 (3)
H8A	0.861902	0.497621	0.065010	0.030*
H8B	0.928130	0.433117	0.140566	0.030*
C9	0.89177 (10)	0.21754 (7)	0.36341 (10)	0.0236 (2)
H9A	0.914711	0.208345	0.296627	0.028*
H9B	0.843029	0.174374	0.373348	0.028*
C10	0.98674 (10)	0.21622 (7)	0.45164 (10)	0.0248 (3)
H10A	0.964942	0.228849	0.518104	0.030*
H10B	1.018780	0.162825	0.457622	0.030*
C11	0.94958 (13)	0.38050 (10)	−0.09824 (13)	0.0406 (4)
H11A	0.907504	0.419996	−0.142798	0.061*
H11B	0.979557	0.342955	−0.141483	0.061*
H11C	1.006491	0.407029	−0.050283	0.061*
C12	0.76208 (11)	0.26635 (8)	−0.10486 (10)	0.0284 (3)
H12A	0.717809	0.241394	−0.061306	0.043*
H12B	0.795342	0.225328	−0.140318	0.043*
H12C	0.718640	0.300404	−0.156636	0.043*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Si1	0.02231 (17)	0.02191 (17)	0.01900 (16)	0.00084 (12)	0.00636 (12)	0.00114 (12)
O1	0.0360 (5)	0.0297 (5)	0.0259 (4)	0.0028 (4)	0.0128 (4)	0.0013 (4)
O2	0.0232 (4)	0.0221 (4)	0.0228 (4)	−0.0002 (3)	0.0034 (3)	−0.0036 (3)
O3	0.0241 (4)	0.0287 (5)	0.0230 (4)	−0.0076 (4)	0.0054 (3)	−0.0008 (3)
N1	0.0338 (6)	0.0237 (5)	0.0288 (5)	0.0025 (4)	0.0011 (4)	−0.0044 (4)
N2	0.0219 (5)	0.0229 (5)	0.0237 (5)	−0.0010 (4)	0.0029 (4)	0.0000 (4)
C1	0.0251 (6)	0.0259 (6)	0.0254 (6)	−0.0010 (5)	0.0012 (5)	−0.0074 (5)
C2	0.0240 (6)	0.0240 (6)	0.0209 (5)	−0.0033 (5)	0.0020 (4)	−0.0039 (4)
C3	0.0214 (5)	0.0206 (5)	0.0195 (5)	−0.0040 (4)	0.0011 (4)	−0.0031 (4)
C4	0.0264 (6)	0.0203 (6)	0.0211 (5)	−0.0049 (4)	0.0026 (4)	−0.0033 (4)
C5	0.0374 (7)	0.0213 (6)	0.0246 (6)	−0.0017 (5)	0.0026 (5)	−0.0019 (5)
C6	0.0283 (7)	0.0370 (7)	0.0363 (7)	0.0046 (6)	0.0072 (5)	−0.0080 (6)
C7	0.0200 (5)	0.0218 (6)	0.0196 (5)	−0.0030 (4)	0.0024 (4)	−0.0033 (4)
C8	0.0306 (6)	0.0210 (6)	0.0246 (6)	−0.0058 (5)	0.0071 (5)	−0.0014 (4)
C9	0.0237 (6)	0.0203 (6)	0.0263 (6)	−0.0027 (4)	0.0034 (5)	−0.0003 (4)
C10	0.0229 (6)	0.0231 (6)	0.0280 (6)	−0.0032 (5)	0.0040 (5)	0.0049 (5)
C11	0.0394 (8)	0.0453 (9)	0.0415 (8)	−0.0018 (7)	0.0192 (7)	0.0115 (7)
C12	0.0370 (7)	0.0264 (6)	0.0204 (6)	−0.0002 (5)	0.0024 (5)	−0.0014 (5)

Geometric parameters (Å, º) top

Si1—O2	1.6435 (9)	C5—H5	0.9500
Si1—O3ⁱ	1.6487 (9)	C6—H6A	0.9800
Si1—C12	1.8443 (14)	C6—H6B	0.9800
Si1—C11	1.8589 (15)	C6—H6C	0.9800
O1—C2	1.3539 (15)	C7—H7	0.9500
O1—H1	0.90 (2)	C8—H8A	0.9900
O2—C8	1.4345 (14)	C8—H8B	0.9900
O3—C10	1.4278 (14)	C9—C10	1.5168 (17)
N1—C1	1.3343 (18)	C9—H9A	0.9900
N1—C5	1.3512 (18)	C9—H9B	0.9900
N2—C7	1.2808 (16)	C10—H10A	0.9900
N2—C9	1.4631 (16)	C10—H10B	0.9900
C1—C2	1.4143 (18)	C11—H11A	0.9800
C1—C6	1.5039 (18)	C11—H11B	0.9800
C2—C3	1.4041 (17)	C11—H11C	0.9800
C3—C4	1.4147 (17)	C12—H12A	0.9800
C3—C7	1.4723 (17)	C12—H12B	0.9800
C4—C5	1.3832 (18)	C12—H12C	0.9800
C4—C8	1.5085 (17)

