C—I⋯N short contacts as tools for the construction of the crystal packing in the crystal structure of 3,3′-(ethane-1,2-di­yl)bis­(6-iodo-3,4-di­hydro-2H-1,3-benzoxazine)

Rivera, A.; Rojas, J.J.; Ríos-Motta, J.; Bolte, M.

doi:10.1107/S2056989017005047

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Volume 73| Part 5| May 2017| Pages 664-666

https://doi.org/10.1107/S2056989017005047

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C—I⋯N short contacts as tools for the construction of the crystal packing in the crystal structure of 3,3′-(ethane-1,2-diyl)bis(6-iodo-3,4-dihydro-2H-1,3-benzoxazine)

Augusto Rivera,^a ^* Jicli José Rojas,^a Jaime Ríos-Motta ^a and Michael Bolte ^b

^aUniversidad Nacional de Colombia, Sede Bogotá, Facultad de Ciencias, Departamento de Química, Cra 30 No. 45-03, Bogotá, Código Postal 111321, Colombia, and ^bInstitut für Anorganische Chemie, J. W. Goethe-Universität Frankfurt, Max-von Laue-Strasse 7, 60438 Frankfurt/Main, Germany
^*Correspondence e-mail: ariverau@unal.edu.co

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 15 March 2017; accepted 31 March 2017; online 7 April 2017)

The asymmetric unit of the title compound, C₁₈H₁₈I₂N₂O₂, consists of one half-molecule, completed by the application of inversion symmetry. The molecule adopts the typical structure for this class of bis-benxozazines, characterized by an anti orientation of the two benzoxazine rings around the central C—C bond. The oxazinic ring adopts a half-chair conformation. In the crystal, molecules are linked by C—I⋯N short contacts [I⋯N = 3.378 (2) Å], generating layers lying parallel to the bc plane.

Keywords: crystal structure; short contacts; benzoxazines; phenolic resins.

CCDC reference: 1541561

1. Chemical context

Benzoxazines have been studied for more than 70 years (Holly & Cope, 1944 ): they are heterocyclic compounds, which have the core structure of a benzene ring fused with an oxazine ring that can be readily synthesized by the Mannich reaction of mixing three components, either in solution or by a melt-state reaction using a combination of a phenolic derivative, formaldehyde, and a primary amine (Wattanathana et al., 2014 ). The importance of these compounds is for the production of the corresponding polymers called polybenzoxazines, which have been developed as a class of ring-opening phenolic resins (Ishida & Sanders, 2000 ). However, the usefulness of benzoxazines as precursors for a class of thermosetting phenolic resins with excellent mechanical and thermal properties was not recognized until recently (Velez-Herrera & Ishida, 2009 ).

As the electrophilic character of the substituents affects the stability both of the reaction intermediates and the benzoxazine ring (Hamerton et al., 2006 ), consequently, when p-iodophenol, formaldehyde and ethylenediamine were allowed to react in a molar ratio of 2:4:1, the title compound (I) was formed. This article forms part of our ongoing research into improving the understanding of the structural features resulting from replacement of the halogen substituent at the para position of the aromatic ring of bis-1,3-benzoxazines. So, an iodine functional bis-1,3-benzoxazine, namely 3,3′-(ethane-1,2-diyl)bis(6-iodo-3,4-dihydro-2H-1,3-benzoxazine) has been synthesized in high yield and purity.

2. Structural commentary

Similar to that observed in the crystal structure of the related compounds (Rivera et al., 2010 , 2016a ), the asymmetric unit of the title compound C₁₈H₁₈I₂N₂O₂, contains one-half of the formula unit; a centre of inversion is located at the mid-point of the central C1—C1(1 − x, 1 − y, 1 − z) bond (see Fig. 1). The six-membered oxazine heterocyclic ring adopts a half-chair conformation, with puckering parameters Q = 0.482 (3) Å, θ =129.6 (2)°, φ = 283.6 (3)°: with respect to the plane formed by O1/C3/C4/C5, the deviations of C2 and N1 are 0.301 (3) and −0.320 (3) Å, respectively. The observed C—O bond length [1.376 (3) Å] is in a good agreement with the related p-fluoro and p-bromo structures (Rivera et al., 2016a,b ), but this value is shorter than for the the p-chloro derivative (Rivera et al., 2010). The C7—I1 bond length [2.107 (3) Å] is in good agreement with the value reported for 4-iodophenol [2.104 (5) Å; Merz, 2006 ]. The C8—C9 bond length [1.378 (4) Å] is shorter than the average C–C bond length of benzene ring [1.398 (4) Å)]. The N1—C2 bond length [1.435 (3) Å] is significantly shorter than those of N1—C5 [1.474 (3) Å] and N1—C1 [1.478 (3) Å], probably due to the presence of a hyperconjugative interaction between the lone-pair electrons of the nitrogen atom and the antibonding σ orbital of C—O bond (nN→σ*_C2–O1). Moreover, the C2—N1—C1 [112.6 (2)°] and C5—N1—C1 [113.0 (2)°] angles are larger than the mean value of sp³ hybridization in ammonia (107°; Olovsson & Templeton, 1959 ).

