1-Nitro-2,3-di-2-pyridyl-2,3-dihydro­indolizine

Schulz, M.; Kloubert, T.; Görls, H.; Westerhausen, M.

doi:10.1107/S1600536809011842

organic compounds

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Volume 65| Part 5| May 2009| Page o957

doi:10.1107/S1600536809011842

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1-Nitro-2,3-di-2-pyridyl-2,3-dihydroindolizine

Martin Schulz,^a Tobias Kloubert,^a Helmar Görls ^a and Matthias Westerhausen ^a ^*

^aInstitute of Inorganic and Analytical Chemistry, Friedrich-Schiller-Universität Jena, August-Bebel-Strasse 2, D-07743 Jena, Germany
^*Correspondence e-mail: m.we@uni-jena.de

(Received 19 March 2009; accepted 30 March 2009; online 2 April 2009)

The title compound, C₁₈H₁₄N₄O₂, was found as a by-product in the nitroaldol reaction between 2-(nitromethyl)pyridine and N-(pyridin-2-ylmethylidene)methaneamine. Its two stereogenic centers give rise to four stereoisomers of which only the anti isomers are found in this crystal structure.

Related literature

For the synthesis of 2-(nitromethyl)pyridine, see: Feuer & Lawrence (1972 ). For nitroaldol reactions, see: Cwik et al. (2005 ). For β-nitroamines, see Lucet et al. (1998 ). For comparison of bond lengths, see: Allen et al. (1987 ).

Experimental

Crystal data

C₁₈H₁₄N₄O₂
M_r = 318.33
Monoclinic, C 2/c
a = 28.0688 (19) Å
b = 7.9672 (6) Å
c = 21.1859 (15) Å
β = 131.408 (4)°
V = 3553.4 (4) Å³
Z = 8
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 183 K
0.06 × 0.06 × 0.05 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: none
10925 measured reflections
4021 independent reflections
2564 reflections with I > 2σ(I)
R_int = 0.057

Refinement

R[F² > 2σ(F²)] = 0.065
wR(F²) = 0.216
S = 0.74
4021 reflections
217 parameters
H-atom parameters constrained
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: COLLECT (Nonius, 1998 ); cell refinement: DENZO (Otwinowski & Minor, 1997 ); data reduction: DENZO and the SQUEEZE option (Sluis & Spek, 1990 ) in PLATON (Spek, 2009 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL/PC (Sheldrick, 2008); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809011842/bt2909sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809011842/bt2909Isup2.hkl

checkCIF report

Comment top

β-nitroamines are promising precursors for vicinal diamines, which themselves are a versatile class of compounds (Lucet et al., 1998). The nitroaldol reaction between 2-(nitromethyl)pyridine 1 (Feuer & Lawrence, 1972) and N-(pyridin-2-ylmethylidene)methaneamine 2 yielded the title compound 3 as a byproduct together with methylamine. Although four stereo isomers are possible, only the anti-isomers are found in the crystal structure. The 2-pyridyl rings of neighbouring molecules are arrangend coplanarily with an approximate intermolecular distance of 3.70 Å. Not surprisingly the five-membered dihydroindolizine ring is strained and conjugation of the six-membered ring with the nitro group is observed regarding the bond lengths. They are found to lie between those for single and double bonds (Allen et al., 1987).

Related literature top

For the synthesis of 2-(nitromethyl)pyridine, see: Feuer & Lawrence (1972). For nitroaldol reactions, see: Cwik et al. (2005). For β-nitroamines, see Lucet et al. (1998). For comparison of bond lengths, see: Allen et al. (1987).

Experimental top

A nitroaldol reaction (Henry reaction) was carried out with 2-(nitromethyl)pyridine 1 (0.20 g; 1.4 mmol) and N-(pyridin-2-ylmethylidene)methaneamine 2 (0.15 g; 1.2 mmol) in 3.5 ml anhydrous THF with hydrotalcite Syntal 696 (0.13 g) as catalyst (Cwik et al., 2005). The mixture was stirred for eight hours at 60 °C and then cooled to r.t.. Then the solvent was removed in vacuo yielding a sticky brown residue. Thereafter 3 ml of diethylether were added and the yellow etheral solution was separated from the insoluble brownish residue, which was then dissolved in THF. From the latter solution yellow crystals of the title compound were obtained at r.t. (0.017 g). The compound is stable at room temperature and under atmospheric conditions. NMR measurements were carried out on a Bruker AC 200 and Bruker AC 400 spectrometer and referenced to the solvent resonances. Signals were assigned by DEPT 135, HSQC, HMBC experiments.

