A triclinic polymorph with Z = 3 of N,N′-bis­(2-pyrid­yl)oxamide

Wan-Ju Zhang; Fang Wang; Gui-Ling Zhang; Xin Xiao

doi:10.1107/S1600536811010294

. 2011 Mar 26;67(Pt 4):o972–o973. doi: 10.1107/S1600536811010294

A triclinic polymorph with Z = 3 of N,N′-bis(2-pyridyl)oxamide

Wan-Ju Zhang ^a, Fang Wang ^a,^*, Gui-Ling Zhang ^b, Xin Xiao ^c

PMCID: PMC3099752 PMID: 21754234

Abstract

The asymmetric unit of the title compound, C₁₂H₁₀N₄O₂, contains three half-molecules. Each half-molecule is completed by crystallographic inversion symmetry. The title compound, (I), is a polymorph of the structure, (II), reported by Hsu & Chen [Eur. J. Inorg. Chem. (2004), 1488–1493]. In the original report, the compound crystallized in the tetragonal space group P Inline graphic 2₁c (Z = 8), whereas the structure reported here is triclinic (P , Z = 3). In both forms, each oxamide molecule is almost planar (with maximum deviations are 0.266 and 0.166 Å) and the O atoms are trans oriented. The principal difference between the two forms lies in the different hydrogen-bonding patterns. In (I), two N—H⋯O and one N—H⋯N hydrogen bonds link the molecules, forming a two-dimensional network, whereas in (II) there are no classical hydrogen bonds to O atoms and only weak C—H⋯O interactions are found along with rings of N—H⋯N bonds.

Related literature

For general background to the use of N,N′-disubstituted oxamides as ligands, see: Bencini et al. (1986 ▶). For the synthesis and related structure, see: Hsu & Chen (2004 ▶).

Experimental

Crystal data

C₁₂H₁₀N₄O₂
M _r = 242.24
Triclinic,
a = 8.459 (2) Å
b = 10.705 (3) Å
c = 11.058 (3) Å
α = 99.555 (9)°
β = 101.344 (8)°
γ = 112.980 (8)°
V = 870.5 (4) Å³
Z = 3
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 298 K
0.26 × 0.26 × 0.20 mm

Data collection

Bruker SMART APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.975, T _max = 0.980
8909 measured reflections
3018 independent reflections
2575 reflections with I > 2σ(I)
R _int = 0.021

Refinement

R[F ² > 2σ(F ²)] = 0.044
wR(F ²) = 0.125
S = 1.07
3018 reflections
245 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.34 e Å⁻³

Data collection: SMART (Bruker, 2002 ▶); cell refinement: SAINT (Bruker, 2002 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP (Siemens, 1994 ▶) and CAMERON (Watkin et al., 1993 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811010294/ez2234sup1.cif

e-67-0o972-sup1.cif^{(17.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811010294/ez2234Isup2.hkl

e-67-0o972-Isup2.hkl^{(145.1KB, 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
N2—H2A⋯O3	0.86	2.39	3.176 (2)	153
N4—H4A⋯O3	0.86	2.27	2.898 (2)	130
N6—H6⋯N3ⁱ	0.86	2.39	3.188 (2)	155

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank the Doctoral Foundation of Huanggang Normal University (No. 09CD157) for financial support.

supplementary crystallographic information

Comment

N,N'-disubstituted oxamides are known to be versatile organic ligands since their coordinating ability toward transition-metal ions can be modified and tuned by changing the nature of the amide substituents (Bencini et al., 1986). The title compound, (I), is a triclinic polymorph of the previously reported crystal structure of this symmetrical N,N'-disubstituted oxamide which crystallizes in the tetragonal space group P-42₁/c (Hsu & Chen, 2004). The relative arrangement of the molecules observed in the current structure is distinctively different from that previously reported.

The molecular structure of (I) is shown in Fig. 1. It crystallizes in the space group P-1 with three molecules in each unit cell. Each N,N'-di(2-pyridyl)oxamide molecule is almost planar and the O atoms are trans-oriented. In the crystal structure, classical N—H···O and N—H···N hydrogen bonds (Table 1, Fig. 2) link the molecules to form a two-dimensional network.

Experimental

2-Aminopyridine (4.7 g, 50 mmol) was dissolved in 200 ml CH₂Cl₂, followed by addition of triethyl amine (10.0 ml, 72.1 mmol) at 273 K. The mixture was then stirred for 10 min. Oxalyl chloride (2.2 ml, 25 mmol) in 10 ml CH₂Cl₂ was then added slowly to the above mixture. After continuous stirring for about 3 h at 273 K, the resulting solution was concentrated under vacuum until a large amount of solid precipitated. The solid was filtered, washed with water and then dried in vacuum. Yield: 4.3 g (71%). Colourless block crystals suitable for X-ray crystallography were obtained by slow evaporation of the solvent from a solution of the title compound in toluene.