Crystal structure of bis­(mesit­yl)(pyrrol-1-yl)borane

Sahin, O.; Wallis, J.D.

doi:10.1107/S2056989022011768

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Volume 79| Part 1| January 2023| Pages 50-53

https://doi.org/10.1107/S2056989022011768

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Crystal structure of bis(mesityl)(pyrrol-1-yl)borane

Onur Sahin ^a ‡ and John D. Wallis ^a ^*

^aSchool of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG1 8NS, United Kingdom
^*Correspondence e-mail: john.wallis@ntu.ac.uk

Edited by A. S. Batsanov, University of Durham, United Kingdom (Received 9 November 2022; accepted 8 December 2022; online 1 January 2023)

In the crystal structure of the title compound, C₂₂H₂₆BN, the B atom acts to reduce the delocalization of the nitrogen lone-pair electron density into the pyrrole ring, so that the two N—C bonds increase in length to 1.4005 (14) and 1.3981 (14) Å. The N—B bond length is 1.4425 (15) Å, which is longer than a typical N—B bond because the nitrogen lone pair is not fully available to participate in the bond.

Keywords: crystal structure; pyrroloborane; N-B bonding; π delocalization.

CCDC reference: 2166138

1. Chemical context

The structure of the title compound 1 is of interest because of the effect of the bis(mesityl)boron group on the electronic structure of the pyrrole, since the nitrogen lone pair, which is essential to the heterocycle's aromatic 6π system, now has the possibility of being donated to the boron atom. This molecule has been investigated previously for its fluorescence, and shows a large Stokes shift, which involves twisted intramolecular charge transfer (TICT) of the excited state, by rotation about the N—B bond (Brittelli & Eaton, 1989 ; Cornelissen & Rettig, 1994 ; Cornelissen-Gude & Rettig,1999 ). It has been used recently in the preparation of conductive polymers (Wildgoose et al. 2019 ).

2. Structural commentary

The crystal structure of bis(mesityl)(pyrrol-1-yl)borane 1 was determined at 120 K and the molecular structure is shown in Fig. 1. The bonding geometries at both the boron and nitrogen atoms are almost planar, with an angle of 16.13 (8)° between these two bonding planes. The N and B atoms lie 0.0351 (11) and 0.0285 (13) Å, respectively, out of the planes defined by their three attached atoms. The planes of the two mesityl groups lie at 58.53 (3) and 61.46 (4)° to the boron atom's bonding plane, and so there is limited donation of their π-electron densities to boron. These dispositions are controlled by the need to maintain separations between their two adjacent pairs of ortho methyl groups [H₃C⋯CH₃ = 3.610 (3) and 3.736 (3) Å], and is supported by the widening of the C—B—C bond angle [125.18 (9)°], compared to the two N—B—C bond angles [118.30 (10) and 116.42 (9)°]. The mesityl groups' planes lie at 77.14 (4)° to each other, and at 69.18 (3) and 67.06 (4)° to the pyrrole ring's best plane. The hydrogen atoms of three methyl groups (C12, C13 and C21) were modelled in two orientations. The positions and displacement parameters of hydrogen atoms on the pyrrole ring were refined, and for those attached to the C_α atoms, the H—C_α—C_β angle showed widening to 131–132°, similar to that in pyrrole (Goddard et al., 1997 ; Lee & Boo, 1996 ).

Figure 1
The molecular structure of 1, with anisotropic displacement parameters drawn at the 50% probability level. Only the more populated orientations for methyl groups C12, C13 and C21 are shown.