¹H-NMR (CD₂Cl₂): δ = 8.59 (d, 1H, J = 4.0 Hz, H13), 8.55 (d, 1H, J = 4.0 Hz, H18), 8.30 (d, 1H, J = 8.8 Hz, H5), 7.80–7.77 (m, 1H, H11), 7.76–7.73 (m, 1H, H6), 7.69–7.65 (m, 1H, H16), 7.58 (d, 1H, J = 6.4 Hz, H8), 7.43 (d, 1H, J = 7.6 Hz, H12), 7.35–7.33 (m, 1H, H15), 7.33–7.31(m, 1H, H17), 7.23–7.20 (m, 1H, H19), 6.74–6.71 (m, 1H, H7), 6.08 (d, 1H, J = 4.0 Hz, H3), 4.89 (d, 1H, J = 4.0 Hz, H2);

¹³C-NMR (CD₂Cl₂): δ = 159.7 (q,C14), 157.5 (q,C4,C9), 150.7 (t,C13), 150.4 (q,C1), 150.1(t,C18), 142.2 (t,C6), 138.0 (t,C11), 137.3 (t,C8), 136.7 (t,C16), 124.5 (t,C15), 124.1 (t,C12), 122.8 (t,C10), 121.8 (t,C17), 119.6 (t,C5), 114.8 (t,C7), 75.3 (t,C3), 54.1 (t,C2).

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997) and the SQUEEZE option (Sluis & Spek, 1990) in PLATON (Spek, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL/PC (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. Molecular structure an numbering scheme of 3. The ellipsoids represent a probability of 40%, H atoms are shown with arbitrary radii.
	Fig. 2. The formation of the title compound.

1-Nitro-2,3-di-2-pyridyl-2,3-dihydroindolizine top

Crystal data top

C₁₈H₁₄N₄O₂	F(000) = 1364
M_r = 318.33	D_x = 1.219 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 10925 reflections
a = 28.0688 (19) Å	θ = 2.6–27.5°
b = 7.9672 (6) Å	µ = 0.08 mm⁻¹
c = 21.1859 (15) Å	T = 183 K
β = 131.408 (4)°	Prism, light yellow
V = 3553.4 (4) Å³	0.06 × 0.06 × 0.05 mm
Z = 8

Data collection top

Nonius KappaCCD diffractometer	2564 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.057
Graphite monochromator	θ_max = 27.5°, θ_min = 2.6°
ϕ and ω scans	h = −36→36
10925 measured reflections	k = −10→8
4021 independent reflections	l = −22→27

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)] = 0.065	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.216	H-atom parameters constrained
S = 0.74	w = 1/[σ²(F_o²) + (0.1821P)² + 4.6408P] where P = (F_o² + 2F_c²)/3
4021 reflections	(Δ/σ)_max < 0.001
217 parameters	Δρ_max = 0.28 e Å⁻³
0 restraints	Δρ_min = −0.26 e Å⁻³

Crystal data top

C₁₈H₁₄N₄O₂	V = 3553.4 (4) Å³
M_r = 318.33	Z = 8
Monoclinic, C2/c	Mo Kα radiation
a = 28.0688 (19) Å	µ = 0.08 mm⁻¹
b = 7.9672 (6) Å	T = 183 K
c = 21.1859 (15) Å	0.06 × 0.06 × 0.05 mm
β = 131.408 (4)°

Data collection top

Nonius KappaCCD diffractometer	2564 reflections with I > 2σ(I)
10925 measured reflections	R_int = 0.057
4021 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.065	0 restraints
wR(F²) = 0.216	H-atom parameters constrained
S = 0.74	Δρ_max = 0.28 e Å⁻³
4021 reflections	Δρ_min = −0.26 e Å⁻³
217 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.

