[2,2′-Imino­diethano­lato(2−)-κ3O,N,O′][4-(meth­oxy­carbonyl­meth­yl)phen­yl]boron

Zein, A.L.; Dawe, L.N.; Georghiou, P.E.

doi:10.1107/S1600536810037864

organic compounds

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Volume 66| Part 10| October 2010| Page o2646

doi:10.1107/S1600536810037864

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[2,2′-Iminodiethanolato(2−)-κ³O,N,O′][4-(methoxycarbonylmethyl)phenyl]boron

Ahmed L. Zein,^a Louise N. Dawe ^a and Paris E. Georghiou ^a ^*

^aDepartment of Chemistry, Memorial University of Newfoundland, St Johns, NL, Canada A1B 3X7
^*Correspondence e-mail: parisg@mun.ca

(Received 7 September 2010; accepted 21 September 2010; online 30 September 2010)

The title compound, C₁₃H₁₈BNO₄, was readily obtained from the reaction of methyl 4-boronobenzene acetate with ethanolamine. A combination of intermolecular N—H⋯O hydrogen bonds and C—H⋯π interactions leads to the pairwise association of molecules.

Related literature

For background to the biological importance of boron, see: Warrington (1923 ); Jabbour et al. (2004 ). For the use of boron-containing reagents in synthetic chemistry, see: Miyaura & Suzuki (1995 ); Corey et al. (1987 ); Liu et al. (2007 ); Jung & Lazarova (1999 ); Chan et al. (1998 ); Evans et al. (1998 ); Lam et al. (1998 ). For related structures, see: Rettig & Trotter (1975 ); Wang & Georghiou (2002 ).

Experimental

Crystal data

C₁₃H₁₈BNO₄
M_r = 263.10
Orthorhombic, P 2₁ 2₁ 2₁
a = 8.3776 (11) Å
b = 8.9269 (11) Å
c = 17.369 (2) Å
V = 1299.0 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 153 K
0.30 × 0.09 × 0.06 mm

Data collection

Rigaku Saturn diffractometer
Absorption correction: numerical (NUMABS; Higashi, 1999 ) T_min = 0.985, T_max = 0.997
16363 measured reflections
1725 independent reflections
1707 reflections with I > 2σ(I)
R_int = 0.037

Refinement

R[F² > 2σ(F²)] = 0.043
wR(F²) = 0.112
S = 1.17
1725 reflections
173 parameters
H-atom parameters constrained
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

Cg3 is the centroid of the C1–C6 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O2ⁱ	0.93	2.06	2.921 (2)	154
C10—H10B⋯Cg3ⁱⁱ	0.99	2.65	3.618 (2)	166
Symmetry codes: (i) $[-x+2, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[-x+2, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: CrystalClear (Rigaku, 2002 ); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810037864/fj2337sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810037864/fj2337Isup2.hkl

checkCIF report

Comment top

Boron is known to be an important trace element in higher plants (Warrington, 1923) and boron-containing compounds have been shown to have a range of diverse biological acvtivities (Jabbour et al., 2004). The use of boron-containing reagents is also widespread in synthetic chemistry and this is due mainly to the pioneering work of H. C. Brown and coworkers and Suzuki and his coworkers (Miyaura & Suzuki, 1995). Corey, Bakshi and Shibata (Corey et al., 1987) discovered that a chrial oxazaborolidine ("CBS" reagent) which contains both boron-nitrogen and boron-oxygen bonds was capable of effecting enantioselective reduction of prochiral ketones, imines, and oximes to produce chiral alcohols, amines, and amino alcohols in excellent yields and ee's. Corey's group has also shown that chiral oxazaborolidine-aluminium bromide complexes (Liu et al. 2007) are also effective catalysts for enantioselective Diels-Alder reactions. In principle, oxazaborolidines are derived from reactions of a boronic acid and aminoalcohols and a less well known application of oxazaborolidines is to facilitate the conversion of a pinacolatoborane, by mild acid-catalysis (Jung & Lazarova, 1999), to the corresponding boronic acid, a key step for cupric acetate promoted coupling of an arylboronic acids with phenols (Chan et al., 1998; Evans et al., 1998; Lam et al. 1998).