The N—B bond is 1.4425 (15) Å long. This is ca 0.04 Å longer than in similar compounds where the nitrogen atom is attached to two sp³ carbon atoms [ROCRAD (two molecules; Morawitz et al., 2008 ), TAYYAV (Araki et al., 2012 ), UWUFID (Smith et al., 2016 ), YOMKAM (Khasnis et al., 1995 ); T ≤ 173 K, N—B range 1.388 (2)-1.412 (3) Å, average 1.40 Å] and where the nitrogen lone pair is fully available for donation to boron. Compared to the molecular geometry of pyrrole itself, as determined by X-ray crystallography at 103 K (Goddard et al., 1997) and by calculation at the B3LYP-631G^* level (Lee & Boo, 1996), the most notable difference is in the increase of the two N—C bond lengths to 1.4005 (14) and 1.3981 (14) Å from 1.365 (2) Å (experimental) and 1.376 Å (calculated) (Table 1). The C_α—C_β bond lengths are 1.3536 (16) and 1.3514 (17) Å and the C_β—C_β bond length is 1.4290 (17) Å. Thus, in contrast to pyrrole, the N—C_α and C_α—C_β bonds are no longer similar in length, due to a reduction in the contribution of the nitrogen atom's lone pair to the electronic π system of the pyrrole ring. When the mesityl groups are replaced by pentafluorophenyl groups in derivative 2, the N—B bond is considerably shorter than in 1 [1.4094 (9) cf. 1.4425 (15) Å] due to greater lone-pair donation from nitrogen towards the more electron-deficient boron. Consequently, compared to 1, the pyrrole ring shows slightly longer N—C bonds [1.4033 (6) Å] and a longer C_β—C_β bond [1.4418 (9) Å], though similar lengths for the C_α—C_β bonds [1.3553 (6) Å] (Table 1). For comparison, the effect of boron on the pyrrole ring in 1 is similar to that when the pyrrole nitrogen atom is substituted with a carbonyl group to form an amide (Table 1).

Table 1
Bond lengths (Å) for 1 and related compounds

	1, T = 120 K	Pyrrole,^a T = 103 K	Pyrrole, calculated^b	2,^c T = 100 K	Pyrrole, N—C=O^d
N—B	1.4425 (15)	–	–	1.4094 (9)	–
N—C_α	1.4005 (14) 1.3981 (14)	1.365 (2)	1.376	1.4033 (6)	1.395
C_α—C_β	1.3536 (16) 1.3514 (17)	1.357 (2)	1.378	1.3553 (6)	1.355
C_β—C_β	1.4290 (17)	1.423 (3)	1.425	1.4418 (9)	1.430
Notes: (a) RUVQII (Goddard et al., 1997); (b) Lee & Boo (1996); (c) CUDZUW01 (Flierler et al., 2009 ); (d) Averaged data for structures containing C-unsubstituted-N-carbonyl pyrrole fragments measured at T < 150 K [BEFFUQ (Hatano et al., 2016 ), BOKSUR (Ariyarathna & Tunge, 2014 ), CIFNIR (O'Brien et al., 2018 ) and LAQFER (Uraguchi et al., 2017 .

3. Supramolecular features

The molecules are packed in layers in the ab plane (Fig. 2). There are no particularly short intermolecular contacts, consistent with the low density of the crystal (1.132 g cm⁻³). Within a layer, the molecules are related by centres of symmetry and translations along a and b. Adjacent layers are related by the twofold screw and n-glide planes. The four shortest intermolecular C⋯H distances are in the range 2.81–2.83 Å. Two of these involve the meta-C atom, C18, with a methyl hydrogen atom and a pyrrole ring's hydrogen atom, which are directed to opposite sides of the phenyl ring [C18⋯H12A(1 − x, 1 − y, 1 − z) and C18⋯H3(−x, 2 − y, 1 − z)]. The two others involve both a meta and a para-C atom of the second phenyl ring and the pyrrole hydrogen atom H2 [C8⋯H2( $[{1\over 2}]$ − x, y − $[{1\over 2}]$ , $[{3\over 2}]$ − z) and C9⋯H2( $[{1\over 2}]$ − x, y − $[{1\over 2}]$ , $[{3\over 2}]$ − z)].

Figure 2
The crystal-packing arrangement for 1, viewed down the b axis, with the shortest C⋯H separations (2.81–2.83 Å) shown in blue. Both orientations of the H atoms on methyl groups C12, C13 and C21 are shown.

