Vibrational Analysis of Different Isomers of Oxalyldihydrazide and the Crystal Structure of the “trans-trans” Form

Abstract Laser Raman, IR, and far-IR spectra of different modifications of oxalyldihydrazide have been obtained and interpreted as a function of the presence of the cis secondary amide group. Assignments for the different structures are proposed and the crystal structure for the most stable conformer has been solved by X-ray diffraction. Mr = 118.1; monoclinic; space group P21/c; unit cell dimensions, a = 3.6188(3) A, b = 6.841(2) A, c = 9.133(2) A, β = 99.23(1)°, V = 223.2(1) A3; Z = 2; Dx = 1.76 g cm−3; Mo Kα (λ = 0.71073 A); μ = 1.4 cm−1; F(000) = 62; T = 295 K. Final R-factor = 0.033; Rw = 0.048, for 458 reflections with I > 3σ(I) out of 531 measurements. The structure has been solved using MULTAN. The molecule is centrosymmetric and has a planar structure. The unusual geometry of the NH2 groups is explained by intermolecular hyrogen bonding. Ab initio calculations, performed on four conformers of oxalyldihydrazide, reveal a large flexibility of the molecule which is also confirmed by the different vibrational spectra.