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The molecular structure of the title compound, C16H18N4O2, adopts the trans conformation, and has an inversion center at the midpoint of the C-C bond in the oxamidate plane. The two phenyl planes are parallel, while the dihedral angle between the oxamidate plane and the phenyl ring is 2.5 (2)°.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802017452/su6000sup1.cif
Contains datablocks global, III

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802017452/su6000IIIsup2.hkl
Contains datablock III

CCDC reference: 198980

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.002 Å
  • R factor = 0.040
  • wR factor = 0.181
  • Data-to-parameter ratio = 12.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry
Yellow Alert Alert Level C:
PLAT_369 Alert C Long C(sp2)-C(sp2) Bond C(8) - C(8)a = 1.54 Ang.
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

N,N'-Disubstituted oxamidates are versatile ligands in coordination chemistry. They can adopt either the cis-(I) or trans-(II) conformation to form metal complexes, which are excellent building blocks for more complicated structures, such as metallosupramolecular frameworks (Chen at el., 1994). As part of our systematic study on the coordination chemistry of N,N'-disubstituted oxamidate ligands, we recently synthesized the ligand N,N'-bis(2-pyridylethyl)oxamide, (III), and analyzed its crystal structure. The symmetric center of (III) is located at the midpoint of the bond C8—C8A. Atoms C7 and C7A are in the oxamidate plane, which is composed ofatoms C8, C8A, N2, N2A, O1 and O1A. The dihedral angle between the oxamidate plane and the phenyl planes is only 2.5°, and the two phenyl rings are parallel to each other. The two CO groups lie on opposite sides of the bond C8—C8A and the molecule adopts the trans conformation. The torsion angle N2—C7—C6—C5 is 178.15 (12)°. Though atoms C8 and C8A are sp2 hybridized, the bond C8—C8A is mainly a single bond and the bond length is 1.537 (3) Å, which is longer than that of a CC double bond. Similar situations were found in the analogue N,N'-bis(2-pyridylmethyl)oxamide, in which the C—C bond lengths are 1.536 (7) and 1.513 (7) Å (Lloret et al., 1989), as well as in other oxamide compounds (Sanada et al., 1998; Ruiz et al., 1997; Chen et al., 1994; Zhang et al., 1996). In the crystal, symmetry-related molecules are linked by two types of intermolecular hydrogen bonds, viz. N—H···N and C—H···O. As indicated in Table 2, the hydrogen bond between N2 and N1i is much stronger than that between C1 and O1ii.