4. Database survey

The structure of the analogue of 1 bearing two 2′-thienyl groups in the pyrrole's 2- and 5-positions (XEQVUM; Taniguchi et al., 2013 ) shows a larger angle (35.1°) between the bonding planes at nitrogen and boron due to avoidance of steric interactions between the thiophene and mesityl groups, and has a longer N—B bond [1.472 (7) Å] though the structure has lower precision. Room-temperature measurements on a series of five indole analogues of bis(mesityl)pyrroloborane, 3–7, show angles of 22.4–32.4° between the two bonding planes and slightly longer N—B bonds [1.442 (3)–1.457 (3) Å] with a correlation between the increasing angle between bonding planes and longer N—B bonds (Cui et al., 2007 ). Two carbazole analogues, 8 and 9, show interplanar angles between the two bonding planes of 23.1 and 27.9° and N—B bond lengths of 1.442 (3) and 1.440 (3) Å, similar to those in 1 (Taniguchi et al., 2013; Weber et al., 2011 ). All structures are reported in the Cambridge Structural Database, release 2021.3 (Groom et al., 2016 ).

5. Synthesis and crystallization

A solution of pyrrole (0.25 g, 3.7 mmol) in THF (10 mL) under nitrogen was treated with sodium hydride (60% dispersion in oil, 0.16 g, 4.0 mmol) and the mixture stirred at 293 K for 2 h. Dimesitylboron fluoride (CARE: gives HF with moisture) (1.09 g, 4.07 mmol) in dry THF (10 mL) was added at room temperature. The mixture was left to stir overnight. The bright orange–yellow mixture was quenched with water (20 mL), extracted with ether (2 × 30 mL) and the combined organic phase was dried over MgSO₄. The crude material was purified by column chromatography (SiO₂) using hexane:dichloromethane (8:1) as eluent to give 1 (0.76 g, 65%) as a slightly oily white solid, from which crystals were grown using ethyl acetate, m.p. 411 K. ¹H NMR (400 MHz, CDCl₃) [ppm]: δ = 6.84 (4H, s, 2 × 3′-,5′-H), 6.81 (2H, t, J = 2.2 Hz, 2-,5-H), 6.37 (2H, t, J = 2.2 Hz, 3-,4-H), 2.32 (6H, s, 2 × 4′-CH₃), 2.11 (12H, s, 2 × 2′-, 6′-CH₃); ¹³C NMR (100 MHz, CDCl₃) [ppm]: δ = 141.7 (2 × 2′-, 6′-C), 139.0 (2 × 4′-C), 136.5 br (2 × 1′-C), 128.3 (2 × 3′-, 5′-C), 126.5 (2-, 5-C), 114.6 (3-, 4-C), 22.8 (2 × 2′-, 6′-CH₃), 21.5 (2 × 4′-CH₃); IR (ATR): 2920, 2853, 1606, 1472, 1451, 1421, 1399, 1378, 1329, 1310, 1287, 1252, 1156, 1122, 1080, 1074, 1043, 1030, 850, 817, 763, 733, 717, 677, 656, 619, 560, 516 cm⁻¹.

6. Refinement

Crystal data and details of data collection and structure refinement are summarized in Table 2. Pyrrole H-atom positions and displacement parameters were refined. All other H atoms were refined using a riding model with C—H bonds fixed at 0.95 Å for hydrogens attached to phenyl carbon atoms and at 0.98 Å for methyl hydrogen atoms. Three methyl groups were refined in two orientations (C12, C13 and C21). The isotropic atomic displacement parameters of the H atoms were set at 1.2U_eq of the parent atom for aromatic groups and at 1.5U_eq for methyl groups.

Table 2
Experimental details

Crystal data
Chemical formula	C₂₂H₂₆BN
M_r	315.25
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	120
a, b, c (Å)	11.9157 (2), 8.0223 (1), 19.6440 (3)
β (°)	99.890 (1)
V (Å³)	1849.89 (5)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	0.48
Crystal size (mm)	0.24 × 0.22 × 0.07

Data collection
Diffractometer	XtaLAB Synergy R, DW system, HyPix-Arc 100
Absorption correction	Gaussian (CrysAlis PRO; Rigaku OD, 2022 $[Rigaku OD (2022). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ )
T_min, T_max	0.589, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	12428, 3650, 3305
R_int	0.021
(sin θ/λ)_max (Å⁻¹)	0.639

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.037, 0.102, 1.06
No. of reflections	3650
No. of parameters	240
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.19
Computer programs: CrysAlis PRO (Rigaku OD, 2022 $[Rigaku OD (2022). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ ), SHELXT2018/2 (Sheldrick, 2015a ), SHELXL2018/3 (Sheldrick, 2015b ), Mercury (Macrae et al., 2020 ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2166138