O2—Si1—O3ⁱ	103.40 (5)	N2—C7—H7	119.4
O2—Si1—C12	106.94 (6)	C3—C7—H7	119.4
O3ⁱ—Si1—C12	112.06 (6)	O2—C8—C4	108.98 (10)
O2—Si1—C11	111.33 (7)	O2—C8—H8A	109.9
O3ⁱ—Si1—C11	109.52 (6)	C4—C8—H8A	109.9
C12—Si1—C11	113.16 (7)	O2—C8—H8B	109.9
C2—O1—H1	104.4 (12)	C4—C8—H8B	109.9
C8—O2—Si1	123.61 (8)	H8A—C8—H8B	108.3
C10—O3—Si1ⁱ	123.50 (8)	N2—C9—C10	110.90 (10)
C1—N1—C5	118.59 (11)	N2—C9—H9A	109.5
C7—N2—C9	118.05 (11)	C10—C9—H9A	109.5
N1—C1—C2	121.46 (12)	N2—C9—H9B	109.5
N1—C1—C6	118.23 (12)	C10—C9—H9B	109.5
C2—C1—C6	120.30 (12)	H9A—C9—H9B	108.0
O1—C2—C3	122.14 (11)	O3—C10—C9	109.10 (10)
O1—C2—C1	117.91 (11)	O3—C10—H10A	109.9
C3—C2—C1	119.92 (11)	C9—C10—H10A	109.9
C2—C3—C4	117.69 (11)	O3—C10—H10B	109.9
C2—C3—C7	120.63 (11)	C9—C10—H10B	109.9
C4—C3—C7	121.57 (11)	H10A—C10—H10B	108.3
C5—C4—C3	118.12 (12)	Si1—C11—H11A	109.5
C5—C4—C8	119.45 (11)	Si1—C11—H11B	109.5
C3—C4—C8	122.36 (11)	H11A—C11—H11B	109.5
N1—C5—C4	124.19 (12)	Si1—C11—H11C	109.5
N1—C5—H5	117.9	H11A—C11—H11C	109.5
C4—C5—H5	117.9	H11B—C11—H11C	109.5
C1—C6—H6A	109.5	Si1—C12—H12A	109.5
C1—C6—H6B	109.5	Si1—C12—H12B	109.5
H6A—C6—H6B	109.5	H12A—C12—H12B	109.5
C1—C6—H6C	109.5	Si1—C12—H12C	109.5
H6A—C6—H6C	109.5	H12A—C12—H12C	109.5
H6B—C6—H6C	109.5	H12B—C12—H12C	109.5
N2—C7—C3	121.19 (11)

O3ⁱ—Si1—O2—C8	68.47 (10)	C2—C3—C4—C8	−176.10 (11)
C12—Si1—O2—C8	−173.10 (9)	C7—C3—C4—C8	0.08 (17)
C11—Si1—O2—C8	−49.03 (11)	C1—N1—C5—C4	0.17 (19)
C5—N1—C1—C2	1.61 (18)	C3—C4—C5—N1	−1.42 (19)
C5—N1—C1—C6	−176.99 (12)	C8—C4—C5—N1	175.64 (12)
N1—C1—C2—O1	179.60 (11)	C9—N2—C7—C3	178.48 (10)
C6—C1—C2—O1	−1.83 (17)	C2—C3—C7—N2	−3.14 (17)
N1—C1—C2—C3	−2.09 (18)	C4—C3—C7—N2	−179.21 (11)
C6—C1—C2—C3	176.48 (11)	Si1—O2—C8—C4	−154.64 (8)
O1—C2—C3—C4	179.01 (11)	C5—C4—C8—O2	−106.34 (13)
C1—C2—C3—C4	0.78 (17)	C3—C4—C8—O2	70.59 (14)
O1—C2—C3—C7	2.80 (17)	C7—N2—C9—C10	108.51 (12)
C1—C2—C3—C7	−175.43 (10)	Si1ⁱ—O3—C10—C9	143.92 (9)
C2—C3—C4—C5	0.87 (16)	N2—C9—C10—O3	−65.04 (13)
C7—C3—C4—C5	177.05 (11)

Symmetry code: (i) −x+2, y, −z+1/2.

Hydrogen-bond geometry (Å, º) top

Cg1 is the centroid of the N1/C1–C5 ring.

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N2	0.90 (2)	1.76 (2)	2.5923 (15)	153.2 (18)
C5—H5···O1ⁱⁱ	0.95	2.69	3.5451 (16)	151
C6—H6A···O2ⁱⁱⁱ	0.98	2.59	3.3464 (17)	134
C7—H7···O3ⁱ	0.95	2.57	3.4882 (15)	162
C9—H9B···O2^iv	0.99	2.60	3.5087 (16)	153
C9—H9B···Cg1^iv	0.99	3.31	4.039 (2)	131
C11—H11A···Cg1ⁱⁱ	0.98	2.85	3.7880 (2)	160

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

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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