Experimental top

N,N'-Bis(2-pyridylethyl)oxamide was prepared according to a procedure similar to that reported by Ojima et al. (1970). An ethanol solution (50 ml) of diethyl oxalate (14.62 g, 0.10 mol) was added dropwise to 100 ml e thanol solution of 2-(2-aminoethyl)pyridine (24.24 g, 0.20 mol) with stirring. The mixture was then stirred and refluxed at 353 K for 1 h. The resulting solution was cooled to room temperature and a white precipitation appeared. The precipitate was filtered off and washed with water and diethyl ether. The yield was approximately 93%. Colourless single crystals were obtained by recrystallization from ethanol.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1998); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. View of the molecule of (III), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
(III) top
Crystal data top
C16H18N4O2F(000) = 316
Mr = 298.34Dx = 1.300 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ytcCell parameters from 2131 reflections
a = 9.489 (6) Åθ = 2.2–26.8°
b = 6.248 (4) ŵ = 0.09 mm1
c = 13.062 (8) ÅT = 293 K
β = 100.28 (1)°Prism, colourless
V = 762.0 (8) Å30.47 × 0.33 × 0.20 mm
Z = 2
Data collection top
Bruker CCD area-detector
diffractometer
1642 independent reflections
Radiation source: fine-focus sealed tube1274 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.018
Detector resolution: 0.781Å pixels mm-1θmax = 27.1°, θmin = 3.2°
ϕ and ω scansh = 1112
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996; Blessing, 1995)
k = 77
Tmin = 0.959, Tmax = 0.982l = 1416
4245 measured reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.040All H-atom parameters refined
wR(F2) = 0.181 w = 1/[σ2(Fo2) + (0.1359P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.06(Δ/σ)max = 0.001
1642 reflectionsΔρmax = 0.22 e Å3
137 parametersΔρmin = 0.13 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.07 (2)
Crystal data top
C16H18N4O2V = 762.0 (8) Å3
Mr = 298.34Z = 2
Monoclinic, P21/cMo Kα radiation
a = 9.489 (6) ŵ = 0.09 mm1
b = 6.248 (4) ÅT = 293 K
c = 13.062 (8) Å0.47 × 0.33 × 0.20 mm
β = 100.28 (1)°
Data collection top
Bruker CCD area-detector
diffractometer
1642 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996; Blessing, 1995)
1274 reflections with I > 2σ(I)
Tmin = 0.959, Tmax = 0.982Rint = 0.018
4245 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0400 restraints
wR(F2) = 0.181All H-atom parameters refined
S = 1.06Δρmax = 0.22 e Å3
1642 reflectionsΔρmin = 0.13 e Å3
137 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
xyzUiso*/Ueq
N20.03947 (14)0.1630 (2)0.89738 (10)0.0489 (4)
O10.17259 (11)0.0845 (2)1.05455 (9)0.0678 (5)
C80.06301 (13)0.0690 (2)0.98966 (11)0.0459 (4)
C70.14418 (17)0.3021 (2)0.86280 (12)0.0503 (4)
N10.21408 (14)0.7539 (2)0.77070 (9)0.0546 (4)
C50.24531 (15)0.6710 (2)0.86563 (10)0.0439 (4)
C60.13294 (17)0.5315 (3)0.89930 (14)0.0549 (5)
C40.37601 (18)0.7055 (3)0.92896 (13)0.0579 (5)
C30.3141 (2)0.8751 (3)0.73874 (15)0.0685 (5)
C20.4470 (2)0.9117 (3)0.79621 (16)0.0674 (5)
C10.47833 (19)0.8265 (3)0.89319 (15)0.0661 (6)
H7B0.1271 (19)0.300 (3)0.7856 (14)0.061 (5)*
H6B0.151 (2)0.531 (3)0.9788 (16)0.072 (5)*
H7A0.238 (2)0.245 (3)0.8888 (13)0.059 (5)*
H6A0.040 (3)0.583 (3)0.8719 (17)0.083 (6)*
H2A0.045 (2)0.149 (3)0.8577 (14)0.061 (5)*
H10.570 (2)0.850 (3)0.9324 (16)0.079 (6)*
H30.284 (3)0.934 (4)0.666 (2)0.105 (7)*
H20.517 (2)0.999 (4)0.7675 (19)0.098 (7)*
H40.392 (2)0.644 (3)0.9969 (16)0.074 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N20.0393 (7)0.0518 (8)0.0541 (7)0.0071 (5)0.0043 (5)0.0035 (5)
O10.0401 (6)0.0871 (9)0.0703 (8)0.0179 (5)0.0067 (5)0.0199 (6)
C80.0346 (7)0.0461 (8)0.0558 (8)0.0043 (5)0.0048 (6)0.0012 (6)
C70.0451 (9)0.0526 (9)0.0546 (9)0.0052 (6)0.0127 (7)0.0024 (6)
N10.0488 (8)0.0641 (9)0.0498 (7)0.0001 (6)0.0058 (6)0.0029 (5)
C50.0417 (8)0.0425 (8)0.0478 (8)0.0013 (5)0.0087 (6)0.0039 (5)
C60.0471 (9)0.0562 (9)0.0645 (10)0.0056 (6)0.0180 (7)0.0025 (7)
C40.0521 (9)0.0694 (10)0.0500 (9)0.0032 (7)0.0031 (7)0.0004 (7)
C30.0736 (12)0.0682 (11)0.0670 (11)0.0040 (9)0.0216 (9)0.0166 (8)
C20.0667 (11)0.0515 (9)0.0905 (13)0.0125 (8)0.0312 (10)0.0023 (8)
C10.0459 (10)0.0697 (12)0.0813 (13)0.0147 (8)0.0072 (8)0.0192 (9)
Geometric parameters (Å, º) top
N2—C81.324 (2)C5—C61.502 (2)
N2—C71.451 (2)C6—H6B1.02 (2)
N2—H2A0.88 (2)C6—H6A0.94 (2)
O1—C81.2224 (19)C4—C11.376 (3)
C8—C8i1.537 (3)C4—H40.95 (2)
C7—C61.520 (2)C3—C21.367 (3)
C7—H7B0.992 (18)C3—H31.01 (3)
C7—H7A0.97 (2)C2—C11.357 (3)
N1—C51.328 (2)C2—H20.99 (3)
N1—C31.338 (2)C1—H10.94 (2)
C5—C41.379 (2)
C8—N2—C7122.37 (13)C5—C6—H6B107.5 (11)
C8—N2—H2A118.6 (12)C7—C6—H6B107.8 (11)
C7—N2—H2A118.9 (12)C5—C6—H6A110.7 (14)
O1—C8—N2125.51 (13)C7—C6—H6A108.3 (13)
O1—C8—C8i120.98 (16)H6B—C6—H6A111.3 (18)
N2—C8—C8i113.51 (14)C1—C4—C5119.71 (16)
N2—C7—C6112.13 (13)C1—C4—H4121.9 (13)
N2—C7—H7B108.1 (11)C5—C4—H4118.4 (13)
C6—C7—H7B108.9 (11)N1—C3—C2124.02 (16)
N2—C7—H7A108.2 (11)N1—C3—H3113.6 (15)
C6—C7—H7A110.4 (11)C2—C3—H3122.3 (15)
H7B—C7—H7A109.0 (15)C1—C2—C3118.31 (16)
C5—N1—C3117.38 (14)C1—C2—H2121.4 (14)
N1—C5—C4121.74 (14)C3—C2—H2120.3 (14)
N1—C5—C6116.62 (13)C2—C1—C4118.80 (17)
C4—C5—C6121.62 (14)C2—C1—H1118.5 (13)
C5—C6—C7111.21 (13)C4—C1—H1122.7 (13)
C7—N2—C8—O11.0 (2)N2—C7—C6—C5178.15 (12)
C7—N2—C8—C8i179.36 (14)N1—C5—C4—C10.9 (3)
C8—N2—C7—C685.67 (18)C6—C5—C4—C1177.05 (15)
C3—N1—C5—C40.7 (2)C5—N1—C3—C22.4 (3)
C3—N1—C5—C6178.75 (14)N1—C3—C2—C12.5 (3)
N1—C5—C6—C785.13 (18)C3—C2—C1—C40.7 (3)
C4—C5—C6—C792.89 (18)C5—C4—C1—C20.9 (3)
Symmetry code: (i) x, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···N1ii0.878 (19)2.204 (19)3.008 (3)152.1 (17)
C1—H1···O1iii0.94 (2)2.452 (19)3.308 (3)151.4 (17)
Symmetry codes: (ii) x, y1/2, z+3/2; (iii) x+1, y+1, z+2.