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989022011768/zv2023sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989022011768/zv2023Isup2.hkl

This is NMR data requested by the referee. DOI: https://doi.org/10.1107/S2056989022011768/zv2023sup3.docx

Supporting information file. DOI: https://doi.org/10.1107/S2056989022011768/zv2023Isup4.cml

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2022); cell refinement: CrysAlis PRO (Rigaku OD, 2022); data reduction: CrysAlis PRO (Rigaku OD, 2022); program(s) used to solve structure: SHELXT2018/2 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/3 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2020); software used to prepare material for publication: Olex2 (Dolomanov et al., 2009).

(Pyrrol-1-yl)bis(2,4,6-trimethylphenyl)borane top

Crystal data top

C₂₂H₂₆BN	D_x = 1.132 Mg m⁻³
M_r = 315.25	Melting point: 411 K
Monoclinic, P2₁/n	Cu Kα radiation, λ = 1.54184 Å
a = 11.9157 (2) Å	Cell parameters from 8967 reflections
b = 8.0223 (1) Å	θ = 4.0–79.1°
c = 19.6440 (3) Å	µ = 0.48 mm⁻¹
β = 99.890 (1)°	T = 120 K
V = 1849.89 (5) Å³	Plate, colourless
Z = 4	0.24 × 0.22 × 0.07 mm
F(000) = 680

Data collection top

XtaLAB Synergy R, DW system, HyPix-Arc 100 diffractometer	3650 independent reflections
Radiation source: Rotating-anode X-ray tube, Rigaku (Cu) X-ray Source	3305 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.021
Detector resolution: 10.0000 pixels mm^-1	θ_max = 80.4°, θ_min = 4.1°
ω scans	h = −15→14
Absorption correction: gaussian (CrysAlisPro; Rigaku OD, 2022)	k = −3→10
T_min = 0.589, T_max = 1.000	l = −23→24
12428 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.037	w = 1/[σ²(F_o²) + (0.0503P)² + 0.5405P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.102	(Δ/σ)_max = 0.001
S = 1.06	Δρ_max = 0.28 e Å⁻³
3650 reflections	Δρ_min = −0.19 e Å⁻³
240 parameters	Extinction correction: SHELXL2018/3 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0035 (4)
Primary atom site location: dual

