Molecular associations of hydrazones. X. Dihydrazones as twin-site donors

Molecular associations of dihydrazones of 1,2-diketones with tetracyanoethylene are investigated and compared with those of the corresponding monohydrazones, in order to verify the influence of the second donor centre on the equilibrium constants. As proved by X-ray determinations (complex 2,3-butandionemonophenylhydrazone/tetracyanoethylene), hydrogen bonding appears to play an important role in the lattice stabilization of monohydrazones complexes. C₁₀H₁₂N₂O·1/2C₆N₄,M _r =240.66, monoclinic,C2/c,a=12.216(2),b=12.824(3),c=16.784(2)Å,=93.74(2)°,Z=8,D _x=1.22 g cm^–3,V=2623.8(8)ų, room temperature, CuK, =1.5418 Å,=6.28 cm^–1,F(000)=1008,R=0.059 for 1398 independent observed reflections. The aromatic ring is planar and the tetracyanoethylene atoms are far more than 3.40 Å from its barycentre. Together with van der Waals forces, H-bonding between two faced hydrazono molecules realizes the packing in the crystal.