There has been only one reported X-ray crystallographic study of the structure of a diethanolamine ester of a phenylboronic acid (1) (Rettig & Trotter, 1975). This compound which was named as B-phenyl-diptychboroxazolidine (alternative names: Tetrahydro-[1,3,2]oxaza-borol[2,3-b][1,3,2]oxazaborole; [[2,2'-(Imino-kN)bis[ethanolato-kO]](2-)]phenylboron) was measured on a diffractometer with Cu K_a radiation and it was revealed to be non-centrosymmetric and in the P2₁ space group. The absolute configuration of the enatiomorphic crystal was determined in this study. In connection with our own work (Wang & Georghiou, 2002), crystals of (2), the corresponding diethanolamine ester of the 4-boronic acid derivative of methyl phenylacetate, were obtained and the structure of the molecule is reported here.

Methyl p-[[2,2'-iminobis[ethanolato]](2-)-N,O,O']phenylacetateboron (2; Figure 1) crystallized in the non-centrosymmetric space group P2₁2₁2₁, however, data collection was performed using molybdenum radiation, and the absolute configuration could not be determined due to the lack of an atom with significant anomalous dispersion. Intermolecular hydrogen bonding between N1—H1···O2ⁱ (N1···O2ⁱ = 2.921 (2) Å) and C—H···π interactions between C10—H10B···Cg3ⁱⁱ (C10···Cg3ⁱⁱ= 3.618 (2); where Cg3 is the centroid of C1—C6) leads to the pair-wise association of molecules (Figure 2). These molecular associates are related via the twofold screw axes in the crystal structure (viewed perpendicular to the b axis in Figure 3).

Related literature top

For background to the biological importance of boron, see: Warrington (1923); Jabbour et al. (2004). For the use of boron-containing reagents in synthetic chemistry, see: Miyaura et al. (1995); Corey et al. (1987); Liu et al. (2007) ;Jung et al. (1999); Chan et al. (1998); Evans et al. (1998); Lam et al. (1998). For related structures, see: Rettig & Trotter (1975); Wang & Georghiou (2002).

Experimental top

To a solution of PdCl₂(dppf) (160 mg, 0.18 mmol) in dioxane (24 ml) was added methyl 4-(trifluoroacetoxyacetate (1.58 g, 5.93 mmol), Et₃N (2.49 ml, 17.8 mmol) and 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.30 ml, 8.9 mmol). After stirring for 20 h at 100 ^oC, the reaction mixture was extracted with benzene. The extract was purified by flash column chromatography (silica gel, 10%EtOAc in hexanes) to afford the arylboronate (1.47 g, 90%) ¹HNMR (500 MHz, CDCl₃) 1.34 (s, 12H), 3.64 (s, 2H), 3.67(s, 3H), 7.27(d, J=10 Hz, 2H), 7.77(d, J=10 Hz, 2H). To a solution of the arylboronate (1.47 g, 5.3 mmol) in diethylether (53 ml) was added diethanolamine (0.6 ml, 5.8 mmol) in 2-propanol (10 ml). The resulting mixture was stirred at ambient temperature for 72 h, the reaction mixture was then filtered and the solid was washed with diethyl ether to give cyclic aminoarylboronate (1.08 g, 77%) as a colorless powder. Crystals suitable for X-ray diffraction analysis were obtained by crystallization from ethyl acetate solution. ¹H NMR (500 MHz, CDCl₃) 2.49–2.51(m, 2H), 2.96–3.03(m, 2H), 3.58(s, 2H), 3.63(s, 3H), 3.70–3.72(m, 2H), 3.79–3.74(m, 2H), 5.83(s, 1H), 7.14(d, J=7.5 Hz, 2H), 7.43(d, J=7.5 Hz, 2H); ¹³C NMR 41.0, 51.1, 51.8, 63.2, 128.3, 132.7, 132.8, 172.6.

Computing details top

Data collection: CrystalClear (Rigaku, 2002); cell refinement: CrystalClear (Rigaku, 2002); data reduction: CrystalClear (Rigaku, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

	Fig. 1. The molecular structure of (2), with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. Intermolecular hydrogen bonds (long dashes) and C—H···π interactions (short dashes) between two associated molecules.
	Fig. 3. Unit cell viewed perpendicular to the b axis, showing the pair-wise ordering of molecules in the crystal lattice. (Cell axes: a = red, b = green, c = blue)

[2,2'-Iminodiethanolato(2-)-κ³O,N,O'][4- (methoxycarbonylmethyl)phenyl]boron top

Crystal data top

C₁₃H₁₈BNO₄	D_x = 1.345 Mg m⁻³
M_r = 263.10	Melting point = 452–453 K
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71075 Å
Hall symbol: P 2ac 2ab	Cell parameters from 5108 reflections
a = 8.3776 (11) Å	θ = 2.6–30.6°
b = 8.9269 (11) Å	µ = 0.10 mm⁻¹
c = 17.369 (2) Å	T = 153 K
V = 1299.0 (3) Å³	Platelet, colorless
Z = 4	0.30 × 0.09 × 0.06 mm
F(000) = 560