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

	x	y	z	U_iso*/U_eq
O1	0.17598 (9)	1.2960 (2)	0.14775 (13)	0.0452 (5)
O2	0.16787 (9)	1.2549 (2)	0.03788 (12)	0.0485 (5)
N1	0.17260 (9)	1.1975 (2)	0.09773 (14)	0.0371 (5)
N2	0.17010 (8)	0.7804 (2)	0.15264 (11)	0.0298 (4)
N3	0.04544 (10)	0.8231 (3)	−0.00295 (16)	0.0518 (6)
N4	0.27897 (9)	0.8055 (3)	0.13515 (12)	0.0357 (5)
C1	0.17419 (10)	1.0305 (3)	0.10757 (14)	0.0325 (5)
C2	0.17024 (10)	0.9055 (3)	0.05051 (14)	0.0323 (5)
H2A	0.1348	0.9368	−0.0097	0.039*
C3	0.15344 (10)	0.7422 (3)	0.07139 (14)	0.0320 (5)
H3A	0.1790	0.6456	0.0776	0.038*
C4	0.17739 (10)	0.9488 (3)	0.16928 (13)	0.0309 (5)
C5	0.18579 (10)	1.0032 (3)	0.23890 (14)	0.0338 (5)
H5A	0.1914	1.1190	0.2528	0.041*
C6	0.18587 (11)	0.8876 (3)	0.28665 (15)	0.0395 (6)
H6A	0.1912	0.9242	0.3337	0.047*
C7	0.17820 (12)	0.7160 (3)	0.26747 (16)	0.0408 (6)
H7A	0.1781	0.6365	0.3008	0.049*
C8	0.17096 (11)	0.6654 (3)	0.20010 (15)	0.0349 (5)
H8A	0.1665	0.5496	0.1866	0.042*
C9	0.08294 (11)	0.7031 (3)	0.00711 (14)	0.0344 (5)
C10	0.06039 (11)	0.5554 (3)	−0.03744 (15)	0.0385 (6)
H10A	0.0886	0.4714	−0.0278	0.046*
C11	−0.00528 (12)	0.5328 (3)	−0.09736 (17)	0.0473 (7)
H11A	−0.0227	0.4328	−0.1299	0.057*
C12	−0.04402 (12)	0.6548 (4)	−0.10870 (16)	0.0451 (6)
H12A	−0.0889	0.6421	−0.1494	0.054*
C13	−0.01697 (13)	0.7973 (4)	−0.0600 (2)	0.0525 (7)
H13A	−0.0443	0.8817	−0.0675	0.063*
C14	0.23253 (10)	0.8989 (3)	0.06895 (13)	0.0317 (5)
C15	0.24114 (12)	0.9906 (3)	0.02183 (15)	0.0394 (6)
H15A	0.2071	1.0545	−0.0250	0.047*
C16	0.29952 (13)	0.9886 (3)	0.04343 (17)	0.0444 (6)
H16A	0.3066	1.0520	0.0123	0.053*
C17	0.34797 (12)	0.8915 (3)	0.11200 (17)	0.0437 (6)
H17A	0.3887	0.8865	0.1286	0.052*
C18	0.33500 (12)	0.8037 (3)	0.15471 (16)	0.0401 (6)
H18A	0.3680	0.7373	0.2013	0.048*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0509 (11)	0.0294 (9)	0.0678 (12)	0.0003 (7)	0.0446 (10)	−0.0052 (8)
O2	0.0574 (12)	0.0393 (10)	0.0642 (12)	0.0097 (8)	0.0467 (11)	0.0178 (9)
N1	0.0373 (11)	0.0281 (10)	0.0527 (12)	0.0046 (8)	0.0327 (10)	0.0056 (9)
N2	0.0270 (9)	0.0276 (10)	0.0322 (9)	−0.0005 (7)	0.0185 (8)	0.0000 (7)
N3	0.0335 (11)	0.0431 (13)	0.0634 (14)	0.0014 (9)	0.0254 (11)	−0.0136 (11)
N4	0.0336 (10)	0.0381 (11)	0.0356 (10)	−0.0006 (8)	0.0229 (9)	0.0012 (8)
C1	0.0313 (11)	0.0288 (12)	0.0382 (12)	0.0004 (9)	0.0233 (10)	0.0015 (9)
C2	0.0326 (11)	0.0305 (12)	0.0303 (10)	0.0002 (9)	0.0193 (10)	0.0020 (9)
C3	0.0313 (11)	0.0285 (11)	0.0366 (11)	0.0008 (9)	0.0226 (10)	−0.0028 (9)
C4	0.0253 (10)	0.0260 (11)	0.0363 (11)	0.0020 (8)	0.0182 (9)	0.0006 (9)
C5	0.0335 (11)	0.0298 (12)	0.0377 (12)	0.0009 (9)	0.0234 (10)	−0.0031 (9)
C6	0.0384 (13)	0.0440 (15)	0.0386 (12)	0.0032 (10)	0.0266 (11)	0.0006 (10)
C7	0.0402 (13)	0.0415 (14)	0.0443 (13)	0.0045 (10)	0.0295 (12)	0.0092 (11)
C8	0.0333 (12)	0.0282 (12)	0.0420 (12)	0.0001 (9)	0.0244 (11)	0.0026 (10)
C9	0.0324 (12)	0.0328 (12)	0.0371 (12)	0.0001 (9)	0.0226 (10)	−0.0013 (9)
C10	0.0377 (12)	0.0325 (13)	0.0449 (13)	−0.0023 (10)	0.0272 (11)	−0.0042 (10)
C11	0.0372 (13)	0.0426 (15)	0.0526 (15)	−0.0113 (11)	0.0256 (12)	−0.0134 (12)
C12	0.0303 (12)	0.0531 (16)	0.0452 (14)	−0.0063 (11)	0.0221 (11)	−0.0039 (12)
C13	0.0345 (13)	0.0471 (16)	0.0651 (17)	0.0043 (11)	0.0284 (13)	−0.0086 (13)
C14	0.0352 (12)	0.0307 (12)	0.0305 (10)	−0.0021 (9)	0.0223 (10)	−0.0032 (9)
C15	0.0469 (14)	0.0398 (14)	0.0369 (12)	0.0043 (11)	0.0299 (12)	0.0055 (10)
C16	0.0566 (16)	0.0427 (15)	0.0532 (15)	−0.0055 (12)	0.0445 (14)	−0.0008 (12)
C17	0.0408 (13)	0.0468 (15)	0.0539 (15)	−0.0062 (11)	0.0357 (13)	−0.0068 (12)
C18	0.0357 (12)	0.0430 (14)	0.0410 (13)	0.0024 (10)	0.0252 (11)	0.0015 (10)