Figure 1
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. Atoms labelled with the suffix A are generated using the symmetry operator (1 − x, 1 − y, 1 − z).

3. Supramolecular features

The crystal-packing arrangement of the title compound is illustrated in Fig. 2. In contrast with related structures (Rivera et al., 2016a,b, 2010), the absence of C—H⋯X or C—H⋯O interactions in the title compound is surprising. The packing of title compound is dominated by short contacts (Table 1), as indicated by a PLATON (Spek, 2009 ) analysis. Short C—I⋯N interactions (Table 1) are observed between neighboring molecules; it is remarkable that these short contacts present in the crystal structure of (I) has structure-directing characteristics.

Table 1
Short-contact geometry (Å, °)

C—I	X	C—I	I···X	C—I···X
C7—I1	N1ⁱ	2.107 (3)	3.378 (2)	169.13 (9)
Symmetry code: (i) x, −y, $[{1\over 2}]$ + z.

Figure 2
Crystal packing of (I)

, displaying C—I⋯N short contacts, which result in chains, forming layers propagating parallel to the bc plane.

4. Database survey

A search of the Cambridge Structural Database (Groom et al., 2016 ) for short N⋯I contacts between an N atom bonded to three C atoms and an I atom bonded to an aromatic ring yielded 47 entries with a distance of less than 3.5 Å. The search yielded four comparable structures, namely 3,3′-ethane-1,2-diylbis(6-methyl-3,4-dihydro-2H-1,3-benzoxazine) (AXAKAM; Rivera et al., 2011 ), 3,3′-ethylenebis(3,4-dihydro-6-chloro-2H-1,3-benzoxazine), (NUQKAM; Rivera et al., 2010), 3,3′-(ethane-1,2-diyl)-bis(6-methoxy-3,4-dihydro-2H-1,3-benzoxazine) monohydrate (QEDDOU; Rivera et al., 2012b ), 3,3′-ethane-1,2-diylbis(3,4-dihydro-2H-1,3-benzoxazine) (SAGPUN; Rivera et al., 2012a ).

5. Synthesis and crystallization

The title compound was prepared as described by Rivera et al. (1989 ). The reaction mixture was stored at room temperature for several weeks until a yellowish precipitate was formed. The solid was separated by filtration, washed with ethanol and crystallized from acetone solution. Yield 45.5%, m.p. 434 K.

6. Refinement details

Crystal data, data collection and structure refinement details are summarized in Table 2. All H atoms were located in the difference electron-density map. C-bound H atoms were fixed geometrically (C—H = 0.95 or 0.99Å) and refined using a riding-model approximation, with U_iso(H) set to 1.2U_eq of the parent atom.

Table 2
Experimental details

Crystal data
Chemical formula	C₁₈H₁₈I₂N₂O₂
M_r	548.14
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	173
a, b, c (Å)	20.4200 (9), 5.9477 (2), 17.8414 (8)
β (°)	123.607 (3)
V (Å³)	1804.69 (14)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	3.50
Crystal size (mm)	0.29 × 0.27 × 0.27

Data collection
Diffractometer	Stoe IPDS II two-circle
Absorption correction	Multi-scan (X-AREA; Stoe & Cie, 2001 )
T_min, T_max	0.395, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	39259, 2531, 2456
R_int	0.076
(sin θ/λ)_max (Å⁻¹)	0.697

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.030, 0.076, 1.22
No. of reflections	2531
No. of parameters	110
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.46, −1.35
Computer programs: X-AREA (Stoe & Cie, 2001), SHELXS97, SHELXL97 and XP in SHELXTL-Plus (Sheldrick, 2008 ), SHELXL2016 (Sheldrick, 2015 ).

