3,3′-Di-tert-butyl-1,1′-[1,3-phenyl­enebis(methyl­ene)]diurea

Musabbir A Saeed; Frank R Fronczek; Md Alamgir Hossain

doi:10.1107/S1600536810005866

. 2010 Feb 20;66(Pt 3):o656–o657. doi: 10.1107/S1600536810005866

3,3′-Di-tert-butyl-1,1′-[1,3-phenylenebis(methylene)]diurea

Musabbir A Saeed ^a, Frank R Fronczek ^b, Md Alamgir Hossain ^a,^*

PMCID: PMC2983681 PMID: 21580407

Abstract

The title compound, C₁₈H₃₀N₄O₂, contains two tert-butyl urea groups, each connected to a benzene ring though a methylene group. One of the groups occupies a position almost normal to the aromatic plane with a C—N—C—C torsion angle of −94.4 (4)°, while the other is considerably twisted from the ring with a C—N—C—C torsion angle of −136.1 (4)°. In the crystal, pairs of molecules are connected to each other, forming centrosymmetric dimers in which two NH groups of one molecule act as hydrogen-bond donors to one carbonyl O atom of the other molecule. The dimers are linked into sheets parallel to (100) by N—H⋯O hydrogen bonds involving the remaining N—H and C=O groups.

Related literature

For general background to urea-based compounds, see: Brooks et al. (2008 ▶); Carr et al. (1998 ▶); Chauhan et al. (2008 ▶); Gomez et al. (2005 ▶); Hiscock et al. (2009 ▶); Hossain (2008 ▶); Kyne et al. (2001 ▶); Lorenzo et al. (2009 ▶); Pérez-Casas & Yatsimirsky (2008 ▶); Tejeda et al. (2000 ▶); Ghosh et al. (2007 ▶). For related structures, see: Jose et al. (2007 ▶); Lo & Ng (2008 ▶).

Experimental

Crystal data

C₁₈H₃₀N₄O₂
M _r = 334.46
Orthorhombic,
a = 18.070 (4) Å
b = 11.760 (3) Å
c = 18.221 (3) Å
V = 3872.0 (15) Å³
Z = 8
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 90 K
0.20 × 0.10 × 0.07 mm

Data collection

Nonius KappaCCD diffractometer with an Oxford Cryosystems Cryostream cooler
43147 measured reflections
3781 independent reflections
2158 reflections with I > 2σ(I)
R _int = 0.081

Refinement

R[F ² > 2σ(F ²)] = 0.081
wR(F ²) = 0.235
S = 1.03
3781 reflections
235 parameters
4 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.86 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: COLLECT (Nonius, 2000 ▶); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor 1997 ▶); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810005866/ci5033sup1.cif

e-66-0o656-sup1.cif^{(20.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810005866/ci5033Isup2.hkl

e-66-0o656-Isup2.hkl^{(185.5KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1N⋯O2ⁱ	0.82 (2)	2.12 (2)	2.909 (4)	162 (4)
N2—H2N⋯O2ⁱ	0.81 (2)	2.28 (2)	3.034 (4)	153 (4)
N3—H3N⋯O1ⁱⁱ	0.86 (2)	2.15 (2)	2.941 (4)	154 (4)
N4—H4N⋯O1ⁱⁱ	0.81 (2)	2.12 (2)	2.889 (4)	160 (4)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This work was supported by the National Institutes of Health, Division of National Center for Research Resources, under grant No. G12RR013459. The purchase of the diffractometer was made possible by grant No. LEQSF (1999–2000)-ENH-TR-13, administered by the Louisiana Board of Regents. This research was also sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy, under contract with Oak Ridge National Laboratory (MAH), and National Science Foundation under grant No. CHE-0821357.

supplementary crystallographic information

Comment

Because of the ability of urea functional groups to form hydrogen bonds with an anion, urea-based compounds are known as effective hosts for a variety of anions (Brooks et al., 2008; Carr et al., 1998; Chauhan et al., 2008; Hiscock et al., 2009; Lorenzo et al., 2009; Tejeda et al., 2000) as well as neutral species (Kyne et al., 2001) and are often used for colorimetric detection for a specific anion in solution (Ghosh et al., 2007; Pérez-Casas et al., 2008). For example, simple acyclic ligands with mono-functional urea or thiourea groups are known to form 1:1 complexes with carboxylates, halides and phosphate in DMSO (Gomez et al., 2005). Encapsulation of sulfate anion was also structurally identified within the cavity formed by two tren-based urea ligands (Jose et al., 2007). In an effort to design multifunctional anion receptors (Hossain, 2008), we synthesized a urea-based compound containing two urea units, that can be useful in anion binding.

Single crystal X-ray analysis reveals that the bis-urea cleft crystallized in an orthorhombic space group without the involvement of solvent molecules. As illustrated in Fig. 1, the carbonyl groups of the two urea fragments are oriented in opposite directions. The methylene groups connected to the aromatic units are almost co-planar with the NH groups, as indicated by C13—N3—C14—N4 and C7—N1—C8—N2 torsion angles of -164.8 (3) and 177.6 (3)°, respectively. The NH groups are oriented almost perpendicular to the aromatic plane.

There are no intramolecular hydrogen bonding in the molecule, however, each C═O group forms two hydrogen bonds with two adjacent NH fragments resulting in the formation of centrosymmetric dimers with N···O distances of 2.889 (4) Å and 2.941 (4) Å (Fig. 2 and Table 1). Each dimer is then connected with four adjacent dimers forming a sheet parallel to the (100) (Fig. 3). Similar intermolecular bonding was previously reported for a mono-functional urea-based compound (Lo & Ng, 2008).

Experimental

To a solution of m-xylylenediamine (0.10 g, 1.0 mmol) in CH₃CN (20 ml) was added two equivalents of tert-butyl isocyanate (0.20 g, 2.0 mmol) and the mixture was stirred overnight at room temperature. The white precipitate formed was separated by filtration, washed by diethyl ether, and dried under vacuum. Yield 40%. ¹H NMR (500 MHz, CDCl₃, TMS): δ 7.25-7.12 (ArH, m, 4H), 4.84(CH₂NH, t, J = 5 Hz, 2H), 4.64 (CNH, s, 2H), 4.21 (ArCH₂, d, J = 5 Hz, 4H), 1.30 (CCH₃, s, 18H). A small portion of the sample was re-dissolved in CHCl₃, and crystals suitable for X-ray analysis were grown by slow evaporation of the solvent at room temperature.