Geometric parameters (Å, º) top

O1—N1	1.271 (3)	C6—H6A	0.9500
O2—N1	1.269 (3)	C7—C8	1.363 (4)
N1—C1	1.342 (3)	C7—H7A	0.9500
N2—C8	1.349 (3)	C8—H8A	0.9500
N2—C4	1.367 (3)	C9—C10	1.373 (3)
N2—C3	1.487 (3)	C10—C11	1.395 (3)
N3—C13	1.331 (3)	C10—H10A	0.9500
N3—C9	1.331 (3)	C11—C12	1.356 (4)
N4—C18	1.335 (3)	C11—H11A	0.9500
N4—C14	1.342 (3)	C12—C13	1.377 (4)
C1—C4	1.410 (3)	C12—H12A	0.9500
C1—C2	1.513 (3)	C13—H13A	0.9500
C2—C14	1.519 (3)	C14—C15	1.381 (3)
C2—C3	1.545 (3)	C15—C16	1.380 (4)
C2—H2A	1.0000	C15—H15A	0.9500
C3—C9	1.517 (3)	C16—C17	1.394 (4)
C3—H3A	1.0000	C16—H16A	0.9500
C4—C5	1.400 (3)	C17—C18	1.370 (4)
C5—C6	1.367 (3)	C17—H17A	0.9500
C5—H5A	0.9500	C18—H18A	0.9500
C6—C7	1.402 (4)

O1—N1—O2	120.7 (2)	C6—C7—H7A	120.7
O1—N1—C1	120.4 (2)	C7—C8—N2	119.8 (2)
O2—N1—C1	118.9 (2)	C7—C8—H8A	120.1
C8—N2—C4	123.25 (19)	N2—C8—H8A	120.1
C8—N2—C3	124.12 (19)	N3—C9—C10	123.3 (2)
C4—N2—C3	112.24 (18)	N3—C9—C3	114.8 (2)
C13—N3—C9	117.5 (2)	C10—C9—C3	121.8 (2)
C18—N4—C14	117.4 (2)	C9—C10—C11	117.9 (2)
N1—C1—C4	125.2 (2)	C9—C10—H10A	121.1
N1—C1—C2	123.4 (2)	C11—C10—H10A	121.1
C4—C1—C2	111.29 (19)	C12—C11—C10	119.4 (2)
C1—C2—C14	110.71 (18)	C12—C11—H11A	120.3
C1—C2—C3	101.58 (17)	C10—C11—H11A	120.3
C14—C2—C3	114.49 (18)	C11—C12—C13	118.6 (2)
C1—C2—H2A	109.9	C11—C12—H12A	120.7
C14—C2—H2A	109.9	C13—C12—H12A	120.7
C3—C2—H2A	109.9	N3—C13—C12	123.4 (2)
N2—C3—C9	107.82 (17)	N3—C13—H13A	118.3
N2—C3—C2	103.72 (17)	C12—C13—H13A	118.3
C9—C3—C2	112.33 (18)	N4—C14—C15	122.4 (2)
N2—C3—H3A	110.9	N4—C14—C2	116.42 (19)
C9—C3—H3A	110.9	C15—C14—C2	121.2 (2)
C2—C3—H3A	110.9	C16—C15—C14	119.4 (2)
N2—C4—C5	117.9 (2)	C16—C15—H15A	120.3
N2—C4—C1	107.89 (19)	C14—C15—H15A	120.3
C5—C4—C1	134.2 (2)	C15—C16—C17	118.6 (2)
C6—C5—C4	119.2 (2)	C15—C16—H16A	120.7
C6—C5—H5A	120.4	C17—C16—H16A	120.7
C4—C5—H5A	120.4	C18—C17—C16	118.0 (2)
C5—C6—C7	121.2 (2)	C18—C17—H17A	121.0
C5—C6—H6A	119.4	C16—C17—H17A	121.0
C7—C6—H6A	119.4	N4—C18—C17	124.2 (2)
C8—C7—C6	118.7 (2)	N4—C18—H18A	117.9
C8—C7—H7A	120.7	C17—C18—H18A	117.9

