STRUCTURES OF 1,1-DIPHENYL-2-AZA-1,3-BUTADIENES .4. 4-DICHLOROPHENYL)-1,1-DIPHENYL-2-AZA-1,3-BUTADIENE (24CLPD) AND -DIMETHOXYPHENYL)-1,1-DIPHENYL-2-AZA-1,3-BUTADIENE (24MOPD)

The 2,4-disubstituted derivatives [24CLPD: ophenyl)-2-(diphenylmethyle neamino)propenonitrile, C22H14Cl2N2; 24MOPD: phe-nyl)-2-(diphenylmethy leneamino)propenonitrile, C24-H20N2O2] have the Z configuration, as in the previously described monosubstituted representatives from this se ries. The C1c-C3 bond length [in Phc-C3=C2(CN)-N1=C1(pha)(Phb)] is 1.4 59(5)angstrom in 24CLPD, which is slightly longer than in 24MOPD, 1.44 8 (3) angstrom, while the C3-C2 bond in 24CLPD, 1.337 (5) angstrom, is shorter than in 24MOPD, 1.357 (4) angstrom. The c ring is twisted out of the C1c-C3=C2(N1)-C4 plane by 10.9 (2) and 21.8 (2)-degrees for 24 CLPD and 24MOPD, respectively. The C1=N1-C2-C3 torsion angle in 24MOPD , 151.6 (3)-degrees, is the largest among those determined so far. In 24CLPD, this angle has the mean value 135.9 (3)-degrees. The dihedral angles between the N1=C1(C1a)-C1b plane and the a and b phenyl rings a re 15.0 (1)/20.4 (3) and 58.3 (1)/62.3 (1)-degrees for 24CLPD/24MOPD, respectively. Correspondingly, the C1a-C1 bond distances, 1.481 (4)/1. 488 (5) angstrom, are shorter than C1b-C1, 1.488 (4)/1.490 (3) angstro m. The molecules are held together only by dispersion forces and both compounds obey the close-packing principle. The structure of 24MOPD ca n be described as layers of centrosymmetric dimers, related by inversi on centers and parallel to the ac face of the unit cell. In the struct ure of 24CLPD, the layers are parallel to the ab face and are related by a system of 2 and 2(1) axes; in the layer, the centrosymmetric dime rs are ordered in chains extended along the ab face diagonals and rela ted only by inversion centers.