Experimental details

Crystal data
Chemical formulaC16H18N4O2
Mr298.34
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)9.489 (6), 6.248 (4), 13.062 (8)
β (°) 100.28 (1)
V3)762.0 (8)
Z2
Radiation typeMo Kα
µ (mm1)0.09
Crystal size (mm)0.47 × 0.33 × 0.20
Data collection
DiffractometerBruker CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996; Blessing, 1995)
Tmin, Tmax0.959, 0.982
No. of measured, independent and
observed [I > 2σ(I)] reflections
4245, 1642, 1274
Rint0.018
(sin θ/λ)max1)0.640
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.181, 1.06
No. of reflections1642
No. of parameters137
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.22, 0.13

Computer programs: SMART (Bruker, 1998), SMART, SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 1998), SHELXTL.

Selected geometric parameters (Å, º) top
N2—C81.324 (2)C8—C8i1.537 (3)
N2—C71.451 (2)C7—C61.520 (2)
O1—C81.2224 (19)C5—C61.502 (2)
C8—N2—C7122.37 (13)C5—C6—C7111.21 (13)
N2—C7—C6112.13 (13)
Symmetry code: (i) x, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2—H2A···N1ii0.878 (19)2.204 (19)3.008 (3)152.1 (17)
C1—H1···O1iii0.94 (2)2.452 (19)3.308 (3)151.4 (17)
Symmetry codes: (ii) x, y1/2, z+3/2; (iii) x+1, y+1, z+2.
 

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