Data collection top

Rigaku Saturn diffractometer	1725 independent reflections
Radiation source: fine-focus sealed tube	1707 reflections with I > 2σ(I)
Graphite - Rigaku SHINE monochromator	R_int = 0.037
Detector resolution: 14.63 pixels mm^-1	θ_max = 27.5°, θ_min = 2.6°
ω scans	h = −10→10
Absorption correction: numerical (NUMABS; Higashi, 1999)	k = −11→11
T_min = 0.985, T_max = 0.997	l = −22→22
16363 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.112	H-atom parameters constrained
S = 1.17	w = 1/[σ²(F_o²) + (0.0529P)² + 0.4126P] where P = (F_o² + 2F_c²)/3
1725 reflections	(Δ/σ)_max < 0.001
173 parameters	Δρ_max = 0.20 e Å⁻³
0 restraints	Δρ_min = −0.22 e Å⁻³

Crystal data top

C₁₃H₁₈BNO₄	V = 1299.0 (3) Å³
M_r = 263.10	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 8.3776 (11) Å	µ = 0.10 mm⁻¹
b = 8.9269 (11) Å	T = 153 K
c = 17.369 (2) Å	0.30 × 0.09 × 0.06 mm

Data collection top

Rigaku Saturn diffractometer	1725 independent reflections
Absorption correction: numerical (NUMABS; Higashi, 1999)	1707 reflections with I > 2σ(I)
T_min = 0.985, T_max = 0.997	R_int = 0.037
16363 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.043	0 restraints
wR(F²) = 0.112	H-atom parameters constrained
S = 1.17	Δρ_max = 0.20 e Å⁻³
1725 reflections	Δρ_min = −0.22 e Å⁻³
173 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

The crystal was a weak anomalous scatterer collected with Mo Kα radiation. Friedel mates were merged (MERG 4) and the absolute configuration was not determined.