Supporting information

CCDC reference: 1541561

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989017005047/hb7668sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017005047/hb7668Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989017005047/hb7668Isup3.cml

checkCIF report

Computing details top

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA (Stoe & Cie, 2001); data reduction: X-AREA (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

3,3'-(Ethane-1,2-diyl)bis(6-iodo-3,4-dihydro-2H-1,3-benzoxazine) top

Crystal data top

C₁₈H₁₈I₂N₂O₂	F(000) = 1048
M_r = 548.14	D_x = 2.017 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 20.4200 (9) Å	Cell parameters from 39259 reflections
b = 5.9477 (2) Å	θ = 3.3–29.9°
c = 17.8414 (8) Å	µ = 3.50 mm⁻¹
β = 123.607 (3)°	T = 173 K
V = 1804.69 (14) Å³	Block, colourless
Z = 4	0.29 × 0.27 × 0.27 mm

Data collection top

Stoe IPDS II two-circle diffractometer	2456 reflections with I > 2σ(I)
Radiation source: Genix 3D IµS microfocus X-ray source	R_int = 0.076
ω scans	θ_max = 29.7°, θ_min = 3.6°
Absorption correction: multi-scan (X-AREA; Stoe & Cie, 2001)	h = −28→28
T_min = 0.395, T_max = 1.000	k = −7→8
39259 measured reflections	l = −24→24
2531 independent reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.030	w = 1/[σ²(F_o²) + (0.0378P)² + 4.0804P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.076	(Δ/σ)_max = 0.002
S = 1.22	Δρ_max = 1.46 e Å⁻³
2531 reflections	Δρ_min = −1.35 e Å⁻³
110 parameters	Extinction correction: SHELXL2016 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0034 (2)

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
I1	0.60686 (2)	−0.05887 (3)	0.93105 (2)	0.02375 (9)
O1	0.68205 (12)	0.6146 (3)	0.71878 (13)	0.0231 (4)
N1	0.60465 (12)	0.4020 (4)	0.58050 (14)	0.0174 (4)
C1	0.53347 (15)	0.5410 (4)	0.54603 (16)	0.0207 (5)
H1A	0.545662	0.699539	0.541455	0.025*
H1B	0.516975	0.534394	0.588747	0.025*
C2	0.67584 (15)	0.5254 (5)	0.63881 (17)	0.0214 (5)
H2A	0.678708	0.651795	0.604633	0.026*
H2B	0.721287	0.425521	0.657944	0.026*
C3	0.66459 (15)	0.4585 (4)	0.76215 (17)	0.0187 (4)
C4	0.62686 (14)	0.2547 (4)	0.72243 (15)	0.0171 (4)
C5	0.60538 (15)	0.1994 (4)	0.62851 (16)	0.0199 (4)
H5A	0.643793	0.090235	0.632478	0.024*
H5B	0.552776	0.128136	0.594033	0.024*
C6	0.61047 (15)	0.1080 (4)	0.77133 (16)	0.0191 (4)
H6	0.585192	−0.031336	0.745502	0.023*
C7	0.63083 (15)	0.1641 (5)	0.85739 (16)	0.0208 (5)
C8	0.66757 (17)	0.3687 (5)	0.89574 (17)	0.0250 (5)
H8	0.681043	0.407706	0.954297	0.030*
C9	0.68424 (17)	0.5143 (5)	0.84831 (17)	0.0236 (5)
H9	0.709313	0.653654	0.874439	0.028*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
I1	0.02726 (12)	0.02815 (12)	0.01965 (12)	0.00072 (6)	0.01537 (9)	0.00344 (6)
O1	0.0281 (9)	0.0214 (8)	0.0185 (8)	−0.0058 (7)	0.0121 (7)	−0.0023 (7)
N1	0.0167 (9)	0.0205 (9)	0.0129 (8)	0.0030 (7)	0.0069 (7)	0.0024 (7)
C1	0.0207 (11)	0.0228 (11)	0.0130 (10)	0.0046 (9)	0.0060 (9)	0.0010 (8)
C2	0.0188 (10)	0.0271 (12)	0.0168 (10)	−0.0008 (9)	0.0089 (9)	0.0013 (9)
C3	0.0185 (10)	0.0207 (11)	0.0150 (10)	0.0001 (8)	0.0081 (9)	0.0021 (8)
C4	0.0166 (9)	0.0219 (10)	0.0109 (9)	0.0022 (8)	0.0064 (8)	0.0017 (8)
C5	0.0248 (11)	0.0198 (10)	0.0133 (9)	0.0014 (9)	0.0093 (9)	−0.0005 (8)
C6	0.0196 (10)	0.0197 (10)	0.0154 (10)	0.0005 (8)	0.0081 (8)	0.0009 (8)
C7	0.0235 (11)	0.0227 (11)	0.0163 (10)	0.0011 (9)	0.0110 (9)	0.0030 (9)
C8	0.0338 (13)	0.0266 (13)	0.0156 (10)	−0.0017 (11)	0.0144 (10)	−0.0019 (9)
C9	0.0311 (13)	0.0224 (11)	0.0151 (10)	−0.0037 (10)	0.0114 (10)	−0.0032 (9)