O1—N1—C1—C4	2.2 (3)	C6—C7—C8—N2	−1.2 (3)
O2—N1—C1—C4	−178.0 (2)	C4—N2—C8—C7	1.3 (3)
O1—N1—C1—C2	179.84 (19)	C3—N2—C8—C7	−170.9 (2)
O2—N1—C1—C2	−0.4 (3)	C13—N3—C9—C10	−0.8 (4)
N1—C1—C2—C14	74.7 (3)	C13—N3—C9—C3	178.4 (2)
C4—C1—C2—C14	−107.4 (2)	N2—C3—C9—N3	56.2 (3)
N1—C1—C2—C3	−163.3 (2)	C2—C3—C9—N3	−57.5 (3)
C4—C1—C2—C3	14.6 (2)	N2—C3—C9—C10	−124.6 (2)
C8—N2—C3—C9	69.8 (3)	C2—C3—C9—C10	121.8 (2)
C4—N2—C3—C9	−103.2 (2)	N3—C9—C10—C11	1.4 (4)
C8—N2—C3—C2	−170.94 (19)	C3—C9—C10—C11	−177.8 (2)
C4—N2—C3—C2	16.1 (2)	C9—C10—C11—C12	−0.7 (4)
C1—C2—C3—N2	−17.3 (2)	C10—C11—C12—C13	−0.4 (4)
C14—C2—C3—N2	102.0 (2)	C9—N3—C13—C12	−0.5 (5)
C1—C2—C3—C9	98.8 (2)	C11—C12—C13—N3	1.0 (5)
C14—C2—C3—C9	−141.83 (19)	C18—N4—C14—C15	0.1 (3)
C8—N2—C4—C5	−0.3 (3)	C18—N4—C14—C2	−177.2 (2)
C3—N2—C4—C5	172.68 (18)	C1—C2—C14—N4	80.8 (2)
C8—N2—C4—C1	179.81 (18)	C3—C2—C14—N4	−33.3 (3)
C3—N2—C4—C1	−7.2 (2)	C1—C2—C14—C15	−96.5 (2)
N1—C1—C4—N2	172.5 (2)	C3—C2—C14—C15	149.4 (2)
C2—C1—C4—N2	−5.3 (2)	N4—C14—C15—C16	−0.7 (4)
N1—C1—C4—C5	−7.3 (4)	C2—C14—C15—C16	176.4 (2)
C2—C1—C4—C5	174.8 (2)	C14—C15—C16—C17	0.8 (4)
N2—C4—C5—C6	−0.5 (3)	C15—C16—C17—C18	−0.4 (4)
C1—C4—C5—C6	179.3 (2)	C14—N4—C18—C17	0.4 (4)
C4—C5—C6—C7	0.5 (3)	C16—C17—C18—N4	−0.3 (4)
C5—C6—C7—C8	0.4 (4)

Experimental details

Crystal data
Chemical formula	C₁₈H₁₄N₄O₂
M_r	318.33
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	183
a, b, c (Å)	28.0688 (19), 7.9672 (6), 21.1859 (15)
β (°)	131.408 (4)
V (Å³)	3553.4 (4)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.06 × 0.06 × 0.05

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	10925, 4021, 2564
R_int	0.057
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.065, 0.216, 0.74
No. of reflections	4021
No. of parameters	217
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.26

Computer programs: COLLECT (Nonius, 1998), DENZO (Otwinowski & Minor, 1997) and the SQUEEZE option (Sluis & Spek, 1990) in PLATON (Spek, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL/PC (Sheldrick, 2008).

Acknowledgements

We thank the Deutsche Forschungsgemeinschaft (DFG, Bonn–Bad Godesberg, Germany) for generous financial support. We also acknowledge funding from the Fonds der Chemischen Industrie (Frankfurt/Main, Germany). Additionally we thank Südchemie AG (München, Germany) for providing the hydrotalcite Syntal 696.

References

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