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	Occ. (<1)
N1	0.18097 (7)	0.77715 (11)	0.59306 (5)	0.0222 (2)
C1	0.18799 (10)	0.78480 (14)	0.66489 (6)	0.0252 (3)
H1	0.2424 (11)	0.7174 (17)	0.6936 (7)	0.027 (3)*
C2	0.10761 (10)	0.89098 (15)	0.68019 (6)	0.0276 (3)
H2	0.0938 (12)	0.9190 (18)	0.7256 (8)	0.034 (4)*
C3	0.04576 (10)	0.95241 (15)	0.61633 (6)	0.0263 (3)
H3	−0.0173 (12)	1.0297 (19)	0.6110 (7)	0.034 (4)*
C4	0.09209 (9)	0.88346 (14)	0.56483 (6)	0.0243 (2)
H4	0.0713 (11)	0.8919 (17)	0.5145 (7)	0.028 (3)*
C5	0.31151 (9)	0.51849 (13)	0.59337 (5)	0.0203 (2)
C6	0.43044 (9)	0.49950 (13)	0.59754 (5)	0.0204 (2)
C7	0.48525 (9)	0.35880 (14)	0.62875 (5)	0.0220 (2)
H7	0.565353	0.348470	0.631666	0.026*
C8	0.42558 (9)	0.23297 (14)	0.65577 (5)	0.0225 (2)
C9	0.30873 (9)	0.25156 (14)	0.65143 (5)	0.0224 (2)
H9	0.266773	0.165907	0.669121	0.027*
C10	0.25120 (9)	0.39203 (14)	0.62194 (6)	0.0222 (2)
C11	0.50069 (9)	0.63324 (14)	0.57070 (6)	0.0250 (3)
H11A	0.465994	0.662557	0.523314	0.038*
H11B	0.578176	0.591750	0.571152	0.038*
H11C	0.503495	0.732173	0.600204	0.038*
C12	0.48501 (11)	0.08266 (16)	0.69069 (7)	0.0324 (3)
H12A	0.566645	0.089460	0.689114	0.039*	0.459 (14)
H12B	0.473774	0.079013	0.738926	0.039*	0.459 (14)
H12C	0.453368	−0.018501	0.666784	0.039*	0.459 (14)
H12D	0.429213	0.010521	0.707435	0.039*	0.541 (14)
H12E	0.522084	0.020969	0.657624	0.039*	0.541 (14)
H12F	0.542491	0.118483	0.729766	0.039*	0.541 (14)
C13	0.12378 (10)	0.39744 (16)	0.62051 (7)	0.0318 (3)
H13A	0.092836	0.501380	0.598706	0.038*	0.663 (14)
H13B	0.087803	0.302290	0.594031	0.038*	0.663 (14)
H13C	0.108254	0.392161	0.667858	0.038*	0.663 (14)
H13D	0.099760	0.295840	0.641691	0.038*	0.337 (14)
H13E	0.104792	0.494931	0.646366	0.038*	0.337 (14)
H13F	0.084341	0.405060	0.572538	0.038*	0.337 (14)
C14	0.23755 (8)	0.71202 (13)	0.47517 (5)	0.0203 (2)
C15	0.19186 (9)	0.59532 (14)	0.42397 (6)	0.0227 (2)
C16	0.17238 (9)	0.64178 (15)	0.35462 (6)	0.0267 (3)
H16	0.139938	0.562717	0.320900	0.032*
C17	0.19871 (9)	0.79950 (16)	0.33310 (6)	0.0271 (3)
C18	0.24852 (9)	0.91129 (15)	0.38323 (6)	0.0245 (2)
H18	0.269808	1.018547	0.369374	0.029*
C19	0.26830 (9)	0.87098 (14)	0.45335 (6)	0.0217 (2)
C20	0.16008 (10)	0.42065 (15)	0.44205 (7)	0.0310 (3)
H20A	0.226974	0.364914	0.468333	0.046*
H20B	0.133123	0.358118	0.399531	0.046*
H20C	0.099533	0.425544	0.470029	0.046*
C21	0.17317 (13)	0.8475 (2)	0.25774 (7)	0.0422 (3)
H21A	0.197459	0.962807	0.252349	0.051*	0.603 (17)
H21B	0.214358	0.773065	0.231077	0.051*	0.603 (17)
H21C	0.091124	0.837973	0.240847	0.051*	0.603 (17)
H21D	0.137835	0.753090	0.230500	0.051*	0.397 (17)
H21E	0.120936	0.942831	0.251772	0.051*	0.397 (17)
H21F	0.244170	0.877924	0.242002	0.051*	0.397 (17)
C22	0.32315 (11)	1.00106 (15)	0.50381 (6)	0.0291 (3)
H22A	0.263881	1.069083	0.519144	0.044*
H22B	0.372504	1.072516	0.481251	0.044*
H22C	0.368705	0.946066	0.543823	0.044*
B1	0.24540 (10)	0.67087 (15)	0.55475 (6)	0.0209 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0223 (4)	0.0212 (5)	0.0232 (5)	0.0039 (4)	0.0045 (4)	0.0042 (4)
C1	0.0285 (6)	0.0243 (6)	0.0233 (5)	0.0026 (5)	0.0056 (4)	0.0045 (5)
C2	0.0328 (6)	0.0251 (6)	0.0275 (6)	0.0012 (5)	0.0124 (5)	0.0024 (5)
C3	0.0235 (5)	0.0232 (6)	0.0339 (6)	0.0043 (5)	0.0099 (5)	0.0035 (5)
C4	0.0225 (5)	0.0227 (6)	0.0276 (6)	0.0044 (4)	0.0042 (4)	0.0047 (4)
C5	0.0206 (5)	0.0198 (5)	0.0202 (5)	0.0023 (4)	0.0028 (4)	0.0000 (4)
C6	0.0207 (5)	0.0217 (5)	0.0186 (5)	0.0015 (4)	0.0031 (4)	−0.0026 (4)
C7	0.0194 (5)	0.0251 (6)	0.0209 (5)	0.0043 (4)	0.0022 (4)	−0.0022 (4)
C8	0.0267 (5)	0.0211 (5)	0.0190 (5)	0.0054 (4)	0.0018 (4)	−0.0010 (4)
C9	0.0263 (5)	0.0194 (5)	0.0216 (5)	−0.0002 (4)	0.0047 (4)	0.0007 (4)
C10	0.0214 (5)	0.0222 (5)	0.0230 (5)	0.0018 (4)	0.0039 (4)	−0.0003 (4)
C11	0.0207 (5)	0.0253 (6)	0.0292 (6)	0.0003 (4)	0.0046 (4)	0.0016 (5)
C12	0.0328 (6)	0.0283 (6)	0.0355 (7)	0.0095 (5)	0.0040 (5)	0.0069 (5)
C13	0.0224 (5)	0.0272 (6)	0.0467 (7)	0.0020 (5)	0.0087 (5)	0.0082 (5)
C14	0.0166 (5)	0.0205 (5)	0.0235 (5)	0.0045 (4)	0.0028 (4)	0.0007 (4)
C15	0.0164 (5)	0.0242 (6)	0.0270 (6)	0.0034 (4)	0.0020 (4)	−0.0024 (4)
C16	0.0204 (5)	0.0332 (6)	0.0255 (6)	0.0020 (5)	0.0014 (4)	−0.0063 (5)
C17	0.0206 (5)	0.0383 (7)	0.0226 (5)	0.0058 (5)	0.0043 (4)	0.0017 (5)
C18	0.0223 (5)	0.0259 (6)	0.0265 (6)	0.0047 (4)	0.0073 (4)	0.0049 (5)
C19	0.0197 (5)	0.0215 (5)	0.0245 (5)	0.0044 (4)	0.0051 (4)	0.0008 (4)
C20	0.0297 (6)	0.0246 (6)	0.0361 (7)	−0.0027 (5)	−0.0015 (5)	−0.0027 (5)
C21	0.0445 (7)	0.0562 (9)	0.0246 (6)	0.0007 (7)	0.0026 (5)	0.0051 (6)
C22	0.0364 (6)	0.0214 (6)	0.0295 (6)	−0.0021 (5)	0.0057 (5)	0.0009 (5)
B1	0.0177 (5)	0.0188 (6)	0.0256 (6)	−0.0012 (4)	0.0023 (4)	0.0007 (5)

