Crystal structures of 1,1-di(p-substituted phenyl)-2,2-dinitroethylenes

The X-ray crystal structures of 1,1-di(p-methylphenyl)-2,2-dinitroethylene (2), 1,1-di(p-methoxylphenyl)-2,2-dinitroethylene (3), 1,1-di(p-fluorophenyl)-2,2- dinitroethylene (4), 1,1-di(p-chlorophenyl)-2,2-dinitroethylene (5), and 1-phenyl-1- (p-nitrophenyl)-2,2-dinitroethylene (6) are reported and compared with that of 1,1-diphenyl-2,2-dinitroethylene (1). Owing to steric repulsion between the aryl rings, the single bond lengths between C(1) and the two ring carbons atoms are longer than the normal sp2–sp2bond distance of 1.46 Å. For 4–6in which the aryl rings contain electron-withdrawing substituents (F, Cl, NO2), the double bonds between C(1) and C(2) are shorter than those in 2and 3, whose aryl rings containing electron-donating substituents. Furthermore, the steric repulsion between the aryl rings and C $$---$$ NO2fragments results in an appreciable twist about the central double bond. The two aryl rings of compounds 1–6make dihedral angles of 77.7, 66.6, 62.8, 80.9, 82.0, and 71.2°, and the two C $$---$$ NO2fragments make dihedral angles of 68.5, 67.8, 65.9, 76.9, 73.0, and 71.9°, respectively.