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

	x	y	z	U_iso*/U_eq
O1	1.00908 (19)	0.47529 (18)	0.35582 (9)	0.0281 (4)
O2	0.85897 (19)	0.47478 (17)	0.23631 (9)	0.0268 (4)
O3	0.5232 (2)	−0.2735 (2)	0.39057 (11)	0.0422 (5)
O4	0.6510 (3)	−0.2494 (3)	0.50205 (13)	0.0617 (7)
N1	1.0730 (2)	0.2952 (2)	0.25504 (10)	0.0249 (4)
H1	1.0599	0.1919	0.2577	0.030*
C1	0.7998 (3)	0.2734 (2)	0.34181 (12)	0.0243 (4)
C2	0.6576 (3)	0.2247 (3)	0.30806 (13)	0.0253 (4)
H2	0.6285	0.2624	0.2589	0.030*
C3	0.5568 (3)	0.1220 (3)	0.34475 (13)	0.0261 (5)
H3	0.4626	0.0888	0.3195	0.031*
C4	0.5932 (3)	0.0679 (3)	0.41775 (13)	0.0263 (5)
C5	0.7326 (3)	0.1174 (3)	0.45272 (13)	0.0296 (5)
H5	0.7589	0.0827	0.5028	0.035*
C6	0.8342 (3)	0.2173 (3)	0.41551 (13)	0.0276 (5)
H6	0.9294	0.2482	0.4406	0.033*
C7	1.1685 (3)	0.4963 (3)	0.33084 (14)	0.0302 (5)
H7A	1.2382	0.5254	0.3744	0.036*
H7B	1.1743	0.5747	0.2906	0.036*
C8	1.2172 (3)	0.3441 (3)	0.29856 (15)	0.0313 (5)
H8A	1.3108	0.3534	0.2641	0.038*
H8B	1.2427	0.2729	0.3405	0.038*
C9	0.8982 (3)	0.4085 (3)	0.16438 (13)	0.0283 (5)
H9A	0.8939	0.4839	0.1226	0.034*
H9B	0.8231	0.3263	0.1520	0.034*
C10	1.0671 (3)	0.3484 (3)	0.17388 (14)	0.0297 (5)
H10A	1.0875	0.2650	0.1376	0.036*
H10B	1.1469	0.4283	0.1649	0.036*
C11	0.4878 (3)	−0.0470 (3)	0.45767 (13)	0.0287 (5)
H11A	0.4717	−0.0173	0.5120	0.034*
H11B	0.3821	−0.0498	0.4323	0.034*
C12	0.5624 (3)	−0.1999 (3)	0.45463 (15)	0.0330 (5)
C13	0.5926 (4)	−0.4222 (3)	0.3835 (2)	0.0499 (8)
H13A	0.7093	−0.4143	0.3831	0.060*
H13B	0.5563	−0.4686	0.3354	0.060*
H13C	0.5589	−0.4840	0.4272	0.060*
B1	0.9234 (3)	0.3847 (3)	0.30025 (14)	0.0236 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0291 (8)	0.0257 (8)	0.0296 (8)	−0.0045 (7)	0.0027 (6)	−0.0029 (7)
O2	0.0318 (8)	0.0203 (7)	0.0283 (8)	0.0029 (7)	0.0023 (7)	0.0014 (6)
O3	0.0412 (10)	0.0352 (10)	0.0503 (10)	0.0057 (9)	−0.0049 (9)	−0.0132 (9)
O4	0.0875 (17)	0.0522 (12)	0.0453 (11)	0.0243 (14)	−0.0164 (12)	0.0011 (9)
N1	0.0271 (9)	0.0181 (8)	0.0295 (9)	0.0004 (8)	0.0027 (8)	0.0024 (8)
C1	0.0254 (10)	0.0195 (10)	0.0279 (10)	0.0014 (9)	0.0055 (8)	−0.0020 (9)
C2	0.0263 (10)	0.0228 (10)	0.0268 (10)	0.0030 (9)	0.0023 (9)	0.0005 (9)
C3	0.0232 (10)	0.0234 (10)	0.0318 (11)	0.0010 (9)	0.0011 (9)	−0.0018 (9)
C4	0.0289 (10)	0.0213 (10)	0.0286 (10)	0.0009 (9)	0.0075 (9)	−0.0026 (9)
C5	0.0360 (12)	0.0291 (11)	0.0236 (10)	−0.0050 (10)	0.0014 (10)	0.0013 (9)
C6	0.0282 (10)	0.0270 (11)	0.0276 (10)	−0.0031 (10)	0.0000 (9)	−0.0030 (9)
C7	0.0285 (11)	0.0286 (12)	0.0334 (12)	−0.0054 (10)	−0.0020 (9)	0.0032 (10)
C8	0.0262 (11)	0.0284 (12)	0.0393 (13)	−0.0005 (10)	−0.0021 (10)	0.0054 (10)
C9	0.0349 (12)	0.0233 (11)	0.0266 (11)	−0.0002 (10)	−0.0020 (9)	0.0003 (9)
C10	0.0347 (12)	0.0259 (11)	0.0285 (11)	0.0016 (10)	0.0062 (10)	0.0010 (9)
C11	0.0308 (11)	0.0261 (11)	0.0291 (11)	−0.0023 (9)	0.0051 (9)	−0.0008 (9)
C12	0.0345 (12)	0.0316 (12)	0.0330 (11)	−0.0013 (11)	0.0057 (10)	0.0010 (10)
C13	0.0444 (15)	0.0340 (14)	0.071 (2)	0.0026 (13)	0.0060 (15)	−0.0162 (15)
B1	0.0261 (12)	0.0188 (11)	0.0258 (11)	0.0004 (10)	0.0020 (10)	−0.0009 (9)

Geometric parameters (Å, º) top

O1—C7	1.417 (3)	C5—C6	1.392 (3)
O1—B1	1.449 (3)	C5—H5	0.9500
O2—C9	1.421 (3)	C6—H6	0.9500
O2—B1	1.474 (3)	C7—C8	1.525 (4)
O3—C12	1.333 (3)	C7—H7A	0.9900
O3—C13	1.455 (4)	C7—H7B	0.9900
O4—C12	1.193 (3)	C8—H8A	0.9900
N1—C10	1.488 (3)	C8—H8B	0.9900
N1—C8	1.491 (3)	C9—C10	1.523 (3)
N1—B1	1.681 (3)	C9—H9A	0.9900
N1—H1	0.9300	C9—H9B	0.9900
C1—C2	1.397 (3)	C10—H10A	0.9900
C1—C6	1.405 (3)	C10—H10B	0.9900
C1—B1	1.607 (3)	C11—C12	1.502 (3)
C2—C3	1.400 (3)	C11—H11A	0.9900
C2—H2	0.9500	C11—H11B	0.9900
C3—C4	1.391 (3)	C13—H13A	0.9800
C3—H3	0.9500	C13—H13B	0.9800
C4—C5	1.388 (3)	C13—H13C	0.9800
C4—C11	1.520 (3)