Geometric parameters (Å, º) top

N1—C1	1.4005 (14)	C13—H13A	0.9800
N1—C4	1.3981 (14)	C13—H13B	0.9800
N1—B1	1.4425 (15)	C13—H13C	0.9800
C1—H1	0.951 (14)	C13—H13D	0.9800
C1—C2	1.3536 (16)	C13—H13E	0.9800
C2—H2	0.962 (15)	C13—H13F	0.9800
C2—C3	1.4290 (17)	C14—C15	1.4129 (15)
C3—H3	0.966 (15)	C14—C19	1.4135 (15)
C3—C4	1.3514 (17)	C14—B1	1.5848 (16)
C4—H4	0.979 (14)	C15—C16	1.3928 (16)
C5—C6	1.4135 (14)	C15—C20	1.5097 (16)
C5—C10	1.4139 (15)	C16—H16	0.9500
C5—B1	1.5765 (15)	C16—C17	1.3870 (18)
C6—C7	1.3924 (15)	C17—C18	1.3877 (17)
C6—C11	1.5106 (15)	C17—C21	1.5093 (16)
C7—H7	0.9500	C18—H18	0.9500
C7—C8	1.3913 (16)	C18—C19	1.3950 (15)
C8—C9	1.3883 (15)	C19—C22	1.5087 (16)
C8—C12	1.5030 (15)	C20—H20A	0.9800
C9—H9	0.9500	C20—H20B	0.9800
C9—C10	1.3925 (15)	C20—H20C	0.9800
C10—C13	1.5144 (15)	C21—H21A	0.9800
C11—H11A	0.9800	C21—H21B	0.9800
C11—H11B	0.9800	C21—H21C	0.9800
C11—H11C	0.9800	C21—H21D	0.9800
C12—H12A	0.9800	C21—H21E	0.9800
C12—H12B	0.9800	C21—H21F	0.9800
C12—H12C	0.9800	C22—H22A	0.9800
C12—H12D	0.9800	C22—H22B	0.9800
C12—H12E	0.9800	C22—H22C	0.9800
C12—H12F	0.9800