Geometric parameters (Å, º) top

I1—C7	2.107 (3)	C3—C4	1.400 (3)
O1—C3	1.376 (3)	C4—C6	1.399 (3)
O1—C2	1.460 (3)	C4—C5	1.515 (3)
N1—C2	1.435 (3)	C5—H5A	0.9900
N1—C5	1.474 (3)	C5—H5B	0.9900
N1—C1	1.478 (3)	C6—C7	1.391 (3)
C1—C1ⁱ	1.523 (5)	C6—H6	0.9500
C1—H1A	0.9900	C7—C8	1.394 (4)
C1—H1B	0.9900	C8—C9	1.378 (4)
C2—H2A	0.9900	C8—H8	0.9500
C2—H2B	0.9900	C9—H9	0.9500
C3—C9	1.397 (4)

I1···N1ⁱⁱ	3.378 (2)

C3—O1—C2	113.3 (2)	C6—C4—C5	122.1 (2)
C2—N1—C5	108.45 (19)	C3—C4—C5	119.3 (2)
C2—N1—C1	112.6 (2)	N1—C5—C4	111.6 (2)
C5—N1—C1	113.0 (2)	N1—C5—H5A	109.3
N1—C1—C1ⁱ	111.0 (3)	C4—C5—H5A	109.3
N1—C1—H1A	109.4	N1—C5—H5B	109.3
C1ⁱ—C1—H1A	109.4	C4—C5—H5B	109.3
N1—C1—H1B	109.4	H5A—C5—H5B	108.0
C1ⁱ—C1—H1B	109.4	C7—C6—C4	120.7 (2)
H1A—C1—H1B	108.0	C7—C6—H6	119.7
N1—C2—O1	113.5 (2)	C4—C6—H6	119.7
N1—C2—H2A	108.9	C6—C7—C8	120.1 (2)
O1—C2—H2A	108.9	C6—C7—I1	120.46 (19)
N1—C2—H2B	108.9	C8—C7—I1	119.41 (18)
O1—C2—H2B	108.9	C9—C8—C7	119.7 (2)
H2A—C2—H2B	107.7	C9—C8—H8	120.2
O1—C3—C9	116.9 (2)	C7—C8—H8	120.2
O1—C3—C4	122.7 (2)	C8—C9—C3	120.5 (3)
C9—C3—C4	120.3 (2)	C8—C9—H9	119.7
C6—C4—C3	118.6 (2)	C3—C9—H9	119.7

C2—N1—C1—C1ⁱ	150.8 (3)	C1—N1—C5—C4	−77.2 (2)
C5—N1—C1—C1ⁱ	−85.9 (3)	C6—C4—C5—N1	161.7 (2)
C5—N1—C2—O1	−65.2 (3)	C3—C4—C5—N1	−18.6 (3)
C1—N1—C2—O1	60.5 (3)	C3—C4—C6—C7	0.4 (4)
C3—O1—C2—N1	47.5 (3)	C5—C4—C6—C7	−179.9 (2)
C2—O1—C3—C9	167.3 (2)	C4—C6—C7—C8	0.3 (4)
C2—O1—C3—C4	−14.5 (3)	C4—C6—C7—I1	−179.47 (18)
O1—C3—C4—C6	−179.0 (2)	C6—C7—C8—C9	−0.6 (4)
C9—C3—C4—C6	−0.9 (4)	I1—C7—C8—C9	179.2 (2)
O1—C3—C4—C5	1.2 (4)	C7—C8—C9—C3	0.1 (4)
C9—C3—C4—C5	179.3 (2)	O1—C3—C9—C8	178.9 (3)
C2—N1—C5—C4	48.3 (3)	C4—C3—C9—C8	0.7 (4)

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

Short-contact geometry (Å, °) top

C—I	X	C—I	I···X	C—I···X
C7—I1	N1ⁱ	2.107 (3)	3.378 (2)	169.13 (9)

Symmetry code: (i) x, -y, 1/2+z.

Acknowledgements

JJR is grateful to COLCIENCIAS for his doctoral scholarship.

Funding information

Funding for this research was provided by: Dirección de Investigaciones, Sede Bogotá (DIB) de la Universidad Nacional de Colombia (award No. 35816).

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