C7—O1—B1	109.67 (18)	N1—C8—H8B	111.1
C9—O2—B1	110.55 (17)	C7—C8—H8B	111.1
C12—O3—C13	114.9 (2)	H8A—C8—H8B	109.1
C10—N1—C8	114.44 (19)	O2—C9—C10	105.45 (19)
C10—N1—B1	105.44 (17)	O2—C9—H9A	110.7
C8—N1—B1	103.17 (17)	C10—C9—H9A	110.7
C10—N1—H1	111.1	O2—C9—H9B	110.7
C8—N1—H1	111.1	C10—C9—H9B	110.7
B1—N1—H1	111.1	H9A—C9—H9B	108.8
C2—C1—C6	116.5 (2)	N1—C10—C9	104.23 (19)
C2—C1—B1	123.6 (2)	N1—C10—H10A	110.9
C6—C1—B1	119.9 (2)	C9—C10—H10A	110.9
C1—C2—C3	121.8 (2)	N1—C10—H10B	110.9
C1—C2—H2	119.1	C9—C10—H10B	110.9
C3—C2—H2	119.1	H10A—C10—H10B	108.9
C4—C3—C2	120.7 (2)	C12—C11—C4	110.81 (19)
C4—C3—H3	119.7	C12—C11—H11A	109.5
C2—C3—H3	119.7	C4—C11—H11A	109.5
C5—C4—C3	118.2 (2)	C12—C11—H11B	109.5
C5—C4—C11	120.3 (2)	C4—C11—H11B	109.5
C3—C4—C11	121.5 (2)	H11A—C11—H11B	108.1
C4—C5—C6	121.0 (2)	O4—C12—O3	123.2 (3)
C4—C5—H5	119.5	O4—C12—C11	124.8 (3)
C6—C5—H5	119.5	O3—C12—C11	112.0 (2)
C5—C6—C1	121.7 (2)	O3—C13—H13A	109.5
C5—C6—H6	119.1	O3—C13—H13B	109.5
C1—C6—H6	119.1	H13A—C13—H13B	109.5
O1—C7—C8	104.28 (19)	O3—C13—H13C	109.5
O1—C7—H7A	110.9	H13A—C13—H13C	109.5
C8—C7—H7A	110.9	H13B—C13—H13C	109.5
O1—C7—H7B	110.9	O1—B1—O2	112.28 (19)
C8—C7—H7B	110.9	O1—B1—C1	111.41 (18)
H7A—C7—H7B	108.9	O2—B1—C1	116.1 (2)
N1—C8—C7	103.34 (19)	O1—B1—N1	101.97 (18)
N1—C8—H8A	111.1	O2—B1—N1	100.39 (17)
C7—C8—H8A	111.1	C1—B1—N1	113.35 (18)

Hydrogen-bond geometry (Å, º) top

Cg3 is the centroid of the C1–C6 ring.

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2ⁱ	0.93	2.06	2.921 (2)	154
C10—H10B···Cg3ⁱⁱ	0.99	2.65	3.618 (2)	166

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

Experimental details

Crystal data
Chemical formula	C₁₃H₁₈BNO₄
M_r	263.10
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	153
a, b, c (Å)	8.3776 (11), 8.9269 (11), 17.369 (2)
V (Å³)	1299.0 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.10
Crystal size (mm)	0.30 × 0.09 × 0.06

Data collection
Diffractometer	Rigaku Saturn diffractometer
Absorption correction	Numerical (NUMABS; Higashi, 1999)
T_min, T_max	0.985, 0.997
No. of measured, independent and observed [I > 2σ(I)] reflections	16363, 1725, 1707
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.112, 1.17
No. of reflections	1725
No. of parameters	173
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.20, −0.22

Computer programs: CrystalClear (Rigaku, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top

Cg3 is the centroid of the C1–C6 ring.

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2ⁱ	0.93	2.056	2.921 (2)	154
C10—H10B···Cg3ⁱⁱ	0.99	2.650	3.618 (2)	166

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

Acknowledgements

We thank the NSERC and the Department of Chemistry for financial support. We are also grateful to the Ministry for Higher Education, Egypt, for a scholarship to ALZ.

References

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