C1—N1—B1	127.34 (9)	C10—C13—H13C	109.5
C4—N1—C1	106.43 (9)	H13A—C13—H13B	109.5
C4—N1—B1	126.05 (9)	H13A—C13—H13C	109.5
N1—C1—H1	119.3 (8)	H13B—C13—H13C	109.5
C2—C1—N1	109.23 (10)	H13D—C13—H13E	109.5
C2—C1—H1	131.5 (8)	H13D—C13—H13F	109.5
C1—C2—H2	126.4 (9)	H13E—C13—H13F	109.5
C1—C2—C3	107.45 (10)	C15—C14—C19	118.05 (10)
C3—C2—H2	126.1 (9)	C15—C14—B1	120.96 (10)
C2—C3—H3	126.2 (8)	C19—C14—B1	120.83 (10)
C4—C3—C2	107.50 (10)	C14—C15—C20	121.94 (10)
C4—C3—H3	126.3 (8)	C16—C15—C14	119.87 (11)
N1—C4—H4	119.1 (8)	C16—C15—C20	118.17 (10)
C3—C4—N1	109.38 (10)	C15—C16—H16	118.9
C3—C4—H4	131.4 (8)	C17—C16—C15	122.27 (11)
C6—C5—C10	118.19 (9)	C17—C16—H16	118.9
C6—C5—B1	121.64 (9)	C16—C17—C18	117.70 (10)
C10—C5—B1	120.09 (9)	C16—C17—C21	120.93 (12)
C5—C6—C11	120.89 (9)	C18—C17—C21	121.38 (12)
C7—C6—C5	120.17 (10)	C17—C18—H18	119.0
C7—C6—C11	118.90 (9)	C17—C18—C19	122.01 (11)
C6—C7—H7	119.2	C19—C18—H18	119.0
C8—C7—C6	121.62 (10)	C14—C19—C22	122.03 (10)
C8—C7—H7	119.2	C18—C19—C14	119.99 (10)
C7—C8—C12	121.64 (10)	C18—C19—C22	117.98 (10)
C9—C8—C7	118.13 (10)	C15—C20—H20A	109.5
C9—C8—C12	120.21 (10)	C15—C20—H20B	109.5
C8—C9—H9	119.0	C15—C20—H20C	109.5
C8—C9—C10	121.96 (10)	H20A—C20—H20B	109.5
C10—C9—H9	119.0	H20A—C20—H20C	109.5
C5—C10—C13	123.26 (10)	H20B—C20—H20C	109.5
C9—C10—C5	119.89 (10)	C17—C21—H21A	109.5
C9—C10—C13	116.82 (10)	C17—C21—H21B	109.5
C6—C11—H11A	109.5	C17—C21—H21C	109.5
C6—C11—H11B	109.5	H21A—C21—H21B	109.5
C6—C11—H11C	109.5	H21A—C21—H21C	109.5
H11A—C11—H11B	109.5	H21B—C21—H21C	109.5
H11A—C11—H11C	109.5	H21D—C21—H21E	109.5
H11B—C11—H11C	109.5	H21D—C21—H21F	109.5
C8—C12—H12A	109.5	H21E—C21—H21F	109.5
C8—C12—H12B	109.5	C19—C22—H22A	109.5
C8—C12—H12C	109.5	C19—C22—H22B	109.5
H12A—C12—H12B	109.5	C19—C22—H22C	109.5
H12A—C12—H12C	109.5	H22A—C22—H22B	109.5
H12B—C12—H12C	109.5	H22A—C22—H22C	109.5
H12D—C12—H12E	109.5	H22B—C22—H22C	109.5
H12D—C12—H12F	109.5	N1—B1—C5	118.30 (10)
H12E—C12—H12F	109.5	N1—B1—C14	116.42 (9)
C10—C13—H13A	109.5	C5—B1—C14	125.18 (9)
C10—C13—H13B	109.5

N1—C1—C2—C3	0.71 (13)	C15—C14—C19—C18	2.85 (15)
C1—N1—C4—C3	−0.47 (13)	C15—C14—C19—C22	−176.89 (10)
C1—N1—B1—C5	14.84 (16)	C15—C14—B1—N1	−117.91 (11)
C1—N1—B1—C14	−168.66 (10)	C15—C14—B1—C5	58.32 (14)
C1—C2—C3—C4	−1.00 (14)	C15—C16—C17—C18	1.52 (16)
C2—C3—C4—N1	0.90 (13)	C15—C16—C17—C21	−178.10 (11)
C4—N1—C1—C2	−0.17 (13)	C16—C17—C18—C19	−2.32 (16)
C4—N1—B1—C5	−159.49 (10)	C17—C18—C19—C14	0.13 (16)
C4—N1—B1—C14	17.01 (16)	C17—C18—C19—C22	179.88 (10)
C5—C6—C7—C8	0.76 (16)	C19—C14—C15—C16	−3.63 (15)
C6—C5—C10—C9	−1.72 (15)	C19—C14—C15—C20	177.97 (10)
C6—C5—C10—C13	−179.75 (10)	C19—C14—B1—N1	57.41 (13)
C6—C5—B1—N1	−122.50 (11)	C19—C14—B1—C5	−126.35 (11)
C6—C5—B1—C14	61.33 (15)	C20—C15—C16—C17	179.94 (10)
C6—C7—C8—C9	−0.56 (16)	C21—C17—C18—C19	177.29 (11)
C6—C7—C8—C12	−178.79 (10)	B1—N1—C1—C2	−175.40 (11)
C7—C8—C9—C10	−0.83 (16)	B1—N1—C4—C3	174.83 (10)
C8—C9—C10—C5	1.98 (16)	B1—C5—C6—C7	−176.49 (10)
C8—C9—C10—C13	−179.85 (10)	B1—C5—C6—C11	5.66 (15)
C10—C5—C6—C7	0.38 (15)	B1—C5—C10—C9	175.21 (10)
C10—C5—C6—C11	−177.47 (10)	B1—C5—C10—C13	−2.83 (16)
C10—C5—B1—N1	60.69 (14)	B1—C14—C15—C16	171.82 (9)
C10—C5—B1—C14	−115.48 (12)	B1—C14—C15—C20	−6.58 (15)
C11—C6—C7—C8	178.65 (10)	B1—C14—C19—C18	−172.60 (9)
C12—C8—C9—C10	177.43 (10)	B1—C14—C19—C22	7.66 (15)
C14—C15—C16—C17	1.48 (16)

Bond lengths (Å) for 1 and related compounds top

	1, T = 120 K	Pyrrole,^a T = 103 K	Pyrrole, calculated^b	2,^c T = 100 K	Pyrrole, N—C═O^d
N—B	1.4425 (15)	–	–	1.4094 (9)	–
N—C_α	1.4005 (14) 1.3981 (14)	1.365 (2)	1.376	1.4033 (6)	1.395
C_α—C_β	1.3536 (16) 1.3514 (17)	1.357 (2)	1.378	1.3553 (6)	1.355
C_β—C_β	1.4290 (17)	1.423 (3)	1.425	1.4418 (9)	1.430

Notes: (a) RUVQII (Goddard et al., 1997); (b) Lee & Boo (1996); (c) CUDZUW01 (Flierler et al., 2009); (d) Averaged data for structures containing C-unsubstituted-N-carbonyl pyrrole fragments measured at T < 150 K [BEFFUQ (Hatano et al., 2016), BOKSUR (Ariyarathna & Tunge, 2014), CIFNIR (O'Brien et al., 2018) and LAQFER (Uraguchi et al., 2017.

Footnotes

‡Current address: Istinye University, Faculty of Pharmacy, Basic Pharmacy Sciences, 34010, İstanbul, Turkey; email: onur.sahin@istinye.edu.tr.

Acknowledgements

Nottingham Trent University, UK, is thanked for support for diffraction facilities.

Funding information

OS thanks Tübitak, Turkey, for an International Postdoctoral Research Fellowship.

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